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5.4 Worker-Related Element Gr ouping |197
processes as well as to transient situations such as startups,
shutdowns, and batch processes.
Good OPs also describe the process, identify process hazards,
and describe the measures required to safeguard against those
hazards, not only process safety but also environmental, health,
and occupational safety. Good OPs also describe safe operating
limits, a troubleshooting guide, and emergency actions.
Consequences of deviating beyond safe operating limits must be
included to m aintain the sense of vulnerability .
Operators m ust be trained on a procedure before they follow
it in the field, and they m ust understand everything contained in
the OPs. Following training, performance assurance should be
done to m ake sure the operator follows and continues to
understand the procedure. Ideally, training on procedures should
be based on the procedure docum ent itself, rather than on
separate training m aterials. When it is necessary to have separate
training m aterials, and especially when the separate training
m aterials are being used in lieu of the procedure, this is a warning
sign that the procedure is not adequate.
The necessity of following procedures was discussed in section
5.1 (Conduct of operations). This means also that procedures
should be written so that they match what operators actually do.
Moreover, procedures should be written in plain language,
written to a com prehension level of no higher than 8th grade. Text
should be well spaced with a line length no longer than the text
on this page. Tables, figures, and illustrations should be provided
as needed to enhance comm unication. All these m easures will
help operators follow the procedures and resist their tem ptation
to stray from the procedure, leading to normalization of deviance .
Operating procedures should be controlled documents that
are kept up to date whenever there is a change. Operators must
use the current OP, and no old versions should exist except in the
document management system. Most changes com e through the |
Hazard Identification
Learning Objectives
The learning objectives of this chapter are as follows. Having completed the chapter, the reader
should be able to:
Understand hazard identification methods.
Participate in hazard identification studies, and
Create a potential process safety incident scenario.
Incident: Esso Longford Gas Plant Explosion, Victoria, Australia, 1998
Incident Summary
A major explosion and fire occurred at Esso’s Longford gas processing site in Victoria, Australia
in 1998. Two employees were fatally injured, and eight others injured. The incident caused the
destruction of Plant 1 and shutdown of Plants 2 and 3 at the site. This shutdown resulted in
total loss of gas supply to Victoria and cons equential business interruption and economic
impact.
A process upset in a set of absorbers eventu ally caused temperature decreases and loss
of flow of a “lean oil” stream. This allowed a metal heat exchanger to become very cold and
brittle. When operators restarted flow of the lean oil to the heat exchanger, it ruptured,
releasing a cloud of gas and oil. When the cloud reached an ignition source, the fire flashed
back to the release point resulting in addition al equipment ruptures and an escalating fire.
Figure 12.1. Photograph of th e failed end of GP905 reboiler
(LRC)
|
38 PROCESS SAFETY FOR ENGINEERS: AN INTRODUCTION
Figure 3.2. DOT-117 train car
(DOT 2015)
Lessons
Compliance with Standards . The MMA SOP required a prescrib ed number of hand brakes to
be set depending on the number of railcars and the grade of the parking location. The MMA-
002 train was not in compliance with this requ irement. Additionally, the brake effectiveness
check was not performed correctly in that the check was conducted with the air brakes set.
Standards, whether governmental or company, should be followed. When standards are not
followed and work is completed based solely on one’s experience or judgment, then the
benefit of other person’s experiences, hard learnings, and even expert calculations are a
resource and opportunity wasted.
Asset Integrity and Reliability . The locomotive that failed had engine problems in
October 2012 and a repair was made. Two days before the Lac-Megantic incident the
locomotive engineer reported problems with th e same engine surging. When the locomotive
was parked at Nantes, the smoke and oil spra y was noticed by the taxi driver, but the
locomotive engineer and the rail traffic contro ller felt it could wait until morning to be
addressed. Nonetheless, this sa me engine was the only one left running and the sole source
of air pressure for the parked train. After the incident, tests showed that the cam bearing had
fractured when the mounting bolt was over-tightened after the non-standard repair in
October. Repairs should be made following expert direction. Making do with materials on hand
and over-tightening bolts are frequently noted in accident reports. Additionally, operational
issues with equipment that has just been repaired should be reported and investigated to
ensure that it is fit for continued service.
Management of Change . This incident is an example of creeping change in an industry
over multiple years. The industry was, for the most part, satisfied with the performance of the
DOT-111 cars. However, the number of cars in a single train, the volume of crude oil being
transported, and the properties of the crude oil we re changing significantly. The impact of this
|
292 | Appendix E Process Safety Culture Case Histories
A facility included a KPI based on the num ber of overdue ITPM
tasks in the AI/MI element, which m any facilities do. The facility
defined the KPI as any ITPM task that was overdue in 2 m ain asset-
tracking software packages. One software was used to m anage
rotating equipment, instruments, and electrical equipment, while
the other was used to m anage fixed equipment pressure vessels,
tanks, piping, and relief devices. Upon im plementation, this KPI
revealed a few items overdue month-to-month, but the value was
low, as was the aging of the overdue ITPM tasks.
Two years later, during a PSMS audit, auditors found that there
were other ITPM tasks that were important to process safety that
were overdue but were not tracked in either of the two tracking
software packages and therefore were excluded from the KPI. And
those results were m uch less favorable.
The Fire Chief tracked fire system ITPM in his electronic
calendar. The annual fire pum p flow tests had not been
conducted for two years and the ITPM tasks required by NFPA-25
were not included in the calendar. The Instrument shop
supervisor tracked the annual calibration of testing equipment in
a spreadsheet and there were ten pieces of test equipment that
were overdue for annual calibrations. |
Piping and Instrumentation Diagram Development
202
11.3 Different Types of Heat
Exchangers and
Their Selection
Different types of heat exchangers are used in the process
industry. The reason for the different available types is the differences in indirectly contacting two fluids to each other.
For example in shell and tube heat exchangers cold and
hot streams transfer the heat through the peripheral area of several tubes.
The most common type of heat exchanger is the “shell
and tube” (S&T HX) type. In this type of heat exchanger, a bundle of tubes is secured on one or both sides in tube sheets and is placed inside a cylindrical body, or shell. A tube sheet is a perforated sheet that secures the tubes in its holes. One fluid is flowing through the tubes and the other fluid is flowing in the space between the outside of the tubes and the shell.
If a tube bundle comprises only one tube, this could be
considered as a variation of a S&T HX and it is named a “double pipe heat exchanger. ”
After shell and tube heat exchangers, possibly the most
common heat exchangers are “plate and frame (P&F HX) types. P&F HXs provide channels for each stream.
In this type of heat exchanger, several plates are put
together in the form of a sandwich and are secured between two “jaws. ” Plates are generally in rectangular shape. The plates are separated from each other by peripheral gaskets, which provide a gap between every two adjacent plates. Hot streams and cold streams flow through these narrow gaps, or channels.
The last type of heat exchanger is the spiral type.
To visualize this type of heat exchanger, consider a P&F HX with a larger‐than‐usual plate size. If someone rotates and wraps this “sandwich” around a core, then a spiral heat exchanger is obtained. Spiral heat exchangers are the least common and the most expensive type of heat exchangers.
There are plenty of criteria that should be considered
for decision on a specific type of heat exchanger. Table 11.1 summarizes some rules of thumb for the selection of heat exchangers.
Another rule of thumb uses the required heat transfer
area for the selection of heat exchangers. This rule of thumb is presented in Figure 11.2.
At the end of this section one important piece of
te
rminology needs to be discussed.
Each heat exchanger has two enclosures in contact
with each other and with a common wall.
Process heat ex changer
Utility heat ex changer
Furnace
Figure 11.1 Usage of hea t transfer units in process plants.Table 11.1 Rule of thumbs for selec
ting heat exchanger types.
Heat exchanger type When?
Shell and tube
(S&T) heat exchangerFixed headDefault choice but applicable if desired temperature is less than 50–60
°C (or le
ss than 80–90 °C wit
h
expansion ring)
Floating headWhere the desired temperature is more than 50–60
°C
●Where the shell side fluid is fouling
Double pipe heat exchangerWhen the decision is S&T but the required heat duty is low
Plate and frame (P&F) heat exchanger
●Wherever is not enough room for an S&T type but enough pressure is available
●Pressure and temperature cannot be severe otherwise the tolerance of the gaskets of the P&F HX will be exceeded
●Where the required heat duty is not certain and the modular structure of P&F helps in the future addition of plates (and increase in the heat transfer area)
Spiral heat exchanger For very fouling services
Aerial cooler When cooling down to
approximately 65
°C is ade
quate
Helical coil For small heat duties, for example sample coolers and pump seal water heat exchangers
Helical coilD ouble pipe
5 m220 m21,000 m25,000 m2Shell & Tube-floating headHeat transfer area
Shell & Tube-fixed head
Figure 11.2 Selec tion of heat exchangers based on the required heat transfer area. |
Appendix B. Inherent Safety Analysis
Approaches
Inherent safety (IS) can be analyzed in a number of ways, but in all cases,
the intent is to formalize the consid eration of inherent safety, rather
than to include it by circumstance. By formally including inherent safety,
in either a direct or indirect way, facilities can fully realize the potential
benefits of inherent safety. In additi on, all IS considerations will be fully
documented.
Three analysis methods can be used to evaluate implementation of
IS:
1.Inherent Safety Analysis: Guided Checklist Process Hazard
Analysis (PHA)
2.Inherent Safety Analysis: Indepe ndent Process Hazard Analysis
(PHA)
3.Inherent Safety Analysis: Integr al to Process Hazard Analysis
(PHA)
Method 1 employs a specialized ch ecklist containing a number of
practical inherent safety consider ations organized around the four
strategies of minimization, substitu tion, moderation, and simplification.
The advantage of this approach is that it is very direct and asks pointed
questions that have proven to be va luable in reducing hazards at past
locations. The disadvantage is that, as with any checklist, it may be
limiting in that other ideas may surf ace if the team was asked to more
creatively determine applications for the inherent safety strategies given
a safety objective. (Note that the checklist appearing here is only a
representative subset to illustrate its use. See Appendix A for the
complete checklist.)
For the second method, the team is asked to avoid a particular
hazard at a designated part of the pr ocess. In this case , the team reviews
a problem, determines which of th e inherently safer strategies may
apply, and then brainstorms possible ways the hazard can be reduced
or eliminated.
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DETERM INING ROOT CAUSES 217
At this point, the logic tree structur e is examined to en sure that the tree
is logically consistent and compatible with the known facts. In some
instances, there may be inconsistencies, and application of the
fact/hypothesis matrix will be appropriat e. Inconsistencies found at this point
require further tree development or rearrangement.
Once the logic tree structure appear s to be consistent, the first of three
quality assurance tests is applied by examining the overall logic tree structure
for completeness. The logic in each branch of the tree should be tested to
determine if it is necessary and sufficient. (Details and tips for testing the
logic are discussed in Section 10. 5.2.) If the tree appears to be complete, the
next quality assurance test is initiated. If the tree is incomplete, then the fact or logic problem is identified and the entire process is
repeated. This is called
an iterative loop.
If the logic tree appears to be complete, then the second quality control
test is applied by asking the questi on, “Are the causes that have been
identified actually relat ed to management systems?” If the answer is yes,
then the investigation proceeds to the third quality control test—the final
overall review. If management system causes have not been found, then the
iterative loop process is used.
It is important to note that not all management system causes may be
located at the extreme bottom points on the logic tree. Some of the
management systems-related causes can be - and often are - located in the
upper or middle portions of the logic tree diagram. Some causes can also be
identified by the logic tree structure it self. For example, an overview of the
entire tree structure may indicate significant gaps or overlaps in
responsibilities, or it may disclose conflicting activities or procedures. These
insights may be overlooked if the inve stigators limit their cause search to
only the bottom level of the structure and fail to review the entire tree and
the interrelationships between branches.
If the test for systems-re lated causes is satisfac tory, then the third and
final quality assurance test is applied. This is an overall review of the logic
tree as a whole for both facts and logi c. A conscientious review of each
branch should be made to look for possible conflicts or inconsistencies. It is
a pause to focus on the logic tree fr om an overall perspective, not just each
branch. The final logic diagram should be thoroughly checked against the
final timeline to ensure that these two are in complete agreement. The team
should also verify that none of the facts is in conflict with the tree. If the
incident investigation team is satisfied with the causes i dentified, then the |
142 | 4 Applying the Core Pr inciples of Process Safety Culture
steadily increasing share price. Therefore, boards are heavily
influenced to focus their attention on matters that relate directly
to the share price. As discussed relative to the financial
com munity, this can unintentionally motivate m anagement to
normalize deviance .
Some boards are more independent or more supervisory than
others. Com panies with weaker process safety cultures often
have boards that acquiesce in management decisions and take
little interest in process safety. Com panies with stronger process
safety cultures have boards that recognizes that a strong PSM S
and culture will help reduce risk and protect the company im age,
two things that help increase share price. B oards should oversee
auditing program s to ensure that they have a true measure of the
health of the company’s process safety effort. Towards this, some
com panies have found it helpful to have one or more board
m em bers who understand process safety concepts. This
approach is expected to gain in practice in the com ing years.
4.5 Process Safety Culture Metrics
Like other aspects of a PSMS, process safety culture should be
m easured periodically to monitor progress, guide improvem ent,
and detect regression. Culture changes, especially positive
changes are usually slow and hard to discern. Nonetheless,
historic experience dem onstrates that regular monitoring can
reveal cultural changes over time.
Practical experience as well as formal study by the
International Atom ic Energy Agency (IAEA) (Ref 4.16) has shown
that a single quantitative measurem ent of culture m ay be
impossible. Instead, culture can be sensed from qualitative
indicators. Therefore, facilities and com panies should select a
range of indicators that reflect the individual culture core
principles. These indicators m ay be based on observable
behavior, conscious attitudes, perceptions, or beliefs |
16 INVESTIGATING PROCESS SAFETY INCIDENTS
This example illustrates that event trees can be useful models of an
incident sequence because they provide a graphical, logic-based depiction
of the various potential consequences that could occur, depending on the p a t h w a y of a n e v e n t . T h i s i s a mor e structured sequen ce model than the
three-phase model, but it does not fu lly address the weaknesses in barriers
and the management systems behind them.
2.1.3 Swiss Cheese Model
Another way to represent the staged even ts and conditions that result in an
incident is by using the Swiss Cheese model (Reason, 1990). This model takes
one of the failure paths d efined in the event tree that leads to a consequence
of concern. The protective barriers (safety systems) are represented by
parallel slices of Swiss cheese. Thes e barriers represent the equipment,
procedures/practices, and people that comprise elements of the
management system for the facility.
Ideally each barrier shou ld be robust, but like th e holes in Swiss cheese,
all barriers have weaknesses (Figure 2.2) resulting from:
Active failures (e.g., equipment fa ilures, unsafe acts, human errors,
procedural violations, etc.).
Latent failures (e.g., design/equipment deficiencies, inadequate/
impractical procedures, time pressure , unsafe conditions, fatigue, etc.) –
see Section 2.1.4 below.
These weaknesses can lead to manage ment system failures resulting in
a process safety incident (see Section 2.2.2 below).
Figure 2.2 Swiss Cheese M odel
|
22 Human Factors in emergencies
22.1 Learning objectives of this Chapter
This Chapter provides an overview of the Human Factors of emergency response.
By the end of this chapter, the reader should be able to:
• Understand how Human Factors affe ct performance and management
of emergency situations.
• Recognize the importance on non-technical skills in emergency
response.
22.2 An example accident
22.2.1 Milford Haven refinery explosion, Wales, 1994
On July 24th, 1994, a large explosion occurred at Texaco Refinery, Milford Haven in
Wales, which caused injury to 26 peop le [87]. The blast from the explosion
damaged properties in a 10 mile (16 kilo meter) radius and was heard 40 miles (64
kilometers) away. The site suffered severe damage to the process plant, the
building, and storage tanks. A summary of the event is given in B.4 (page 389).
During the sever electrical storm that proceeded the explosion, operators and
operations management failed to identify the underlying causes of the problem or
to recognize that they had the potentia l to lead to hazardous consequences,
despite these data being available to them. They continued to operate in a
disturbed environment for five hours prior to the explosion. All the information,
including alarms, was available to the operators via six distributed control systems
(DCS) screens, which were used to contro l the process and to diagnose faults.
Many alarms, in the plant were sounding simultaneously, all with the same -
high priority. In the 15 minutes before the explosion, operators were receiving
alarms at a rate of one every two seconds. Thirty minutes before the accident, a
critical alarm went off. Had the operator s recognized the criticality of the final
alarm and taken appropriate action, the explosion may not have happened.
The accident was caused by a combination of factors, including:
• A control valve shut when the control system indicated it was open.
• A modification that was carried ou t without proper assessment of
consequences.
• Control panel graphics that did not provide the necessary process
overview.
• Attempts to keep the unit running when it was supposed to be shut
down.
• Inadequate emergency management. Human Factors Handbook For Process Plant Operations: Improving Process Safety and System
Performance CCPS.
© 2022 CCPS. Published 2022 The American Institute of Chemical Engineers. |
152 PROCESS SAFETY FOR ENGINEERS: AN INTRODUCTION
Table 9.1 continued
Severity
Points Consequence Categories
Safety/Human
Health c Direct Cost
from Fire or
Explosion Material
Release
Within Any 1-
Hr Period a, d,
e Community
Impact Off-Site
Environmental
Impact b, c
9 points — A fatality of an
employee,
contractor, or
subcontractor, or
— A hospital
admission of a
third party. Resulting in
$10,000,000 ≤
Direct Cost
Damage
<$100,000,000 Release volume
9x ≤ Tier 1 TQ <
27xoutside of
secondary
containment. Officially declared
evacuation > 24
hours < 48 hours. — Resulting in
$10,000,000 ≤
Acute
Environmental
Cost
<$100,000,000,
or
— Medium-
27
points — Multiple
fatalities of
employees,
contractors, or
subcontractors,
or
— Multiple
hospital
admission of
third parties, or Resulting in
≥$100,000,000 of
direct cost
damages. Release volume ≥
27x Tier 1 TQ
outside of
secondary
containment. Officially declared
evacuation > 48
hours. — Resulting in
≥
$100,000,000
of Acute
Environmental
Costs, or
— Large-scale
injury or death
of aquatic or
land-based
a Where there is no secondary containment, the quanti ty of material released from primary containment
is used. Where secondary containment is designed to only contain liquid, the quantity of the gas or
vapor being released and any gas or vapor evolving from a liquid must be calculated to determine
the amount released outside of secondary containment.
b Judging small, medium or large-scale injury or deat h of aquatic or land-based wildlife should be
based on local regulations or Company guidelines.
c The severity weighting calculation includes a category for “Off-Site Environmental Impact” and injury
beyond first aid (i.e. OSHA “recordable injury”) level of Safety/Human Health impact that are not
included in the Tier 1 PSE threshold criteria. However, the purpose of including both of these values is
to achieve greater differentiation of severity points for events that result in any form of injury or
environmental impact.
d For the purpose of Severity Weighting, general paving or concrete under process equipment, even when
sloped to a collection system, is not credited as secondary containment.
e Material release is not tabulated for fires or explosions. These events severity will be determined by the
other consequence categories in this table.
|
Piping and Instrumentation Diagram Development
234
If the relieving gas/vapor is not innocent, other, more
expensive, options should be considered.
The options depend on the nature of the released gas/
vapor; if it is flammable it can be burnt in a flare; if it is
absorbable in water the stream can be sent to a catch vessel.
Figure 12.31 shows the different available options for
gas/vapor relieving.
The last choice for gas/vapor relieving is “system
relieving. ” As was mentioned before, system relieving is not common for gases and vapors. However there are some cases that no other option is available and system relieving is the only technically doable option, for example in the oil extraction industry. Well pads are not necessarily close to the central plant, which has a flare system. There are, however, some units on well pads that have PRDs. Sometimes a large “pop tank” is located to release gases from the PRDs on the well pad. Pop tanks can be used for liquid relieving too.12.16.3
Two‐Phase Flow Handling
Here two‐phase flow refers to gas–liquid two‐phase flow.
We generally don’t provide a “two‐phase flow disposal
system. ” What we try to do is to separate the two‐phase flow to its components, gas and liquid, and then deal with each of them separately.
The reason for the separation of two‐phase flow is two‐
fold. On the one hand the design and fabrication of a two‐phase flow collection network is more complicated and expensive. On the other hand it is not easy to find a disposal system suitable for both liquid and gas at the same time.
However, if the liquid fraction or gas fraction of two‐
phase flow is very small, the two‐phase flow can be con-sidered to be a single‐phase flow.
The two phase separators could as simple as Tee‐
se
parators, to the more complicated options of cyclone
separators and knock‐out drums (blow‐down drums) (Figure 12.32).
Sometimes even a combination of them is used.
To Atm.
To Safe Location
Flare DisposalQuench/Catch Tank
Figure 12.31 Differ ent gas/vapor disposal systems.
Min. 3 m
15mGround or platformMin. 2 mFigure 12.30 Gener al meaning of “safe location” for
releasing to atmosphere. |
261
is not forgotten or overlooked as personnel and organizational changes
occur (Ref 10.8 CSChE). Hendershot (Ref 10.15 Hendershot) argues that
this is especially critical when dealin g with inherent safety and inherently
safer design (ISD) features. He gives several examples where ISD
features were essentially put at risk because the reasons they were implemented were not clearly and ad equately documented. Potentially,
this could compromise facility safety when future modifications are made by people who do not understand the original designer’s intent, or
what is involved in a particular sa fety feature. Examples include why a
certain size feed line for limiting ma ximum reagent flow is part of the
safety design basis, or how the routing of a pipe is intended to minimize consequences of a spill.
ISD features are particularly susc eptible to lapses in corporate
memory given that, unlike an add-on device such as a high-pressure
alarm, they are such a fundamental pa rt of the design that their purpose
may not be obvious (Ref 10.15 Hend ershot; Ref 10.1 Amyotte). All these
inherently safer design features must be documented in original design
manuals, and appropriate process safe ty information, including P&IDs
and SOPs, must be readily available. This issue is also pertinent to M a n a g e m e n t o f C h a n g e i n t h a t a proposed modification should be
reviewed carefully to ensure no ISD features are being compromised.
10.8.1 IS Review Documentation Whichever type of IS analysis is cond ucted, a report of the review should
be generated to document the study. This report should include, at
minimum, the following information:
A summary of the approach used for the IS review (i.e.,
methodology, checklist used, etc.).
Names and qualifications of the team facilitator/leader and team
makeup, including positions, names, and any relevant experience or training.
IS alternatives considered, as well as those already implemented
or included in the design.
If an independent inherently safer systems analysis was conducted, documentation should include the method used for the analysis, what inherently sa fer systems were considered, and
the results of each consideration. If an IS checklist was used, |
170 GUIDELINES FOR MANAGING ABNORMAL SITUATIONS
called a pitot tube. The difference between these two pressures,
corrected for air density/height, is used by the flight computer to
calculate the velocity of the aircraft relative to the air.
The A330 features three sets of pitot tubes (“probes” – see
Figure 7.1) (BEA 2012) and six static pressure sensors. The probes are
fitted with drain holes to prevent water from accumulating and are
heated to prevent icing. In December 2001, Air France had its first
delivery of the A330 airc raft, which were all originally fitted with pitot
probes manufactured by Thales, model number C16195AA. The A330 on
flight AF447, registration F-GZCP, fi rst went into service in April 2005.
Figure 7.1. The Three Pitot Tubes on the A330 Aircraft
|
374 Human Factors Handbook
This model uses the terms active and latent failures.
• Active failures are the unsafe acts committed by people who are in
direct contact with the system. These include slips, lapses, or mistakes,
such as omitting an operational task or performing a task incorrectly.
• Latent failures are “resident pathogens” within a system caused by
decisions made by engineers, proc edure authors, and management for
example. These can create “error pr ovoking conditions” such as time
pressures and understaffing and poor procedures. They may lay
dormant for many years until a comb ination of events reveals them.
Latent failures are also referred to as “psychological precursors” as they also
create the conditions for error.
This model has been used to help understand accidents and the role that the
systems of management created the (hidde n) conditions for human error. This
includes the notion that latent failures can cause multiple defenses to fail, and
thereby undermine “defense in depth” sa fety management systems. The model is
also used to prompt the identification and resolution of latent failures before they
contribute to an accident. The concept being that resolving one latent failure would
avoid many active failures.
A.2 Compliance concepts
A.2.1 “Violations”
The term “violations” is not typically used in current human performance
discussions. However, Professor James Re ason in his 1997 book “Managing the
risks of organizational accidents” [119] st ated that “Violations are deviations from
safe operating procedures, standards or rules. Such deviations can be either
deliberate or erroneous…” (p72).
Reason listed three major catego ries of safety violations:
• Routine: these tend to be habitual “corner-cutting” in skilled
performance. They may be associat ed with “clumsy” procedures and
rare sanctions.
• Optimizing: Professor Reason describe s these as “violating for the thrill
of it”.
• Necessary: These involve non-compliance being “essential” “to get the
job done”. These tend to be related to organizational failings such as
tools.
Reason defined these as non-malevolent acts. The actions are intended but the
harmful consequences are unintended. |
120 Human Factors Handbook
Figure 10-1: Competency Management
|
DETERM INING ROOT CAUSES 225
Consider the incident scenario discussed previously:
A worker was walking on a co ncrete walkway in the process
unit. There was some lube oil on the pad. He stepped into the
oil, slipped, and fell. It was a sunny day; the worker was not
carrying anything, was not dist racted, and was not doing any
urgent task .
The top portion of the logic tree may look something like the tree in
Figure 10.11.
Figure 10.11 Example Top of the Logic Tree, Employee Slip
Each of the succeeding lower level events is further developed by
repeatedly asking the question, “Why did this event occur?” Pursuing just
one branch, for example the Oil Spilled on Pad branch would lead to at least
two possible sources: Leak from Pipe and/or Hand Carried Containers , as
shown in Figure 10.12 and Figure 10.13 .
Figure 10.12 Example Logic Tree Branch Level, Oil Spill
|
92 GUIDELINES FOR MANAGING ABNORMAL SITUATIONS
operations team situational awareness is one way for operating companies
to enable a proactive operating posture. (Bullemer & Reising, Effective
Console Operator HMI Design (2nd Editio n), 2015). This is also the case for
the outside (field) operators who interface/interact with the valves, gauges,
and other pieces of equipment. Design engineers normally play an
important role in recommending the design and layout of the console
displays, alarm systems, field equipment and almost all other features of
the HMI. Therefore, design engineers should be made aware of the
management of abnormal situations, which should be included in their
training sessions. This is especially important when al arm structure and
display are being considered. Some published RAGAGEP standards such as
those by ISA, EEMUA, and IEC (ANS I/ISA 2009; EEMUA 1999/Revised 2013;
IEC 2014) should be applied when appropriate.
In addition to applying these RAGA GEP standards, several techniques
that can be employed in the design of the HMI include:
Alarm configuration such as “First out alarm reporting” is key to
understanding the initial alarm that directly indicates the presence
of a developing abnormal situation. It is, by definition, what alarm
cascade management is intended to solve.
Alarm management strategy such as “alarm flood suppression” is
the ability to support alarm cascade management by limiting initial
alarms to those that are meaningful and actionable. For example, if
a high-high level trip activates on a compressor inlet knockout
drum, shutting down the compressor, the op erator only requires
an alarm indicating the high-high level and the trip. The operator
does not need subsequent alarms for high suction pressure, low
discharge pressure, low lube oil pressure, and all of the other
alarms that would accompany a compressor shutdown, which can
make it harder for the operator to determine what happened and
what to do next. This strategy is typically applied to complex
process equipment systems such as refrigeration systems, burner
management systems, and self-c ontained packaged units.
The design and layout of plant and control equipment in the field is also
highly relevant to the effective management of abnormal situations. The
logical positioning of controls and valves relative to the items they affect will
h e l p t o e n s u r e t h a t t h e c o r r e c t d e v i c e i s o p e r a t e d i n a n e m e r g e n c y .
The clear and correct labelling of equipm ent, locally visible valve position |
353
been home to chemical/processing industry facilities, including oil
refineries and chemical plants.
Following a series of serious indust rial accidents, the County enacted
the Industrial Safety Ordinance (ISO ) in 1999 and has revised it several
times since then, most recently in 2 014 (Ref 14.4 CCC ISO). Designed to
be “the most stringent in the United States, if not the world,” (Ref 14.6
CCHS 2017) the ordinance expands on the California Accidental Release
Prevention (CalARP) Program (Ref 14.1 CalARP) for petroleum refineries
and chemical plants in the County. The City of Richmond, CA, located
within Contra Costa County, adopted its own ordinance in 2001 (Ref 14.3 RISO). The Richmond Industrial Safety Ordinance (RISO) mirrors the county ordinance.
Inherent Safety Requirement of the CCC ISO/RISO . A facility covered by
the CCC ISO or RISO is required to conduct an inherently safer systems
analysis (ISSA) for each covered proc ess as follows (Ref 14.4 CCC ISO):
The facility conducts an ISSA on existing covered processes every
five years.
The facility conducts an ISSA in the development and analysis of
recommended action items identified in a PHA.
Whenever a major change is prop osed at a facility that could
reasonably result in a major chem ical accident or release, the
facility conducts an ISSA as part of the required management of
change review.
If an incident occurs and the inci dent investigation report or its
associated root cause analysis recommends a major change that
could reasonably result in a major chemical accident or release,
the facility commences and completes an ISSA of the recommended major change as soon as administratively practicable after completion of the incident investigation or root
cause analysis report.
The facility conducts an ISSA duri ng the design of new processes,
process units and facilities. Imme diately upon completion of the
ISSA report advise CCHS of the av ailability of the ISSA report.
The facility prepares a written report documenting each ISSA
including identification and description of the inherently safer system(s) analyzed in the ISSA, description of the methodology
used to analyze the inherently safer systems(s), the conclusions |
254 INVESTIGATING PROCESS SAFETY INCIDENTS
Figure 10.29 Analysis of the Human Engineering Branch
When the first causal factor is analyzed using the remaining applicable
branches (i.e., Work Direction, Pr ocedures, and Management System), the
following root causes are identified:
1. Monitoring alertness needs improvement.
2. Shift scheduling needs improvement.
3. Selection of fatigued worker.
4. The “no sleeping on the job” policy needs to have a practical
way to make it so that people can comply with it.
The investigation team then repeats the process by considering the
remaining causal factors one at a time:
• Fire hose ruptures
• Automatic shut -off jumpered
• Contract operator cannot hear alarm due to noise
Finally, the investigation team considers generic causes that pertain to
the overall management system for th e process plant by considering the
operating history and any other incidents that may have related causes.
|
1. Introduction 5
• Provides an explanation of how people think and behave, why people
make mistakes, and how to help people perform process operational tasks successfully. This includes how to support human performance
through procedures and job aids, training and learning, effective task
planning, high reliability communicat ions, fatigue risk management,
development of error management skills, and preparing people to
perform emergency response tasks.
• Briefly covers the Human Factors of change management and managing
contractors. It also offers help on how to learn from errors, and how to
use indicators of human performance to improve support to people.
1.2.2 Other guidance
How does this handbook fit with other guidance documents?
Safety culture, leadership, and
process safety management are covered in other CCPS publications,
as shown by the book front covers.
Most chemical process businesses have a set of process safety
management systems in place
already. The advice in this handbook can be integrated into these process
safety management systems.
Human Factors methods, such as
error analysis and Human Reliability
Assessment, typically applied during
a “Hazard Identification and Risk
Analysis”, are not covered in this handbook. CCPS books on “Bow Ties
in Risk Management” and “Guidelines
for Integrating Process Safety into Engineering Projects” are available if further information is needed. This
handbook does outline forms of
error assessment that can be used by everyone involved in task planning and task management.
|
OVERVIEW OF IN CIDEN T CAUSATION 19
causes for the loss of containment or energy and implementation of
appropriate remedial actions can pr event a more serious outcome in the
future.
Appropriate remedial actions are likel y to follow Inherently Safer Design
(ISD) principles such as the measures lis ted in Figure 2.4 to prevent, control,
and mitigate incidents (based on Haddon, 1980).
Figure 2.4 Incident Prevention Strategies
Haddon recognized that not all hazard s (chemical/energy sources) can
be eliminated, and to protect vulnerable receptors (e.g., people), most
remedial actions will likely reduce risk by applying additional safeguards or
improving the management of existing sa feguards. This is consistent with
CCPS guidance on Inherently Safer Design (ISD), which recommends a
hierarchical and iterative approach covering first order (hazard elimination)
and second order (reduction of severity or likelihood) ISD approaches (CCPS,
2007b).
It is also important to consider why the magnitude of the consequence
of an incident was, or under slightly different circumstances could have been,
as severe. The potential consequence of an incident is often a function of the
following five factors:
1. Inventory of hazardous material : type and amount
2. Energy factor : energy of a chemical re action or material state
3. Time factor: the rate of release, its du ration, and the warning time
4. Intensity-distance relation : the distance over which the hazard may
cause injury or damage
|
Piping and Instrumentation Diagram Development
194
mentioned that the maximum discharge pressure of
these pumps is limited by the pressure of the air source.
The other option is used in “solenoid driven pumps. ”
In “solenoid driven pumps” the drive is a stroking shaft driven by a repeatedly magnetized solenoid.
Companies may or may not decide to show the pump
drives. Figure 10.36 shows the P&ID representation of different drives.
Even if it is decided to not show pump drives, it is very
difficult to not show air‐operated drives as they are a type of process elements.10.7.6
Sealing S
ystems for PD Pumps
PD pumps similar to centrifugal pumps may need a sealing system. However, their system is not standardized and is designed by the vendor. If the rpm of the shaft is low enough, the designer may decide to use packing rather than a mechanical seal and then the need for a sealing system is eliminated.
In a reciprocating pump the shaft is reciprocating
rather than rotating and the sealing concept could be totally different.
10.7.7
Met
ering Pumps (Dosing Pumps)
Metering pumps or dosing pumps are pumps that are able
to generate flow with adequate accuracy within a reasona-ble range of upstream and downstream pressures.
Because obviously changing upstream and downstream
pressures will change the flow rate of centrifugal pumps they cannot be categorized as metering pumps. Metering pumps are generally referred to as PD pumps. The majority of metering pumps are reciprocating type PD pumps because they have more flexibility in controlling them.
Dosing pumps may be controlled through VSD and
also change in stroke length (refer to Chapter 15).
As the amount of injected chemical is generally
important, the injecting flow rate should be checked occasionally by operators. In the majority of cases this is done by providing a drawdown (calibration) column on the suction side of the pump. The rounding operator closes the blocking valve upstream of the calibration column and allows the pump to get suction from the liquid inside of the column (instead of the upstream container) and measures the time for a specific drop in the liquid of the calibration column to calculate real flow rate (Figure 10.37).
In some cases it is very important to install a back‐
pressure regulator. This is to mitigate one condition that may cause uncontrolled injection of chemical to the host stream. If the pressure of the host stream (which could be fluctuating) goes below the suction pressure of the Reciprocating pump sR otary pumps
Electro motor
Solenoid
Air operated(in diaphragm pumps)
(in diaphragm pumps)Electro moto rMM
Figure 10.36 PD pump driv es.
PG
123
Figure 10.37 P&ID repr esentation of a dosing pumps.
MT MT
MT
MT
Figure 10.35 Differ ent arrangements of dissimilar pumps in series. |
Piping and Instrumentation Diagram Development
106
A valve is either throttling or blocking based on the
structure and shape of the valve’s plug. These plugs are
discussed later in this chapter.
When placing a non‐special valve in a system, the first
question is if a throttling or blocking valve should be used. Since each calls for different types of valves, a wrong decision may cause internal valve leakage (passing‐by) or premature failure of the valve. The design process engi
neer can decide whether the suitable duty of valve is throttling or blocking for a specific situation.
Furthermore valves can also be classified according to
the number of ports: two‐port or multi‐port valves. The most common valves are the two‐port valves, which have only two ports (i.e. one inlet and one outlet). However, multi‐port valves have more than two ports, possibly three or four. They also have more than one inlet or outlet ports. Also they can be called by various names depending on the function of the valve.
Table 7.1 shows the four types of valves and their
spe
cific
function. Based on the table a two‐port stopping valve is called an isolation valve. A two‐port adjusting valve is called an adjusting valve. A multi‐port stopping valve is called a diverting valve. A multi‐port adjusting valve is called an adjusting‐diverting valve. The two‐port valves
are by‐default valves, and although the term “two‐port” is not stated, it is generally assumed to be two‐port valve.
Diverting valves are valves that divert the flow from
one destination to another. Each diverting valve can be replaced with two or more blocking valves in a specific arrangement. Adjusting‐diverting valves are valves that divert a portion of flow from one destination to another. Each adjusting‐diverting valve can be replaced with two or more throttling valves in a specific arrangement.
Multi‐port valves have no advantage over the two‐port
valves except saving space and money. They are not as robust as two‐port valves. Through the use of multi‐port valves, a huge cost saving is gained specially if using remotely operated valves (ROT). The remotely operated valves will be discussed later, but in a nutshell, they are actually valve actuators. When it is supposed to use remotely operated valves, merging few of them together and using multi‐port valve generates a big saving as the saving in valve actuators are big.
7.4.1
Valv
e Plug: Throttling vs. Blocking Valves
Throttling valves can adjust the flow anywhere from 0%
(fully closed valve and no flow) to 100% (fully open valve and full flow). However, the performance of the majority of these valves is best when they operate between 20 and 80% of flow.
In contrast, blocking valves allow for full flow or no
flow at all. Although using a blocking valve in a throttling application is possible, it is detrimental to the valve inter
nals in the long term. Throttling valves can also be used for isolation purposes, and although this does not damage the valve internals, they do not generally provide a tight shutoff (TSO). Blocking valves can be purchased as a TSO type. The concept is outlined in Table 7.2.
Table 7.1 Valve action vs. the number of ports.
Conventional
(two‐port) Multi‐port
Stopping flow Blocking valve Diverting valve
Adjusting flow Adjusting valve Adjusting‐diverting valve
Table 7.2 Fea
tures of throttling vs. blocking valves.
Throttling Blocking
Application Throttling Stopping (blocking, on/off)
Stem travel: appropriate
positions0–100% wide (20–80%) Zero OR 100% wide
Passing by? Generally no tight shutoff (Could be) tight shutoff
Example A fully open valve may allow, for example, 45
m3 h−1 of flow; then a fully closed valve
creates zero flowA fully open valve may allow, for example, 45 m3 h−1
of flow; a partially closed valve may allow, for example, 30
m3 h−1 of flow
Interchangeability? Can also be used in blocking applications Cannot be used in throttling applications
Valve operator
Valve plug
Figure 7.1 Struc ture of a typical valve. |
CHEMICAL HAZARDS DATA SOURCES 125
NFPA 704 Standard System for the Identification of the Hazards of Materials for Emergency
Response . This system is used by emergency resp onders to quickly identify the risks of
hazardous materials involved in an emergency. This helps inform the response method, the
materials used in the response, and the personal protective equipment that may be required.
The NFPA 704 graphic uses a diamond as shown in Figure 7.3.
The four corners of the diamond represent he alth (blue), flammability (red), reactivity
(yellow) and special hazards (white) with numbers or symbols in each corner indicating the
severity or type of special hazard. A summary is provided in Table 7.2. Full details are contained
in the NFPA 704 standard.
Figure 7.3. Example NFPA 704
(OSHA f)
|
40 GUIDELINES FOR MANAGING ABNORMAL SITUATIONS
The investigation into the Texas City incident resulted in 81
recommendations and led to majo r changes in process safety
management that went far beyond the immediate causes of the
incident.
3.2.1 Process Control Systems –the First Line of Defense
The first line of automated defense is usually the process control system.
These systems vary from simple analog or digital control instrument
loops and alarms, through complex Di stributed Control Systems (DCS),
and even to Advanced Process Control Systems (APC). APC refers to
advanced control techniques, such as feedforward, decoupling,
multivariable, and inferential control that are often used to automatically
optimize and monitor the operating variable set points to achieve
production targets with lower costs, while adhering to the safe operating
limits. CCPS has published two book s that provide clear and concise
information on guidance for control systems: Guidelines for Safe
Automation of Chemical Processes (CCPS 2017c) and Guidelines for Safe and
Reliable Instrumented Protective Systems (CCPS 2017b). When properly
designed, tested, and maintained, th ese systems can provide a highly
reliable approach to managing many abnormal process situations that
were generally anticipated and had th erefore been identi fied during the
design process.
Some abnormal situations, however, may not be anticipated at the
process design stage, when the protective safeguards are being
developed, or when they are subseq uently modified. These may include,
but are not limited to, a liner that co llapses in a vessel, agitators that
decouple, a packing collapse in a column, a chemical composition
change, a plugged instrument sensing line or nozzle, and in some cases,
processes being impacted by certain weather extremes such as freezing
of instrument lines or process vent s. The ability to troubleshoot and
quickly recognize such issues as ab normal situation-conditions is the
goal of this book. Chapter 5 of th is book discusses several tools and
methods that fall under Hazard Identi fication and Risk Analysis (HIRA),
including: Hazard and Operability An alysis (HAZOP), Fault Trees, and
other methodologies that can be he lpful in pre-emptively identifying
abnormal situations at the design stag e to ensure that adequate controls
are provided. |
141
researcher is asked to assign a “lev el of severity” to each factor, and
then total all the figures. A si mplified example is shown below:
Index Sheet for the Proposed Di-lithium Crystal Process:
Toxicity/Flammability/Reactivity: 5
Quantity: 4
Reaction Conditions (T, P, corr/ero, dust, operability): 2
TOTAL: 11
Comments: Need additional proposals
From an IS standpoint, the higher the resulting number, the higher the
hazard of the chemistr y or process. Several alternative chemistries
and/or processes must be proposed , and an index sheet completed for
them as well. If competing chemis tries and/or processes exhibit a
lower total “level of severity,” th en the researcher is obligated to
defend his choice. No chemistry that exhibits "severe" factors in all
categories is accepted.
8.3.1 Inherently Safer Synthesis Personnel engaged in research activi ties, e.g., chemists, engineers, and
other scientists have many possi ble opportunities to incorporate
inherent safety in the developmen t of process technology, including:
synthesis routes
catalysis leading to less severe operating conditions
the use of a less reactive reagen t, or enzyme-based chemistry
and bio-synthesis
reduction or elimination of hazardous solvents
reduction of solvent hazards by tempering a reaction by using a
more volatile solvent that will boil and more reliably remove the
heat of reaction
immobilization of hazardous reagen ts and catalysts by attaching
active groups to polymeri c or immobile backbones
dilution of reagents
reactions in water as opposed to those that proceed in a
hazardous solvent
elimination of hazardous unit operations |
ACRONYMS xix
PSSR Pre-Startup Safety Review (Ch. 5)
PSV Pressure Safety Valve (Ch. 6)
RAGAGEP Recognized And Generally Accepted Good
Engineering Practice (Ch. 3)
RBI Risk Based Inspection (Ch. 3)
RBPS Risk Based Process Safety (Ch. 1)
RCM Reliability Centered Maintenance (Ch. 3)
SA Situational Awareness (Ch. 3)
SIS Safety Instrumented System (Ch. 3)
SME Subject Matter Expert (Ch. 4)
SMS Safety Management Systems (Ch. 7)
SOP Standard Operating Procedure (Ch. 4)
TOH Transient Operation HAZOP (Ch. 5)
UCDS User Centered Design Services (Ch. 1)
VCE Vapor Cloud Explosion (Ch. 2)
VDU Vacuum Distillation Unit (Ch. 7)
|
CONTINUOUS IMPROVEMENT 163
Management review can also be applied to improve how abnormal
situations are addressed by the facilit y. However, the review should be
part of a larger review process that addresses any weakness in RBPS
elements, including those that are re lated to abnormal situations. The
depth and frequency of each manage ment review should be governed
by past incidents and abnormal si tuations, in addition to results
obtained through auditing, metric s, and previous reviews, and
management’s view of perceived risk posed by abnormal situations.
6.6 SUMMARY
This chapter has highlighted the importance of integrating the
management of abnormal situations within a facility’s existing safety
management system, as many of the RBPS elements can be applied to
reduce abnormal situations. Th e aim should be continuous
improvement in how a facility addre sses abnormal situations. To this
end, four elements of RBPS (metrics , incident investigation, auditing,
management review & continuous improvement) are the primary
elements that can deliver continuous improvement.
Chapter 7 provides an in-depth revi ew of three case studies detailing
serious events that could have been avoided by the implementation of
a continuous improvement process for managing abnormal situations. |
358
In the 2007 ISO Annual Report, CCHS reported that the number and
severity of Major Chemical Accident s or Releases (MCARs) have been
decreasing since the implementation of the ISO. However, the small
number of MCARs (fewer than a dozen total incidents in any given year
since 1999) makes it difficult to demonstrate a linear trend, or to
establish a direct causal relati onship between the ISO and/or
implementation of ISS and the numbe r of incidences. Figures 14.1-14.3,
taken from the 2017 ISO Annual Report (Ref 14.6 CCHS 2017), display, respectively, the number and severity of MCARs that have occurred in the county since 1999–incidents at the eight ISO/RISO and CalARP covered facilities,
Figure 14.1: Major Chemical Accidents and Releases (MCAR)
|
HUM AN FACTORS 263
Figure 11.1 Common Human Factors M odel (CCPS, 2007)
Workers interact with facilities an d equipment and management systems
every day. Human performance problems are typically the result of these
complex interactions.
Facility designers should strive to design equipment to meet workers’
expectations, which may vary throughout the world. For example, to turn on
a light switch in the US, the switch is pushed up, but to turn it on in Europe
it is pushed down. Color- coding schemes may vary from plant to plant. The
best approach is to ask the end users abou t any local practices for equipment
operation.
A good human factors design is import ant. For most normal operating
conditions, the human operator can cope with the incremental additional
mental load of inconsistencies. Duri ng emergencies or other high-stress
periods, however, each ad ditional mental task is an opportunity for error.
Examples:
1. Conforming to certain expected conventions and meeting normal
patterns of actions and habits can enhance human performance. The incident investigation team should be alert for built- in design deviations from normal conventions.
In some countries, people expect the hot water tap to be on the left
side and the cold water on
the right side. W hen this is not the case,
they can become confused and make mistakes. Rising- stem gate valves are expected to clos e if the handle is turned
in a clockwise
|
DETERM INING ROOT CAUSES 237
At this point, the investigation team reaches a stage where they have
more than one hypothesis for the reason the isop entane line ruptured. The
pressure could have exceeded the desi gn pressure for the pipe or the pipe
could have failed at a point below the design pressure.
The team could use a simple fact-h ypothesis matrix to decide which
branch to pursue. An example matrix is shown as Figure 10.20.
Figure 10.20 Fact/ Hypothesis M atrix for the Kettle Exit Piping Failure
In this example, assume the team obtained pipe samples of some of the
remaining pipe and finds evidence of external corrosion. The team
concluded that the feed line failed du e to higher than normal pressure
combined with corrosion of the pi ping system (an AND-gate). These
relationships are shown in Figure 10.21.
|
APPENDIX D – REACTIVE CHEMICALS CHECKLIST 485
heat is generally only removed through an ex ternal surface of the reactor. Heat removal
capability increases with the square of the lin ear dimension. A large reactor is effectively
adiabatic (zero heat removal) over the short time scale (a few minutes) in which a runaway
reaction can occur. Heat removal in a small la boratory reactor is very efficient, even heat
leakage to the surroundings can be significan t. If the reaction temperature is easily
controlled in the laboratory, this does not me an that the temperature can be controlled in
a plant scale reactor. You need to obtain the heat of reaction data discussed previously to
confirm that the plant reactor is capable of maintaining the desired temperature.
6. Use multiple temperature sensors, in di fferent locations in the reactor for rapid
exothermic reactions.
This is particularly important if the reaction mixture contains solids, is very viscous, or if
the reactor has coils or other internal elements which might inhibit good mixing.
7. Avoid feeding a material to a reactor at a higher temperature than the boiling point of
the reactor contents.
This can cause rapid boiling of the re actor contents and vapor generation.
|
172
Vessels with passive design can fully withstand any achievable
overpressure without exce eding the yield stress of the materials. If the
overpressure in a vessel remains in the elastic range, the metal returns
to its normal crystalline state after st retching. Systems designed to “bend
but not break” slightly exceed the plastic region of the metal and are
deformed (hardened). The vessel is th en actually made stronger by this
process; however, the new hazard that is introduced is that the vessel
will not stretch and will usually burst if the scenario is repeated. Thus,
vessels subjected to plastic range stresses require more frequent
inspections for deformation and integr ity. A truly passive design is not
only safer, it is more cost effectiv e when the lifetime te st and inspection
requirements are considered.
A robust design must be extended to include all system hardware
elements. Little is gained if contai nment is lost when connected piping,
joints, or instruments are designed for lower pressure than the vessel
and then fail due to overpressure . In designing the process and
equipment, the same engineering prin ciples described in Section 8.3
should be used to minimize the accu mulation of, and to contain, energy
or materials:
Specify design pressures high enough to contain pressures
generated during exothermic re actions and avoid opening the
relief valve and/or exceeding the maximum allowable working
pressure of the vessel (the sa fe upper pressure of the safe
operating envelope).
Use physical limits of pipe size , restrictive orifices, and pump
sizing to limit excessive flow rates.
Use gravity flow in the equipment layout where feasible to minimize the need for pumps or solids handling equipment for hazardous materials.
Review injection points and piping runs for erosion concerns. Design injection points, elbows, turns, and other erosion-prone
areas for lower velocities.
Use materials of construction with low corrosion rates.
Use materials of construction that are applicable over the full range of operating conditions, su ch as normal startup, normal
shutdown, emergency shutdown, and system draining. For |
68 Human Factors Handbook
Table 6-5: Pros and cons of electronic job aids
Pros Cons
Can hold a large amount of
information
Can provide interactive functions Can be centrally updated Can provide enhanced functionality,
such as entry of data and completion
of records
Can enable automated calculations to
be performed
Can have look up functions to search
databases, such as lists of parts when maintaining equipment
Can enable remote verification of a
task step, a condition, or location
when a second person is not available at the location Limited use on sites with zones in which an explosive or flammable gas
atmosphere could exist.
Potential problems in navigating
through screens and sub-screens
Screen size may create problems in
legibility of information
Glare and bright light conditions may
reduce visibility.
Complex imagery may be limited on a
small screen
Power (of the device) and internet /
data transmission mode access may
not be available all of the time
Wireless devices may be subject to
cyber intercept or attack.
6.5 Key learning points from this Chapter
Key learning points include:
• The need for a job aid depends on task safety criticality, frequency, complexity and time available to complete the task.
• Many types of job aids are available.
• The best type of job aid depends on the type of task performance.
|
54 Human Factors Handbook
• Less frequent, more complex tasks
Less frequent, more complex and crit ical tasks may benefit more from
step-by-step instructions and checklists. An example is process start-up.
Such tasks may be prone to errors (s lips and lapses), especially if they
have many steps or take a long time . If the task is complicated and
involves judgment and decision-mak ing, then SOPs and job aids can
support “rule-based” performance.
If the task is infrequent and complex, then it may be helpful to use
decision-making aids, such as diagnostic flow charts. These can give
operators the knowledge they need to decide what actions to take,
especially in abnormal or unique oper ational situations, such as process
upsets.
• Time critical emergency response tasks
Time critical emergency response tasks may be best supported by
shorter and easy-to-read job aids. A very detailed and long SOP may not
be practical if it cannot be applied in the time available to perform the
task.
The “Miracle on the Hudson” (see Chapter 2) involved the use of an
emergency response procedure. The pilots started to work their way through the procedure but stopped when they realized that they would
crash before being able to complete the procedure.
A short “grab card” is likely to be mo re practical if an operator has to
decide what actions to take within a few minutes, as when responding to an emergency. In this instance a single sheet of laminated paper could
be the best format, stored in the control room for example. The grab
card should be technically correct, up to date and specific to the process.
6.2.2 A flow chart for determining need for a job aid
6.2.2.1 Overview
Figure 6-1 provides a flow chart to help judge whether a step-by-step guide or a
job aid may be more useful for a task. The best type of procedure or job aid depends on:
1. The complexity of the task.
2. The frequency that the task is performed.
3. The importance or criticality of the task.
4. The time available to use the job aid and complete the task.
|
Evaluating the Prior PHA 61
3.3 PRIOR PHA TOPICS FOR ADDITIONAL EVALUATION
In addition to the factors listed in Sectio ns 3.1 and 3.2, as well as Chapters 2 and
4, a few other items to consider when evaluating the prior PHA are addressed in
this section.
3.3.1 Status of Prior PHA Recommendations
Recommendations from the prior PHA should be resolved before the
revalidation, but occasionally, due to their complexity or difficulty of
implementation, some recommendations may still be unresolved. The
recommendations that were resolved were either accepted or rejected.
Regardless of their status, all recommendations should be considered during
preparation for the revalidation meetings:
Accepted Recommendations. An accepted recommendation usually results in
some change to the process equipment or procedures. Thus, in most cases,
there will be a corresponding MOC evaluating the hazards of the change, but not
always. For example, there may be no explicit MOC for resolution of
recommendations for “training.” Th e reviewer should look for the
implementation of those changes when evaluating the operating experience (as
discussed in Chapter 4). If no MOC can be found, or if it appears that the actions
taken may not have adequately accomplishe d the intent of the prior team, those
recommendations should be highlighted for reconsideration by the revalidation
team.
Rejected or Declined Recommendations. If a prior PHA recommendation was
rejected or declined, is there any evidence that the prior PHA team was involved
in that decision? Perhaps the prior team worded the recommendation poorly
and it was rejected because management simply did not understand its value.
Another possibility is that the prior team made a technical error of which the
upcoming revalidation team should be aware. Perhaps previous management
was willing to accept an elevated risk of that particular hazard and documented
this decision. Regardless, rejected recommendations should be given special
attention by the current revalidation team to verify their concurrence that no
further action is warranted.
Unresolved, Open, or In-Progress Recommendations. Any unresolved, open,
or in-progress recommendations from th e prior PHA should be specifically
reviewed during the revalidation. If the te am concurs that the risk is elevated, it
should reaffirm the recommendation in the revalidation report. If the team |
CON TIN UOUS IM PROVEM EN T 331
15.3 CAUSAL CATEGORY ANALYSIS
Each company’s management style an d safety management systems have
strengths and weaknesses. These strengths and weakness tend to influence
the types and severity of incidents that might occur. An analysis of incident
investigation findings, in terms of causal factors and root causes, may
identify broad areas or management systems that co ntribute to a higher
proportion of incidents.
Causes of incidents that repeat over t i me may al so b e i n di c at i v e of a
weakness in the investigation system (e.g., lessons are not being learned).
The determination of these management system failures allows a broader,
more effective approach to the reduction of common cause weaknesses and
prevention activities than addressing individual causes might. Table 15.3 is
an example of one way to accumulate this data for analysis by using causal
categories.
|
180 Guidelines for Revalidating a Process Hazard Analysis
Q T E
Were all pertinent hazards (fire, explosion, boiling liquid expanding
vapor explosion [BLEVE], toxicity, chemical burn, asphyxiation, etc.)
associated with releases addressed in the PHA?
Was all equipment containing HHCs, or that could contain HHCs,
addressed in the PHA? (Compare th e analysis nodes to process flow
diagrams and/or P&IDs)
Was contamination of process chem icals addressed in the PHA?
Was loss of utilities addressed in the PHA?
Was the unit flare header (and knock out drum if one is provided)
addressed in the PHA or in a separate PHA?
Were the documented hazards consistent with hazards listed on
safety data sheets (SDSs) for HHCs?
Have incidents since the prior PHA revealed new hazards that were
not previously identified?
Was there evidence that the PHA team evaluated the range of
effects for loss scenarios postulated (e.g., impact area, references to
SDSs, health/safety effects possibly identified as part of the hazards
of the process, use of a risk matrix)?
Was there evidence the organization’s risk tolerance criteria were
consistently and correctly applied?
Were there recommendations for additional risk controls where
consequences of interest were lis ted in the worksheets with no (or
weak) existing safeguards?
If the prior PHA included recommendations for operability
improvements, were their resolutions documented? Were any
safety implications of the econ omic loss scenarios overlooked?
Did the documentation for closure of previous safety
recommendations meet all requirements?
|
36 GUIDELINES FOR MANAGING ABNORMAL SITUATIONS
Example Incident 3.2 – Union Carbide, Bhopal, India 1984 –
(cont.)
Lessons learned in relation to abnormal situation management
Abnormal situation recognition: No Management of Change
(MOC) was in place to approve the plant operating conditions
during the accident. Abnormal situation status was either not
recognized or more likely was a ccepted without a risk analysis.
Organizational rol es and work processes: Personnel response
to the accident was inadequate and lacked direction from the
supervisor. Plant site culture appeared to accept operating
without critical safeguards functioning and appeared to allow
“Normalization of Deviance” in the plant’s process control
limits and alarms.
Knowledge and skills: Training and education for responding
to upset situations and offsite response was inadequate.
Process Monitoring and Control: Some of the MIC equipment
was not functioning, was offline, or was inadequate to monitor
the process and safety equipm ent properly. Compensating
measures should have been considered to address the
absence of key process safeguards.
The long-term consequences of “Bhopa l” are still being felt, since the
area has not been fully decontamin ated. The Institution of Chemical
Engineer’s director of policy, Andy Furlong, stated in 2014:
“… even though three decades have passed since Bhopal, we must
never stop reminding ourselves that the lessons from the past are
there to be learned, and crucially, acted upon.” (Furlong Press
Release 2014)
The BP Texas City Example Incide nt 3.3 resulted in tremendous
losses, in both the human casualties and injuries and financial losses.
|
Appendix E – Classifying Process Safety Events Using API RP 754 3nd Edition
E.1 Criterion for PSE
This appendix covers how incidents can be classi fied using the guidance provided in API RP
754, 3rd Edition as is discussed in Section 9.3. The CCPS Process Safety Incident evaluation app
can assist in classification of a PSE. This app is available at app stores.
Classification of a PSE as Tier 1 or 2 requir es understanding of several criteria. The first
criterion is that there must be a Loss of Primary Containment (LOPC).
E.2 Criterion for Classification
Tier 1 and 2 PSEs are LOPCs that occur within any 60-minute window with certain
consequences, the severity of which determine th e classification tier. These consequences, as
shown in Table E.1, include injury; direct co st from resulting fire and explosion damage;
community impact; unsafe release from engineered pressure relief or upset emission from a
permitted regulated source; and or acute release above a defined threshold quantity.
Loss of Primary Containment (LOPC) - An unplanned or uncontrolled
release of material from primary co ntainment, including non-toxic and
non-flammable materials (e.g., st eam, hot condensate, nitrogen,
compressed CO 2 or compressed air). (CCPS Glossary)
Note: Steam, hot condensate, and compressed or liquefied air are only
included in this definition if their release results in one of the
consequences other than a threshold quantity release. However, other
nontoxic, nonflammable gases with defined UN Dangerous Goods
(UNDG) Division 2.2 thresholds (such as nitrogen, argon, compressed
CO 2) are included in all consequences including, threshold release. (API
RP 754).
Primary Containment - A tank, vessel, pipe, transport vessel or
equipment intended to serve as the primary container for, or used for
the transfer of, a material. Primary containers may be designed with
secondary containment systems to cont ain or control a release from the
primary containment. Secondary cont ainment systems include, but are
not limited to, tank dikes, curbing around process equipment, drainage
collection systems into segregated o ily drain systems, the outer wall of
double-walled tanks, etc. (CCPS Glossary)
Process Safety Event – An event that is potentially catastrophic, i.e., an
event involving the release/loss of containment of hazardous materials
that can result in large-scale heal th and environmental consequences.
(CCPS 2019) |
| 343
APPEN DIX F: PROCESS SAFETY CULTURE ASSESSM EN T
PROTOCOL
F.1 Introduction
The following questions that can be used to assess the status of
the process safety culture in an organization. Some questions are
intended to highlight evidence of a positive, while others help
diagnose negative process safety culture.
Like any checklist or protocol, it is inherently incomplete.
Answers to questions m ay prom pt deeper investigation, and
facilities may have cultural aspects that this protocol does not
address.
Any symptom identified through this protocol whose impacts
are severe or have resisted correction should be subjected to a
separate form al analysis.
The questions in this protocol were derived from other
sections of this book, particularly Chapter 4, which describes the
relationship of process safety culture to each PSMS element, as
well as from the references cited at the end of this section.
F.2 Culture Assessm ent Protocol
Establish an Im perative for Safety1. Has the organization adopted a minimalist approach to PSMS
applicability? A minimalist approach refers to a conscious
effort to limit the PSMS boundaries only to the strict limits
defined by any applicable process safety regulations affecting the
facility and nothing else. This is sometimes referred to as a
compliance-only approach. The use of a minimalist approach is
usually an overt decision but may also occur because of all of the
actual process safety risks have not been fully evaluated.
For example, the inclusion of utility, support, and other systems
that do not contain any process safety related chemicals but are
critical to process safety. The failure of some
Essential Practices for Creating, Strengthening , and Sustaining Process
Safety Culture , First Edition. CCPS . © 2018 AIChE . Published 2018 by
John Wiley & Sons, Inc. |
28 | 3 Obstacles to Learning
In this section we examine some of the most common obstacles to
learning from past incidents (Table 3.1). A more detailed discussion of
obstacles to institutional learning was described by Schilling and Kluge
(Schilling 2009). Keep in mind that not all companies experience every
obstacle, and companies may overcome obstacles in the future; meanwhile
new ones may arise. It is important to continuously assess the corporate
learning process and to address obstacles as they appear.
Table 3.1 Common Obstacles to Individual and Company Learning
Individual Company
Organizational changes Cost and business pressures
Retirements and job changes Reverse incentives
Natural memory loss and
normalization of deviance Leaner organizations
Insufficient or incomplete
evaluation of hazards Risk misperception
Lack of understanding about
hazards Compliance-only mindset and
over-anticipation of litigation
Difficulty to see beyond own
experience or type of industry Too many high priorities or rapidly
changing priorities
Both
It can’t happen here attitude—loss of sense of vulnerability
Ivory tower syndrome or lack of communication
Assessing blame rather than correcting root causes
Misplaced conservatism
3.1 The Impact of Individuals
In any organization, the personnel roster is in constant flux. People change
roles, get promoted, or leave the company for other opportunities.
Organizational change can impact corporate memory in several ways. Almost
by definition, each organizational change results in an incumbent being
replaced by someone with less organizational memory related to that position.
Unless the organizational memory has been captured in the company’s PSMS,
standards, policies, and culture, memory will be continuously lost. |
that they are committed to reducing the potential hazard zones
in the area of a plant.
•Develop methods to measure various inherent safety process options, an essential first step to widespread implementation.
•Develop a method to measure inhere nt safety using “fuzzy logic”
mathematics (a concept in which “ranges of truth” rather than discrete true or false values) - something that is now being researched.
•Government programs now suppo rt concepts research and
development, such as green chem istry, solvent substitution,
waste reduction, and sustainable growth, all of which are related
to inherent safety. A similar approach involving industry, government and academia ca n enhance inherently safer
chemical processes discovery, development and implementation.
16.6 REFERENCES
16.1 Center for Chemical Process Safety (CCPS 1993). Guidelines
for Engineering Design for Process Safety . New York: American Institute of
Chemical Engineers, 1993.
16.2 Center for Chemical Process Safety (CCPS 1998). Guidelines
for Design Solutions to Process Equipment Failures. New York: American
Institute of Chemical Engineers, 1998.
16.3 Center for Chemical Process Safety (CCPS 2007). Guidelines
for Safe and Reliable Instrumented Protective Systems. New York:
American Institute of Chemical Engineers, 2007.
16.4 Dow Chemical Company (1994a). Dow's Chemical Exposure
Index Guide , 1st Edition . New York: American Institute of Chemical
Engineers, 1994.
16.5 Dow Chemical Company (1994b). Dow's Fire and Explosion
Index Hazard Classification Guide , 7th Edition. New York: American
Institute of Chemical Engineers, 1994. 439 |
216
Inherent Safety can affect thre at. For some adversaries, the
reduction or absence of the hazard s may lessen or eliminate their
interest in a target, or their opportunity to commit an attack. However,
inherent safety strategies do not necessarily remove the threat, as a
determined adversary may not be persua ded, especially if the inherently
safer elements result in a safer operation but doesn’t completely eliminate the opportunity for them to inflict damage.
Vulnerability is any weakness that can be exploited by an adversary.
Vulnerabilities may include, but are not limited to:
1.structural characteristics
2.equipment properties
3.personnel behavior
4.locations of people, equipment and buildings
5.operational, cyber, an d personnel practices
Vulnerabilities are estimates of an as set’s ability to withstand specific
attack scenarios, considering existing security elements. The scenarios are usually derived from a combin ation of facility brainstorming
(“knowing what I know abou t this asset, this is how I’d bring it down”) and
intelligence estimates or other info rmation about the motivations and
tactics of specific adversaries. The Department of Homeland Security provides specific scenarios to fac ilities required to conduct Security
Vulnerability Analyses (SVAs) under CFATS.
Vulnerability may be less affected by inherent safety than other
factors unless sources are consolidated, quantities of dangerous chemicals reduced, or otherwise chan ged. It is more likely that the
vulnerability is the same following the inherent safety application to the
hazard itself (1st or 2nd order) , but, as mentioned before, the
consequences may be different. Inhere nt safety applied to layers of
security may be effective in making the layers robust, but this isn’t
necessarily reducing the hazard.
Attractiveness is the perceived value of attacking a given asset. The
perceived attractiveness of a specific asset depends upon the goals of
the attacker, and how well the potential consequences of a successful attack align with those goals. Other factors that may increase an asset’s
attractiveness include: |
350 PROCESS SAFETY FOR ENGINEERS: AN INTRODUCTION
Safety Instrumented System (SIS) - A separate and independent
combination of sensors, logic solvers, final elements, and support
systems that are designed and managed to achieve a specified safety
integrity level. A SIS may implement one or more Safety Instrumented
Functions (SIFs). (CCPS Glossary)
Safety Integrity Level (SIL) Discrete level (one out of four) allocated to
the SIF for specifying the safety integr ity requirements to be achieved by
the SIS. (CCPS Glossary)
IEC 61508 is applicable to all industries and describes methods to apply, design, deploy
and maintain instrumented safety-related sy stems. IEC 61511 supports IEC 61508 with a focus
on the process industry. ANSI/ISA 84.00.01 is essentially the same as IEC 61511.
IEC 61508 defines an engineering process called the safety life cycle intended to maintain
the integrity of the safety instrumented system ov er its life cycle. This includes direction on
assessment, design, and verification of SIS, amongst other topics.
Safety integrity levels are defined as shown in Table 15.2. SIL can be thought of as a
performance level for the safety instrumented f unction. A typically refinery process unit likely
has several SIL 2 SIFs protecting the highest ri sk process units. SIL 4 systems are seen in the
protection of nuclear power plants.
Table 15.2. Safety integrity levels
(IEC 61508)
SIL Low-Demand Mode
Probability of Failure on Demand
(PFD avg) High-Demand (Continuous) Mode
Probability of Failure on Demand
(PFD avg ) per hour
4 >=10-5 to <10-4 >=10-9 to <10-8
3 >=10-4 to <10-3 >=10-8 to <10-7
2 >=10-3 to <10-2 >=10-7 to <10-6
1 >=10-2 to <10-1 >=10-6 to <10-5
What a New Engineer Might Do
A new engineer will likely be engaged in hazard id entification and risk analysis studies, MOCs,
or design activities where safeguards, barrier s, and IPLs are identified and evaluated.
Understanding the difference between these terms and making sure that only the appropriate
measures are credited is important to the inte grity of LOPA studies and SIF specification.
New engineers may be involved in explaining process safety concepts or initiatives to
operators, maintenance technicians and others. Models such as the Swiss Cheese Model and
Bow Tie Model are simple to create and easy to understand and can be very helpful in process
safety communication.
New engineers may be tasked with engineering calculations related to the specification of
common risk reduction measures such as the sizing of pressure relief valves and the |
172 Guidelines for Revalidating a Process Hazard Analysis
CRITERIA Yes/No
Prior PHA Methodology (Section 3.1.1)
Was the PHA method used from this approved list or was an
appropriate equivalent methodology used?
• What-If
• Checklist
• What-If/Checklist
• Hazard and Operability (HAZOP) Study
• Failure Mode and Effects Analysis (FMEA)
• Fault Tree Analysis (FTA)
Was the prescribed PHA method appropriate for the complexity of
the process (i.e., was it suitably rigorous for identifying the
process hazards present and evaluating their risk)?
Was the prescribed PHA method applied in accordance with
company guidelines?
Prior PHA Inputs (Section 3.1.2)
Did the qualifications of the PHA leader/facilitator meet all
company and regulatory requirements (i.e., was the
leader/facilitator trained, experienced, and competent in the PHA
method used)?
Did the PHA team make-up/qualifications meet all company and
regulatory requirements include, as a minimum:
• Operations team member(s) with adequate process and
equipment knowledge, including recent hands-on
operating experience?
• An engineer with industry and specific process knowledge
and experience?
• An employee who has experience and knowledge specific
to the process being evaluated?
Was the PHA based on current, complete, and accurate process
safety information (PSI)?
Prior PHA Scope (Section 3.1.3)
Did the physical scope include all equipment “covered” by
regulation and company policy?
Did the PHA address all the relevant operational configurations
(e.g., did the team consider diffe rent batch operations, seasonal |
48 Human Factors Handbook
accidents. This is especially import ant for emergency or unplanned events and
novel situations where no set rules or no previously agreed course of action exist.
These references can also help people write operating and maintenance
procedures and instructions.
It is important to note that the provision of job aids is not an
alternative to training. It is not feasible for people to develop
knowledge and skills just by reading procedures. Training, job
aids and having a defined safe way of performing tasks work
together to support successful task performance.
Be aware, that the dissemination of too many job aids and written procedures,
can create risks including:
• Operators may be unable to navigate th rough or be able to identify the
relevant aids for the work at hand,
• Operators may develop a perception that the volume of procedures is
excessive and unrealistic, and
• Operators may develop an excessive reliance on procedures instead of
thinking and applying their knowledge and judgement.
There may be situations, such as em ergency response and process upsets,
where actions cannot be defined in detail due to the number of potential events
and complexity of responses.
5.4 Approach to developing effective job aids
5.4.1 Attributes of effective job aids
The attributes of effective job aids include:
1. Fit for purpose
2. Valid specification of a safe operating procedure
3. Practical and easy to use
4. Intuitive
5. Unambiguous and succinct
6. Accepted by users
7. Up to date
More information can be found in the CCPS Guidelines for Writing Effective
Operating and Maintenance Procedure [25].
Fit for purpose
The type of job aid selected should be the most appropriate way to
communicate the information and advice it provides. It should match task
demands. For example, a manual can provid e an understanding of a process, while
a “grab card” may provide brief reminders of emergency actions in times of limited
response. A flow chart may communicate how to decide on an emergency
|
332 Human Factors Handbook
25.5 Sharing and acting on human performance indicators
Lessons learned about human performa nce should be fully understood and
shared. This sharing can take place during toolbox talks and team briefings, or
during any other meetings between operators and supervisors.
Lessons should focus on successful events as well as failure events. Successful
events provide opportunities to learn from activities that helped improve human
performance.
Lessons learned should be fed back into the wider organization, in order to
show others how to benefit from the experiences. In particular, where other
business units may experience similar issues or be exposed to similar error traps.
The effectiveness of lesson sharing should be evaluated, and if actions arising from
the lessons learned are appropriate to another unit or team, they should be
implemented. The action implementation cy cle shown in Figure 25-5 should result
in improved company-wide performance.
Figure 25-5: Lessons learned – knowledge sharing
Reflect on performance
Identify lessons learned
Explore lesson sharing
Monitor indicators of performance
Share lessons learned
Check effectiveness of lesson sharing
Implement actions |
Heat Transfer Units
215
Generally speaking there is more than one burner in
each fired heater, therefore a burner header may be
needed. It is very important to provide the fuel to several burners of a fired heater with the same flow and pres -
sure. This required distribution is specific to the fuel pipe of burners.
It discussed in Chapter 17, there are two main types of
flow distribution, tree type and loop type. As there is more chance of pressure and flow swinging in fuel oil – rather than fuel gas – the fuel oil is distributed amongst the several burners of a fired heater through a loop distribution. A ring header around the furnace pro-vides a fairly even fuel oil for the burners.Figure 11.19 shows the P&ID of a fuel gas burner with
pilot gas.
As part of SIS, if for whatever reason the flame put off,
the unburnt fuel‐air mixture inside of furnace should be displaced as soon as possible. The steam can be used for this purpose. This steam is known as “snuffing steam. ”
11.13 Fire Heater Arrangement
Fired heaters are rarely placed in series or parallel. Fired heaters are such expensive pieces of equipment that it is preferred to only have one of them in service.
Burner
To Burn erTo Burn erTo Burn erTo Burn er To Burn er
To Burn er To Burn er
To Burn er
Duplex FiltersDuplex Filters
Natural Gas headerANO THER Natural Gas headerTo Burn er
PT
123
PC
123SD SDSD SDMajn gas ring Pilot gas ringFuel Gas
Fuel gas ring for one fi red heaterFuel ga s ring for one fi red heaterPilot Gas
Figure 11.18 P&ID of a fuel gas burner with pilot gas .
Control Valve Station Fuel PeparednessBurner
BurnerBurner Header
(for each heater)
Safety Shutdown
Valving SystemSafety Shutdown
Valving System
Safety Shutdown
Valving System
Figure 11.19 Fundamen tals of the fuel route to burner. |
16
substituting less hazardous materials, using less hazardous process
conditions, and designing processes to reduce the potential for, or consequences of, human error, equipment failure, or intentional harm. Overall safe design and operation options cover a spectrum from inherent through passive, active and procedural risk control measures. There is no clear boundary between inherent safety and other strategies.”
This is consistent with the definition of inherent safety and its related
terms found in the current CCPS Process Safety Glossary (Ref 2.12 CCPS
Glossary). In North America, the State of New Jersey, the State of California, Contra Costa County, California, and the federal
Environmental Protection Agency are currently the only regulators with mandatory IS-related requirements. In Europe the Belgian Chemical Risks Directorate has published guidan ce for the implementation of the
Seveso III Directive (Ref 2.14 Seveso) in Belgium which includes guidance
on inherent safety, although this guidance is not mandatory (Ref 2.5
Belgian). Similarly, the UK HSE ha s published extensive non-mandatory
guidance on the subject of inherent safety (Ref 2.26 UK HSE HSG-143) (Ref 2.27 UK HSE HSL 2005). The defini tion provided above is consistent
with the definitions used by these tw o regulators. Both jurisdictions have
used the definitions provided in the previous edition of this book to
formulate their Inherent Safety (I S) requirements, and both require
mandatory IS reviews/analysis but not mandatory process changes. See Chapter 14 for a detailed discussion of inherent safety regulatory
initiatives implemented in the United States.
2.3 SHARED CHARACTERISTICS
While the above definition succinctly captures what inherent safety
includes, its application encompa sses a broader set of shared
characteristics:
It is a concept - Inherent safety (and related terms such as
inherently safer design, inherently safer technologies, etc.) represents a set of concepts rather than a distinct set of rules. In
this book, the terms and acro nyms Inherent Safety (IS),
Inherently Safer Technology (IST ), and Inherently Safer Design
(ISD) will be used interchangeably. All three terms are used in the
literature and in the field, but actually have different |
302 INVESTIGATING PROCESS SAFETY INCIDENTS
conditions during the time period from 48 hours up to 1 hour before the
occurrence, and a third section may address th e background immediately
(1-60 minutes) before the occurrence.
The background sections may also include information on past incidents
in the process unit, including past incide nts that are identica l or nearly so to
the actual incident (a “rep eat incent”). Near-misse s and minor incidents are
of interest to determine if th ere were any precursor events.
13.4.4 Sequence of Events and Description of the Incident
In this section of the report, the occurrence is descr ibed (usually in
chronological order) and the outcomes are identifi ed. This is the WHO–
WHAT–WHEN–WHERE portion of the report. It includes the actions taken to
deal with the situation throughout the timeline of the event. It may give
precise and specific information, such as identification numbers and location
of process equipment involved in some fa cet of the incident. The extent of
injury, details of the da mage, and an estimated ou t-of-production time can
be included in this section. Diagrams are often more useful than long
paragraphs. If a timeline has been dev eloped, it may be included in the
report. The observations can be backed up with statements from those
involved. Supporting documentation in the form of drawin gs, photographs,
flow diagrams, and calcul ations can be included.
13.4.5 Findings
Factual findings are presented in this section. The findings flow from all
investigation activities including wi tness interviews, scene and equipment
inspection, process data, laboratory tests, equipment testing protocols,
engineering analyses, mode ling, etc. The findings provide the foundation
for subsequent causal factor identi fication and root cause analyses.
It may be helpful to mention the vari ous types of evidence that support
the causal factors and root cause conclusions:
People (interviews)
Physical (for example, equipment, machinery, parts, analytical analysis, metallurgical analysis, testing )
Electronic (for example, operating data recorded by a control
system, both current and histor ical, and controller set points)
Positions (people and equipment)
Paper (for example, procedures, ch ecklists, process data, permits,
etc.) |
244 | 7 Sustaining Process Safety Culture
are not quickly brought up to speed on the culture and their PSMS
duties, conflicts can arise that impact com munication and trust.
Changes in process safety related policies and procedures:
Changes of all kinds should be expected as the culture and the
PSMS improves. These inevitably lead to new and potentially
unfam iliar responsibilities and activities. These can cause stress
and m ay require adjustm ents to com pensation and authority,
along with the needed training. As culture is im proved, these
personnel issues should be m anaged carefully. New
responsibilities also need to be codified in job descriptions, so
they can be sustained through future personnel changes. This will
help build mutual trust and empowerment . Neglecting these issues
m ay lead to resentment, making the culture improvement effort
less likely to succeed.
Lapses in leadership and failing to learn and advance the culture:
As stated at the beginning of this chapter, any lapse of
leadership can lead to norm alization of deviance and overall
decline of process safety culture. Therefore, leadership of the
process safety culture must com e from the top, be encouraged by
the B oard of Directors, and cascade through the organization. To
com bat this, good checks and balances need to be in place to
review adherence on a regular basis.
Central to success sustaining culture in the above examples,
and in the overall life of the com pany, is making a firm and full
com mitment to continuously improving process safety culture.
This commitment can be m aintained through six critical success
factors that are summarized in figure 7.1.
Take Cultural Snapshots Leaders should remain alert to changes in the culture. Periodic
reassessm ents are important, and included as one of the success |
46 GUIDELINES FOR MANAGING ABNORMAL SITUATIONS
Example Incident 3.5 – Buncefield Explosion, 2005 (cont. )
The lighter fractions of the winter blend of gasoline had volatilized,
forming a flammable cloud that was estimated to cover an area of
some 80,000 m2.
The immediate cause was the failure of the level gauge, which was
stuck at a fixed reading, preventing the subsequent activation of a
high-level alarm. An independent hi gh-high level alarm also failed to
activate. The operators had failed to observe or act on the stuck level
gauge. They also did not estimate the time to fill the tank, instead
relying on the instrumentation. The level gauge was known to be
unreliable and the high-high level al arm, a float switch, incorporated
a test level that had not been corr ectly repositioned or fitted with a
padlock after a high-level trip test had been conducted. Locking of the
level trip instrument was not fully understood by site personnel and
the UK HSE issued an alert notice for users of similar equipment at
other sites.
The Investigation Board report contained some 25 recommendations,
several of which are relevant to a discussion on abnormal situations.
Many of the recommendations were associated with improvements in
the safety management systems, leadership, and culture on the site.
Lessons learned in relation to abnormal situation management:
Procedures: Provide effective st andardized procedures for key
activities in maintenance, testing, and operations.
Knowledge and Skills: Improve training, experience, and
competence assurance of staff for safety-critical tasks and
environmental protection activities.
Work Environment: Define appropriate workload, staffing levels,
and working conditions for frontline personnel.
Communications: Ensure robust communications management
between sites and contractors and with operators of distribution
systems and transmitting sites.
|
53 4
Application of Process Safety to Wells
4.1 BACKGROUND
This chapter addresses the primary equipment, risks, and key process safety
measures involved in drilling, completions, workovers and interventions, referred to
collectively as well construction. It show s how the concepts contained in RBPS can
be applied to further enhance current design, operational practices, and process safety performance. Special attention is given to well control and the safety barriers
for preventing and mitigating a loss of well control event. The final section reviews selected process safety tools a pplicable to well construction.
Well construction terminology makes use of many unique terms and acronyms
that may be unfamiliar to those new to the upstream industry. Basic definitions are included here to enable the reader to understand the topic, but for full definitions one may refer to industry reference books (see list below).
In this book, the terms drilling, completion, workover and intervention are
derived from the Schlumberger online glossary (www.glossary.oilfield.slb.com).
All the terms are associated with a potentially pressurized well that must be
managed to prevent a loss of containment event.
Drilling: The process of creating a wellb ore down to the reservoir production
zone, including casing and cementing to achieve all needed isolations.
Completion: The collection of downhole tubulars and tools necessary for the
safe and efficient production of hydrocarbons. It usually includes perforating
the casing and isolating the well from the reservoir with explosives to provide
access to the reservoir fluids.
Workover or Intervention: The repair or stimulation of a well to enhance its
production rate. It usually involves inserting tools into the wellbore. A
workover requires the presence of a rig, whereas an intervention does not.
Some process safety topics are common with production activities, covered in
Chapters 5 and 6, and in some cases the read er is directed to those chapters rather
than repeating the material in this chapter.
This section provides an introduction to the technology necessary to understand
the application of RBPS to well construction activities. Section 4.2 then addresses risks and key process safety measures, while Section 4.3 covers process safety
methods and tools.
Details on well construction technology may be obtained from industry
references, including the following.
●IADC Drilling Manual , Vols 1 and 2 (IADC, 2015a
)Process Safety in Upstream Oil and Gas
© 2021 the American Institute of Chemical Engineers |
82 | 3 Leadership for Process Safety Culture Within the Organizational Structure
In other words, process safety leadership starts with the Board
of Directors and senior leadership, and involves the entire
organization. Everyone from the Board to the plant floor m ust
have the necessary com petence in process safety. The PSLG
recognized that some Directors, especially those com ing from
other sectors, would not have competence in process safety. To
com pensate, they recom mended that one Board member be
highly experienced. See sections 5.3, 5.12, and Appendix D for
m ore about com petence.
After considering the leadership literature, Stricoff, PSLG, the
expertise of the CCPS Culture Comm ittee (See page xix), and other
sources, some broad themes of process safety leadership can be
seen: Achieve a balance between m anagem ent and leadership:
o Establish clear roles and responsibilities for managers
and others who function as leaders.
o Use management to define clear process safety work
processes and manage them ,
o Manage organizational change; and
o Use process safety metrics for decision making and
balanced scorecards.
Inspire subordinates and peers:
o Display visible support through felt leadership, leading
by passionate example,
o Provide adequate, competent resources and annual
budget for process safety; and
o Follow through on verbal support with personal
actions.
These characteristics are expanded and described in m uch
m ore detail in Sections 3.2 and 5.1, as well as in Appendix D.
•
• |
APPLICATION OF PROCESS SAFETY TO OFFSHORE PRODUCTION 127
Fire protection
Firefighting capability (water and foam) is available from hydrants, sprinkler and
deluge systems on modern offshore installations and from monitors on offshore
support vessels. One advantage offshore is there is an abundance of firewater supply
– so long as power is available. However, there is limited line of sight to attack fires
inside modules or deep within a congested layout other than using sprinklers or
deluge systems installed above vulnerable equipment.
Fire protection is a mix of active and passive systems. Active systems include
fire and gas detection, alarms, fire water pumps, fire water ring main(s),
hydrants/monitors, water sprays, foam sy stems, and deluge systems. Emergency
shutdown and isolation of hydrocarbon flows is also an important element of active
fire protection. Passive systems include fireproof coatings, fire walls, blast walls and
drainage.
Escape, Evacuation and Rescue
An aspect for offshore operation is the greater difficulty of personnel to escape
compared with onshore facilities. Jumping into the water is typically not a good
option due to height, ocean conditions, and oftentimes remoteness from shore or
other facilities. Offshore facilities typically conduct an EER (Escape, Evacuation
and Rescue) study to plan for significant process safety events and to make sure
escape pathways and safe refuges are defined, and adequate equipment (e.g.,
lifeboats) and plans are in place. Temporary safe refuges (TSRs), or temporary
refuges, are designed to protect personnel against the possible process safety event
consequences for some defined period of time, especially fire or smoke, until an
evacuation is ordered, or the situation is resolved.
Evacuation offshore is usually achieve d using lifeboats, although there are
supplementary systems using escape chutes and life rafts. The authority having
jurisdiction may set minimum requirements for lifeboats / life rafts. Helicopter
evacuation is an option but it may not be poss ible to land on the helideck if there are
flammable vapors present, fire and smoke, or the offshore installation is listing. An
inherently safer evacuation exists for bridge linked platforms, where evacuation is
by walking over the bridge.
Rescue is typically achieved using an offshore support vessel, most of which
have firefighting capabilities. These type of support vessels are mandatory in many
offshore locations.
Oil spill response is another impor tant consideration for offshore Emergency
Management . Drain systems are designed to in tercept hydrocarbon leaks preventing
them from flowing overboard. Booms and other mitigation equipment are usually
present (on the facility or on a nearby support vessel) to contain spills. After the
Deepwater Horizon incident, operators in the US and many around the globe joined
to form response consortia. These maintain dispersants, oil spill containment, and
recovery equipment suitable for rapid deployment to any significant spill incident. |
20 INVESTIGATING PROCESS SAFETY INCIDENTS
5. Exposure factor : a factor that mitigates the potential effects of an
incident
Therefore, incident invest igators should consider not only what went
wrong, but also corrective actions bas ed on second order ISD principles that
could be taken to minimize the impact of future incidents.
2.2.2 Management System Failure
Most active failures and latent failures, whether they are equipment
deficiencies, human errors, or unsafe acts/conditions, are the result of
weaknesses, defects or breakdowns in the management system(s).
Consequently, there is a strong link between root caus es and management
systems. Causal factors are unplanned contributors (negative events or
undesirable conditions) to an incident, that if e liminated would have either
prevented the incident, or reduced its severity or frequency. Therefore, a
strong link also exists with causal fa ctors, as these negative events and
undesirable conditions involve some of the active and latent failures that contributed to the incident.
On rare occasions, an individual may deliberately damage a chemical
process to cause an incident, but even then a management system weakness
(such as facility security or employee fitness for duty) may be involved.
Risk is a measure of human injury, environmental damage, or economic
loss in terms of both the incident likelihood and its severity. One reason the management system concept has receiv ed broad recognition relative to
chemical incident investigation is that it builds directly on fundamental
process safety principles. To manage risk, appropriate management systems
need to be in place to ensu re that the barriers agains t incidents remain intact.
These preventive, error detection, and mitigation management systems
make up the bulk of process safety e fforts. Examples of these include the 20
elements of CCPS’s process safety management system (CCPS, 2007a), such
as operating and maintenance procedures, effective training, control of up-
to-date process safety information, management of change, performance
measurement, auditing, etc.
As most root causes are associat ed with weaknesses, defects, or
breakdowns in the management system(s), investigators should look for
weak barriers. These weak barriers coul d be associated with various aspects
of the management system, including, but not limited to, the attributes in
Table 2.1. |
74 | 6 Implementing the REAL Model
during the investigation phase to aid in identifying root causes and causal
factors; and then while developing recommendations.
The review of incidents should go beyond considering similar industries
and processes to include those with similar root causes and causal factors,
regardless of industry or process type.
Risk Register
Many companies maintain a risk register. This is a document or system in
which process safety and other risks are determined (for process safety via
PHA and Layer of Protection Analysis) and sorted. Leadership uses this
information as a guide in managing operations and looking for improvement
opportunities. It is natural to focus process safety learning on the highest
process safety risks. However, many companies recognize the benefits of also
addressing potential scenarios with the most severe consequences, regardless
of risk. As process safety pioneer Trevor Kletz said on many occasions, “What
you don’t have, can’t leak.”
Gut Feel and Warning Sign Analysis
CCPS found that people interviewed during incident investigations
frequently used the phrase, “I knew we were going to have that incident” (CCPS
2011b). Deeper inquiry showed that the interviewees came to that realization
by noticing things that often don’t show up in metrics, audits, or other ways of
measuring process safety performance. During a conference commemorating
the 25th anniversary of the North Sea Piper Alpha disaster, Steve Rae, an
engineer who escaped the platform, talked about the warning signs he had
seen (Rae 2013):
I want to share with you my initial thoughts on my arrival on Piper Alpha
and the three months after:
1. I looked at Piper Alpha on arrival and thought wow, it looks old and
tired … when in fact it wasn’t old at all.
2. Obvious that additional structures and modules had been added.
3. Somewhat confusing to navigate around, somewhat of a rabbit’s
warren.
4. During nights there were few people around, in particular around the
control room where I had to go permits to work.
5. There were times when Piper vibrated significantly, it almost felt like
it would be shaken to pieces. |
166 | 12 REAL Model Scenario: Overfilling
have resulted in our country shoring up its sea defenses to meet the safety
level of a flood chance once every 10,000 years for the west and once every
4,000 years for less densely populated areas. The primary flood defenses are
tested against this norm every five years.”
”That’s all very interesting, but how does that apply to us?” Frederik said.
Alexandre responded, “I wanted to show the great lengths and expense our
country is going through to protect us from flooding. Then, I wanted to follow
it up with how we are aligned, with our processes set up to handle a flood
chance once every thousand years. We’re in good shape, but we have to make
sure that when we revalidate our PHAs every five years, we check that our
assumptions about flood protection remain valid.”
They presented their findings to Jan the following week. Jan said, “Good
work team. It’s a comprehensive solution that addresses our problems today,
while looking toward the future. I’m willing to invest in upgrades, as long as
there are solid justifications for them.”
12.7 Implement
Frederik developed a communications plan for the new procedure on tank
level readings after a severe storm. The plan focused on how this added
verification step was meant to make the plant safer, which meant keeping
everyone safer. He took some notes during Alexandre’s presentation on
overflow incidents and planned to share a finding from the CSB, that
“overfilling was cited as the most frequent cause of an accident during
operation; among the 15 overfill incidents found, 87% led to a fire and
explosion.” He also planned to show a brief video on Buncefield and Bayamon
to drive the point home.
With Reed’s help, Frederik rolled out the new procedure to the three shifts,
and although there was some grumbling, the operators all understood that
this extra work was for the greater good of the organization, and perhaps
more importantly, for their own safety. Showing the videos really helped get
the message across. Sometimes, pictures, or in this case videos, are worth
more than a thousand words.
Pamela, in the meantime, developed a list of skills that would be required
of the new hires. She wanted to make sure that when they transitioned over
to the radar gauges, there would be no issues around accepting the new
technology. |
138 PROCESS SAFETY IN UPSTREAM OIL & GAS
Projects (CCPS, 2019b) provides advice as to which process safety studies occur
when in the design activity.
7.4 PROCUREMENT AND CONSTRUCTION
Once the detailed design is complete, with all associated process safety assessments,
then the project goes out for procurement and construction bidding. Important RBPS
Incident: Piper Alpha Design Issue
The Piper Alpha incident has been described previously in Chapter 6. While
primarily due to miscommunication related to work permit status that allowed a
startup with parts of the pipework still open, an important design issue also
existed. The facility had been very succes sful and highly productive. The operator
sought an increase in production, and this was granted, subject to a condition that
gas also be piped to shore and not flared.
A gas treatment plant with compression was retrofitted, but the facility design
was not changed to add blast walls to acc ount for the greater potential of an
explosion event. Also, the compression module was close to occupied spaces
(refer to Figure 6-2 in Chapter 6).
Broadribb (2014) discusses important changes to design that occurred due to this
incident and the Cullen Inquiry recommendations. Among other things, the
Inquiry recommended that, forthwith, all facilities in the UK carry out certain
studies to enhance inherently safer desi gn. These are known as the ‘forthwith
studies’.
●Systematic analysis of fire and explosion hazards
●Analysis of smoke and gas ingress into living quarters, and the requirement
for a temporary (safe) refuge capable of surviving the initial fire/explosion
and any escalation for a r easonable duration to perm it evacuation and escape
●Analysis of the vulnerability of safety critical equipment or elements, such
as emergency shutdown valves (ESDVs)
●Analysis of escape, evacuation and rescue in the event of major incidents
One effect of the forthwith studies was th at the design of North Sea installations
changed from essentially square cross sections to rectangular. This allowed for
increased spacing between major hazard modules and vulnerable areas. Where
feasible, bridge linked platforms were used to further increase separation to the
accommodation module.
RBPS Application
Management of Change and Hazard Identification and Risk Analysis : The
changes recommended by the Cullen Inquiry are now commonly applied to
offshore installation design process safety studies and are embedded in UK
regulations. |
E.39 Playing the Odds |329
drill on the launch pad. The investigation determined that the
oxygen atmosphere in the capsule caused a m inor electrical short
to accelerate into a significant fire. The crew and launch
attendants outside the capsule tried to open the hatch, but the
com bustion gasses had raised the cabin pressure enough so that
the inward-swinging hatch would not budge.
B efore the incident, Apollo astronauts had expressed m any
concerns about their new spacecraft, including a significant
amount flamm able nylon webbing throughout the crew cabin.
The investigation board noted that NASA had failed to identify
flam mability hazards so that they could have been addressed.
During the investigation hearings, an astronaut termed the
failure to connect flamm ables plus oxygen to fire was a “Failure of
Im agination.” Of course, it was not a failure of im agination
because the Apollo 1 crew had im agined it – and have even
com plained about it.
If the crew com plained about a safety problem was there was
an understanding of hazards and risk , but a failure at some level of
the organization to act on these hazards and risks ? Were the crew
aware of the hazards but other astronauts failed to imagine it? If
so, was there a gap in open and frank communication ? Did the
others not have the same sense of vulnerability , or did they not
trust their colleague’s judgment?
Establish an Imperative for Safety, Maintain a Sense of
Vulnerability, Understand and Act Upon Hazards/Risks.
E.39 Playing the Odds
A young engineer overseeing his first plant trial
batch was discussing the first step of the operating
instructions with a 35-year experienced operator.
“We can skip the inerting step,” the operator said. “That will save
us some time to have coffee and eat those nice donuts you
brought for me and m y buddies.”Actual
Case
History |
222
Figure 9.2: Elements in a CCPS Security Vulnerability Assessment (Ref 9.4
CCPS)
|
APPLICATION OF PROCESS SAF ETY TO ENGINEERING DESIGN,
CONSTRUCTION AND INSTALLATION 133
The three FEL stages carry out similar process safety activities, but with greater
refinement as the project option is select ed and refined. Some companies develop a
process safety in design philosophy to ensure the appropriate process safety
activities occur at each stage.
7.2.1 FEL-1
The primary activities in FEL-1 relate to Compliance with Standards (particularly
the regulatory aspects that must be complied with) and Hazard Identification and
Risk Analysis . At this stage, there are multiple options but with few details yet
developed. This may appear as simple block diagrams of major parts of the process.
Decisions address location, technology, proc ess and how to achieve inherently safer
design. Standards and prior projects help with some design assumptions, and HIRA
takes the form of simple checklists of potential hazards (e.g., CCPS, 2019b Table
3.1). The aim at this stage is to rank possible project design options based on likely
economic advantages, process safety (including environmental impact), and other
factors such as project risk.
It is good practice to develop a risk register at this stage. This risk register lists
hazards, their potential cons equences, their likelihood, and overall risk. The register
is used to support project decisions and is updated as the design progresses. This
helps to ensure that no identified risk is neglected when there is a design
modification and MOC, or if the project team changes or new personnel join, as
happens over the life cycle. The risk regi ster may also identify inherently safer
options where some risks may not be present at all, and thus not require mitigation.
Inherently safer design (ISD) activities start in FEL-1 when there is the greatest
potential to eliminate or minimize risks. Onshore this might be to choose options
with immediate export of produced gas and liquids and without any local storage.
Offshore this might include some partial subsea processing or a very low staffing
option for operating “from the beach”. An exam ple is presented later in this chapter
that further illustrates ISD concepts.
Some projects carry out an initial Concept Risk Analysis (CRA) based on
assumptions for inventories and process conditions. CRA can be a simplified QRA
or a simpler assessment limited to potential consequences of worst case or maximum
credible events that uses basic information only. It may use prior similar designs to
allow sensible assumptions. At the FEL-1 stage, the CRA is more of a screening
level risk estimate, and it is useful for comparing different options or identifying
major risks that may be difficult to mitigate at later design stages or in operation.
7.2.2 FEL-2
The primary objective of FEL-2 is to select the option to take forward in the project.
As before, the primary activities in FEL-2 relate to Compliance with Standards and
Hazard Identification and Risk Analysis but now sufficient detail is available such
that issues related to Asset Integrity and Reliability can be defined. |
83 | 6.6 Prepare
Ideally, the team will also include one or more individuals who will ultimately
be responsible for implementing any changes that result from the team’s
work.
The team develops recommendations addressing the corporate learning
objectives, just as a team investigating an internal incident or near-miss would.
The team may also consider developing additional recommendations that
address findings of interest from external incidents. CCPS covers the
recommendations process in detail (CCPS 2019b). In summary, the
recommendations must:
• be SMART, that is, specific, measurable, attainable, realistic, and time
bound
• address the corporate improvement goals developed in Step 1
• address specific root causes and/or causal factors
• result in improvements to one or more PSMS elements, standards,
policies, or business practices that apply broadly
• map the action to the learning and demonstrate how risk will be reduced.
Ways to reduce risk include:
o correcting an ineffective barrier
o reducing potential consequences
o reducing the probability of occurrence
o a combination of the above.
The team may offer more than one recommendation addressing any
given corporate improvement objective. The recommendations may be either
alternative, additive, or both. Alternative recommendations offer multiple
options for addressing a given improvement objective; after evaluation, the
best can be selected. Additive options work together, with each option moving
the company closer to meeting an improvement objective.
6.6 Prepare
In this step, recommendations become action
plans. These may involve one or more of the
following:
• changes to a policy
• changes to a standard
• capital expenditures
• new risk-reduction measures
|
235
stages), and benefits of ISD—such as reduced inventories, smaller
equipment, and fewer add-on safeguards to be maintained, etc.—as well
as its limitations. The evaluation of both initial and on-going costs
associated with inherently safer de signs can often help enhance this
understanding. Many IS improvements can be implemented cost-
effectively, particularly incremental improvement in existing plants. Kletz
(Ref 10.18 Kletz,) discusses cultural and management barriers to the
implementation of inherently safe r designs, as well as the actions
needed to overcome these barriers. Khan and Amyotte (Ref 10.17 Khan) also provide guidance for making th e use of inherently safer design
principles more routine.
Turney (Ref 10.22 Turney) lays ou t five steps, taken from the
European Process Safety Centre’s St atement of Good Practice, which are
necessary for effective adoption of inherent safety within an organization:
Support by a champion
Suitable training
Application from the earliest stage of a project
Reviews throughout project development
Recognition and reward of th ose involved in the project
By incorporating inherently safer design into the organizational
culture, inherent safety becomes an on-going way of examining and addressing processes and their ha zards, and this philosophy then
permeates all aspects of the process safety management systems. For example, once its application is fully understood, the concept of simplification with respect to human factors can become an inherent
aspect of the writing of standard operating procedures.
10.4.1 Multiple Demands of IS in the PSM program Dowell (Ref 10.11 Dowell) points out that excellence in operations, which
must include personnel and process safety, requires a comprehensive
management system approach. The challenge is to integrate the many
ESH compliance standards (PSM, RM P, Responsible Care®, RP750,
company requirements, etc.) and spec ial program activities (ISO 9000,
Sustainability, etc.) into the fabric of the system of making chemicals,
which, in turn, is grounded in company culture. These activities must go |
108 | 4 Applying the Core Pr inciples of Process Safety Culture
Human behavior usually contributes to process safety
incidents through human errors. This includes acts of omission –
som ething a person fails to do – and acts of commission –
som ething a person does that they should not. Experience and
research has shown that some hum an error is inevitable. B ut
hum an error can be affected by so-called perform ance-shaping
factors, stresses and influences that increase or decrease human
error. Many of the performance-shaping factors can be m anaged
through the practice of human factors design, discussed in depth
by CCPS (4.1). Culture also plays a significant role.
A person could rightfully ask, “Does behavior create the
culture, or does the culture create the behavior?” Arguments can
be m ade either way. A key prem ise of this book has been that the
behavior of people engaged in any set of tasks will be affected by
the culture surrounding those tasks. However, the culture itself
can be strengthened or weakened by behaviors. Indeed,
behaviors aligned to the culture core principles discussed in this
book should strengthen culture. Meanwhile, behaviors counter to
the culture core principles, such as breaking trust or
norm alization of deviance, weaken culture.
The research of Daniellou (Ref 4.2) supports this notion of
hum an characteristics that can be influenced by culture to drive
behavior. These characteristics can be driven by positive culture
to create good safety behavior, and can be driven by negative
culture to threaten safety.
Daniellou noted that hum an errors, though generally
unintentional, are made as the result of conscious acts performed
without malice. That is, people choose to perform incorrectly, and
do so with good or neutral intentions. In this context, associating
error with words such as “fault” or “liable” is doubly counter-
productive. Not only does this prevent the organization from
identifying the real reason, it also prevents open and frank |
21. Fostering situation awareness and agile thinking 269
Table 21-3: Clues for recognizing impaired Situation Awareness
Impaired situation
awareness Communication tips to resolve the loss of
situation awareness
Ambiguity –
information from two
or more sources does
not agree. Ask probing questions, such as:
• Why do you think these two pieces of
information are different?
• How can we reconcile the differences?
• What can cause the different readings?
Fixation (tunnel vision)
– focusing on one
thing and excluding
everything else. Use gentle “nudges” or questions, such as:
• Have you thought about the bigger picture?
• What may be the impact of this failure on the
plant?
• Which other factors may have caused this?
Confusion –
uncertainty or
bafflement about a
situation. Use gentle “nudges” or questions, such as:
• Which aspect are you not sure about?
• Can you explain to me what is happening?
• Why do you think this is happening?
Lack of required
information. Use of leading questions, such as:
• Have you considered checking pressure
levels/valve B?
• Who is the right person to ask about the
situation?
• Who would you normally ask for assistance?
• Would anyone else have access to this
information?
Failure to:
• Maintain the task.
• Meet expected
targets or check
points.
• Resolve
discrepancies. Ask a series of questions to identify shared situation
awareness, such as:
• How is the task progressing?
• Why is it not progressing the way it should?
• Is there anything I could help you with?
• Who else is working with you on this task?
• What are your colleagues or teammates views on
these discrepancies?
|
Manual Valves and Automatic Valves
125
It is very confusing that in tagging regulators CV repre
sents control valve, but it is not the tag for control valve, but for regulator. “Process parameter” here can be any process parameter including “P” for pressure, “F” for flow, “L” for level, or “T” for temperature. The third footprint of regulator on P&ID is their set point. It is again important to recognize the difference between control loop and regulator here. On P&IDs, when there is a control loop, the set point of control loop is not shown on P&ID. The set point of control loops and P&IDs can be found in “Control and alarm set points table. ” The set points of regulators are generally noted on P&IDs. Therefore, if there is a pressure regulator on a P&ID, the set point of the regulator should be mentioned beside the regulator on P&ID, for example, “set point; 20 kPag. ” For a flow regulator the set point is mentioned beside the flow regulator symbol like this: “set point; 30 m
3 h−1.”
Regulators similar to control valves have failure posi
tion. They could be “FC” or “FO” or “FL. ” However, the difference between regulator failure position and control valve failure position should be recognized. In control valves the designer has opportunity and the freedom to choose his/her favorite failure position. But this is not the case for regulators. Regulators have a natural built‐in failure position that cannot be changed by the process engineer. For example, the failure positon of all pressure regulators are FC.
The failure position of all backpressure regulators is FO
and the failure position of flow regulators is always FL.
Figure 7.25 shows the set point and failure position of
regulators on P&IDs.
The last thing about regulators is that they do not
generally need bypass like what we see in control loops. As it was discussed we generally have a specific arrangement that we may need control loop station but there is no such thing for regulators.
As a rule of thumb, whenever we need to automatically
control a process parameter, we need to put a control loop including sensor, controller, and control valve. However, in some cases, this system can be replaced by a single regulator. Those are the cases in which we are seeking simplicity in the system and the service fluid is not dirty and the pipe size is not very big. Regulators are plugged easily if they are used in dirty services. Regulators also are not available in big sizes, say, larger than 6
in.
7.15.3 Saf
ety‐Related Valves
The safety‐related valves are the valves that act when a process parameter wildly violates from its normal level. This violation could be in the lower or higher side of the parameter. Therefore unsafe condition happens when a process parameter goes to the higher side of the normal level or the lower side of that. Therefore it can be said that safety‐related valves act when a process parameter goes much higher or much lower than its normal level.
As there are five different process parameters, namely,
flow, pressure, temperature, level, and composition (Table 7.20), it can be assumed that there are at least five different safety‐related groups of valves, which are roughly correct:
Pressure relief valves are the valves that open when
pressure increases and reaches a preset value.
Vacuum relief valves are the valves that open when
pressure decreases and reaches a preset value.
Temperature relief valves are the valves that open
when temperature increases and reaches a preset value.
Table 7.20 Differ ent groups of safety‐related valves.
Process parameter Corresponding safety valve Action
Flow Excess flow valve Closes when flow goes beyond a preset value
Pressure Internal Pressure relief valve Opens when pressure goes beyond a preset value
External Vacuum relief valve Opens when vacuum goes beyond a preset value
Temperature Temperature relief valve Opens when temperature goes beyond a preset value
Level No valve, only overflow nozzle “Opens” when level goes high
Composition Not available Not availableSet point: 20 kPag
FC
Set point: 50 kPag
FO
FL
Set point: 30 m3h–1
Figure 7.25 Regula tor set point and failure position. |
22 Guidelines for Revalidating a Process Hazard Analysis
HIRA is a term that
encompasses all activities
involved in identifying haz-
ards and evaluating risk at
facilities, throughout their life
cycle, to make certain that
risks to employees, the public,
or the environment are con-
sistently controlled within the
organization’s risk tolerance.
A PHA is one form of HIRA and
is sometimes required to
meet specific regulatory re-
quirements. The concepts of
revalidation described in this
book can be applied to a PHA
or HIRA to address the key
principles of RBPS:
• Maintain a depend-
able practice
• Identify hazards and evaluate risks
• Assess risks and make risk-based decisions
• Follow through on assessment results
Manage Risk and Learn from Experience. From the time an initial PHA is
completed on a process until the PHA is revalidated, risk is being managed
throughout the revalidation cycle. Changes are implemented, incidents are
investigated, work is performed, operat ing experience is gained, and external
conditions may change. The PHA revalidatio n is an opportunity for the facility to
look back at this operating experience an d learn from it to reduce risk in the
process. Whether the PHA revalidation is a focused Update , a complete Redo , or
a combination of these approaches larg ely depends on what has happened in
the process since the last PHA.
The PHA can be used to:
• Identify which safeguards should be
classified as critical
• Help develop preventive maintenance
schedules and priorities for safety-
critical instrumentation
• Identify scenarios for emergency
response training drills
• Identify which written operating
procedures should be classified as
critical
• Help develop a training program for
new operators
• Establish the baseline for MOC reviews |
186
Adequate IS related documentation is the first layer of defense against
losing the technical rationale for de cision-making that resulted in IS
measures. The Management of Change (MOC) program is the next layer
of defense. The importance of MO C is addressed in Section 8.7.
Using inherently safer principles , there are some Simplification
improvements that are possible duri ng construction and commissioning
or operations stages of life that have minimal impact of the design and
functionality of the process and ca n be accomplished at modest cost.
Most of these improvements make the process more tolerant of human error, which is the basic de finition of Simplification:
Altering valve design if possible so that the valve position is
obvious at a glance. See Chapte r 11 for the example of a ball
valve handle that was installed us ing the incorrect convention of
the valve handle being out-of- line with the piping and flow
direction when the valve is open.
Use of different flange sizes or characteristics so that valves
cannot be installed backwards, particularly check valves.
Replacing slip blinds with spectacl e flanges so that the status of
the blind is always obvious at a glance.
Replacing FRP (fiber reinforced plastic) tanks and piping with
translucent materials so that fl ow and level are visible without
the aid of flow or level instrumentation. If non-translucent FRP materials were initially used, this will likely have to wait until the components require replacement due to normal wear, or at the first available planned outage.
Replacement of flexible hoses wi th fixed piping where possible.
Piping with flexible joints that can accommodate equipment
vibration and the use of articulated arms for loading and unloading are examples.
Using quick-disconnect couplin gs only where absolutely
necessary and replace unnecessary couplings with bolted joints
that require a controlled work environment and the issue of a
safe work permit to disassemble.
These and other examples of Simplification are presented by Kletz
and Amyotte (Ref 8.53 Kletz 2010). |
5.1 Senior Leader Element Grouping |161
understand these warning signs and opportunities. Establishing a
strong process safety culture will help this happen by fostering
mutual trust and by ensuring open and frank communication .
When senior leaders visit the workplace, they should engage
with workers about process safety, put them at ease, and
encourage them to speak freely. Then, following the culture
principle Understand and Act on Hazards/Risks , the input should be
acted upon. Just as im portantly, senior leaders should insist that
the other leaders in their organization do the same. This could
take the form of ad hoc discussions on the plant floor, or form al
workforce involvement m eetings.
Such interactions need not focus exclusively on process safety.
The principle of workforce involvem ent can also help identify
warning signs and improvement opportunities related to quality,
productivity, occupational safety, etc. Workforce involvement also
has the potential to improve labor relations, easing future
negotiations.
Workforce Involvement should ensure that the em ployees
closest to the process hazards realize protecting their safety and
welfare is the primary goal of the PSMS and their input is not only
desired, but is im perative to the PSM S being effective. Workforce
Involvement and PS Culture work hand-in-glove to build
cooperation and trust am ong all workgroups.
Organizations that fail to achieve workforce involvem ent stand
to lose m ore than first-hand knowledge of warning signs and
improvements. Without workforce involvem ent, prime opport-
unities to build trust and open com munication channels are lost.
This can lead workers to believe that process safety is som eone
else’s job, underm ining the imperative for process safety . And as
seen in the Columbia case history (Section 2.4), workers may
decide not to report an actual serious situation because they
believe their report will be ignored.
|
Piping and Instrumentation Diagram Development
102
6.14.2 Specialty I tems
A plant is a combination of three hardware: equipment,
instruments, and pipes. During the design of plant, the designers have an opportunity to design the equipment based on their process requirements. The instruments are selected based on the control requirement of the plant by instrument engineers. However, for pipe and pipe appurtenances, there is no such freedom. The pro-cess engineer must use whatever size of pipe or other piping items desired for the plant and put it on the P&ID.
The Piping group in each engineering company is
responsible for purchasing piping and piping items, and they generally provide a list of all the acceptable standard types and sizes of piping and piping items that can be used in each project. This list is part of a document called a Piping Material Specification. Basically the Piping group tells process engineers that only items on the Piping Material Specification list must be used on a cer -
tain project. However, there are some cases that a pro-cess engineer or instrument engineer needs a piece of piping item, and it is not in piping spec. In such cases, the first option is to try to replace the desired item with another item in the piping spec. If that does not work, the Piping group may agree to this as an exception. These exceptions are considered SP items and definitely cannot be a long list. Therefore, it could be every non‐equip-ment item that has not been included in the piping spec.
The Piping group does not care for SP items because
they already know the complete specification of each item in the piping spec, and it is easy for them to buy the items from the market. However, for each SP item, the person who asked for a specific SP item (more than likely the process engineer) needs to prepare a data sheet for the item and submit it to the Piping group.
On the P&ID, a SP item is shown as a little box beside
the item, and the acronym SP with a number, which is the a tag number (Figure 6.86).
To decide if an element is an SP items, the piping spec
of the project should be consulted. That also means that there is no universal rule that a non‐slam check valve is a SP item. However, an experienced engineer may know that, generally speaking, where there is a check valve in the project’s piping specs, it is a conventional check valve, and if non‐slam check valves are required, they are most likely SP items. When a process engineer includes an element as an SP item, he/she needs to be aware that he/she does not have flexibility to choose the sizes needed as SP items are generally off‐the‐shelf items. Figure 6.87 shows few examples.
In this figure, a non‐slam check valve, an injection
quill for a chemical injection system, and a flexible joint are all SP items. In a P&ID, the designer may decide to put definition of the SP item beside the symbol. This is acceptable if the definition is one to three words in length. Otherwise it is better to not put the SP item definition on a P&ID and keep it only on the SP item data sheet.
Sometimes, there is a dispute between the Mechanical
group and the Piping group if one specific element is SP item or actually equipment. This is a valid dispute because if the element is a piece of equipment, it should be tagged and bought by the Mechanical group, and if it is an SP item, it should be tagged and bought by the Piping group. As a rule of thumb, SP items should be small items on the pipe, meaning elements with less than 0.5
m3 in volume without any utility connection and
without any complexity in its structure. If an element is small but it has a complicated structure, it is better to classify it as equipment rather than an SP item.
6.14.2.1 Flange‐Insulating Gasket
Here, insulating refers to electrical insulation and not
heat insulation. Galvanic corrosion is arguably the most common type of corrosion in process plants. Galvanic or electrochemical corrosion happens when two dis -
similar metals are put in contact with each other. However, there are some cases that mating flanges are not similar from material point of view. These situations happen when there is a spec break in the pipe. The spec break is almost always on a flange. The flange could be for pipe, valve, or any other pipe appurtenance. One side of the flange is from one metallic material, and the other side is from another metallic material. In such cases, an electrically nonconductive gasket should be placed between two mating faces of the flange to prevent elec -
trochemical corrosion. Flange‐insulating gaskets can be tagged as SP items.
SPSP
Figure 6.86 Specialty it em tags.
SP
SP SP
Non-slam Injection quill Flex. joint
Figure 6.87 Specialty it em examples. |
130 PROCESS SAFETY IN UPSTREAM OIL & GAS
●Compliance with Standards – These include industry standards, regulations
and RAGAGEP. There are many design standards based on years of
learnings that are available to guide a project design.
●Hazard Identification and Risk Analysis – The project should identify
hazards and employ inheren tly safer design approaches as the first step in
managing risk across the asset life cycle. Risk analysis aids in decisions on
risk reducing measures.
●Asset Integrity and Reliability – The design greatly affects this element.
Selection of materials appropriate for the design conditions and designing
equipment to facilitate maintenance both serve to maintain integrity.
●Workforce Involvement – Operations personnel should be included in the
design team. This helps to ensure that operational experience is included in
design decisions, not ju st for hazard identification, but to aid operability
and maintainability issues, and to contribute to inherently safer design.
●Management of Change – Changes to design should be reviewed,
especially after hazard identification, in case these impact safety or
environmental barriers assumed present in the hazard identification study.
During both greenfield and brownfield construction, and in initial start-up,
additional RBPS elements become important including the following.
●Contractor Management – This addresses construction safety and SIMOPS
control. Many people may work on di fferent activities in a small space, and
managing this work is key to safety including verifying competencies,
required certifications and that personnel understand the interface
requirements.
●Operational Readiness – This activity verifies that the facility is complete
and ready for operation. Are all the safe ty features agreed in design now
implemented in the constructed facility and is it safe to start-up?
●Safe Work Practices – This addresses safety during construction and
ongoing operations. Safe Work Practices are essential to support the safe
working on the project during construction, commissioning, startup, and
into production.
●Operating Procedures – Procedures should be developed for startup and
ongoing operations. Before startup, th ese procedures need to be written,
available and understood.
●Training and Performance Assurance – This element aims to ensure that
personnel are well trained for startup and for operations. This training
should ensure understanding of Safe Work Practices and Operating
Procedures .
7.1.2 Project Life Cycle Terminology
There are multiple terminologies used by different companies for life cycle stages;
this chapter uses the terminology from the CCPS Guidelines for Integrating Process
Safety into Engineering Projects . The main stages are listed in Table 7-1. The life |
EVIDEN CE IDEN TIFICATION , COLLECTION & M ANAGEM ENT 141
For these reasons, the investigation environment can be challenging,
and therefore a systemat ic approach is necessary for the successful
investigation of major process incidents.
8.1.3 Priorities for Managing an Incident Investigation Team
The incident investigation team has the responsibility for determining the
root causes of the occurrence and therefore needs access to the incident
scene and other sources of information as quickly as possible. The plant and
site management have the primary responsibility for preserving data and site
evidence and for preventing the destruc tion of any eviden ce. Nevertheless,
the investigation team should provide information to management on the
evidence to preserve, method of pr eservation, resources needed to collect
and test evidence, and other ev idence related activities.
One noteworthy example is the preser vation of time-sensitive data from
DCS and PLC systems where uncompressed data may be held in a circular
buffer that is being continuously ov erwritten and batter y backups have a
limited life. However, there are other priorities, espe cially in the early stages
of the investigation. (Ferry, 1988). It is extremely important to note that the
investigation team’s responsibilities are significantly different from those of
an emergency response team or search and rescue team.
Some key activities at the incident scene and the responsible parties are
listed in Table 8.1. The investigation team may not be on site until several of
the issues listed below are resolved.
|
DETERM INING ROOT CAUSES 247
Unlike the procedure followed in developing logic trees, the
investigation team does not construct th e tree. Rather they apply each causal
factor to each branch of the predefined tree in turn, and those bran ches that
are not relevant to the incident are eliminated. This prescriptive approach
offers consistency and repeatability by presenting different investigators
with the same standard set of possible root causes for each incident.
The consistency offered by predefin ed trees with stan dard categories
and subcategories of root causes also facilitates statistical trend analysis. This
allows an organization to more eas ily collect and analyze data from the
investigation of incidents and near misse s over a period of time to determine
any trends not apparent from single incidents. Some organizations
deliberately structure th e root cause categori es and subcategories along the
lines of their management system i n o r d e r t o f o c u s o n c o m m o n system
issues.
While the use of predefined trees do es not directly challenge the
investigation team to think laterally of other possible causes, many
predefined trees present a wide range of causes, some of which the team
may not have otherwise considered. It is therefore possible that the incident
could involve a novel root cause that was not previously experienced by
those who developed the predef ined tree. The addition of a final test based
on another tool, such as brainstorming, can overcome this potential
weakness
10.8.1 Predefined Tree Methodology
Although there are differences between various predefined trees, the basic
method to perform a root cause analysis using the trees is similar, whichever
tree is used. The following basic steps apply:
1. First, it is necessary to identify the multiple causal factors of the
incident. The procedures in Chapte r 8 (Section 8.4-Timelines and
Sequence Diagrams) may be used to identify the causal factors from
a timeline or sequence diagram.
2. The first causal factor is then analyzed, starting at the top of the pre-
defined tree and working down the branches as far as the facts
permit. If the category of a particular branch appears to be an appropriate cause of the inciden t, the branch is followed to
successively lower levels until a subcategory is identified as an |
108 PROCESS SAFETY IN UPSTREAM OIL & GAS
An example of a relatively simpler and lower congestion offshore platform is
given in Figure 6-1. This platform in 237 ft (72 m) of water has two main decks with
a helideck on the left and a flare tower to the right. The upper deck houses living
quarters, offices, a galley and various storage and production equipment; and the
lower deck houses various other rooms and equipment including the Motor Control
Center. Most equipment is outside, not in enclosed modules.
An example of a more complex and congested offshore production facility was
Piper Alpha, which was located in the North Sea in 474 ft (144 m) of water. The
module layout is shown in Figure 6-2. This shows most equipment to be in modules
with tight spacing in both the horizontal and vertical directions. In Piper Alpha’s
original design, the accommodation was sited as far as possible from major hazard
areas, such as the wellhead and separation modules. However, a regulatory change
was implemented by the Government to require gas to be recovered rather than
flared. A gas compression area was added as a modification and this was close to
the accommodation. This module was a major hazard due to large amounts of high-
pressure gas being processed.
Offshore production usually starts with flow from a reservoir as a mixture of
oil, gas, and water. The production facility may be directly over a single wellhead
or may be centralized to process the feed from multiple wells and may use a system
of gathering pipelines. Subsea systems are growing in complexity from simple
mixing of streams to also include some processing. Topside separation facilities are
similar to those shown in Figure 5-2 for onshore as the raw feed is similar. Typically,
1st and 2nd stage separators are used at high and low pressure to degas the oil and
separate the oil and water. Gas is treated as necessary (e.g., removal of H 2S,
dehydration) and compressed for export, used for power generation on board, or
Figure 6-1. Example of shallow water facility Gulf of Mexico
BSEE Panel Investigation into West Delta Block incident in 2014
|
83
alternatives have been identified . REACH is discussed further under
Regulatory Initiatives in Chapter 12.
4.8 REFERENCES
4.1 Canadian Center for Occupational Health and Safety
(CCOHS), Substitution of Chemicals – Considerations for Selection,
www.ccohs.ca/oshanswers/chem icals/substitution.html.
4.2 Catanach, J.S., and Hampton, S.W., Solvent and surfactant
influence on flash points of pesticide formulations. ASTM Spec. Tech. Publ.
11, 149-57, 1992.
4.3 Dale, S.E., Cost-effective design considerations for safer
chemical plants. In J.L. Woodward (ed.). Pr oceedings of the International
Symposium on Preventing Major Chem ical Accidents, February 3-5,
1987, Washington, D. C. (pp. 3.79-3.99). New York: American Institute of
Chemical Engineers, 1987.
4.4 Davis, G.A., Kincaid, L., Menk e, D. , Griffith, B., Jones, S.,
Brown, K., and Goergen, M., The Product Side of Pollution Prevention:
Evaluating the Potential for Safe Substitutes . Cincinnati, Ohio: Risk
Reduction Engineering Laborato ry, Office of Research and
Development, U. S. Environmental Protection Agency. 1994.
4.5 DeSimone, J.M., Maury, E.E., Guan, Z., Combes, J.R.,
Menceloglu, Y.Z., Clark, M.R., et al., Homogeneous and heterogeneous
polymerizations in environmentally-responsible carbon dioxide. Preprints
of Papers Presented at the 208th AC S National Meeting, August 21-25,
1994, Washington, DC (pp. 212-214). Center for Great Lakes Studies,
University of Wisconsin-Milwauke e, Milwaukee, WI: Division of
Environmental Chemistry, Amer ican Chemical Society, 1994.
4.6 Edwards, V. and Chosnek, J., Making Your Existing Plant
Inherently Safer, Chemical Engineering Progress, January 2012.
4.7 Flam, F., Laser chemistry: The light choice . Science 266, 215-
217, 14 October 1994.
4.8 Govardhan, C.P., and Margolin, A.L. Extremozymes for
industry: From nature and by design. Chemistry & Industry, 689-93, 14
October 1994. |
Overview of the PHA Revalidation Process 11
Thus, like LOPA, it can be used to es timate the frequency of specific loss
scenarios. Additional guidance on the app lication of bow tie barrier analysis can
be found in the CCPS concept book Bow Ties in Risk Management: A Concept Book
for Process Safety [19].
Quantitative Risk Analyses (QRA). QRA is the collective term for a variety of
detailed quantitative analysis tools used in risk calculations. In a QRA, the
calculated consequences and the calculat ed frequency of each scenario may be
used (separately or combined) to determin e individual scenario risks. Individual
scenario risks can be further combined to provide an overall picture of
cumulative site risks. For example, QRA consequence analysis tools can account
for particular release characteristics, such as the density and state (solid, liquid,
gas) of the released material, its direct ion and momentum, its chemical reactions
and interaction with humidity in the atmosphere, its interaction with
surrounding structures or terrain, the bi ologic effects on potentially exposed
individuals, and so forth. Other consequence analysis tools can calculate
detailed fire or explosion effects. Simila rly, QRA frequency analysis tools, such
as Fault Tree Analysis (FTA), can predic t the frequency of system failures from
data on the failure rates of specific components. Event Tree Analysis (ETA) and
Human Reliability Analysis (HRA) can calculate the likelihood (probability or
frequency) of particular lo ss scenarios. All of these methods require construction
of a valid logic model and its reduction to sets of basic causes for which data is
available. Failure data is available from sources such as the CCPS book Guidelines
for Process Equipment Reliability Data, with Data Tables [20].
These QRA frequency analysis techniques are not encumbered by the
conservative assumptions embedded in a simplified QRA technique such as
LOPA, so they typically produce better estimates of event frequencies. However,
they require significantly more analytical and computational effort than the
simplified techniques. QRA tools are often used in facility siting studies, in risk
analyses of occupied structures, or in th e design of Safety Instrumented Systems
(SISs). Additional guidance on the application of QRA can be found in the CCPS
book Guidelines for Chemical Proce ss Quantitative Risk Analysis [21].
1.4 PHA REVALIDATION OBJECTIVES
The primary objective of a PHA revalidat ion is to produce a revised PHA that
adequately identifies and evaluates risk controls for the hazards of the process,
as they are currently understood . |
107 6
Application of Process Safety to Offshore
Production
6.1 BACKGROUND
Offshore oil production, particularly in deepwater, has become a major part of
upstream operations. Offshore is often divided into shallow water and deepwater
production. Shallow water is usually cons idered to be anything under 1,000 ft
(305 m). Deepwater is anything greater than this and the term “ultradeep water” for
fields in greater than 5,000 ft (1,524 m) water depth is also used. In the Gulf of
Mexico, many shallow water fields are sm all and are declining in production.
Shallow water structures in the Gulf ar e simple steel jackets. When similar
designs were first employed in harsher environments of wind and wave, such as the North Sea, some initial failures (e.g., Se a Gem 1965) showed that greater strength
was required. This either strengthened the steel structure or introduced novel designs
such as gravity based concrete structures. Some designs improved process safety by separating accommodation from processing on bridge linked platforms.
As well construction technology advanced and large fields were discovered in
deepwater; floating producti on facilities became necessary as fixed structures are
impractical. Deepwater floating facilities have several possible designs, each with
advantages and disadvantages (see Chapter 2 for examples). All the designs enable
oil and gas production and have separation facilities. Export by pipeline is typical
while FPSOs allow for storing oil in the hull for subsequent transfer to a shuttle tanker. A more recent development for gas fields is FLNG – Floating Liquefied
Natural Gas facility, which includes a liquefaction plant as well as the usual
treatment facilities. It also stores its LNG product onboard and transfers this
periodically to LNG carriers for export. FLNG facilities add extra complexity to
offshore facilities including cryogenic pr ocessing and greater inventories of
hydrocarbons.
In principle, the process safety risks in deepwater facilities are often higher than
for shallow water designs as the economics of deepwater mean the facilities are
bigger and more costly to develop and the number of crew on board is greater.
However, all facilities are subject to loss of containment incidents that can give rise
to serious consequences. A number of historical incidents are discussed later in this
section. One feature of offshore facilities important for process safety is that the
workforce usually lives on board and thus off-shift personnel are potentially close
to hazards. Onshore, off-shift personnel are at home or in accommodation modules located more remotely. On-shift personne l may be close to hazards onshore or
offshore, but offshore they may be sited above or adjacent to process hazards,
whereas this is less common onshore. Process Safety in Upstream Oil and Gas
© 2021 the American Institute of Chemical Engineers |
INVESTIGATION M ETHODOLOGIES 29
3.1 HISTORY OF INVESTIGATION M ETHODOLOGIES AND TOOLS
Investigation methodologies for process safety incidents have evolved over
time, becoming more systematic, objective and scientific. It is relevant to
review the history of investigatio n methodologies to learn from the
weaknesses of historical methods and appreciate the approaches in modern
methods.
3.1.1 One-on-One Interview
The historical approach to investigating incidents was an informal, one-on-
one interview, typically between the pe rson involved in th e incident and his
or her immediate supervisor. This approa ch has generally been less effective
than structured investigation methodol ogies for process safety incidents,
especially complex incidents resulting in, or having the potential to result in, serious or catastrophic consequences. Informal one-on-one interviews are
still often used as an approach for investigating low
severity incidents,
including minor occupational injuries.
The focus of informal, one-on-one investigations has often been limited
to determining the immediate remedies that would preven t an exact repeat
of the incident circumstances. For example, a common finding may have
been that an operator failed to follow an established procedure . Based on that
finding, the investigator might have proceeded to evaluate how best to
motivate this specific operator to follow the proc edure as a recommendation
to prevent recurrence. This informal type of investigation required little time
or training, but the weakness of this approach for significant process safety
incidents is that it do es not determine the fund amental reason for the
occurrence of the incident in the first pl ace. If the fundamental reason (root
cause) is not identified, then measur es cannot be taken to address this
fundamental reason, and the incident, or a very similar one, may recur.
3.1.2 Brainstorming
Brainstorming is essentially an unstructured tool, but it can provide more
perspective and experience than one-on-one investigations. Brainstorming
brings together a group of people fr om diverse backgrounds to discuss the
incident and intuitiv ely determine the causes of the incident. The group will
typically understand the sequ ence of occurrences that led up to the incident
through a timeline or sequence diagram. The group may also have identified
causal factors, and typically focuses on establishing barriers to reduce the
risk (probability or consequences) of recurrence. |
196 INVESTIGATING PROCESS SAFETY INCIDENTS
or unsafe conditions of the inciden t, as an intermediate step before
proceeding to determining the root causes.
9.6.1.3 Identifying Causal Factors
The simplest technique for identifyin g causal factors involves reviewing each
event or condition on the timeline. The investigator repeatedly asks the
following question:
W ould the result have been significantly different if the event
or condition had not existed at the time of the incident?
If the answer is YES, that is, the incident would have been prevented or
mitigated by the eliminatio n of a negative event or undesirable condition,
then the fact is a causal factor. Generally, process safety incidents involve
multiple causal factors. This te chnique is equivalent to step #15 in Figure 9.3.
Once identified, the causal factors be come the candidates to undergo root
cause analysis.
The investigator may streamline this technique by focusing upon each
unplanned, unintended, and/or adverse fact (negative event or undesirable
condition) on the timeline. It is also important to recognize those items that
are still speculative and based on an assumption, as these should be tested later to verify if they are accurate facts.
It is critically important that the wo rding or the phrasing of each causal
factor accurately and clearly describes the factor. Teams will struggle with
cause analysis if the causal factor is not crystal clear to all. In the
case of an
incident arising from work on a pump th at has not been adequately isolated
from energy sources, an investigation team may say one causal factor is “no
lockout/tagout (LO/TO)”. However, this short statement can be interpreted
in a number of ways, depending upon individual team members’ views of
the evidence and personal biases.
For example, “no lockout/tagout” can mean:
• No procedures for LO/TO exist
• Procedures exist but the employees involved
had no knowledge of them
• An attempt was made to perform LO/TO, but it was performed
incorrectly
• LO/TO was performed on the wron g equipment or missed on one
item
• No effort was made to perform LO/TO. |
12 Identifying learning requirements
12.1 Learning objectives of this Chapter
Phase 3 of the Competency Management focuses on assessment of gaps in
competency, and limitations in current training.
By the end of this Chapter, the reader should be able to:
• Understand a Competency Gap Analysis, and a Training Needs Analysis.
• Identify and describe learning objectives.
Competency Gap Analysis and Training Needs Analysis are important stages in
identifying learning objectives, and training needs. Normally, they would be carried
out together, as information from the Comp etency Gap Analysis feeds directly into
the Training Needs Analysis.
12.2 Competency gap analysis
Competency Gap Analysis is discussed in Chapter 11 and makes use of defined
competency standards matrices. Competen cy Gap Analysis assesses individual
competency against those outlined in the standards. It answers the following
questions:
• Which competencies do people currently possess?
• What is the level of their competency (e.g., awareness, basic application,
skilled application, mastery)?
• How can the competency gap analysis bridge the gap between the
competency people possess now, and the competency needed?
Competency Gap Analysis needs to recognize any prior experience and
qualifications and consider how they may satisfy parts of competency
requirements. Competency Gap Analysis should consider whether any types of
experience or qualifications are needed in satisfying a performance standard.
Competency Gap Analysis identifies what gaps exist between employees’
current competency and the competen cy required to fulfil performance
standards. Human Factors Handbook For Process Plant Operations: Improving Process Safety and System
Performance CCPS.
© 2022 CCPS. Published 2022 The American Institute of Chemical Engineers. |
5 Facility Shutdowns
5.1 Introduction
This chapter discusses the transient operating modes associated with
a facility shutdown: the shut-down fo r a facility shutdown (mode Type
5, Table 1.1) and the start-up af terward (Type 6, Table 1.1). The
considerations and types of larger projects requiri ng a process unit or
facility project-related shutdown are described in Section 5.3. This
chapter then provides a discussion on preparing for a facility project-
related shutdown (Section 5.4), starting up after a shutdown (Section 5.5), and provides an incident that occurred during these transient operating modes with lessons learned . This chapter concludes with a
discussion on the applicable RBPS elements for the facility shut-downs
and start-ups afterwards (Section 5.7).
5.2 The facility shutdown
Larger capital projects that invol ve shutting down the equipment
associated with an entire process uni t, an entire facility, or even
multiple, interconnected production facilities are designated as a
facility shutdown in this guideline. These projects are complex, involve
many different groups, and—distingui shing them from the smaller,
planned projects discus sed in Chapter 4—have an extended timeline
for the work, covering weeks or even months of both the preparation time beforehand and the execution ti me during the project. Often the
longer, larger projects that stop op erations for the long period are
called a turnaround or an outage, as well. The facility project timeline
was shown in Figure 4.3. These proj ects are intense and often stressful
times due to their scope (or scopes), and the complex demands can Guidelines for Process Safety During the Transient Operating Mode: Managing Risks during Process Start-ups and Shut-downs .
By CCPS.
© 2021 the American Institute of Chemical Engineers |
EQUIPMENT FAILURE 235
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IOGP 2019, “Risk Assessment Data Directory - Report 434-01 Process release frequencies”,
International Association of Oil & Gas Producers,
https://www.iogp.org/bookstore/product/434-00- risk-assessment-data-directory-overview/.
Kelley, J. Howard, “Understand the F undamentals of Centrifugal Pumps”, Chemical Engineering
Progress , October 2010. |
330 | Appendix E Process Safety Culture Case Histories
The engineer shook his head and explained patiently that it
was necessary to inert the reactor, because otherwise the
flam mable atmosphere could ignite, especially because the
solvent was not being fed through a dip-pipe. “Yeah, I’ve heard of
that,” the operator said, “but take it from me, it is a waste of time
to inert the reactor because 9 times out of 10 it does not explode.”
“Uh, let’s have that coffee and talk about it,” the engineer said.
They went into the breakroom , took their coffee, and sat across
the table from each other with the box of donuts between them.
The engineer reached for a donut. “The thing is,” he said, “if it
doesn’t explode 9 tim es out of 10, then it does explode that other
one time. I don’t know about you, but my goal is this.” He held the
donut up in front of him , showing the operator the big sweet 0.
The operator grabbed the donut and stuffed it in his m outh.
After washing down that donut with a gulp of coffee, he put 2
m ore donuts in his pocket, left the breakroom and started inerting
the reactor.
The operator appeared to understand the hazard and possibly
even the risk. If so, did he need to have it explained to him again?
Or did he need som ething else? Did the operator frequently skip
other safety steps in procedures? Was this normal behavior within
the plant? Should the engineer have questioned the Plant’s
imperative for safety ?
How did the engineer convince the operator? Was it through a
logical argument? Establishing mutual trust ? Or was the operator
testing the engineer’s leadership ?
Establish an Imperative for Safety, Provide Strong Leadership,
Maintain a Sense of Vulnerability, Understand and Act Upon
Hazards/Risks, Defer to Expertise, Combat the Normalization of
Deviance. |
2.2 Resources for Learning | 19
• European Commission Major Accident Reporting System (European
Commission 2020)
• Infosis ZEMA (ZEMA 2020)
• Lessons Learned Database (IChemE 2020)
• Marsh 100 Largest Losses in the Hydrocarbon Industry (Marsh 2018).
2.2.3 Publications
Whether your bookshelf is on the wall, on a hard drive, in the cloud, or in a
virtual or physical corporate library, you probably have a few books describing
how to investigate incidents and extract lessons you can learn from them.
Table 2.4 describes the most popular of these books. Additionally, most books
about process safety use case histories featuring actual incidents to highlight
key concepts.
Table 2.4 Books About Incidents and Incident Investigation
Author and/or Publisher Name of book or series
CCPS/AIChE and Wiley Guidelines for Investigating Process
Safety Incidents, 3rd ed.
Incidents That Define Process Safety
More Incidents That Define Process
Safety
Earl Boebert and James Blossom,
Harvard University Press Deepwater Horizon: A Systems Analysis
of the Macondo Disaster
Andrew Hopkins, CCH Australia Failure to Learn: The BP Texas City
Refinery Disaster
Lessons from Longford: The ESSO Gas
Plant Explosion
Trevor Kletz, Butterworth
Heinemann/IChemE What Went Wrong? series
Frank Lees, Elsevier Loss Prevention in the Process
Industries, eth ed.
Roy Sanders, Butterworth
Heinemann Chemical Process Safety Learning from
Case Histories, 3rd ed. |
EQUIPMENT FAILURE 237
Patnaik, T., “Solid-Liquid Separation: A Guide to Centrifuge Collection”, Chemical Engineering
Progress , July 2012.
PSLP a, Jarvis, H.C. “Butadiene Explosion at Texas City-2”, Plant Safety & Loss Prevention , Vol. 5,
1971.
PSLP b, “Butadiene Explosion at Texas City-1”, Plant Safety & Loss Prevention , Vol. 5, 1971.
PSLP c, Keister, R.G., et al. “But adiene Explosion at Texas City-3”, Plant Safety & Loss Prevention ,
Vol. 5, 1971.
Ramzan, Naveeed, et al, “Root Cause Analysis of Primary Reformer Catastrophic Failure: A
Case Study”, Process Safety Progress , Vol. 30, No. 1, March 2011.
Sherman, R.E., “Carbon-Initiated Effl uent Tank Overpressure Incident”, Process Safety Progress ,
Vol. 15, No. 3, Fall 1996.
Shutterstock, Royalty-fr ee stock photo ID: 1340068283
Sulzer Chemtech Ltd., www.sulzer.com/en/
TEMA, Tubular Exchanger Manufacturers Association, http://kbcdco.tema.org/
Urban, P.G., Bretherick's Handbook of Reactive Chemical Hazards 7th Edition , Academic Press,
New York, NYISBN:978-0-12-372563-9, 2006.
|
118 INVESTIGATING PROCESS SAFETY INCIDENTS
way. Perhaps the supervisors and ma nagement were aware of these types
of issues prior to the ev ent and could have done so mething to correct them.
If the investigation reveals that staff routinely fails to follow procedures, this
may be indicative of more fundamen tal cultural issues that require
addressing by management.
For example, an operator may skip a pre-operational check of a system
because he believes the check will not discover any problems and takes
valuable time that could be used to produce product. In other words, the
operator believes the check is a waste of time. Perhaps the operator had
skipped the preoperational check many times, and it had never caused any
problems. His supervisor may have known he normally did not perform the preoperational checks but had said no thing because it resulted in increased
production. Skipping the checks was not a malicious act or act of sabotage or even an act of negligence; it was an ‘accepted’ practice. However, this
time when the operator skipped the ch eck, the system failed and a release
of process chemicals occurred. Will the operator tell the incident investigation team that he skipp ed the preoperation al check? What
motivation would there be? What potential punishme nts are there? Unless
the operator believes that it is in his own best interest to divulge the
information, he probably will not. Unless boisterous play, negligence, or
sabotage are clearly involved, individu als should not be punished for the
information revealed during incident investigation interviews. If witnesses are aware of this, they are more likely to openly share the information they
have. The investigation team’s responsibility is to gather facts and draw conclusions. Punishment is not part of the investigation process. This philosophy should be emph asized as part of the tr aining requirements, as
outlined in Chapter 4. Any disciplinary action arising from an investigation is part of a separate process involving Human Resources personnel/policies.
Cultural issues, including company cu lture and country/regional culture,
should also be considered. This may include factors such as a tendency to
agree with whatever is said by someon e perceived to be in authority or a
more senior position, and an unwillingness to divulge information that could reflect poorly on a co-worker.
7.3.2 Collecting Information from W itnesses
The accuracy and extent of witne ss information is highly dependent on
the
performance of the interviewer. The interviewer’s ability to establish rapport
and create an atmosphere of trust affects the quality and quantity of
information disclosed. |
Ancillary Systems and Additional Considerations
389
with the pipe it is installed in. If the pipe needs winteri-
zation provisions, the inline instrument also needs it.
For non‐inline (offline) the requirement depends on
whether it is fluid‐in type or not.
The fluid‐in instruments like Bourdon tube in pressure
gauges may need winterization arrangement. But non‐fluid‐in types definitely don’t need any winterization arrangement.
Figure 18.8 shows some examples of winterization of
instruments.18.3.3
Deciding on the Ext ent of Insulation
From a purely theoretical viewpoint, when it is decided that an “item” is to be insulated, the “whole” item should be insulated. However in reality we don’t always insulate whole the item, unless it is fully justifiable from an economical viewpoint. The full insulation may also make the normal operation of the system of interest problematic.
There are cases where the designer needs to decide on
the extent of insulation. This means he needs to decide if all the pipes/equipment of interest should be insulated or only a portion of them.
The extent of insulation is generally mentioned on
P&IDs; on the main body of the P&ID or in the note area.
For example, one general question is whether a full
tank, including body and roof, should be heat insulated if the tank needs to be insulated or not. All the tank could be insulated if it is decided so, but the cost of insulation could be saved by insulating the body of the tank. As the main reason for this insulation is to keep the liquid content “warm, ” possibly the roof of the tank doesn’t need to be insulated. Even on the body of the tank, only the portion that is in contact with liquid could be decided to be insulated. The additional reason for not insulating the roof is that the heat transfer coefficient of gas/vapors is much less than for liquids, and the heat transfer from the roof is already low. A company may decide that: “if a tank needs to be heat insulated, only the body of the tank up to the high liquid level should be insulated. ”
For pipes almost always all the body of the pipe could
be insulated. The only exception could be large bore
TW
00081TT
0008088TI
00080
PP
*PT
00080FT
00080
I/S O/S
ET N
Note 3PI
00080FQI
00080
FI
00080
FX
00080
Figure 18.8 Win terization of some instruments.Table 18.8 P&ID presen
tation of winterization for different items.
Pipe Equipment Instrument
W
And/or in pipe tag
6/uni2032-HLS-AS-1003-64H-GT
P–07111–2–B39W–50H–ET
222–163L–2/uni2033–IhST(w)(1–1/2/uni2033)Not common unless for
small equipment
E
G
ST
ETS |
EVIDEN CE IDEN TIFICATION , COLLECTION & M ANAGEM ENT 171
timing marks. On the other side of the line, imprecise or approximate data is
listed within the period in which it occurred. This is usually displayed as an
event occurring someti me between two timing marks.
Figure 8.7 is an example of a timelin e that uses a mixture of precise and
imprecise data from the incident example discussed in detail in Appendix D.
One additional benefit of this technique is that the imprecise
approximate times can often be narr owed when compared to the precise
data. For instance, the operator may realize that when he manually closed
valve A, valve B had already been automatica lly closed. Therefore, the period
within which he closed valve A is narrowed.
Timelines do not have to end at the time of the occurrence or incident.
Sometimes post occurrence data can be valuable. Often, it is important to
understand how the emergen cy response actions affected the ultimate
outcome of the occurrence. This type of data can be used to improve
emergency response actions in the future. Also , changes made during
emergency response to positions (valves, switches, debris positions, etc.) can
be important to interpretation of the data.
When timelines are combin ed with simulations, they become powerful
tools, both in understanding the sequence of the events leading up to the
incident and in the development of accurate recreations. This allows for a
more thorough and comprehensive analysis.
|
70 GUIDELINES FOR MANAGING ABNORMAL SITUATIONS
Example Incident 3.13 – Styrene Runaway Reaction and Release,
2020 (cont.)
The only temperature indication in the storage tank concerned was at
the base, and the pressure safety valve from the tank emitted directly
to the atmosphere and not via a flare system or other emission control
system.
Lessons learned in relation to abnormal situation management:
Abnormal Situation Recognition: The temporary closure of a
facility requires special consideration, particularly if the duration
of the closure is unknown at the start.
Organizational Roles: Responsibi lities and Work Processes: With
a reduced workforce, revised procedures and responsibilities
should have included extra checks on high-risk areas. These
considerations should fall under a Management of Operational
Change (MOOC) procedure.
Procedures: Procedures should have been revised to address
high-risk scenarios due to wo rk force and organizational
changes.
Process Monitoring and Control: Provided the risk had been
identified, additional automatic control measures, including
better temperature measurement could have been specified.
3.4.2.4 Turnaround/Shutdown/Decommissioning
Turnaround, shutdown, and/or de commissioning of process plant
equipment is a normal activity during the life cycle of a chemical process.
Because of this both scheduled, preventive, and unplanned emergency
maintenance of mechanical equipment has become a critical function of
highly performing organizations. Re pair costs, production downtime,
leak containment integrity, and regu latory inspections are all factors
involved in developing and execut ing maintenance shutdown strategy.
Advanced mechanical integrity pla nning methods include sophisticated
tools such as Risk Based Inspec tions (RBI), Reliability Centered
Maintenance (RCM), thickness testing, and monitoring. Asset Integrity
engineers and maintenance speciali sts who have received specific |
78 Human Factors Handbook
Table 8-2: Checklist for layout of job aids
1. Make headings large to help people identify information.
2. Make headings stand out from the surrounding text to help people
identify information.
3. Use spacing, images, and/or blank or white areas to reduce clutter, and
to make it easier to identify and recognize information.
4. Use bullet points to make reading easier.
5. Number sections and task steps.
6. Communicate one action per task step.
7. Present different types of information in different formats and fonts
(with supporting icons) so they are distinct and different (e.g., is it a
warning or instruction, or is it background information?).
8. Clearly indicate who should perform th e task step if the task involves
more than one person.
9. Present supporting information separa tely from the task instruction.
8.2.2 Examples of job aids
Examples are shown in:
• Figure 8-1: SOP. Good features include:
o One instruction per numbered line;
o Use of color and icons (see 8.6) to indicate the status of each
point of information;
o Use of space to reduce clutter;
o Use of bullets to make requirements easier to read.
• Figure 8-2: Grab Card, with some key features highlighted.
• Figure 8-3: Decision Flow Chart. Good features include:
o Short sentences;
o Binary decision points;
o Unambiguous decision criteria;
o Color coded and large font for key text;
o Fits on one page. |
F.2 Culture Assessment Protocol |359
other measurem ents of hazard/risk in a way that avoids the
need for recomm endations? This m ay be a cultural issue with
a given HIRA/PHA team, but it m ay also represent a system ic
problem in the organization at large.
133. Are HIRAs/PHAs performed “by the num bers” with little free
thinking about what can go wrong? In recent years Layer of
Protection Analysis (LOPA) has become a prevalent analytical
m ethod for determ ining “how safe is safe enough,”
particularly for high risk hazard scenarios identified during
HIRAs/PHAs. LOPA has provided a consistent and repeatable
m ethod for determ ining how m any independent protection
layers are necessary to reduce the risk to a tolerable level.
While LOPA is very useful analytical technique to analyze a
hazard/risk, but it is not a very good technique for identifying
a hazard/risk. Therefore, if the HIRA/PHA process at a facility
relies solely on m anipulating num erical credits to reach an
acceptable cell on a risk m atrix, without the cause and effect
analysis and open discussion that occurs during HAZOP or
What-If studies, the HIRA/PHA process may have lost an
opportunity to identify additional important risks.
134. Are the recommendations emerging from the hazard/risk
assessments meaningful? Do they address and reduce the
risks identified?
135. Do risk reduction measures in HIRAs/PHAs over rely on
hum an based safeguards such as operator training, the
experience of personnel, or the existence of written
operating procedures?
136. What are the bases for rejecting risk assessm ent
recomm endations? Are the reasons for rejection
predom inantly driven by cost considerations?
137. Are the risk assessment tools appropriate for the risks being
assessed? Are the right tools to assess risks associated with
low frequency – high consequence events? Are the tools
deemed appropriate by recognized risk assessment
professionals? |
324
Inherent safety is assessed relative to a particular hazard, or perhaps
a group of hazards, but essentially never relative to all hazards. A
chemical process is a complex, in terconnected organism in which a
change in one area of the system can impact the rest of the system, with
effects cascading throughout the pr ocess. These interactions must be
understood and evaluated. Similarly, the chemical industry can be
viewed as an ecosystem with comp lex interactions, interconnections,
and dependencies. Understanding these relationships is necessary in order to reach a well-balanced reso lution when technological options
conflict.
13.2 EXAMPLES OF INHERE NT SAFETY CONFLICTS
13.2.1 Continuous vs. batch reactor
The use of continuous, rather than ba tch reactors is a strategy that is
often proposed for improving the inherent safety of a chemical process
(Ref 13.4 CCPS 1993). This modification generally succeeds because a
continuous reactor is usually much smaller, reducing the material and
energy inventory of the process, in creasing heat transfer per unit of
reaction mass, and improving mixing. However, batch reactors may also
have safety advantages, and, under the right circumstances, may be judged to be inherently safer.
Consider a simple reaction:
The reaction is exothermic and pr oceeds virtually instantaneously to
complete conversion in the presence of Catalyst C. The process hazard of concern is that the reaction mass becomes extremely unstable if Reactant B is overcharged, or Catalyst C is left out. The resulting buildup
of unreacted Reactant B may result in a potentially explosive reaction if
Reactant B exceeds a known critical concentration. Two processes are
proposed for this reaction, a batch process (Figure 13.1) and a continuous process (Figure 13.2).
|
412 INVESTIGATING PROCESS SAFETY INCIDENTS
Table G.2 Process Safety Inci dents & Severity Categories
Severity Level
(Note 4) Safety/ Human
Health
(Note 5) Fire or Explosion
(including
overpressure) Potential Chemical
Impact
(Note 3) Community/
Environment
Impact (Note 5)
NA Does not meet
or exceed Level
4 threshold Does not meet
or exceed Level
4 threshold Does not meet or
exceed Level 4
threshold Does not meet
or exceed Level
4 threshold
4
(1 point used
in severity rate
calculations for
each of the attributes which apply to the incident)
Injury requiring treatment beyond first aid to employee or contractors (or equivalent, Note
1) associated with
a process safety incident
(In USA, incidents
meeting the definitions of an
OSHA recordable
injury) Resulting in $25,000 to $100,000 of direct cost Chemical released within secondary containment or contained within the unit - see Note 2A Short-term remediation to address acute environmental impact.
No long term
cost or company
oversight
Examples would
include spill cleanup, soil and vegetation
removal
3
(3 points used
in severity rate calculations for
each of the
attributes which apply to the incident) Resulting in
$100,000 to 1MM
of direct cost Chemical release
outside of
containment but
retained on company property
OR
Flammable release
without potential for
vapor cloud explosives -see Note 2B Minor off-site impact with
precautionary
shelter-in-place
OR Environmental
remediation
required with
cost less than $1MM. No other regulatory oversight required.
OR
Local media
coverage
|
| 1
IN TRODUCTION
1.1 IM PORTAN CE OF PROCESS SAFETY CULTURE
The 2014 FIFA World Cup sem ifinal between Germ any and Brazil
featured two of the most technically proficient team s to contest a
m atch. Within a half-hour, however, the difference between the
two emerged, as Germany scored five goals on a shell-shocked
B razil on the way to a 7-1 rout.
The difference? Neymar da Silva Santos, the captain, leader,
and culture-setter of the B razilian side, had suffered a fractured
vertebra in the previous match, and could not even cheer his
teammates on from the sidelines. With their culture-leader
absent, B razil failed to execute their usually form idable gam e plan
and suffered a catastrophic loss.
Sim ilarly, process safety cannot
succeed without culture leadership.
Investigation of numerous incidents in major hazard operations has clearly
revealed culture deficiencies. The data show that without a
healthy process safety culture, even the most well-intentioned,
well-designed process safety management system (PSMS) will be
ineffective. For example, Union Carbide was known as a process
safety technology leader in the early 1980s. However, weak
culture at its Bhopal facility allowed many “Normalization of
Deviance” failures leading to the December 3, 1984 tragedy.
Simply stated, a strong, positive process safety culture enables the
Essential Practices for Creating, Strengthening , and Sustaining Process
Safety Culture , First Edition. CCPS . © 2018 AIChE . Published 2018 by
John Wiley & Sons, Inc.PSMS = Process
Safety M anagement
System 1 |
Figure 15.6: Aqueous Ammonia: Limita tions of Magnitude of Deviations
Table 15.3 gives the total vapor pressure of aqueous ammonia for
conditions near the design point. The tank design pressure will be
405 |