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288 Human Factors Handbook
Figure 22-4: Stress management – training strategies
22.4.3 Achieving shared situation awareness in emergencies
Shared situation awareness means the ability of
team members to gather and use information to
develop a common understanding of the task and
the environment. Lack of situation awareness is
another factor that can contribute to errors.
Individuals often form different impressions of a
situation without realizing they are doing so. Differences in understanding of a
situation contribute to difficulties in decision-making and thereby impact the
resolution of the problem.
It is important that individuals receive information. However, this should only
be information that is relevant to their jo b role and to the task in hand. Providing
each team member with all the available information relevant to the error or
incident would create information overlo ad. Effective error management requires
awareness of individual team members’ tasks, and the whole situation.
Cognitive control –mindfulness
Individuals learn how to regulate
distracting thoughts, to allow them
to maintain concentration on the
task in hand.
Physiological control –tactical
breathing
Individuals learn how to step away
from situations, calm their bodies'
responses (shaking, heavy
breathing), and regain control of
their breathing.
Modeling
Learners are given the opportunity
to observe another team in a
stressful situation, and to then
assess the effectiveness of their
performance.
Time-sharing skills
Learners get the chance to work
on task prioritization skills.
Overlearning
Learners are over-trained beyond the
level of proficiency that would
normally be required for the particular
task.
See Chapters 20 and 21 for
information on situation
awareness or loss of
situation awareness. |
10 • Risk Based Process Safety Considerations 201
potential failures that could forese eably occur in a complex process.
Thus, the prudent PHA approach used in Element 7 assumes that all
the other elements in Pillar III have been adequately designed,
implemented, and are being sustained . This includes assuming that a
robust ITPM program exists and is effective. Thus, “unexpected”
equipment failures should not occur. A more detailed discussion of the
types of assumptions made by a PHA HAZOP Team are provided in the
Appendix.
As was discussed in Chapter 4, the maintenance strategy for
process shutdowns includes coordina ting the schedules between the
operations and maintenance groups, as the equipment should be available when its maintenance is performed. Inspections and tests which do not require time for a process unit or utilities shutdown time are easier to schedule and perform; those that do require a shutdown
time should be coordinated wi th the production schedulers.
Emergency repairs on equipment that failed unexpectedly delay the expected production schedule, adding undue stress to personnel across the organization. Again, a ro bust ITPM program should be in
place to help prevent unexpected failures, especially for critical
equipment used in the engineeri ng controls required for safe
operations.
One approach to ensure a robust ITPM program poses two
questions that help identify critical equipment: How are the essential controls identified and how are the controls maintained to prevent unexpected failure? These question s apply to all operating modes:
normal, abnormal, emergency, and t ransient. The answers to these
questions follow.
1) How are the essenti al controls identified? The critical engineering and
administrative controls can be id entified through a Process Hazard
Analysis (PHA), often by selecting high-risk scenarios from a Hazards and Operability Study (HAZOP) and pe rforming a Layer of Protection |
Sustaining Process Safety Performance
Learning Objectives
The learning objectives of this chapter are:
Understand the importance of investigating and learning from incidents, and
Understand methods to sustain and continuously improve process safety
performance.
Incident: Space Shuttle Columbia, 2003
Incident Summary
The NASA Space Shuttle, Columbia, was destro yed during its re-entry into the Earth’s
atmosphere at the end of a 16-day voyage, ju st 16 minutes before scheduled touchdown.
During the launch, a large piece of insulation foam became detached from the area where the
shuttle had been attached to the external fuel tank and hit the leading edge of the left wing.
After the incident, it was discovered that a fr agment of the thermal protective panel drifted
away from the wing while in space. At the critical part of re-entry when friction with the Earth’s
atmosphere is at its greatest, superheated air entered the left wing, destroying the structure
and causing the spacecraft to lose aerodynamic control, and break up (Figure 22.1). All seven
of the crew were fatally injured. Within tw o hours of loss of signal from Columbia, the
independent Columbia Accident Investigatio n Board (CAIB) was established following
procedures that had been put in place after th e Challenger disaster 17 years earlier. (CCPS
2008)
Key Points:
Process Safety Culture – It can take time to build a strong process safety
culture but not long for it to degrade. Having a strong process safety
culture requires constant vigilance and leadership.
Measurement and Metrics – “You get what you measure” is a quote
attributed to Peter Drucker, a widely recognized management
consultant. However, if you are not measuring the right things, you likely
won’t get the best results. Choose what you measure carefully.
Description
Columbia was launched on January 16, 2003 for the 28th time. At 81.7 seconds into the flight,
a large piece of insulation foam became detach ed. The detached piece of foam hit the leading
edge of the left wing 0.2 seconds later (Figure 22.2). The event was not observed in real time.
This event was not detected by the crew or ground support functions until detailed
examination of the launch photographs and vide os took place the following day. A Debris
Assessment Team was created to determine whet her the event had caused critical damage to
the shuttle. No adverse effects were noticed by the crew or support staff as the mission |
Plant Process Control
295
Here, plant‐wide hydraulics means the adjustment of
parameters in such a way as to guarantee the movement
of fluid from point “ A” at the beginning of a plant to point “Z” at the end of the plant.
Flow, pressure, and level control loops are what pri-
marily dictate the hydraulics of a process plant.
Table 15.1 shows their functions in different process
items.
This table basically says:
●A pressure loop in a gas container is similar to a level loop in a non‐flooded liquid container.
●A pressure loop on a gas pipe is similar to a flow loop on a liquid pipe
However, it should be mentioned that it is not very
common to use pressure loops on liquid‐filled enclo-sures (including pipes and containers).
Possibly the best approach is to use flow/pressure
loops paired with level/pressure loops on an adjacent container (Figure 15.3).
However, the question still remains: what would be
the “arrangement” of flow/pressure loops paired with level/pressure loops on an adjacent container? This question will be answered when we learn about surge control.15.4 Surge Control
The second purpose of plant‐wide control is surge management and control.
Change, surge, disturbance, fluctuation, or whatever
you want to call it, is part of our life. Everything around us is changing. However, a plant is supposed to generate a product with a specific flow rate and a specific compo-sition (quality). Therefore, somehow surge needs to be managed in a plant. This is one of the duties of plant‐wide control.
Be careful: when we install a control valve on a pipe,
we don’t “eliminate” surge; we only try to prevent the surge from spreading to downstream equipment. This “blocked” surge needs to be managed somehow.
The following section explains different types of
disturbances in a process plant.
15.4.1
Disturbanc
es in Process Parameters
Let’s have a look at some examples of disturbances occur -
ring with each process parameter:
●Flow. Process plants always experience disturbances in
flow. This is the most important and most frequent parameter to consider when considering disturbance management.
●Temperature. You can have a disturbance when there is a change in ambient temperature that will affect the process. Temperature disturbance can be com-pensated for (managed) in heat transfer equipment. There are two main types of heat transfer equip-ment: fired heaters and heat exchangers. Temperature disturbance is managed in a better way if there is a fired heater. When there is a heat exchanger, the temperature disturbance can be managed in a better way when it is a utility heat exchanger, rather than a process heat exchanger.Table 15.1 Plan t hydraulic control.
Purpose Gas/vapor Liquid
Container Inventory
controlP‐loop Non‐flooded: L‐loop
Flooded: F‐loop
Pipe Material
transportation controlP‐loop(or F‐loop if it is around a gas mover)F‐loop
Level/pressure loop on a container Level/pressure loop on a container
Flow/pressure loop o a pipe Flow/pressure loop o a pipe
Figure 15.3 Plan t‐wide control – third attempt. |
TOOLS AND METHODS FOR MANAGING ABNORMAL SITUATIONS 147
Many of these categories are appropriate across the process
industries.
Practical measures have been deve loped that can assess both the
process of acquiring situational aw areness (SA) and the product of
situational awareness. Improvement of situational awareness seems to
focus on two main strategies, either the design of the system interface
to encourage better sampling and re duce the cognitive workload or
training in situational awareness at the individual and team levels.
CRM assessment and training can therefore be an effective tool to
help in the management of abnormal situations, and not just in the
aviation sector. It has been adopte d in other areas including medical,
shipping, nuclear, as well as the oil and gas sectors. The assessment uses
a behavior rating system based on a defined set of skills, with their
component elements and associated examples of desirable and
undesirable behaviors. Suggested content for a training syllabus for
CRM can be found in the IOGP guide (IOGP 2020) and in the Energy
Institute Guide (Energy Institute 2014).
For the chemical and process in dustries, the shift teams could
undergo a similar assessment to ensure they work together effectively,
especially during an abnormal situation.
5.8 LEARNING FROM ABNORM AL SITUATION INCIDENTS
CCPS has included Learn from Experience as a pillar for Risk Based
Process Safety and listed Incident Investigation as one of the primary
elements under Learn from Experience. Table 5.9 references some tools
that are frequently applied to learni ng from incidents and can be applied
to abnormal situation incident prevention.
|
16 Task planning and error assessment
16.1 Learning objectives of this Chapter
By the end of this chapter, the reader should understand:
• The importance of effective and realistic task planning.
• The role that “error assessment” can play in foreseeing and preventing
error, by engaging in effective task planning and preparation.
Task planning refers to developing a maintenance or turnaround plan, a start-
up plan, temporary operating instructions , re-commissioning plan or producing a
work instruction. It may also include setting people to work in operating a process,
such as briefing operators at the start of a shift.
16.2 Incident example
16.2.1 What happened?
The Energy Institute’s “Toolbox” provides many examples of failures in task
planning. One example, planning a confined space entry, is repeated in Table 16-1.
If heating oil had been introduced into the tubes while personnel were in the
heater, they could have been injured.
The example refers to locked blinds, as part of HEC (Hazardous Energy Control).
In some countries it is more common to use blind tags. The U.S. OSHA equivalent
of HEC is LOTO (Lock Out- Tag Out).
Human Factors Handbook For Process Plant Operations: Improving Process Safety and System
Performance CCPS.
© 2022 CCPS. Published 2022 The American Institute of Chemical Engineers. |
6 Guidelines for Revalidating a Process Hazard Analysis
Regardless of the origin of a partic ular What-If or Checklist Analysis
question, the analysis prompts the haza rd evaluation team to consider and
document potential abnormal situatio ns, their consequences, and the risk
controls. The team judges whether the risks are controlled within the
organization’s tolerance, and if not, makes recommendations for improvement.
FMEA. The FMEA technique is a systematic analysis of single component or
functional failure modes and each failure mode’s potential effect(s) on a system.
For each failure mode, the team (1) determ ines if any consequences of interest
would result, (2) identifies engineering and administrative safeguards and
controls protecting against the failure mo de, (3) evaluates risk associated with
the failure mode, and (4) if necessary, makes recommendations to reduce the
likelihood of the failure mode or the severity of the consequences.
The FMEA method is best suited for analysis of mechanical and electronic
systems, so it is sometimes selected as the core methodology for processes
involving compressors, centrifuges, or highly automated systems. However,
FMEA is poorly suited for processes involving reactive chemistry or human
interactions where the PHA needs to co nsider human errors as causes of
hazardous events. Therefore, the overwhelming majority of PHA teams use the
HAZOP or the What-If/Checklist combination as their core methodology. FMEA is
more often applied as a complement ary analysis for specific, complex
equipment to generate a systematic refe rence list of components, their failure
modes and effects, and prioritized ma intenance task lists for increasing
equipment reliability.
1.2.2 PHA Complementary Analyses
In a PHA, complementary analyses are used by the PHA team in addition to the
core methodology to help provide focus and direction on specific topics. The two
most common complementary analyses address human factors and facility
siting. These complementary analyses are often reviews of checklists that have
been developed by a company or adap ted from industry publications and
standards. However, complementary analyses can involve much more
sophisticated studies such as comput ational fluid dynamic analysis and
modelling of vapor dispersion or finite element analyses of structural response
to overpressure and dynamic loads. While the selection, development, and
application of these analyses are outside the scope of this book, it is important
to note that complementary analyses required by a regulation or company policy
must also be revalidated. |
284 INVESTIGATING PROCESS SAFETY INCIDENTS
Recommendations targeted at “softer” issues, such as human and
organizational factors including the work environment, safety culture,
leadership and management.
12.3.1 Inherently Safer Design
Recommendations that lead to inherently safer designs are preferred to
those that add extra mitigative or preventive features (Kletz, 1985).
Inherently safer designs limit reliance on human performance (e.g., following
procedures), equipment reliability (such as control systems and interlocks),
and properly functioning preventi ve maintenance programs for the
successful prevention of an inci dent. Inherently safer design features are
more practical and economical if they are implemented during the design
stages of a facility. Making design ch anges to an existing process may not
be feasible or practical. Nevertheless, the investigation team should consider
whether there is an oppo rtunity to recommend a study on possible design
changes that incorporate inherent safety concepts.
An early reference to inherent safe ty was the subject of a lecture by
Trevor Kletz in 1977 entitled: “What you don’t have, can’t leak.” This principle
has evolved over the years and is typically presented in a hierarchy
(minimization, substitution, moderat ion and simplification (Amyotte, 2018),
as explained below:
1. M inimize: Advancements in process control, improvements in
logistics and changing acceptable risk standards may have removed
the initial justification for large inventories of hazardous raw
materials, intermediates or prod ucts. For example, tight quality
control of on-time deliveries of hazardous raw materials may allow
for a one or two day supply on hand versus a one- or two-week
supply.
2. Substitute: Sometimes substitution of a less hazardous material is
feasible. For example, many chlorinating systems for water
purification have been converted from pressurized cylinders of liquid
chlorine to a pelletized, hypochlorite salt.
3. M oderate: Sometimes it is possible to achieve significant
reductions in reactor size (and inventory) with improved mixing
technology. Another example of inte nsification is changing from a
batch operation to a smaller scale continuous operation.
4. Simplify: It may be possible to use a totally different process or
method to accomplish the same objectives.
|
INVESTIGATION M ANAGEM ENT SYSTEM 71
are practical and will adequately address the root ca uses. Additionally,
site management should ensure that any changes to equipment or
procedures as a result of recommendations are properly evaluated before
implementation.
The space shuttle Challenger disaster is a classic example of the need to
evaluate proposed recommendations. Before the Challenger incident,
NASA was aware of the poor performance (Winsor, 1989) of the ring joint
seal systems from previous near-miss incident investigations. In a well-
meant effort to improve the safety margin, a decis io n was m ade to
increase the pressure test from 100 to 200 psig (6.8 to 13.6 atmospheres)
after the ring joints were reassembled. In reality, this recommendation
actually decreased the integrity and reliability of the ring joint seals by
increasing the deformation of the sea ling putty. An effective MOC analysis
might have uncovered this increased risk.
Chapter 12 provides guidance for formulating effective responses to
investigation findings.
4.2.10 Recommendation Responsibilities
The incident investigation team has the responsibility to develop practical
recommendations and submit them to management. The investigation team
may include comments on resuming no rmal operations and/or suggesting
recommendations to be implemented befo re restarting the process. It is
then the responsibility of management to:
review the recommendations;
approve them as written or ask for clarification, revisions, or alternative
solutions;
establish process safety re-start and ramp-up (normal capacity),
criteria (CCPS, 2007)
approve the final recommendations;
assign action item priorities and target completion dates;
allocate resources; and
track implementation stat us and effectiveness.
Regulatory agencies usually take special interest in the status of previous
recommendations made at the same fa cility or similar recommendations
made across the organization. Lawyers give this issue significant attention.
The assumption is that prudent and responsible managers should promptly |
174 | 13 REAL Model Scenario: Internalizing a High-Profile Incident
13.4 Drilldown
As an experienced process safety professional, Rakesh knew well the concept
described in CCPS Vision 20/20 of “Disciplined Adherence to Standards (CCPS
2020), especially as it applied to equipment designed to an older version of a
standard. He clearly understood that even if the equipment, process, or
practice has been legacied, the company must still determine if that process,
practice, or standard manages risk adequately. With that in mind, he felt
confident to skip the drilldown on the Baton Rouge incident and proceeded to
examine the additional supporting cases.
• Port Neal: Reading further, Rakesh discovered that not only was the
automatic pH control out of service, the jacket coils that were supposed
to keep the reactor warm during shutdowns without overheating had also
failed. Essentially, the site operators had allowed failures to accumulate
and were improvising to keep running; this was classic normalization of
deviance.
• Anonymous 2 and Aichi: The incident investigations did not describe the
training the operator had received or how the layout of the systems could
have fooled the worker into doing the wrong thing. Both factors could
have contributed to the incident. But in any case, not verifying the material
being unloaded and not sampling for a flammable atmosphere are both
failures of operational discipline.
• Healdsburg: Rakesh had previously worked in a brewery and was familiar
with the type of hatch door used in the industry. Did the hatch seal go
bad? he wondered. That would have caused a slower leak. Normally, the
spring tension would provide enough resistance to keep the hatch shut,
so perhaps the spring failed. Perhaps, he thought, the quick-release
handle snagged on the belt or pocket of a passing worker, providing a
much larger opening for the wine to drain out. Either way, a critical
component that put the entire process at risk had not been maintained.
At his former brewery, they had changed their procedures (from car-
sealing the valve handle to locking it) to protect the handle from snagging
on pallets of product being moved by forklift.
• Shuttles: In both cases Rakesh reviewed, NASA was under tremendous
political and economic pressure to launch. This pressure drove leaders to
minimize the safety concerns raised by members of the program team
and continue to operate under unsafe conditions. Rakesh recognized the
conflict between production and safety when he saw it. |
336 Human Factors Handbook
26.2 The importance of understanding error
26.2.1 Preventing reoccurrence
People often assume that learning occurs automatically once an incident has been
analyzed and lessons have been drawn from it. This thinking excludes the most important element of learning, which is ch ange. This refers to the application of
learning (behavioral change) into the work environment.
Learning is a continuous, ongoing proc ess, and takes place in day-to-day
activities.
The possibility of human error occurring exists in every task performed by any
person working in the process industry. Error can happen, but it is manageable.
Error should be fully understood to prevent
its repetition. Individuals should look beyond the immediate causes and focus on the root causes and the sequence of events that took
place before the error occurred.
Blaming an individual is a barrier to truly
understanding the error and will likely lead to
the error reoccurring. For example, if the
individual is blamed, then the procedure does
not get rewritten and the operators will still be overly fatigued due to poor shift patterns. The
error is likely to happen again.
As stated by Todd Conklin [106]:
"You can blame and punish or learn and
improve, but you cannot do both."
Learning requires that a person understands an issue and takes action. It
requires changing behaviors and systems.
Both understanding and behavioral change need to take place for learning
to be fully accomplished. This will ensu re that the lessons learned are robust,
and sustainable across time and changing circumstances.
For example, do not focus on
the operator failing to follow
procedure.
Instead, focus on the fact
that the procedures were
poorly written and difficult to comprehend, and that a high
level of fatigue in the
operator made it even harder to follow the
procedure accurately. |
B.2 Advancing Safety in the Oil and Gas Industry – Statement on Safety Culture |263
Leaders take action to address hazards and PSMS
deficiencies.
Leaders value safety efforts and expertise.
The PSMS specifies an accountable officer with authority
and control for hum an and financial resources.
The PSMS specifies direct reporting lines between
personnel with key process safety roles and the
accountable officer.Timely action taken to mitigate hazards even when it is
costly.
Process safety roles receive equal status, authority, and
salary to other operational roles.
Leaders stand up for process safety even when production
suffers. This usually presents an ethical dilemma for
leaders. See Section 4.3 for a discussion of process safety
culture and ethics.
Safety is regularly discussed at high-level meetings, not just
after an incident.
Foster M utual Trust
Attributes and descriptors for mutual trust include:
Everyone proactively reports errors, near-misses, and
incidents.
Policies are in place to encourage everyone to raise safety-
related issues.
Employees know and believe that they will be treated fairly
if they are involved in a near-miss or incident.
Disciplinary policies are based on an agreed distinction
between acceptable and unacceptable behavior.
Mistakes, errors, lapses are treated as an opportunity to
learn rather than find fault or blame.
Positive labor relations.•
•
•
•
•
•
•
•
•
•
•
•
•
• |
188 Guidelines for Revalidating a Process Hazard Analysis
Example Facility Siting Checklist 1
OBJECTIVE: To aid in identifying facility siting issues relevant to process safety
issues within the scope of the PHA. Th e PHA team completing this checklist
should seek assistance from subject matter experts as necessary.
Q T R
I. Spacing Between Process Components
Are operating units and the equipment within units spaced and
oriented to minimize potential damage from fires or explosions in
adjacent areas?
Are there multiple safe exit routes from each unit?
Has equipment been adequately spac ed and located to safely permit
anticipated maintenance (e.g., pulling heat exchanger bundles,
dumping catalyst, lifting with cranes) and hot work?
Are vessels containing highly ha zardous chemicals (HHC) located
sufficiently far apart? If not, what hazards are introduced?
Is there adequate access for emergenc y vehicles (e.g., fire trucks)?
Can adjacent equipment or facilities withstand the overpressure
generated by potential explosions?
Can adjacent equipment and facilities (e.g., support structures)
withstand flame impingement or radiant heat exposures?
When provisions have been made fo r relieving explosions in process
components, are the vents directed away from personnel and
equipment locations?
II. Location of Large Inventories
Are large inventories of HHCs locate d away from the process area?
Is temporary storage provided for raw materials and for finished
products at appropriate locations?
Are the inventories of HHCs held to a minimum?
Where applicable, are reflux tanks, surge drums, and run-down tanks
located in a way that avoids the concentration of large volumes of
HHCs in any one area?
Where applicable, has special consideration been given to the
storage and transportation of explosives?
Have the following been considered in the location of material
handling areas:
• Fire hazards?
• Location relative to important buildings and off-site exposures?
• Safety devices (e.g., sprinklers)?
• Slope and drainage of the area?
|
76 Human Factors Handbook
Further guidance on the management of job aids is given in the CCPS
“Guidelines for Risk Based Pr ocess Safety” [5]. The United States’ Department of
Energy guide “DOE-STD-1029-92 Writer's Gu ide for Technical Procedures” [36] is
also useful.
7.7 Key learning points from this Chapter
Key learning points include:
• The content of job aids, including in structions, warnings and cautions,
can be produced from task analysis , task walk-throughs and the results
of HIRA.
• Job aids should be developed with the engagement and involvement of
front-line personnel who use the written guidance, if company human
performance programs are to be sustained.
• All job aids should be validated and kept up to date.
|
79
The steps for conducting an Inform ed Substitution process are as
follows:
1.Form a team to develop a plan
2.Examine current chemical use
3.Identify alternatives
4.Assess and compare alternatives
5.Select a safer alternative
6.Pilot the alternative
7.Implement and evaluate the alternative
There are a number of resources fo r researching alternatives to
hazardous chemicals. These resource s include chemical substitution
case studies and alte rnatives, including:
•SUBSPORT - Substitution Support Portal – Moving Towards Safer
Alternatives (www.subsport.eu/case-stories-database)
•Intergovernmental Forum on Chemical Safety (IFCS) – Substitution and Alternatives Case Studies, Examples and Tools
(www.who.int/ifcs/documents/sta ndingcommittee/substitution/
en/)
•University of Massachusetts Lowell Toxics Use Reduction
Institute (TURI) Case Studies (www.turi.org/TURI_Publications/Case_Studies)
•ISTAS Risctox (in Spanish only) (www.istas.net/web/abreenlace.asp?idenlace=3911)
•U.S. Environmental Protection Agency – Safer Chemical
Ingredients List (www.epa.gov/sa ferchoice/safer-ingredients)
Completed alternatives assessments (Interstate Chemicals
Clearinghouse, www.theic2.org/aa- wiki-archive) are also included.
Performing a single search of mu ltiple online resources related to
substitution is another rapid way to identify possible alternatives. Guidance is also provided for asse ssing hazards, performance and cost
(Ref 4.40 US OSHA). Comparati ve Assessment T ools include the
following:
•European Commission, Minimising Chemical Risk to Workers’
Health and Safety Through Substitution , 2012
•Ontario Toxics Reduction Program, Reference Tool for Assessing
Safer Chemical Alternatives , 2012 |
68
Hydrofluoric acid (HF) has a number of industrial uses, including
petroleum refining as an al kylation catalyst, detergent
component manufacturing, metals processing, glass etching, organofluoride manufacture, semiconductor manufacturing, and uranium enrichment. Recent process developments have
resulted in possible substitutes for liquid HF acid:
oSolid HF catalysts have been demonstrated as a substitute for liquid HF alkylation processes. Alkylation units in petroleum refineries are used to produce high octane gasoline blending components that have no sulfur or aromatic content. One such process, currently
under development, uses a liquid phase riser reactor
with a solid catalyst similar in concept to a Fluidized Catalytic Cracking Unit (FCCU). The reactor operates at
about 350 psia (24 bar) and refrigerated temperatures of
50-100°F (10 - 38°C). These operating conditions are similar to existing liquid HF Alkylation units, as are the feed input ratios (isobuta ne-to-olefin). Catalyst
reactivation and regenerati on are key steps in these
processes (Ref 4.21 McCarthy).
oSolid bed HF catalysts are used in the production of linear alkylbenzenes, a material used in the generation of sulfonation compounds. These are components used
in the manufacture of bi o-degradable detergents.
oThe use of sulfuric acid as an alkylation catalyst in refineries, although less effici ent as a catalyst, presents a
demonstrated opportunity for replacement of HF with a less hazardous alternative. Several refineries have
performed this conversion as a way to reduce risk. HF
often presents the potential for a large off-site (as well as on-site) impact in the event of a catastrophic release,
whereas sulfuric acid norma lly presents a hazard to
personnel in the immediate re lease area only, and as a
liquid, is easier to contain. However, there is a risk transfer issue associated wi th using sulfuric acid in
refinery alkylation units. Unlike HF alkylation units, where the HF acid can be regenerated and re-used, the |
D Competency performance standards
Table D-1 Competency standard s template – Skill-based task
Task/sub-task
knowledge & skills
requirements Basic operational knowledge.
Utilization of basic available information.
Low new idea generation.
Narrow range of knowledge.
Established and familiar.
Offer a clear choice of routine responses.
Involve some prioritizing of tasks from known solutions.
Competency
standards 1. Monitor functioning of compressors & pumps. Take
necessary action following Standard Procedures (SP).
2. Control (level & capacity) of materials to specification
following SP.
3. Operate equipment as per job requirement following
SP.
4. Maintain records to job requirement following SP.
Safety criticality
(High, Medium, Low) Medium
Monitor process indicators & keep within safe operating
limits.
Share information about equipment faults or failures.
Complexity of task
(High, Medium, Low) Low
Freq. of task (High,
Medium, Low) Medium
Time required to
complete task (Long,
Medium, Short) Medium
Competency -
Knowledge, Skills and
Attitudes required Knowledge
Function of equipment including safety devices.
Interpret signs, signals, & symbols.
Knowledge of safe operating limits, & process hazards.
Procedural
Establish procedures.
Skills
Alertness, communication, task planning, interpreting
info, basic reading & writing. Human Factors Handbook For Process Plant Operations: Improving Process Safety and System
Performance CCPS.
© 2022 CCPS. Published 2022 The American Institute of Chemical Engineers. |
25. Indicators of human performance 329
25.4.5 Observations of performance
Observations of performance can also cont ribute to leading indicators. The focus
of these observations may include:
• Mistakes and Lapses:
o Are individuals making frequent mi stakes/lapses? If so, is there
a pattern in these mistakes/lap ses? Is there a common cause?
• Task completion:
o Are tasks being completed on time? Are they being completed
effectively, or do they need to be redone or corrected?
• Effectiveness of audits:
o Do audits detect errors and om issions? For example, do they
detect failure to tag lock outs?
• Lessons learned:
o Are lessons learned and applied? For example, have incident
recommendations been implemented?
25.4.6 Signs of psychological safety and teamwork
Psychological safety is an important indica tor of safety culture and allows for free,
open discussion about human performance. Indicators of psychological safety
include:
• Open reporting of errors without fear of repercussion.
• Conversations about lessons learned.
• Discussions about potential error traps.
• Challenging others (including superior s) on safety-related issues e.g.,
mistakes, incorrect commands.
• Effective communication and informat ion sharing across business units.
• Leaders tend to reserve judgment until all facts are obtained and not
jump to conclusions, blame workers, and seek unwarranted disciplinary
action.
It should be noted that task safety observations conducted in the field by a
small group of individuals (e.g., a mana ger, a supervisor, and the worker) often
results in a psychologically safe environment in which the worker may freely
escalate concerns. The reality of leakin g pipes, broken equipment, and faulty
instrumentation are in clear view of the manager and/or supervisor when they are
in the field together with the worker. Di rect engagement with the worker by the |
5.1 Senior Leader Element Grouping |163
Contractor Management (Elem ent 11)
Companies frequently use contractors in place of employees,
for several reasons. Contractors can for example provide unique
skills needed only occasionally and supplement staff during
periods of high activity such as turnarounds. Contractor
assignments m ay range from short assignm ents of hours or days
to quite long-term . Contractors also provide professional services
such as engineering, asset integrity inspections and expert
consulting.
Contractors may be exposed to the sam e process safety risks
as em ployees, and in some cases the risks may be greater.
Therefore, any process safety risk management activities should
control the risk that contractors face to the same level as
employees. However, preparing the contractors to work safely
and within the framework of the facility’s PSMS can be
com plicated. Often, the terms of the contract specify that the
facility cannot manage or train contractors directly, to avoid co-
employment issues. In such cases, the facility must instruct the
m anagement of a contractors’ company about hazards and
protection measures, and then the contractors’ management
m ust instruct them . Similarly, providing corrective feedback may
also have to go to the contractor through their m anagem ent.
Finally, contractors sometimes use sub-contractors, and this adds
to the management challenge.
As challenging as managing contractors within the facility’s
PSMS can be, aligning contractors with the facility’s culture can be
m uch harder. Contractors arrive influenced by their own
com pany’s culture and the cultures of other facilities at which
they’ve worked. They are also usually motivated by business
com mitments to provide services on a com petitive schedule and
price, enhanced by a fear that failure to meet commitments could
hinder repeat business. As discussed in section 2.9, this
environment is quite conducive to norm alization of deviance. |
DETERM INING ROOT CAUSES 215
10.4.1 Gather Evidence and List Facts
The first task is to develop a list of all known facts. This list includes not only
facts relating to the incident sequence, but also all pertinent background
data, specifications, and recent past or external events that could or did have
an influence on the overall system.
A fact should be a true, proven piec e of data. Avoid drawing conclusions
or making judgments at this stage. An example fact is— Hearing protection
boundaries in the area are not marked . A conclusion may be that the
boundaries are not clear, but do not make that jump yet. Sticking to the facts
will help prevent people involved in the inciden t from becoming defensive
and will prevent the team from jumping to conclusions. Sticking to the facts
will also assist readers in understanding th e complete incident report.
The team needs to take care to avoid being trapped by hidden or
erroneous assumptions. All facts should be tested. The facts are essential
inputs to ensure that the correct scenar io is selected later. Any apparently
conflicting facts should be resolved throug h additional data gathering.
Listing the source of each fact will facilitate conflict identification and
resolution.
10.4.2 Timeline Development
Next the team develops a chronology of events based on the available
known times and sequences and prepares a timeline or sequence diagram.
Unconfirmed assumptions regarding chronology should be clearly identified
as unconfirmed, and action should be initiated to verify assumptions. Many
investigators use relatively simple timelines (instead of sequence diagrams)
with the logic tree methods because the logic tree itself shows the
interactions of events and conditions.
10.4.3 Logic Tree Development
After the initial facts have been listed and the initial timeline has been
developed, the logic tree diagram can be cons tructed. The tree diagram is a
dynamic document; it continues to expand and may even be rearranged as
additional information becomes available or when new information changes
the understanding of the original facts.
Once the facts have been gather ed and the timeline developed, there
may be sufficient information available to confirm or refute a hypothesis in
the early stages of logic tree development. For many simple and
straightforward failures, general knowledge of th e component failure mode |
ACRON YM S YYYJ
LNG Liquefied Natural Gas
LOPA Layer of Protection Analysis
LOPC Loss of Primary Containment LOTO Lockout/Tagout LSHH Level Sensor High High LT Level Transmitter
MARS Major Accident Reporting System
MAWP Maximum Allowa ble Working Pressure
MCSOII Multiple-Cause, Systems-Oriented Incident*OWFTUJHBUJPO
MES Multilinear Event Sequencing
MHIDAS Major Hazard In cident Data System
MI Mechanical Integrity
MIC Methyl isocyanate
MM Million
MOC Management of Change
MOM Singapore’s regulatory standard for incident JOWFTUJHBUJPO
MORT Management Oversight Risk Tree
MSDS Material Safety Data Sheet
NAICS North American Indust ry Classification System
NFPA National Fire Protection Association
N
2 Nitrogen
NOM Mexico’s regulatory standard for incident JOWFTUJHBUJPOT
NTSB National Transportation Safety Board
IOGP International Association of Oil and Gas Producers
OREDA The Offshore Reliability Data project
ORPS Occurrence Reporting and Processing System
OSBL Outside Battery Limits OSHA United States Occupati onal Safety and Health "ENJOJTUSBUJPO
P
fatality Probability of Fatality
Pignition Probability of Ignition
Pperson present Probability of Person Present
P Probability
P& ID Piping and Instrumentation Diagram
PCB Polychlorinated Biphenyl
PFD Probability of Failure on Demand
PHA Process Hazard Analysis
PI Pressure Indicator LI Level Indicator
LIC Level Indicator—Control |
410 PROCESS SAFETY FOR ENGINEERS: AN INTRODUCTION
Figure 19.6. OSHA QuickCard on permit-required confined spaces
(OSHA)
|
282
safety measures have been verified before work begins. Additionally, the
increasing practice of combining a ll safe work issues on one single
permit form, i.e., basic job informatio n, authorization, and closure; hot
work; confined space; equipment opening; lockout/tagout; PPE; vehicle entry; etc. has made these all-in-o ne permit forms very complicated.
While this practice may reduce the number of separate permits required
for a given job, it makes the all-pu rpose permit form very complex and
more difficult to use.
Finally, SWP permitting processes sh ould not be allowed to evolve
into “check-the-box” activities. This can occur when complicated permits
are used in a manner that does not give due consideration to each item on the permit and they are rapidly filled-out. This can sometimes be
detected when each item is not indivi dually addressed, i.e., a line with a
d o w n a r r o w i s u s e d t o q u i c k l y a n s w e r a l i s t o f q u e s t i o n s . I f t h e
importance of having a completed pe rmit document seems to outweigh
the thought process associated with carefully recognizing and
addressing the hazards of each indivi dual job, then the permit processes
may have become a “check-the-box” activity. Unfortunately, this may
only become apparent when hazards are not addressed properly and
incidents or near misses occur.
11.7 ASSET INTEGRITY AND RELIABILITY
Asset integrity (sometimes referred to as Mechanical Integrity) includes
a broad range of technical activities in a PSM/RBPS program, including:
Identification of equipment to be included in the asset integrity
program.
Written maintenance procedures.
Inspection, testing, and preventive maintenance (ITPM)
programs
Maintenance personnel training and qualification.
Management of asset in tegrity deficiencies.
Asset integrity quality assurance (QA), which involves the design,
fabrication, and installation of the equipment, as well as the replacement of materials.
Each of these sub-areas of asset in tegrity can involve consideration
of the four IS strategies. For example, Substitution , Moderation , and |
F.2 Culture Assessment Protocol |349
42. Are process safety perform ance and leadership significant
considerations in career advancem ent and succession
planning?
43. Has a com pany-level PSM S leader been designated? Is this
designation m ade in writing and by title? Is this person
technically com petent in PSM ? Does this person have
sufficient positional authority to contribute m eaningfully to
the most significant process safety related decisions, and has
that authority been influential?
44. Has a facility-level PSM S leader been designated? Is this
designation m ade in writing (e.g., job descriptions,
organizational charts, etc.) and by title? Is this person
technically com petent in process safety? Does this person
have sufficient positional authority to contribute m eaningfully
to the m ost significant PSMS-related decisions, and has that
authority been influential? Note: This position can be either
full tim e or part time, depending on the size of the com pany,
the num ber of facilities included in the PSM S, and the
applicability and com plexity of the com pany PSMS.
45. Are process safety issues identified dealt with by m anagem ent
and not just "filed".
46. Have process safety culture surveys and/or assessments been
conducted, and have actions or priorities resulting from the
survey been resolved? Have the surveys/assessments resulted
in changes to the process safety culture?
47. Are the same process safety issues raised at each
m anagem ent meeting, but not resolved? Note: Management
m eetings can consist of a variety of forums, from daily
production meetings, maintenance m eetings, project
m eetings, process safety m etrics, or other related meetings?
48. Does management resist taking responsibility for process
safety concerns when they are faced with them ?
49. Does m anagement use em pty slogans regarding process
safety repeatedly? |
W ITNESS M ANAGEM ENT 117
A classic example of this “filtering” co ncept is the fable of four blind men
who encounter an elephant as they walk down the ro ad together. Each blind
man encounters a different part of the elephant and tries to communicate to
his associates what he has found. The first man touches the trunk and
believes they have met a boa constricto r. The second man grabs the tail and
thinks it is a rope. A third who has en countered a leg begins to argue saying
that both of his friends are wrong and th at the thing is a tree trunk. The last
man, who has hit the side, insists they ha ve hit a wall of some sort. Each blind
man was basing his conclusion on the information available combined with
his previous experience. The entire pict ure is not accurately interpreted until
the composite information is assimi lated. The task of the incident
investigation team is to put these four stories together and realize that the men have encountered an elephant an d not a snake, rope, tree, or wall.
Another natural human characteristic is to recall events, actions,
observations, etc., out of chronologica l order. The human ‘replay’ mechanism
does not function in order like a video pl ayer. This characteristic is one reason
why retelling their account of what happened several times may help individuals remember additional details.
Sometimes, witnesses may choose not to tell the complete story. A
witness may have several motives for purposely modifying statements or
choosing not to tell the incident investigation team all of the relevant
information they have. The most signific ant of these influences is fear of
punishment, either for themselves or a friend or colleague. When evaluating
witness statements, the investigatio n team may need to consider the
possibility that a statement given in an interview might be incomplete or
modified. The strategies for dealing with fear of punishment are similar to
those for encouraging the reporting of n e a r m i s s e s . T h e f o c u s o f t h e
investigation is on fact finding, not fault-finding. Although some incidents
may be a result of horseplay, negligence, or malicious/criminal acts of
sabotage, these causes are, by far, the exception. Th e root causes of the vast
majority of incidents are associ ated with management-system or
organizational failings. This message should be clearly communicated to
everyone involved in the investigation, particularly to the witnesses.
It is important for witnesses to understand that th e purpose of the
investigation is to determine the root causes of the in cident to prevent a
similar occurrence. In cases that in volve a failure to follow safety or
operational instructions, personnel may have thought that the rules are
unnecessary, incorrect, or an inefficien t use of time and it was in the best
interest of the individual and the organi zation to perform the task in another |
5 • Facility Shutdowns 79
outdoors), the following preserva tion techniques may need to be
considered [31, p. 25]:
Periodically turning or rotating motors;
Capping of open piping connec tions to partially installed
equipment, vents to atmosphere, or flares;
Maintaining nitrogen blankets;
Coating or filling machinery with oil, and
Using desiccants or biocides if necessary.
In all cases, a multi-discipline project team, in cluding process
safety and asset integrity experts f amiliar with the equipment’s design,
should determine the appropriate preservation approaches. Further information and guidance on asset integrity of m othballed facilities is
available elsewhere [23] [43]. Inadequate preparation and handover
during these project shut-downs an d start-ups have led to incidents.
5.3.5 Effective contractor mana gement during the project
Contractors are more likely to be in volved in facility shutdowns due to
their technical expertise, construction-related skills, and broader experience base. For this reason, contractor management becomes much more crucial since there are more opportunities for essential information to be missed during the handover communications
between groups. The contractors and their sub-contractors have a clear understanding of all process sa fety expectations, the safe work
practices, and most importantly, th ey have the operational discipline
to adhere to them. A case study show ing the successful application of
a successful contractor-managing ap proach for major, complex facility
shutdowns is provided in Section 5.6 [44]. Further information and
guidance on contractor management is available elsewhere [14] [31].
When managing a facility shutdown, complex project-related
issues that can adversely affect pr ocess safety can and do arise. The
next section will cover the two facility shutdown transient operating |
Table B.1. Generic Risk Matrix (R)
457 |
Anatomy of a P&ID Sheet
19
Whether to keep the design notes or not is another
issue. Some companies believe that the intention of
design notes is directing other designers during the design stage of a plant and that all of the design notes should be eliminated after issuing IFC version of P&IDs. However, other companies leave the design notes because they can be helpful during the operation of the plant when something needs to be changed and replaced with another design note. Also the deletion of each note – either the design note or the operator note – does not leave a clean space as the note number should be left so that the remaining note numbers still stand.
Visual notes can be used in some circumstances. They
can be the detail of construction for a complicated part. They are, however, are not usually placed on P&IDs.
3.6 Main Body of a P&ID
On the main body of P&ID, the main elements that can be seen are “item identifiers, ” which will be discussed in the next chapter.
There is always a debate about what needs to put on
the main body of the P&ID. If the P&ID is a focal document in the process plant, do all the information provided by
all groups need to be put on the P&ID? It is NOT easy to decide what and how things should be shown on P&IDs; this topic will be expanded more in Chapter 4.
However, it should be mentioned that the amount of
information shown on a P&ID can be problematic. Thus a P&ID is created “universal” for everyone involved in process plant.
If the amount of information is not enough, the P&ID
becomes useless. If the amount of information shown on P&ID is too much, the P&ID also becomes useless because of its illegibility. It is important to know that a P&ID will be used in the process plant during operation, including emer -
gency situations. An operator should be able to grasp the information needed from a P&ID as quickly as possible.
However, it is not always easy to gauge and find the
sweet window for the amount of information that should be shown on a P&ID (Figure 3.9).
There was a time that there was no single “footprint” of
interlock system on P&IDs. Now, a lot of P&IDs show the interlock systems, too.Lack of information Legibility Congestion
Figure 3.9 The amoun t of content on P&IDs. |
58 | 5 Learning Models
Gardner’s work has led many other educators to develop evaluation and
teaching tools based on this framework. Typically categorized as following the
Learning Styles Model, these tools help educators and trainers present lessons
and communications in forms that best fit their students’ intelligences, in
order to boost learning.
Gardner’s theory of multiple intelligences was intended to be used
primarily in box III (Check) of Figure 5.1. However, since learning and
communication are opposite sides of the same coin, Gardner’s model should
also be extremely useful for helping to refresh learning, a key feature needed
in box IV of the model (Act).
In all but the smallest companies, we can expect that all eight forms of
intelligence—and therefore all eight learning styles—will exist among our
leadership and workforce. It follows that to effectively drive learning about
process safety across the company, we need to communicate using multiple
styles. This will also help promote workforce involvement.
5.2.2 Career Architect® Model
Lombardo and Eichinger have developed a model for individual learning and
development in a corporate setting (Lombardo 2010) in which individuals
partner with their managers (and possibly with mentors) to identify
competencies they should develop and career hurdles they can overcome.
The learning-and-development plan the employee and manager agree on
focuses on providing the employee with on-the-job experiences in the areas
where development is needed. During these experiences, about 70% of an
employee’s learning comes from doing, 20% by interacting with and observing
those around them, and only 10% from courses and reading.
The model identifies 167 different competencies an employee may have
to develop. For each, Lombardo describes a process to assess the need for
development, then suggests means of learning from self-study, feedback,
development in the current position, and development in a new position.
The Career Architect® Model’s focus on a broad list of possible employee
and company objectives links corporate goals in box I (Plan) and box II (Do) of
Figure 5.1. The 167 potential development competencies represent an
important use of metrics to guide where learning should take place. Use of
metrics is a necessary feature of the new learning model that is the
centerpiece of this book. |
105
eliminated if the vaporizer which precedes it is equipped with a
disengaging space, which duplicates the functionality of the catch pot
(Ref 6.10 Kletz 2010). By incorporating the technique of reactive
distillation, a process which uses a reaction step with subsequent
distillation can be simplified by combining the reaction and primary separation steps into one vessel, si mplifying the design and eliminating
several separate distillation columns. Not only is this design simpler, it
also results in greatly reduced in-pro cess inventory (Minimization!), and
involves less vessels, piping, and fl anges which can leak. An important
consideration with reactive distillation is that it does make the process
itself slightly more difficult to operate, however the tradeoff in reduction in risk more than offsets th is. See Figures 6.1 and 6.2.
6.2 ELIMINATING U NNECESSARY SPARES
In many plants, spare pumps are prov ided as a standard design, without
a proper analysis as to whether each installed spare is truly justified, based on the duty requirements. Non- installed spares are estimated to
cost 5 to 6 times less than installe d spares, and eliminating unnecessary
installed spares simplifies piping in stallation, and also may eliminate
unnecessary contained volume in th e piping (an application of the
“Minimize” technique. (Ref 6.10 Kletz 2010)
|
384
implemented early in the facility development, and have broad and
wide-ranging impacts on the proc ess design. Tactical approaches,
including the active and procedural categories of the hierarchy of
controls, can be implemented late in the design process and are
characterized by repetition and high costs associated with maintenance
(Ref 14.9 Hendershot). Costs have to be evaluated on a holistic basis, and
it has been proven that the life cycl e costs and risks may be reduced after
implementing IS measures. Both the Contra Costa County and New
Jersey programs explicitly include a consideration of economic feasibility
as part of an IS evaluation.
14.3.2 Needed Tools Chapter 12 discusses a number of tools and approaches for evaluating
different and potentially conflicting IS options and measures. Additional
tools and approaches will be needed to support IS regulatory programs
including those to support system atic IS reviews, and economic
evaluation and performance evaluations.
Systematic review methods . Methods for systematic IS reviews are
needed to provide consistent and comparable IS evaluations within and
across facilities. Such an approach provides greater assurance that dissimilar facilities will conduct reasonab ly equivalent IS evaluations, and
that the results of those evalua tions will be understandable and
acceptable to regulators and the public.
Economic valuation methods . Since economic feasibility is a critical
factor in identifying viable IS opportunities, better methods for
estimating this variable would benefit both regulatory and voluntary IS programs. Methods to estimate the va lue of IS and to quantitatively
assess whether a given process is “as inherently safe as is practicable” are currently unavailable or unproven. Though examples are increasingly available in the literat ure, case studies documenting the
economic benefit of IS projects do not cover a wide array of industrial
situations.
Evaluation of performance . A constraint to regulation is the lack of
consensus on appropriate IS metrics. Assuming that the regulation is
performance-based, rather than spec ification-based, metrics should be
developed to help provide consistenc y. It is difficult to measure the |
198 PROCESS SAFETY FOR ENGINEERS: AN INTRODUCTION
Distillation (see Figure 11.16), stripping, an d absorption frequently involve flammable
materials; therefore, loss of containment can re sult in fires and explosions. High temperatures
are used, especially in the reboilers, to drive the distillation/stripping; therefore, the thermal
stability of the materials being handled should be understood. Loss of cooling to a reflux
condenser can affect the composition of materi als in a distillation, which again leads to the
need to understand the effect of composition on the thermal stability characteristics of the
material being handled. The Concept Sciences expl osion in Chapter 7 is an example of a failure
that led to a higher, and more hazardous, concentration than expected or intended. High levels
of liquid in columns can lead to plugging of inte rnals, high pressure, and loss of containment.
The Texas City explosion in Section 3.1 is an ex ample of this. Higher liquid loading on trays can
result to damage to trays and result in more serious temperature upsets. An electrical power
failure will stop all cooling water pumps but no t necessarily any fired heaters. Thus, heat
continues to enter the process, but no cooling occurs. This is often the design basis for the
largest flare case for a process.
Packing material fires can occur where hydrocarbon residue that remains on column
packing can self-ignite at elevated temperatur es when exposed to the atmosphere. Iron
sulfide, which is pyrophoric, can form from sulfur found in crude oil. Corrosion of carbon steel
components can settle on packing and can ignite when exposed to the air or oxygen (Ender
and Mannan).
Adsorption processes are exothermic. Carbon bed adsorbers are subject to fires due to
this overheating. For certain classes of chemic als (e.g. organic sulfur compounds [mercaptans],
ketones, aldehydes, and some organic acids) reaction or adsorption on the carbon surface is
accompanied by release of a heat that may ca use hot spots in the carbon bed. Adsorption of
high vapor concentrations of organic compounds also can create hot spots. If a flammable
mixture of fuel and oxygen are present, the heat released by adsorption or reaction on the
surface of the carbon may pose a fire hazard (e .g., a fire may start if the temperature reaches
the autoignition temperature of the vapor and ox ygen is present to support ignition) (OSHA a
and Naujokus). Figure 11.17 is a schematic of a carbon bed system, In Figure 11.17, the top
bed is in absorption mode and the bottom bed is in recovery mode. |
Evaluating Operating Experience Since the Prior PHA 83
the training and performance a ssurance systems are not being
adequately resourced are warning signs. The previous PHA team’s
judgments about the likelihood of human errors causing upsets
and the probability that operators will fail to properly respond to
indications and alarms may be overly optimistic, so the risk
assessments need to be reviewed and Updated , as appropriate. If
the affected number of nodes or scenarios is significant then a Redo
may be justified.
• Conduct of Operations. Are routine activities being reliably
executed? Is good housekeeping being performed? Are signs,
labels, and lighting being properly maintained? Any metrics that
indicate a breakdown in operational discipline are warning signs.
The previous PHA team’s judgments about the likelihood of upsets
may be overly optimistic, so the risk assessments need to be
reviewed and Updated , as appropriate.
• Emergency Management. Is there a backlog of overdue tests or
inspections of equipment relied upon to execute the emergency
response plan or procedures? Are emergency drills or exercises
overdue? Are tabletop exercises be ing postponed? Any metrics that
indicate the emergency systems are not being adequately
resourced are warning signs. The previous PHA team’s judgments
about the mitigation of losses of primary containment may be
overly optimistic, so the risk assessments need to be reviewed and
Updated , as appropriate.
Metrics can provide leading indicators of performance that are critical to a
facility’s ability to determine if process safety incidents are likely to occur. The
revalidation study leader should make a judgment as to whether any current
performance gaps are being corrected or whether they will likely persist. The
more widespread the performance gaps and the longer they are likely to persist,
the more likely the Redo approach is needed to judge current risks accurately.
4.3 HOW OPERATING EXPERIENCE AFFECTS THE
REVALIDATION
A review of operating experience since the prior PHA revalidation should be
completed as part of the assessment to determine whether a Redo or an Update
will be the more appropriate approach fo r the upcoming revalidation. Chapter 5
will discuss making this revalidation a pproach selection in detail, but the
operating experience review by itself can necessitate one approach over the
other. |
8. Format and design of job aids 81
Figure 8-2: An example grab card
(Compiled by CCPS for this handbook.)
Figure Note: This grab card is for managi ng gas leaks in a public gas pipe network
where the gas leak may not be known at first. Therefore, it starts with identifying
the gas leak and then makes reduces the likelihood of ignition sources (makes
them “safe”).
|
Figure 6-3: Example of a formal safety critical task assessment
Safety
Critical Task
index Hot oil furnace flame detector proof test (drawn from Step Change in Safety [30])
Major Accident Hazard
scenarios Loss of containment of flammable gas
Nature of tas k Maintenance Roles Instruments
Task criticality overview
How hazardous
are the systems
involved? 3 To what extent are
ignition sources
introducing during the
task? 0 To what extent does the
task involve changes to
the operating
configuration? 1 To what extent
could incorrect
performance of
the task cause
damage? 3 To what extent
does the task
involve defeating
protection
devices? 3 Total 10
Task and human error analysis
Preconditions
Interface with the control room to identify the test to take place
Task/ error
identifier Task Error
guideword Error
description Failure class MAH consequence
of error Existing controls /
recovery Training &
competency Actions
required
1.1 Liaise with the
control room
to and carry
out risk
assessment Wrong info Wrong info
passed on Mistake No MAH Trips
1.2 Ensure test
measuring
equipment
calibrated Operation
omitted Use
incorrectly
calibrated
equipment Lapse MAH fail to detect
flame out Yearly calibration
(adapted from [30]) |
348 Human Factors Handbook
Figure 26-3: “New” Just Culture Process
(adapted from [114] )
*Expectations: Expected conduct in line with Values and Behaviors, Code of Conduct, rules, policies, and
procedures
8
871
2
3
4
5
6
71
2
3
4
5
6 Was the individual instructed / influenced
to do this by the supervision or other figure
of authority?Assess Interpret Behavior 2 1
Start Here
The individual acted on the instructions or
under the influence of an authority figure.
Was the expectation clear? If there was a
procedure was it clear, available, current and
workable?The expectations were
unclear or impractical.
Did they understand what was required, and
did they have the knowledge, experience, skills,
physical capacity and resources to do it?The individual did not have the capability
or the resources to meet the expectations.
Did they intend to act with
company expectations, but made a mistake?The individual made an unintentional error.
Were they following custom-and-practice which
was common among their peers?A custom-and-practice
had developed among the team.
Substitution test: Could another person with
the same knowledge, skills & experience have
done the same thing in the identical situation?The individual found
themsleves in a difficult situation.
Is there evidence to suggest they acted to
help self or company to save time and effort?The individual acted to
benefit themselves of the company.
Is there evidence to suggest they
intended to cause harm, damage or loss?This is a special case
- always consult Huam Resources.
It's not clear why this happened.
You may need to investigate furtherYes
Yes
Yes
Yes
Yes
YesNo
NoYesNo
Yes
No
No
No
No
No |
11.8 Embed and Refresh | 153
engaged. Posting the newsletter around the rig was a passive form of
communication, but it took little time to do.
The last part of the plan was probably the most fun for the crew—creating
a safety slogan or jingle. The valuable prize for the winner was additional time
off. When it was time to judge the entries, there were so many to choose from.
Some were very straightforward: “If you don’t think it will happen to you, find
the person who had it happen to them.” Others were catchier: “If you mess up,
‘fess up.” Some were downright morbid: “Arms work best when attached to
the body.”
Lucas also received some musical suggestions. Although none of the crew
could carry a tune, many of them remembered the new wave hit “Safety
Dance,” by Men Without Hats (Doroschuk, 1982). He also had a few people
suggest a search on YouTube for safety songs. He had a good chuckle over a
safety rap and decided he would suggest that Oliver occasionally play a
YouTube video at the safety meetings instead of having someone read a
newsletter out loud. Lucas was so pleased with the results that he decided to
run the contest every quarter, but with a prize of a dinner for two, instead of
time off.
11.8 Embed and Refresh
A year later, the pilot was deemed successful. There was a positive change in
the attitude of the crew and no impact on operational efficiency. Lucas said to
Charlotte, “I’m glad you took the initiative to try to make change. Sometimes,
it takes a fresh pair of eyes to bring in a new perspective.” “So…does that mean
I’m getting promoted?” Charlotte joked. Lucas laughed and said, “Keep this up
and you most certainly will be.”
Charlotte smiled. “Now that a year has passed, it’s time to do the fatigue
assessment. It’ll be easier this time since Oliver and Mason have bought into
the value it brings,” she said. Lucas said, “True, but don’t rest on your laurels.
We have to keep reminding people it’s important to operate safely.” Lucas then
started to hum the new song he’d heard at the morning safety meeting—the
winner of the latest safety jingle contest. “It’s been stuck in my head all
morning,” he said. “Our crew is more musically talented than I thought!” |
10 • Risk Based Process Safety Considerations 207
Table 10.2 Examples of good operationa l discipline for operations and
maintenance.
(Adapted from [49, p. Table 1])
Process Safety
SystemRBPS Element Examples of Good Operational Discipline During Transient Operations
Operating
ProceduresResourcing the operating facility adequately during the transition time; writing
safe start-up, shut-down, and emergency shut-down procedures, including
defining safe operating limits during the transition times; following these safe
operating procedures (e.g., do not exceed safe operating limits); maintaining
procedures; ensuring shift-to-shift consistency; and reviewing and validating
critical procedures
Safe Work
PracticesFollowing safe work procedures (e.g., permit to work; job safety analyses; hot
work, electrical isolation, etc.).
Training and
Performance
AssuranceDefining position qualifications for the start-up and shut-down times; testing for
theoretical understanding during the transition times; qualifying through skills
demonstration during the transition time; and scheduling essential refresher
training
Contractor
ManagementUsing qualified contractors (e.g., to install equipment or to inspect and
refurbish/maintain the safeguards)
Maintain Process
Integrity and ReliabilityAsset Integrity
and ReliabilityEnsuring an effective Inspection, Testing and Preventive Maintenance (ITPM)
program for all safeguards; resourcing maintenance teams adequately in preparation for planned or extended shutdowns; adhering to the scheduling planned maintenance on critical safeguards; using qualified personnel to inspect, test, and refurbish safeguards, as needed before start-ups or commissioningOperate Safe
Processes |
2.1 Establish and Imperative for Process Safety |27
The work to establish an im perative for process safety
parallels any other culture change a com pany would wish to
m ake. A clear organizational vision and mission should be
established, ideally with input from the front line. The vision and
m ission should be exciting, and be urgent enough to create
excitem ent and motivation for the employees. At the same time,
it should be achievable, so that it is not shrugged off as
impossible. Finally, the vision and mission should have a long-
term outlook, to assure everyone that the new process safety
culture is here to stay. (Ref 2.3)
Signs that an imperative for process safety have been
established include: The organization is very attentive to safety and process
safety. The organization can anticipate areas of potential
failure and maintain resilient processes and systems that
can survive upset and return to norm al operation despite
challenges. (Ref 2.4) Operational aspects of process safety are integrated into
operations, but corporate oversight for process safety is
m aintains independence. This helps align process safety
with operations, while helping avoid conflict of interest.
Sm aller organizations with lim ited staff with m ultiple
functions should think this through carefully (see also
section 4.3 ethics). Process safety resources survive budget cuts during
downturns. This does not mean that process safety
budgets are never cut. However, the process safety
com petency required to operate safely should not be
com promised. Management praises process safety as a value to the
com pany. The process safety organization has
strengthened due to its perform ance and has gained
influence in the decision-making process. •
•
•
• |
8. Format and design of job aids 83
Regarding color contrasts, some guidelines are:
• Only use color where it helps to convey meaning;
• White text on red, blue, green, brown or dark grey backgrounds;
• Black on white, or yellow/amber or beige background, and vice versa;
• Pink, purple and orange backgrounds have lower contrasts but are best
paired with black, white and black text respectively.
It is also possible to utilize tone variance with color variance, especially to cater
for color blindness. For example, a saturated red and a soft green.
Figure 8-4: An example of icon and color coding
|
218 INVESTIGATING PROCESS SAFETY INCIDENTS
investigation proceeds to the recommendation stage. If a problem or some
incompleteness is noted, then the iterative loop is reactivated.
After the tree is developed, an d before moving on to the
recommendations and deliberations, the team should ask, “Are there any
other causes that anyone had in mind at the beginning of this meeting that
are not included in the tree?” If additional causes are identified, the team
adds them to the tree if there is logic to support them. Some team members
may have specific concerns that the logic tree has not adequately resolved.
This is the point at which remain ing issues are brought forward and
addressed. It is important that any new causes also pass the necessary and
sufficient testing.
In the deductive process of identify ing root causes, known facts are
assembled and used to develop and test one or more possible scenarios. The
process normally requires multiple iterations of the cycle shown in Figure
10.4 until at least one plausible scenario is identified that fits all the known
facts.
If a scenario is disproved by the known accepted facts, the reasoning is
documented and the scen ario need not be invest igated further. If the
scenario needs additional data in order to be proven or disproved, then the
iterative loop path is followed and additional inform ation is gathered.
Sometimes this new information is very specific, precise, and limited in scope.
Examples of tasks initiated by this iterative loop include:
• Follow-up witness interviews,
• Revisiting or reexamining a certai n area of the incident scene, and
• Commissioning expert consultant opinions.
If the deductive process continues to indi cate progress, then additional
facts are sought or the logic tree is restru ctured. For example, one witness
stated a particular valve was open, yet the post-incident inspection found it
to be closed. The team must be careful to ensure that the valve is closed
because of the actions taken prior to the incident, and not as a result of post-
event response activities. The position of this particular valve may be a critical
item in determining which of two scenarios is the more probable case. The
incident investigation team would then initiate a short-term action item to
resolve this question.
If the deductive process has stall ed and no further progress seems
possible or likely, then the iterative loop calls for application of inductive |
23. Working with contractors 307
23.4 Key learning points from this Chapter
Key learning points include:
• Working with contractors can create additional Human Factors risks.
• Risks of working with contractors should be included in task assessment
and planning.
• Time and resource should be applied to provide the support contractors’
need, especially where they are unfamiliar with the site, its hazards,
and/or its safety procedures.
• Specific actions, such as joint planning, mobilization and readiness
reviews, can help ensure that contractors are effectively supported.
|
6 • Recovery 104
Figure 6.2 Transient operating modes associated with abnormal and
emergency operations.
(Adapted from [15])
This section continues with how abno rmal situations can be addressed
(Section 6.4.2) and concludes with a description of how the operations
group can respond to expected deviations with a successful recovery (Section 6.4.3).
6.4.1 Recovering from an abnormal situation
Recovery actions for abnormal situ ations in both continuous and
batch operations are the operating group’s response efforts to keep
the process under control—to recover from the abnormal situation. During the normal operation, the proc ess is operating within its safe
limits for both steady-state cont inuous and unsteady-state batch
|
358 | Appendix F Process Safety Culture Assessment Protocol
before it is m ade. Establishing an MOC program only to
com ply with a regulation and leave a paper trail for each
change does not fulfill the real purpose and intent of MOC.
This is a form of com placency.
Understand and Act Upon Hazards/Risks
126. Does the organization know what standards govern the
design, construction, m aintenance, operations, and
m aintenance of its facilities? As with the boundaries, scope,
and philosophy of application of the PSMS itself, has the
organization taken a m inim alist view of which recognized and
generally accepted good engineering practices (RAGAGEP)
applicable to the organization?
127. Does the organization follow its own procedures or does it
regard them as not m andatory?
128. Are hazard/risk assessments performed consistently for
engineering or operating changes that potentially introduce
additional risks? Who decides if a risk assessment should be
perform ed? What is the basis for not performing a risk
assessment?
129. How are risks for low frequency – high consequence events
judged? Is there a strong reliance on the observation that
serious incidents have not occurred previously, so they are
unlikely to occur in the future? What is the basis for deem ing
risks acceptable – particularly those associated with high
consequence events?
130. Are the appropriate resources applied to the hazard/risk
assessment process?
131. During HIRAs/PHAs are hazard scenario or type of hazard not
included in study because it is bad news and will obligate
m anagem ent to do something tangible to reduce the risk, i.e.,
it will create a liability for management to spend resources to
m ake the necessary changes to reduce the risk?
132. Do HIRA/PHA teams intentionally avoid m aking
recomm endations by applying risk rankings, IPL credits, or |
OPERATING PROCEDURES, SAFE WORK PRACTICES, 405
CONDUCT OF OPERATIONS, AND OPERATIONAL DISCIPLINE
performance targets. The proc ess parameter readings and evaluation portion of operating
discipline and engineering discipline are closely related. Engineers should define what
operators need to evaluate and define how th e evaluation is made. Operators or engineers
should be thinking about what the process para meter readings mean, not just recording them
by rote. When the criteria are not met, the op erator makes decisions (or informs supervision
to receive instructions) to take actions to retu rn the process to the predetermined values. For
example, if a pump should have a certain discharg e pressure to maintain a safe operating limit,
that range is defined by the engineer and included on the evaluation sheet. If the range is
exceeded, the operator notes the exceedance an d notes on the evaluation sheet what is done
to return to normal. The engineer (or unit supervis ion) then closes the loop by shift/daily review
of the evaluation sheets to ensure thes e concerns are adequately addressed.
One of the most common failures in conduct of operations is to have ineffective process
evaluation sheets that have operators simply “taking readings” without evaluating the
equipment. When this happens, the value of understanding how the process is performing
and the opportunity to identify potential up sets before they happen, can be missed.
Good practice for operator evaluation is to include both outside operator evaluations and
board operator evaluations. Since data from th e DCS can be printed or stored, it is often
assumed that operators do not need to collect or write down that information. However, the
purpose of writing the information down isn’t to collect it for someone else. The purpose is for
the board operator to evaluate that variable or parameter and take pre-determined action if
the expected value isn’t observed. Suggestions on how to create an effective process readings
and evaluation sheet are included in Appendix F.
Process Indicators. Engineers should identify process indicators used to track process
safety, environmental, reliability, and economic optimization and have a defined schedule of
review and action taken. Documentation on th ese indicators should include the operating
range, steps to correct the situation if out of ra nge, who is responsible to monitor the indicator
and at what frequency. Safe operating limits are an example of a process indicator. (Refer to
Section 10.5.)
Sample Collection. The process sample schedule should be defined by the engineers,
documented, and be part of standard operating procedure. A good practice is to develop a
process map of defined sample points to optimi ze the round. PPE and other safety precautions
are identified for each sample point. The schedule should include: the sample point, frequency,
technical analysis and target ranges, and action s to take if the sample is out of range.
Operator Line-Up. The most fundamental responsibility of an operator is to understand
and know the position of every valve in their area of responsibility and to control the energy
among all points of material transfer. This resp onsibility is commonly referred to as “line-up.”
While engineers usually don’t operate or “line-up ” equipment, they should clearly understand
this aspect of an operator’s job and take it into account when designing equipment, developing
operating procedures, and conducting operator training.
Practical activities to support consistency in operations and minimize line-up errors,
collectively called “walk the line” are discusse d in two papers by J. Forest. (Forest 2014 and
Forest 2018) |
Piping and Instrumentation Diagram Development
366
piping system. Steam hammering is a phenomenon that
may happen in steam–condensate two‐phase flows where the steam carries the pockets of condensate and smashes them into pipe obstacles like elbows, partially open valves, etc. and damage them.
This concern can be solved by placing steam trap on
pipes with a chance of receiving steam–condensate mixed fluids. This stream trap prevents steam from pass -
ing. As steam traps are available only up to certain sizes (say up to 6″), if the pipe is large enough, instead of a steam trap, a small steam–condensate vessel with level control could be placed.
The generated condensate along the length of a steam
carrying pipe should be removed from the steam as soon as possible. Therefore steam traps are placed along the route of the steam transferring pipes at certain intervals and the steam pipe should be installed so that they slope toward the steam traps. The steam trap inter -
val is case specific and depends on several factors including pipe size, the effectiveness of pipe insulation, and the difference between steam temperature and ambient temperature.
Steam traps are connected to the steam pipes through a
device named a drip leg. Wherever we need to put drip leg, it should be from the bottom of the steam pipe. The detail of drip legs are not always shown on main P&IDs. If the detail of drip legs is not on the main P&IDs they could be on auxiliary drawings or even in piping documents.
After all these consideration there could still be some
condensate in the steam pipes. To avoid directing the generated condensate to the steam branches, all the steam branches should be taken from the top of the steam header. This can be covered as a note in P&IDs.
As the bad reputation of valves in steam services is
widespread, care should be taken to use suitable valves.
17.7 Condensate Collection Network
The condensate collection network is the mating system for the steam distribution network. The condensate col-lection network collects the generated condensate from intentional and/or unintentional conversion of steam. This conversion happens because of heat transfer. The heat transfer could be intentional in steam heaters or unintentional in steam transfer pipes.
As there are generally three types of steams: low pres -
sure, medium pressure, and high pressure, there could be three corresponding condensate collection systems, including low pressure condensate, medium pressure condensate, and high pressure condensate.
17.8 Fuel as Utility
Fuels are needed wherever there are burners in the plant. Burners can be used in different pieces of equipment including furnaces, boilers, some HVAC equipment, and others. Burners are a piece of equipment that has the duty of generating a flame and also maintaining it.
Fuels could be gas, liquid, or solid form.A famous solid fuel is coal. If the usage of coal is justi-
fied it is generally used in a way such that distribution of it is not necessary. Therefore, there is no such thing as coal distribution system in an extended scope.
Here we cover two main types of fuel: fuel gas and fuel oil.Generally speaking fuel gas is the preferred fuel for
burners rather than fuel oil or coal.
17.8.1
Fuel O
il
Fuel oil is another option as fuel in burners. Fuel oil is
less favorable than fuel gas for burning.
17.8.2 Fuel G
as
Gas burners need to be supplied by streams of fuel gas
and air. In some plants, there is one network to distribute natural gas both for blanketing purposes and as fuel gas (if natural gas is used as fuel gas). However, in some other plants there are two separate networks: one for blanket -
ing gas distribution and the other for fuel gas distribu-tion. This could be because the blanketing gas specifications required by the client could be different from the fuel gas specifications. For example, in some Table 17.5 Some t ypical utility users in process plants.
Steam type Pressure Temperature Applications
LPS
(low pressure steam)100–200 K Pag 120–135 °C In utility stations, In heat exchangers (steam heaters)
MPS(medium pressure steam)1000–2700
K
Pag 185–230 °C In heat exchangers (steam heaters)
HPS(high pressure steam)>4000
K
Pag >250 °C In steam turbines, as process steam |
PREPARING THE FINAL REPORT 305
Table 13.2 Findings, Causal Factors, Root Causes and Recommendations
Finding Causal Factors Root Causes Recommendations W ho By
Waste product
streams flowing
from multiple process units to the power house holding tank were
chemically
incompatible. An exothermic reaction started in the waste material holding
tank resulting in
overpressure of the tank. The waste
material holding
tank was originally designed as a storage tank. It was not designed with cooling or
pressure relief for
a chemical reaction.
Management
of Change
(MOC) procedure was not correctly followed when additional
waste streams
were supplied to the tank
Staff carrying out the modifications
did not
remember to follow the MOC procedure 1. Review the MOC
procedure to ensure
it complies with corporate practices and requirements. Mike Feb
2. Issue safety bulletin to demonstrate the need to follow MOC procedure. Ben Mar
3. Include a training pack on MOC procedure with the
annual safety
refresher training. Sue Jul
The chemistries of the processes that send chemicals to the holding tank
have changed in
the 30 years since the power house process was modified allowing waste products to
be used as a
supplementary fuel supply to the boiler. No control of the waste materials being
sent to the power
house by various process units. Failure of management and staff to recognize the
risks associated
with uncontrolled mixing of waste chemicals
No PHA assessments carried out on the mixed waste streams from the
processes 4. Conduct a PHA
assessment of all waste and intermediate streams
where mixing of
chemicals can occur.
5. PHA on boiler fuel waste to be completed before restart of waste
stream Bob Dec
PHAs have not
been conducted on the process for over 10 years. No program for redo of PHAs on the power house 6. Review scope of PHA program to include power house and to ensure that all services areas are included. Ted Dec
Warm weather on the day of the incident likely escalated the
reaction rate. Failure of
management and staff to recognize the
risks associated
with higher ambient temperatures 7. Ensure that PHA scope includes consideration of ambient
temperatures up to
50 °C. Dan Dec
|
INCIDENT IN VESTIGATION TEAM 99
example, the manager of a facility might lead an investigation, but the cause
of the incident may be associated wi th management system problems for
which the manager is responsible. Under these circumstances, the peer and
senior management review should provide independent oversight and a
path to further action, if required.
Often, the investigation team leader’s first task is to systematically
identify the resource requiremen ts and recommend individuals and
organizations that should participate. As with management’s selection of the
team leader, the leader’s selection of the team members will be based on the
severity and nature of the incident. The team leader may choose to involve
experts on an as-needed basis, allowing them to focus on key areas without
affecting their normal work schedule. These experts may be internal to the
organization or be contracted from an outside source. Part-time and expert
participation should be carefully ma naged to ensure the scope is defined
and adhered to, competing prioriti es are considered, and costs are
controlled.
The organization’s in cident investigation ma nagement system should
specify the team leader’s responsibilities and authority. Once selected, the
team leader should meet with senior management to review and agree on
all responsibilities and authority (e.g., selection of team members, financial
and technical resources) associated with the investigation, which should then
be clearly documented. Typical leader responsibilities may include:
• Ensuring incident investigation activities adhere to company, site,
and scene safety practices
• Ensuring that restricted access zo nes are identified and access is
controlled
• Ensuring that evi dence is preserved
• Ensuring that the investigation team activities result in minimum
disruption to the rest of the facility
• Directing and managing the team in its investigation, setting
priorities, and ensuring the objectives and schedules are met
• Serving as principal spokesperson for the team and point of contact
with other organizations and interested parties, including
government agencies
• Preparing status reports and ot her interim reports documenting
significant team activities , findings, and concerns
• Keeping upper management advised of status, progress, and plans
• Organizing team work including schedule, plans, and meetings
• Assigning tasks to team members in accordance with their individual
skills, knowledge, capabilities, and experience |
16. Task planning and error assessment 187
16.5 Key learning points from this Chapter
Key learning points include:
• It is possible to foresee error-likely tasks and situations.
• The potential for error-likely situations and error should be foreseen, as
far as possible, during planning tasks, and when creating work
instructions and Permits to Work.
• Work instructions should include mitigation for potential error-likely
situations.
|
290
• Are equipment designed such that they cannot be
operated incorrectly or carried out incorrectly, e.g., are
valve operators on quarter-turn manual valves configured so that when th e valve operator is in-line
with the flow direction the valve is open and when the valve operator is perpendicular to the flow direction the valve is closed?
• Have DCS and other control panels been designed following well-known conventions for displays, colors, and other characteristics th at will make operations
intuitive and easy-to-understand and therefore reduce human error?
• Have DCS and other control panels been evaluated with respect to alarm management principles and conventions?
• Can rotating equipment and other machinery be stopped locally and from central control rooms or locations?
• Have other design and op erational conventions been
followed so as to obviate human errors?
• Has the opportunity to simplify procedures associated with the process, particularly emergency procedures, been evaluated to simplify the procedures, even if the ch ange was proposed for a
different reason?
11.11 CONDUCT OF OPERATIONS / OPERATING PROCEDURES
Conduct of Operations (COO) is a PS M/RBPS element that covers a broad
range of process safety program activi ties. It is a very important aspect
of process safety as this is elem ent of the program where operating |
INVESTIGATION M ANAGEM ENT SYSTEM 57
questions that are premature or outside the scope of their knowledge or
experience.
The government agency will seek to interview employees. Unless
subpoenaed to testify, employees ma y not be required to submit to
interviews. Moreover, employees are entitled to have counsel, either
company counsel or their own, present during agency interviews. The
company should inform employees of these rights in a factual way that does
not obstruct the government ’s investigative process. Consider involving
legal counsel in these situations.
In addition to conducting interviews, the government agency may also
seek documents and physical evidence. Withou t a warrant, government
investigators may or may not be authorized to take documents. Consider
involving legal counsel when the govern mental agency requests documents.
Generally, a facility should allow reviewing and copying those documents
that the facility is required to keep and make available to the agency. Such
documents may include copies of process hazard analyses, p r io r incidents,
and prior compliance audits. Requ ests for other documents should be
accepted in writing and considered by management and counsel. Procedures
should be implemented to track an y documents supplied to an agency.
Many chemical processing facilities use nonproprietary technologies that
present common hazards. This allows for meaningful sharing of incident
investigation findings throughout the industry. The management system
should address methods for sharing incident causes and lessons learned
through appropriate channels so that others can benefit. It is often a
challenge for a company’s managem ent to share the details of
investigations due to litigation concerns. However, when similar facilities
might benefit, finding a way to share di splays a company’s interest in driving
improved industry safety performance. In addition to litigation issues, practical logistics sometimes make
it difficult to communicate lessons
learned within and between companies. Determining which people or companies have a potential interest in the incident and learnings can sometimes be problematic. Despite these challenges, broad communication of investigation findings is a recognized good practice.
|
132 GUIDELINES FOR MANAGING ABNORMAL SITUATIONS
The third most common failure was the lack of understanding the
i m p a c t o r e f f e c t o f a p r o c e d u r a l a c t i o n o r f a i l u r e t o e x e c u t e a
procedural action.
In total, these top three failur es account for 35 of the 40 (87.5%)
procedural execution failures under abnormal situations. [ASM®
Guideline, Effective Procedural Practices ] (ASM® Consortium - Bullemer,
Hajdukiewicz & Burns 2010).
Typical tools and methods for eval uating the content and accuracy
of process procedures are similar to HIRA tools: HAZOP, What-Ifs, and
Checklists.
An effective approach is to cond uct a procedure observation audit
that involves an observer following along with the procedure as the
operator conducts the work. The ob server ensures that the steps are
followed in order and highlights where any steps are missed, or
identifies confusing items. Another a pproach is to ask a newer operator
to do this task following the step s in the procedure (highlighting any
missing or confusing items that are encountered).
Ensuring that operator technician s follow the most current approved
procedure can be a challenge. Prin ted procedures can quickly become
uncontrolled copies that are outdated or damaged in use (e.g., spills,
tears, missing pages). Electronic copi es of procedures can be difficult to
access quickly in an emergency, espe cially if a power or computer
network outage occurs. Thus, a suitab le balance has to be struck and
procedure control management pr actices must be established,
communicated to personnel, and adhe red to ensure that up to date
procedures are followed.
5.5.2 Emergency Procedures
Responding to emergency conditions requires planning and training.
Identifying the normally anticipate d types of initiating causes for
emergencies such as chemical leaks, fi res, loss of a critical utility supply,
on-site transportation events, or natural weather events are often
already in place across most of the chemical industry. Emergency
procedures for unusual, infrequent, or near impossible events, however,
are not as easy to develop. Theref ore, identifying in advance possible
abnormal situations that may requ ire an emergency response should
start with the HIRA studies of the process plant and associated utility |
Conducting PHA Revalidation Meetings 137
Typically, for a human factors checklist Update , these discussions include
asking questions such as:
• Are housekeeping and the general work environment the same or
have they been improved?
• Have there been any changes in the accessibility and availability of
controls and equipment?
• Is the equipment labeling still accurate and well maintained?
• Have there been any changes in th e feedback/displays of controls?
• Have there been any changes in personnel workload/stress (e.g.,
due to changes in staffing levels, experience or competency,
assignment of new duties)?
• Have the procedures been updated to reflect changes, and have
they been field validated?
• Have workers been trained on changes, and is refresher training up
to date?
Using both Redo and Update approaches is conceivable for complementary
analyses that span the PHAs for multiple units. For example, a comprehensive
facility siting study might have to be Redone for one particular unit and Updated
for all the others. In that case, the expe rts may solicit more specific scenario
information from the core revalidation te am, but the conduct of the revalidation
is essentially the same as an Update.
7.1.3 Revalidation of Supplemen tal Risk Assessments
The core analysis of any PHA includes at least a qualitative risk assessment. The
mere fact that the PHA team made any recommendation implies that they
concluded the “as found” risk exceeded the organization’s tolerance or that there
were other opportunities for impro vement. However, past judgments have
proven to be highly subjective, depending on the individual team members’
personal knowledge, experience, and interests. Thus, many organizations now
require that their PHAs include quanti tative risk analyses that are more
consistent within a particular study, acro ss all their PHAs, and across the entire
organization. Often, only an order-of-magnitude risk analysis is required to align
the PHA team’s risk judgments with the organization’s risk tolerance as
expressed in its order-of-magnitude risk matrix. These simplified quantitative
risk analyses, such as LOPA, follow a conservative set of simple rules that are
standardized across the organization. |
INVESTIGATION M ANAGEM ENT SYSTEM 69
Leader training deserves special attention. Training for leaders could
include role-playing for witness interv iews, conflict resolution, applicable
laws, regulator powers, and confidentiality issues. They should feel free to
request help or training when needed, especially at the early stages of an
investigation. Other investigators ma y handle low to moderate complexity
incidents. Leader training fo r lo w to m o derate co m plexity incid ents
usually consists of classroom training plus expe rienced coaching during
their first few investigations. These individuals can also benefit from
participating as team members on an incident investigation led by an experienced leader. Low complexity in cidents may require one helper (team
member) to support the leader in
data gathering and analysis. Individuals
who will lead major or complex investigations should be able to handle almost
any incident within the company. The training for this level usually consists of considerable experience leading low to moderate complexity incidents and
additional classroom training an d coaching by a more experienced
investigator during their first few major
investigations.
In some cases, employees, rather th an supervisors, lead investigations for
lower level incidents. Companies have found it beneficial for employees to
feel ownership of the investigation results. This philosophy helps
encourage workers to report more near -misses by reducing the fear caused
when a supervisor leads the investigation. Most incidents are low complexity. Many of these are near-misses and benefit from investigation by
persons who are closest to the process.
Chapter 6 provides details on the selection, and organization of
incident investigation teams.
4.2.7 Emphasizing Root Causes
Identifying causes is a major objective of the investigation process, and this
should be specified in the management system. Initial selection ( or custom
development) of the root cause determination process will require special
attention to the concept of multiple causes and to underlying system-
related causes. The approa ch should emphasize find ing management system
weaknesses and failures versus placing blame on individuals. Some
employees may need to adjust to this approach, partic ularly if past methods
did not encourage discovery of causal factors and associat ed root causes.
Everyone involved in the resolution process for recommendations needs to
understand the concept of multiple root causes of an incident. |
Plant Interlocks and Alarms
349
TAH
TAL
TALLTLA
125
TLA
125
TLA
124
TL
PAH
PALPC
131
PAH
131PAL
131PAHH
153
PI
IH
L153
PT
151PC
131
PT
131123TE
124TT
124TAH
124TAL
124TALL
124
Figure 16.26 Some e xample of alarm systems on a P&ID. |
334 | Appendix E Process Safety Culture Case Histories
empowered the hauler and the well owner to make this
verification. However, where does em powerm ent end and
become abdication of responsibility, a culture negative? Did that
happen in this case?
The crude and inconsistent methods of determ ining the B S& W
to hydrocarbon interface was prevalent throughout the industry.
This suggests that hydrocarbon could be present in many such
B S& W pum p-outs. If som e in the industry considered this to be a
hazard and others did not, were there barriers to openly and
frankly communicating this concern? Were there barriers to
learning and advancing the culture ? How did the transfer of safety
responsibility between the three com panies involved in the
operation create other opportunities to weaken safety culture?
Maintain a Sense of Vulnerability, Understand and Act Upon
Hazards/Risks, Ensure Open and Frank Communications.
E.42 Blindness to Chem ical Reactive Hazards
Outside the Chem ical Industry
A plastics extrusion plant suffered a m ultiple
fatality incident when workers were attempting to
open a waste plastic tank to clean it. The vessel pressure gauge
showed no pressure in the vessel, but the gauge had become
blocked with plastic and did not show the actual pressure in the
vessel. After half the bolts fastening the vessel cover had been
removed, the cover flew off, killing the three workers. The cover
also severed hot oil lines, leading to a fire that took several hours
to extinguish.
Investigators (Ref E.9) discovered that the plastic had a
reactive chem ical hazard, an exotherm ic decom position reaction
at hot temperatures. As the plastic in the catch tank cooled on the
outside, the plastic in the center rem ained hot and m olten,
allowing the decom position reaction to continue to build
pressure, while the solid plastic outer shell shielded the pressure
gauge from detecting the high pressure in the tank. Actual
Case
History |
Conducting PHA Revalidation Meetings 153
• Trying to force an Update of the PHA when a Redo is necessary.
Updating a poor PHA can result in a poor revalidation product,
without saving time or resources
o The best course of action after making this revelation
during the PHA sessions is usually to reconvene the team
after the study leader has prepared for a Redo
• Failing to consider the accuracy of previous PHA entries during an
Update. This can allow errors to perpetuate in a PHA
• Underestimating the meeting time requirements prior to the
sessions, and therefore not having enough calendar or meeting
time scheduled for the revalidation
• Failing to perform the core methodology appropriately. For
example:
o Not considering causes if they originated in equipment or
processes beyond the physical boundaries of the PHA
being evaluated or taking credit for safeguards when
evaluating consequences
o Claiming invalid or ineffective safeguards or rejecting
plausible scenarios as non-credible (i.e., "that has never
happened here")
o Using the same safeguards repeatedly without any real
thought as to their effectivene ss or specific application to
a scenario (e.g., overuse of “Operator Training and
Knowledge”)
o Failing to detect common cause failure mode issues
between process control and safety/emergency shutdown
systems
o Inconsistently ranking the risk or consequence severity of
similar scenarios
o Being overly optimistic in estimating consequences or
likelihood, resulting in an underestimation of risk
• Failing to address facility siting, hum an factors, external events, or
other required topics (typically as a complementary analysis)
• Making recommendations that are either too vague or impractical
to implement |
84 | 3 Leadership for Process Safety Culture Within the Organizational Structure
Leaders should understand that process safety culture is
fragile. It can go from good to bad relatively quickly, but it will take
a lot longer to reverse that trend. It takes years to create a positive
PS culture, but only a few errant minutes to decimate it.
Influence and Inspire
Great process safety leaders have the ability to positively
influence their subordinates’, peers’ and even superiors’ behavior
and work practices and inspire them to do the right thing. They
earn the respect of those that they lead by both word and deed
and this respect is not based on fear. Those with responsibilities
in the PSM S will work hard to avoid disappointing leaders they
respect. Although others may exhibit leadership behaviors and
assume a leadership role in the PSMS, facility managers are in fact
leaders of the PSMS. Therefore, more than others, facility
m anagers should strive to be great process safety leaders. Good
leaders serve as role models to the subordinates or their
colleagues. To be most effective as PS leaders, people need to be
capable of influencing up, down, and across the organization.
Act as Change Agents Process safety leaders should be change agents, developing
strategy for developing the process safety culture, and then
improving and sustaining it. When selected, they volunteer, or
they m ake them selves known simply by setting a positive exam ple
with their conduct. They should know the organization’s process
safety culture strategy and the rationale behind it. They should be
the primary communicators of the strategy, shepherding it
through the organization to successfully implement and sustain it
(Ref 3.17).
Perhaps the most im portant leadership skill is to make the
business case for process safety. This entails understanding risk
at the operations level and being proficient at com m unicating that |
APPLICATION OF PROCESS SAFETY TO ONSHORE PRODUCTION 97
shell to weaken and fail catastrophically . The NFPA has been active in alerting
firefighters to this potential and of appropriate response measures. In upstream
facilities it is common to install water sprinklers on pressure vessels that hold large
inventories. The aim is to keep the vessel shell cool until a fire is extinguished. This
protects against BLEVE events.
Key Process Safety Measure(s)
Process Knowledge Management : As in the Lac Megantic incident, it is important
to understand the properties of the materials being handled and use the correct
metallurgy for the equipment, piping and other accessories.
Conduct of Operations : While both the Buncefield UK and Jaipur India incidents
were noteworthy, they both started with a tank overfill. Paying attention to
operations and conducting them appropriat ely each and every time helps to prevent
significant incidents. Also, as in Buncefie ld, when a critical instrument (here a level
gauge) signals a problem, this should be addressed.
5.2.4 Loss of Well Control
Risks
There are several activities during the production phase that can result in a loss of
well control. These are primarily interventions and workovers to maintain or
enhance reservoir production. Refer to Chapter 4 for discussions on these topics.
A potential cause for loss of well control, onshore or offshore, is a wellhead
mechanical impact or corrosion failure that allows well fluids to escape. The barriers
protecting against this event are bollards, the Christmas tree installed on the
wellhead, and a subsurface safety valv e (SSSV) where one is installed.
Another production activity that can result in a loss of well control is associated
with gas or water lift activities. These production enhancement procedures involve
sending gas or water into the annular space and then injec ting this into the
production tubing near the bottom of the well. A loss of hydraulic head or gas
pressure, for example due to surface line da mage near the well head, can result in
reverse flow up the annular space and a lo ss of containment event. The Christmas
tree valve is designed and installed to close off this reverse flow potential.
Subsurface safety valves, if installed, a pply to the production tubing and not the
annular space, and they are not a barrier fo r this event. For the subsurface safety
valve to be effective in a gas lift operation it must be set below all the gas lift
injection points in the tubing. This is seldom practical.
Key Process Safety Measure(s)
Asset Integrity and Reliability : Arranging and protecting wellhead equipment to
minimize the likelihood of mechanical impact aids in preventing loss of well control.
Inspecting for and addressing any corrosion issues through a corrosion control
management system reduces the likelihood of these events resulting from corrosion
failures. |
5 • Facility Shutdowns 80
modes: preparing for a facility project-related shutdown (Section 5.4)
and starting up afterward (Section 5.5).
5.4 Preparing for a facility project-related shutdown
The shut-down for a facility shutdown—transient operating mode
Type 5, Table 1.1—is another transi ent operating time that requires
non-routine procedures in ad dition to the normal shut-down
procedures when stopping the proc ess equipment. Facility shutdown
projects are complex, involve man y different groups, and have work-
related timelines for weeks or even months, including the preparation time beforehand and the executio n time during the project. The
additional time for a facility shutdo wn was illustrated in Figure 4.3.
Personnel in the operations and maintenance groups typically
have additional, sometimes specifical ly, project-related procedures for
the steps used to prepare the proc ess equipment for the extended
period. These additional administrat ive controls, including Safe Work
Practices (SWP), help reduce the li kelihood of personnel exposure to
any hazardous materials and ener gies when they are adequately
written, understood, and followed [14] [21] [37]. Facility shutdowns typically take more time than a process shutdown due to these
additional administrative controls for shutting the equipment down,
preparing the equipment, working on or maintain the preservation
procedures, and then preparing the equipment for handover back to
the operating group.
Since these additional procedur es may not be performed very
often, it is essential that everyone involved in a facility shutdown understands what the different steps are, has the operational discipline to follow these steps, an d can quickly recognize and respond
properly when things are not goin g as planned. When hazards have |
CASE STUDIES/LESSONS LEARNED 185
7.2.2 Incident Overview – Texaco Milford Haven
This case study concerns the release and ignition of flammable liquid and
vapor hydrocarbons from a failed 30 -inch (0.76m) flare knockout drum
outlet pipe.
From the initial electrical disturbances that started at about 07:20 due
to a thunderstorm, to the failure of th e pipe at 13:23 and its ignition some
20 seconds later, there we re a number of failed opportunities by operating
staff to recognize an escalating problem on the facility and take appropriate
action. However, operators were handling many issues at the facility and
were focused on keeping the Fluidized Catalytic Cracker Unit (FCCU) from
shutting down. At one stage, an outlet valve from a distillation column
closed and failed to re-open, but the feed to the column continued until the
level was well above normal. As the column level began to build, the
pressure increased and relief valves op ened, carrying liquid and vapors into
the flare line. Problems with high liquid levels elsewhere on the unit led to
further demands on the flare system, including the use of hoses to drain
hydrocarbons from one vessel and into another.
Faulty and unreliable instrumentation made it difficult for operators to
establish what was going on. The DCS pr oduced hundreds of alarms, all with
the same level of priority but with no overview screen that would have
provided operators with an indication of discrepancies on the mass-
balance.
A modification made several years before meant that an automatic
pump-out facility for the flare knockout drum was not lined up for service.
Previous inspection of the flare line ha d showed that it was thinning and it
was due for replacement in the next major turnaround in the following year.
However, the thickness measurements did not include the point of failure,
which would have indicated that the dr um was in a far worse condition than
the areas that had been measured.
Venting of hydrocarbon liquid and vapors continued from several
sources until the flare knockout drum was overfilled and large volumes of
liquid were carried down the 30-inch piping. It failed at 13:23 at the
weakened 90° elbow, the second bend downstream of the knockout drum.
Up to 20 tonnes (44,000 lbs) of hydroc arbons released and ignited some 20
seconds later. |
Manual Valves and Automatic Valves
115
decide to arbitrarily pick a failure position, such as FC
or FO (which are cheaper than FL), and assign it to the automatic valve. However, some clients ask the practitioner to use a second decision tool if safety does not dictate a failure position. In such cases, the second decision tool (equipment protection) can be used and then followed by process smoothness if needed. This means that if safety does not dictate the failure position of the valve, the designer should check what the best failure position of the valve would be to best
prot
ect the equipment.
A good example of deciding where to locate failure
positions based on equipment protection is to make a control valve on a minimum flow line on a set of centrifugal pumps, all of which are FO. In this case, the decision is made not based on safety, but to protect the pump. Whether this valve is FO or FC does not impact the safety of the plant; however, if it is FC, it will impact the integrity of the equipment or pump. This means that if the valve is FC and instrument air is lost, then the
minimum f
low line
of the pump will be blocked and the pump will not be protected against low‐flow cases and may be damaged.
Process smoothness is the last decision element if the
first two (safety and equipment protection) cannot deter
mine the failure position of the valve. Process smoothness basically recommends the failure position that is the best for the process and that minimizes the fluctuation magnitude and extent when a failure happens.
The concept of valve position is summarized in
Table 7.12. When there is no constraint exerted by safety, equipment protection, or process smoothness, the failure position is decided based on economic factors; if FO and FC valves are the least expensive automatic valves, then one of them is selected. And sometimes the fail position is not mentioned in the P&ID at all.
7.10.3
Mor
e Concepts about Failure Position
of Automatic Valves
●What Is the Failure in Failure Position Discussion?
As was mentioned previously, failure means losing the
driver. Driver is combination of all energy streams that
direct the valve actuator (and consequently the valve
stem) to a specific position. So, in this context, failure
does not refer to mechanical failures or any type of jamming.
Table 7.13 shows the different actuators and their drivers.Table 7.12 Failur e position of automatic valves.
Only for: Automatic valves; blocking or throttling
Concept Position when losing “operator”
Examples
FO FC
Acronyms
FC, FO, FL, FISafety
Equipment protection
Process smoothness
Table 7.13 Failur e reasons of different actuators.
Type Symbol Actuator driver(s) Failure cause(s)
Diaphragm actuator ●Instrument air
●DC electricity ●Losing instrument air
●Losing DC electricity
Piston actuator ●Instrument air
●DC electricity ●Losing instrument air
●Losing DC electricity
Motor‐operated actuatorM ●AC electricity ●Losing AC electricity
Solenoid actuatorS ●DC electricity ●Losing DC electricity |
orders of magnitude less than the aqueous ammonia tank truck. See
Table 15.4 for a comparison of the op tions based on mass differences.
15.5.6 Conclusion and Action
The design team ultimately chose to use anhydrous ammonia vapor to
supply the SCR. Receiving ammonia in the anhydrous vapor form was
determined to be an economically vi able option, and the safety analysis
indicated that the vapor form of anhydrous ammonia was safer than
design options incorporating eith er liquid anhydrous or aqueous
ammonia.
In comparing both the anhydrous va por and aqueous liquid options to
the liquid anhydrous option, using th e vapor decreases risks along the
piping run without introducing ne w risks to the system. Based on
modeling analysis perfor med for the piping run, the liquid aqueous 417 |
106 GUIDELINES FOR MANAGING ABNORMAL SITUATIONS
4.3.3 Skills and Competencies of Trainers
Training may be provided by a vari ety of means, but the objective is
always the same—to help plant operat ors to be successful in meeting
their assigned responsibilities. Tr aining tools and techniques are
discussed further in Section 5.6. Success can be measured by the
number and severity of near-misses or incidents that occur, the number
of emergency situations, and the nu mber of abnormal situations that
have occurred. More details of le ading and lagging indicators are
provided in Chapters 5 and 6.
The quality and success of the tr aining program will most likely
depend on the personnel providing the training. These personnel are
typically assigned as Trainers across a plant site or within a specific
process unit. They may report to a central training organization or a local
process unit leader. The success of th e Trainer often depends upon that
person’s formal training, years of tr aining experience, knowledge of the
chemical process, interpersonal sk ills, willingness to share but also
listen, and measurement of traini ng progress against objectives.
Depending on the size of the facility, the or ganization’s personnel
configuration, and the available st affing, trainers may be assigned
additional tasks. Therefore, it is re commended to have the trainer’s role,
responsibilities, and objectives exp licitly documented. Any changes to
the trainer’s documented scope could affect the overall success of the
training program and should be considered and managed via the MOC
process.
With respect to management of ab normal situations, the training
curriculum should include, at a minimum, the topics that are covered in
Section 4.3.2.
4.4 SUMMARY
This chapter has provided guidance to organizations in the process
industries about organizing and structuring training on management of
abnormal situations, including advice on trainer competencies, training
programs, and focused training topics.
Chapter 5 will introduce the read er to tools and methods for
management of abnormal situations including the range of abnormal
situation control options. Section 5.6 provides advice on training and drills. |
221
Chemical Sites in 2002. The Guidelines desc ribe a risk-based approach to
managing chemical facility security that allows assessment of a wide
range of threats, ranging from vandalism to terrorism. With the
recognition of threats, conseque nces, and vulnerabilities, and the
evaluation of security event risks, a security management system can be
organized to more effectively miti gate the risks identified in the
assessment.
Several trade associations, such as the American Petroleum Institute (Ref
9.2 ANSI/API) and states require companies to use security risk
assessment (SRA) or security vulnerability assessment (SVA) methodologies that meet the design criteria set forth in the CCPS
Guidelines . New Jersey allows facilities to use CCPS or CCPS-equivalent
SVAs to meet the requirements of Administrative Order 2005-05 (see Chapter 10); Maryland and the City of Baltimore also allow facilities,
subject to their chemical security requirements, to use the CCPS or a
CCPS-equivalent SVA methodology.
The U.S. Department of Homeland Security also adopted elements
of the CCPS methodology as part of the Chemical Facility Anti-Terrorism
Standards (CFATS). (Ref 9.5 CFATS) The elements of a typical SVA
approach are shown in Figure 9.2, which describes the methodology published by CCPS in Guidelines for Analyzing and Managing the Security
Vulnerabilities of Fixed Chemical Sites (Ref 9.4 CCPS).
Upon completion of an SVA, a report or other documentation is
prepared to communicate its results to management for appropriate action. The report should be carefu lly protected as company-sensitive
information, because it includes desc riptions of identified vulnerabilities
and related countermeasures recommended to address those vulnerabilities.
9.6 INHERENT SAFETY AND CHEMICAL SECURITY
Application of inherent safety (IS) pr inciples may allow a facility to go
beyond traditional physical security measures. Physical security includes
such considerations as security officers, barriers, and surveillance
equipment. However, some assets may lend themselves to security evaluation using IS concepts, in addition to physical, technical, and even cyber security options. A combination of these strategies, that may also |
122
low oxygen content or toxicity. An in herently safer system is a rotating
pressurized water spray head that does the cleaning without vessel
entry. Another example is to eliminat e filters that requ ire changing, to
reduce the potential for exposure. Th is may require a redesigned filter
(such as a self-cleaning design), or a process change that eliminates the need for a filter at all.
Equipment that can be reached for inspection, repair, or monitoring
from permanent platforms is more likely to be safely inspected, calibrated, repaired, and replaced than equipment that requires
climbing with a safety harness or scaffold.
Calibrating equipment usually requires disconnecting it from the
process. Equipment that requires less calibration is inherently safer.
•For example, a furnace oxygen analyzer is not protecting the furnace while it is being calibrated. Equipment that can function
in abnormal operating conditions is inherently safer than
equipment that fails in those conditions.
•An oxygen analyzer that was designed to stop displaying the oxygen content in a furnace wh en the oxygen content went
below 4%. While the oxygen analyzer shutdown tripped the furnace, it left the operators without any indication of the
furnace oxygen level blind during the shutdown and delayed the
re-start. An analyzer that conti nued to display the actual oxygen
concentration during the upset would be inherently safer.
Equipment should be designed so that there is only one right way to
reassemble it.
•If it is important for a pipe sleeve to be right side up, then it could
be notched or pinned so it will only go in right side up. One plant
experienced a vessel leak caused by a siphon-break hole in a dip
tube which was not oriented away from the vessel sidewall. The
constant impingement of corrosive liquid into the sidewall from
the siphon-break hole resulted in accelerated corrosion/erosion.
•It is common practice to use unique fittings for nitrogen utility
service, different from the fitti ngs used for compressed air or
water, in order to ensure against cross contamination of the nitrogen system. |
INVESTIGATION M ETHODOLOGIES 45
Figure 3.4 Common Features of Investigation M ethodologies
To ensure effective incident investig ation and identification of root
causes, addressing three key challenges can guide the overall investigation
strategy to be selected:
1. “W hat” happened?
A component for describing and schematically representing the
incident sequence an d its contributing events and conditions.
2. “How” it happened?
A component for identi fying the critical events and conditions
(causal factors) in the incident sequence.
|
196
Addressing transportation risk at va rious life cycle stages can increase
the inherent safety of the overall op eration. This may mean minimizing
the number of railcars sitting on trac k within or outside the plant, the
selection of suppliers close to the plant, or other options. This section
provides an overview of inherently safer concepts and their application
to potential transportation risks.
In choosing the location of a new pl ant, or in assessing risks related
to an existing plant, transportation risk must be considered. The design
of new chemical processing units should include at the earliest
opportunity a qualitative or quanti tative risk assessment of the value
chain for the material, including production, use, and transportation of materials in order to minimize overall risk. Risk assessments of existing processes, including an assessment of transportation risk, may result in the conclusion that the process should be moved. Process risk
assessment techniques are availa ble in numerous references (for
example Ref 8.12 CCPS 2000) and the analysis of transportation risk is documented in Guidelines for Chemical Transportation Risk Analysis (Ref
8.14 CCPS 2008).
The assessment of transportation ri sk must include consideration of
the capabilities, equipment, and pr actices of the entire value chain
associated with the manufacture and distribution/shipment of
chemicals. Other than en suring that the carriers, which are separate
entities, have the correct and valid licenses, certifications, training
programs, emergency response plans, and other documented practices.
the fixed facilities where chemicals are manufactured cannot control the
policies, practices, procedures, or equipment of the carriers other than
to deny them business. Once the carrier leaves the facility with a shipment, the fixed manufacturing fa cility has released the materials
into the care of the carrier and cannot directly control the safety or security of the shipment outside its property, even though they usually
are still the owners of the shipment unt il it is delivered to the customer.
The chemical/processing industry , i.e., the shippers by DOT
definition and the carriers (i.e., railroads, trucking companies, marine
transportation firms, air cargo compani es, etc.) have historically worked
together to improve both transpor tation safety and response to
emergencies. The American Associ ation of Railroads (AAR), among |
178
between the variables. Another exam ple of direct readings is in
valve position signals. The position of a valve should be derived
from devices that directly meas ure the valve stem position or
stroke. The signals should not be derived from control signals
that tell the valve to go to a particular position. In other words, the open or closed indication for a valve or control functions
derived from them should on ly be given when the valve
physically reaches the intended position, not when it is “told” to move by the control system.
Operating Modes of Control Systems . Process control and safety
shutdowns must be provided during a ll modes of operation, not only in
the normal, steady-state operatin g mode. This includes startup,
shutdown (normal and emergency), inspection/testing, and temporary operations (if any)
The design of the control system should achieve the highest level
of Simplification for emergency shutdown and other
abnormal/upset situations. If an emergency shutdown capability includes a single operator action to trip (a single mouse click or
the activation of a single manual button/switch), it should be easily found, very clearly labeled, easily operated, and unambiguous as to intended function.
Important controls for higher risk situations should not, if possible, actually cause the pr ocess parameter to approach a
critical safe limit when undergoi ng testing. For example, using
inherently safer principles, a hi gh-level shutdown that can be
tested without actually raising the level in a tank or vessel is safer than one that requires raisin g the level. Another example
involves the overspeed testing of high-speed rotating machinery. The governors should be able to be tested without actually forcing the machine to reach th e trip speed (most electronic
governors incorporate this design feature). Older, mechanical
and electro-mechanical governors do not have this capability.
In order to test the full control loop/function, the final controlled
element(s) must also be tested . To do so without creating a
transient or frequent unit/plant s hutdowns, it is often necessary
to perform full SIS functional tests during shutdown periods. |
Pipes
87
6.6.2 Diversion of Flow
T
he diverting of flow can easily be done by using several
valves or a few multiway valves. One arrangement can be
seen in Figure 6.41. In this arrangement, diverting valves work together to send the flow to destination C, B, or D. Each three‐way valve could be replaced with two con-ventional (two‐way) blocking valves. The multiway valves will be discussed in Chapter 7.
6.6.3
Distribution of F
low
The distribution of flow is more difficult. From a purely
theoretical point of view, it can be said that the solution is manipulating the branches’ diameter and length to get to the desired flow rate. This solution, however, is not practical. The length of pipes is generally out of the con-trol of the process engineer. The designer needs to needs to follow plant layout, which dictates the pipe lengths. Therefore, even though this solution may be financially attractive, it is not practical.
One magic bullet solution is to put control valves on all
branches except one. This solution is shown in Figure 6.42. However, this solution can be expensive, especially when large bore pipes (larger than 12″) are being used.
One branch can always be left without a control valve
because when the flow rates of other branches are regu-lated by control valves, the flow rate of last branch will be regulated automatically.
It is important to consider that the branch without a
control valve cannot be the route with maximum resist -
ance. It means that when deciding on the branch without a control valve, that the branch does not get a minimum flow because the flow cannot be regulated in a pipe with constraints.
One alternative solution that only works when the
intention is to distribute the flow evenly is to use sym-metrical piping. The schematic in Figure 6.43 shows this solution.
The distribution of flow is not uncommon and
where
ver there is parallel operating equipment, this requirement should be met. A note stating, “Symmetrical Piping, ” as in Figure 6.44 shows how this is used.
However, there are still some clients who prefer the
control valve solution for applications like parallel heat exchangers and who are willing to pay the extra cost for that.
Placing a control valve to handle the flow distribution
is known as active distribution, and when it is handled through symmetrical piping, it is known as passive distribution.
The best symmetrical piping arrangement for a precise
flow distribution is the type in which the main pipe (before distribution) is perpendicular to the distribution header. However, in practice there is generally not enough room to implement such a concept. In practice, the main pipe could be connected to the distribution header after a run parallel to the distribution header and after an elbow. This arrangement generates a deviation from an evenly distribution goal.
Air coolers are a type of equipment that require good
distribution because of their multiple inlets (and out -
lets). This will be discussed in more detail in Chapter 11.Figure 6.39 Check valv e.
(a)
(b)
Figure 6.40 (a, b) M ultiple check valves.A BC
D
Figure 6.41 Diver ting flow in a multiple‐destination pipe route.
A BC
D
Figure 6.42 Distributing flo w in multiple‐destination pipe route
by control valves.
AB
DC
Figure 6.43 Distributing flo w in multiple‐destination pipe route
through symmetrical piping. |
26. Learning from error and human performance 361
Table 26-4: Effective learning tips
Tips for information sharing and learning
An incident
description This should be a brief description of what happened, using
only the facts known at that time. Use of photographs (e.g.,
images of the incidents) or other visual aids (e.g., process
flowcharts) can help to understand the incident and to
visualize the event.
The
immediate
action taken This should clearly set out the steps that operators need to
undertake, such as conducting additional checks, suspending certain activities, or stopping use of particular equipment or
processes.
A feedback loop Supervisors should seek confirmation that:
• Everyone has received and discussed the report.
• Individuals have taken on the required actions.
It is then important to evaluate the lessons learned and to monitor the effectiveness of any improvements.
Learning from incidents requires an appropriate attitude and a desire to learn
from them. Further tips supporting learning from incidents include the following:
• Empathize with the people involved. Try to understand the reasons
behind their actions.
• Appreciate the benefits of knowing the end results.
• Pose a series of questions:
• Could this has happened to other people?
• Are the systems robust enough to withstand the threats posed by the
incident under study?
|
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Pesticide Waste Tank Explosion,” U.S. Chemical Safety and Hazard Investigation
Board , Washington, DC., 2011.
[84] M. Endsley and D. Jo nes, “SA Demons: The Enemies of Situation Awareness,” in
Designing for Situation Awareness: An Approach to User-Centered Design , Boca Raton,
CRC Press, 2011, p. pp. 31–41..
[85] International Association for Oil and Gas Producers (IOGP), “Report 502 – Guidelines
for implementing Well Operations Crew Resource Management training,”
International Association for Oil and Gas Producers, www.iogp.org, 2014.
|
361
modification or
removal (8)
• Process re-design to eliminate need
for a second
tower (1) Reduction of inventory by removing dead-leg piping (3)
• Reduced the potential inventory
• Eliminated tankage (thus reducing inventory)
• Eliminated stored aqueous ammonia
• Removed excess piping
• Installation of a tubular reactor that reduced the inventory of ammonia
• Reduced inventory by eliminating tanks or reducing the |
56 Guidelines for Revalidating a Process Hazard Analysis
differences, such as “effects” instead of “consequences”). The unique concern
about PHAs using the FMEA method is whether they adequately considered
scenarios involving issues other than discrete component failures, such as,
human errors, variations in raw material chemical composition/properties, or
other non-equipment related issues. If th e FMEA only lists specific component
failures as causes, such as “valve fails open,” the Redo approach is likely required,
perhaps using the What-If/Checklist or HAZOP method.
3.2.3 Logic Errors and Inconsistencies in the Analysis
Information in PHA reports should be valid, accurate, and logical. To some
degree, the validity can be evaluated by having persons familia r with the process
review the report. Accuracy can be checked (to the degree details are
documented in the prior PHA) by comp aring equipment tag numbers and other
parameters (e.g., set pressure on a re lief valve) to the process knowledge
documentation. Logic errors are best disc overed by reading the hazard analysis
worksheets. The decision to Redo or Update the PHA depends on the prevalence
and magnitude of these errors in the prio r team’s risk judgments. Examples of
logic errors include:
• Listing human error as a cause with no furthe r explanation. Trevor
Kletz is often credited for the idea that “blaming accidents on
human error is equivalent to blamin g falls on gravity” [36, p. 2].
Humans will make mistakes. PHA teams should explore reasons
that an error might occur (i.e., an error-likely situation) and result
in substantial consequences. If fe asible, the PHA team should have
made recommendations to substantially reduce or eliminate the
risk of consequential, unr ecoverable human errors. |
1.2 Definition of Process Safety Culture |7
dimensions of culture. Chapter 4 will address culture from the
standpoint of organizational dynam ics, hum an behavior,
com pensation, ethics, external influences (e.g. contractors,
vendors, public sector), and metrics. Chapter 5 will discuss the
ways in which culture can directly impact each elem ent of CCPS’s
Risk B ased Process Safety (RB PS) PSMS. Chapter 6 will provide a
guide for getting started establishing a strong culture or
improving culture. Chapter 7 will address how to achieve a
sustainable culture. The appendices provide additional
background on culture, case histories that may be useful in
discussing culture issues, and a culture assessment protocol.
Taken together, the concepts discussed in these chapters provide
the concepts and guidance to make these concepts a reality in an
organization.
This book does not discuss regulations, but instead comes
from the point of view that a strong positive culture adequately
addresses process hazards, whether regulated or not. This
represents the first concept of a strong, positive process safety
culture: the organization’s leadership and all personnel believe in
the necessity of process safety and comm it to it, even in the
absence of regulatory requirements.
Some people have expressed the belief that safety culture
cannot change. They consider core principles, com pany values
and principles, and how the com pany behaves. They then
conclude that good cultures will stay good, while poor cultures
cannot improve. Mathis disagrees, suggesting that those who
claim culture is static may be resisting the culture change (Ref 1.5).
From a sociology point of view, cultures of all kinds develop via
social conditioning. With the right conditioning, applied patiently
over time, leaders can build strong positive cultures. Typically, this
requires patience and persistence. It can take some time to build
workers’ trust and to convince them that the intended culture
change is not a temporary fad. |
xxii
B.2 Inherent Safety Analysis - In dependent Process Hazard Analysis
(PHA) 464
B.3 Inherent Safety Analysis – Integral to Process Hazard Analysis
(PHA) 467
Glossary 469
Index 497 |
Piping and Instrumentation Diagram Development
130
rejuvenation all the operation are performed by
operator(s) in the field. In automatic rejuvenation the operation can be done fully automatically without any action by an operator, or can be initiated and observed by an operator from the control room (and not the field).
Manual rejuvenation is done if the rejuvenation doesn’t
need to be very frequent, or the rejuvenation steps are not very complicated, or if the unit of interest doesn’t have very critical role in the plant. Otherwise automatic rejuvenation should be performed.
Below are a few examples of equipment requiring
rejuvenation activities.
Sand filtering in water treatment operation is generally
a semi‐continuous operation. After a certain time period, the filter should be taken out of operation for backwash-ing. This type of operation should be implemented dur -
ing the design and be shown on a P&ID. The backwashing could be manual (in small systems) or automatic. The backwashing operation is a type of “in‐place in‐line care. ”
Another example is a soot blower for heating coils in
the convection section of fire heaters and boilers. These coils get covered with soot after a while. To keep the same efficiency of the fire heater or boiler this soot should be removed from them. A soot blower is a moving set of perforated pipes that slide into the convection section of fire heaters and, by injecting steam, dislodge the precipitated coke or soot.
Another example is the cleaning of bin filters. Bin
filters are a type of in situ treatment of bin vents. Bin and silo vents may have a large amount of dust. To remove the dust from the outgoing gas (air) a bin filter can be installed on the vent of bins or silos. It is very common to use bag filters in the role of bin filter. In each bag filter there are several filter bags (socks) that separate the dust from the gas stream. These socks get full after a while then need to be rejuvenated. The rejuvenation of each sock can be done by backflowing an air jet in it. As there are several socks in each bag filter. One sock can be cleaned during normal operation with marginal impact on the operation of the bag filter.
The last example of rejuvenation is the regeneration of
ion exchange systems. Ion exchangers in, for example, water treatment systems don’t work on a fully continuous basis. They function to adsorb the ions on their “exhaus -
tion period. ” At the beginning of this period the resin beads inside of the ion exchange vessel are fresh and ready to adsorb ions. After a while the resign beads are “filled” with ions and become exhausted. To return them back to their fresh condition, the resin beads should be “regener -
ated. ” This regeneration, which is a type of rejuvenation, is done by sending a solution through the ion exchangers.
A large group of rejuvenation operations are catego-
rized as “cleaning. ” The different cleaning methods are discussed later in this chapter. It is very common to do automatic rejuvenation. The automatic rejuvenation can be provided by a mechanical unit that recirculates the cleaning agent or object. The automatic rejuvenation systems are any of two main types of “mechanical‐in‐place” (MIP) systems, or “clean‐in‐place” (CIP) systems. These systems will be discussed later in this chapter.
Activities related to monitoring equipment in in‐line
care are mainly on the shoulders of the “rounding” operator. The operator could be equipped (beyond just personal safety equipment) or non‐equipped. If the operator is non‐equipped, he/she relies on his/her five senses. Among them, the taste sense never is used. Below is a non‐inclusive list of the use of the remaining four senses of the rounding operator:
●Vision: leakage, vibration, overflow of tanks, checking levels, checking flame color and shape
●Hearing: vibration, cavitation, hammering, PSV release, explosion
●Touch: vibration
●Smell: fire, leakage, PSV release to atmosphere.
To facilitate the duties of the rounding operator, the
process engineer can put some items on the P&ID. The examples are sight glasses to check liquid levels, catalyst levels, or filtering media levels, and peep holes to check the color and shape of flames in a furnace or boiler.
An equipped rounding operator can have some small
measuring devices to check some parameters that can-not be accurately checked without. It could be a portable pressure gauge, portable temperature sensor, etc. If it is the plan to have an equipped rounding operator, the pro-cess engineer needs to provide “test points” on impor -
tant points of the system for him. They could be a “pressure tap” (PT), or “temperature point” (TP). However, these points should not be very important parameters because if one parameter is very important to check and monitor, it should be part of a control loop. An example of a PT could be the suction side of centrifu-gal pumps. In some companies the acronym of PP is used for “pressure point” and TW for “thermowell. ” This con-cept will be discussed in more detail in Chapter 13.
8.4 In‐place Off‐line Equipment Care
“In‐place off‐line” care could be for small repair jobs, inspection, or as a preliminary step for “in‐workshop off‐line care” activities.Table 8.1 Differ ent types of equipment care.
In‐line Off‐line
In‐place By process group By mechanical group
By mechanical group In‐workshop Not applicable |
344
13.7.1 Dow Fire and Explosion Index (Ref 13.14 Heikkilä 1999)
The Dow Fire and Explosion Hazard In dex was developed initially for use
within company operations and was later disseminated in a book
published by the American Institute of Chemical Engineers (Ref 13.8 Dow
1994b). The index quantifies the damage from potential fire and explosion incidents and identifies eq uipment that would be likely to
contribute to the creation or escalation of an incident.
The Dow Index is the product of a Unit Hazard Factor and a Material
Factor . The material factor for a proc ess unit is based on the most
hazardous substances or mixtures pr esent that would result in a worst-
case scenario, and it quantifies the amount of energy released. A material factor is determined for each process unit. The unit hazard factor for a process unit is the product of both general and specific process hazards. General process hazards address such issues as
exothermic chemical reactions, endothermic processes, material handling and transfer, enclosed or indoor process uni ts, access, and
drainage and spill containment. Spec ial process hazard s include factors
for toxic materials, operation in or near flammable range, dust
explosions, relief pressure, low temperature operation, corrosion and erosion, joint and packing leaks, fired heaters and hot oil systems, and rotating equipment.
13.7.2 Dow Chemical Exposure Index Like the Fire and Explosion Index, the Chemical Exposure Index was
developed by Dow to help its e mployees design and operate safer
facilities. In 1998, an AIChE volume brought the index—which by then
was considered a seminal tool for rati ng the relative acute health hazard
potential of a chemical release to workers and the neighboring
community—to the entire process industry. The newest edition uses a
new methodology for estimating ai rborne quantity released, which
allows for more sophisticated proc ess analyses (Ref. 13.7 Dow 1994a).
13.7.3 Mond Index
The Mond Index was developed by I mperial Chemical Industries (now
ICI, an Akzo Nobel Company) after th e Flixborough incident, and is based
on the Dow Fire and Explosion Index . The Dow Index was modified to
address: 1) a wider range of proce sses and storage in stallations; 2) |
296 PROCESS SAFETY FOR ENGINEERS: AN INTRODUCTION
Overpressure Outcomes
Explosion overpressure can cause harm to people inside and outside of buildings. People can
survive a higher overpressure than typical stru ctures can. The overpressure can cause objects
inside the building to be thrown, damage to the building, and building collapse, all of which
can result in harm to the building occupants. An alyzing structural response is a specialist topic
requiring expert civil engineering assistance.
Overpressure duration is important for de termining effects on structures. The same
overpressure level can have markedly different effects depending on the duration. Therefore,
some caution should be exercised in application of simple overpressure criteria for buildings
or structures. These criteria can, in many case s, cause overestimation of structural damage.
An object struck by a blast wave experiences loading. When the blast wave hits the front
wall of a building, it is reflected off the wall and builds up a local, reflected, overpressure which
can be approximately twice the incident (side-on ) overpressure. This is illustrated in Figure
13.12 and fully described in Guidelines for Vapor Cloud Explosio n, Overpressure Vessel Burst,
BLEVE and Flash Fire Hazards . (CCPS 2010) Damage levels observ ed at selected overpressures
are noted in Table 13.14.
Figure 13.12. Interaction of a blas t wave with a rigid structure
(Baker 1973) (CCPS 2010)
|
200 GUIDELINES FOR MANAGING ABNORMAL SITUATIONS
There were five fatalities: four in the control building and one in the
office block. There were two report able injuries (requiring hospital
treatment) and fifteen employees who required treatment for minor
injuries and shock.
This report is mainly based upon the report by the UK Health and
Safety Executive (HSE UK 1994).
7.3.2 Incident Overview – Hickson and Welch fire
Problems were being encountered with the operation of a batch
distillation operation that used a st eam-heated vessel known as “60 Still
Base,” shown in Figure 7.7 (HSE 1994) and a decision was made to open
it up and clean out an accumulati on of sludge on 21 September 1992.
Figure 7.7 Manway at the End of 60 Still Base - Source of the Jet
Fire
|
234 | 6 Where do you Start?
Provide indemnity : Avoid disciplinary action related to the
reported unsafe condition, as far as practical.
Maintain confidentiality : Take steps to prevent identifying
the reporting em ployee on incident reports and
elsewhere.
Make it easy : Remove red tape and make reporting user-
friendly.
Acknowledge rapidly : Thank the reporting em ployee and
provide practical, meaningful feedback as soon as
possible.
Also, be careful delivering m essages. For example, in a strong
culture, leaders and em ployees believe that all incidents are
preventable. However, printing “All incidents are preventable” as
a slogan on a sign may subtly convey the unintended m essage
that m anagement does not want to hear about incidents or near-
m isses. Consider m essages carefully to prevent motivating the
wrong behaviors.
Sim plify The m ore difficult employees find the PSMS, the more likely
they are to seek shortcuts and normalize deviance . Therefore, seek
to simplify the PSMS and the associated policies, practices,
procedures, and activities as much as feasible. Suggestions for
simplification mentioned earlier in this book include:
Use a risk-based approach : Processes and units involving
significant potential hazards and risks warrant a
com prehensive approach. However, lower hazards and
risks may be managed with a m ore streamlined approach.
Most PSMS elem ents can benefit from a risk-based
approach, but PHA, MOC, and MI tend to benefit the m ost. Metrics : As noted above, collect the m inimum set of metrics
and use those metrics that can be obtained easily. Where
possible, automate collecting the metrics (e.g.
automatically extract from operating records) and rolling
up site and corporate data. •
•
•
•
•
• |
200 Human Factors Handbook
Figure 17-5: Schematic of some factors influencing attention span
17.6.2 Supporting attention
The potential attention span should be co nsidered. Where there is a potential for
loss of attention during a task, some tact ics for maintaining attention are noted in
Table 17-3.
Many of these tactics aim to either enab le people to take a break from a task
before they lose attention or increase th eir stimulation levels by factors such as
task or environmental enrichment.
For low demand, task requirements may be created to keep people engaged.
For example:
• Verbal updates of the system status.
• Providing other tasks as a break, such as updating logs.
Taking short but regular breaks or alternating tasks, can help maintain people’s
attention for low demand tasks, such as 20 minutes on a task followed by 5
minutes performing a different task. If tw o people are performing task, they can
switch jobs occasionally or stop and check each other’s work.
The scheduling of additional tasks needs to ensure that they do not distract
from the primary task. For example, the secondary task may be short or performed
with the primary task still within the visual field of the primary task, such as
completing a log at the same workstation.
People’s circadian rhythms (body clocks) respond to light. People’s energy
levels cycle between periods of feeling awake and periods of feeling sleepy. People
are usually least alert between 02:00 and 04:00, and between 13:00 and 15:00. This
does vary between people. If someone’s sl eep is disrupted, they can experience
Sleep cycle
Hot/humid
Fatigued
Singular task
Low workload
Low motivation
Awake cycle
Temperate
Not fatigued
Diverse task
High workload
High motivation
Shorter Longer
Attention span |
339
To get an overall assessment of the process options, it is necessary
to use a variety of indices and qua litative techniques and then combine
the results. A number of quantitative tools for evaluating inherent safety
have been developed or are in the process of being developed. These
include Khan and Amyotte (Ref 13.19 Khan), Heikkilä (Ref 13.14 Heikkilä
1999), and Edwards, et al. (Ref 13.10 Edwards 1996).
13.6.1 Tools for understandi ng and resolving conflicts
The CCPS book, Tools for Making Acute Risk Decisions with Chemical Process
Safety Applications (Ref 13.5 CCPS 1995), presents a list of factors that, in
addition to cost and risk, should be taken into consideration:
Alternatives available for reducing or eliminating the risks
Availability of capital
Codes, standards and regulation s and good industry practices
Company and/or personal liabilities
Company image
Costs of implementing available alternatives
Economic impact of the activity on the local community
Employment opportunities provided by the activity
Frequency level(s) of the risk
Inequities in how the risks and benefits are distributed among
members of society
Number of people at risk
Perceived benefit of the activity and its impact on the public
and/or stockholder image
Profitability of the activity
Societal component of the risk, such as the maximum number of
people impacted by a single event
Strategic importance of the activity to the company’s growth and survival
Type(s) of risk, such as human fatality, injury, and acute
environmental damage
It is impractical to develop an explicit algorithm for selecting a
decision aid. But, decision aids can be flexibly applied, and most can be
adapted to an organization's needs and to a wide range of problems.
However, an understanding of the key characteristics of the problem, and of the decision aids, is basic to making an appropriate selection. |
Piping and Instrumentation Diagram Development
312
Control Valve Versus VFD
We learned that there are at least two methods of con-trolling pumps: by control valve and by VFD. Now the question is, which one should be used? Sometimes when we are not sure, we use both of them in the form of split‐range control. If we cannot afford to use both of them (in the form of split control), we need to choose one of them. Traditionally, we use a control valve because it is an older technology; however, there are cases where a VFD works better.
The main consciously changing parameter in a water
treatment plant is the flow rate. The flow rate is changing and we have to find “something” to adjust the flow rate of different pieces of equipment.
There are mainly two types of device can be used to
adjust the flow rate: control valve and VSD.
A control valve is generally installed on the discharge
line of a pump (or compressor) and the VSD is installed on the electromotor of the pump (or compressor).
These two methods of adjusting flow rates are named
“final control elements. ”
These two methods of controlling the flow rate are
very similar to two methods of controlling the speed of car we are driving. This analogy can be seen below.
Table 15.9 summarizes some process reasons for using
a control valve or a VFD.15.7.1.1.2 Minim um Flow Control
The concept of minimum flow control is shown in Figure 15.34. Let’s assume that this pump has a capacity of 200
m3 h−1. The vendor specified that the minimum
flow rate of the pump is 100 m3 h−1. We can provide a
recirculation line from the outlet of the pump back into the inlet line.
If the flow rate into the pump is 165
m3 h−1, the pump
is happy, since its flow is higher than the minimum flow. In this case, the sensor on the pump outlet sends a signal to the control valve on the recirculation line and it remains closed. However, if the flow drops below 100
m3 h−1, for example to 80 m3 h−1, the flow sensor on
the outlet will send a signal to the controller to say: “I am short of my minimum required flow by 20 m
3 h−1and I
am worried about the pump. Please open the valve enough to recirculate 20 m
3 h−1, so we can fool the pump
into thinking that the flow is 100 m3 h−1, and make it
happy, ” The control valve on the recirculation line will be partially opened to provide a flow of 20
m3 h−1, which
is sent back to the inlet to satisfy the minimum flow condition of 100
m3 h−1, and prevent damage to the
pump. This is the concept of minimum flow control.
It is important to recognize that this “trick” only
increases the flow rate inside the recirculation loop to a number higher than 100
m3 h−1 to “fool” the pump. We
are not able to increase the overall flow in the whole upstream and downstream piping system; the flow in those pipes is still 80
m3 hr−1.
The point here is that the sensor should be placed as
close as possible to the pump and within the recircula-tion loop.
Now the question is whether we need a minimum flow
control loop for all centrifugal pumps or not. The answer is no! We don’t need minimum flow control loop for all centrifugal pumps.
The following examples of pumps may not need a min-
imum flow control loop [1]:
●Small pumps of less than 5 hp; t hey need it, but they
are inexpensive so we don’t bother to put an expensive minimum flow control loop on them.FCOption A
Option BFC
FC
FC VSD
Figure 15.33 Options for c entrifugal pump capacity control.Table 15.9 Options for c
entrifugal pump capacity control.
Control valve VFD
●Generates more shear on the
stream. Not good for shear‐sensitive liquids like oily waters, biomaterial, water carrying flows etc.
●Works for all types of piping circuits ●Generates less shear on the stream
●Doesn’t work in systems where the majority of the pump head is used to overcome static pressure rather than pipe pressure loss |
Ancillary Systems and Additional Considerations
391
In the text below we discuss the usage of each of these
utilities.
Steam: a steam that is used in USs is named utility
steam. We need utility steam whenever we need to clean
stubborn fouling and scales. Generally speaking, steam is the last resort for removing dirt from process equip-ment. If utility steam fails to clean fouled or scaled equip-ment, the next available option is cleaning with solvents or chemicals, which is a very expensive operation.
Air: utility air or plant air is again used to clean dirty
equipment. Utility air is more effective on dry dirt. The other usage of utility air is driving power tools. The quality of utility air is less than the quality of instrument air. However it should be clean and free of any dirt.
Water: utility water is the water from the US. This
water could have quality similar to potable water but in the majority of cases its quality is less than potable water. So it is important to know that utility water is not always drinkable. This water shouldn’t have any scaling or fouling tendency. Utility water again is used for washing and cleaning of dirty equipment.
Nitrogen gas: nitrogen gas could be implemented in
USs for different reasons. The main property of nitrogen gas is its inertness. Thus nitrogen gas can be used for purging and pushing toxic, aggressive, flammable gas from an enclosed space. This action could be taken before letting people enter inside a piece of equipment like a vessel or a tank, or nitrogen gas can be introduced in a process system before starting up.
The type and number of utilities in each utility station
may vary depending on the equipment in the vicinity. It is important to note that the hoses that could be used for a US have a standard length. Therefore each US can only cover a specific radius around itself. The designer needs to decide the location of the US and the utility in each US. The systematic way to do this is by preparing a list of equipment in the plant and then listing all the required utilities for each piece of equipment during maintenance. Then, based on a plot plan, the designer can decide upon the number of required USs in the plant in a way that covers all the equipment (Figure 18.11).
Utility stations are not necessary located on the ground
floor and they could be on the platforms around the equipment too. However, elevated USs generally have only gas or vapor utilities. If a utility like “plant water” is to be provided for an elevated utility station, provisions should be considered to prevent splashing plant water on the personnel who are unaware and passing by on the ground.
In each plant, before developing US drawings, the
plant owners should be consulted for the availability of different utility steams, their pressures, and the length of the standard hose for USs.
The exact location of a US cannot be recognized from
P&IDs. However, a US can be seen in utility distribution drawings (Figure 18.12).
Product Tank Product TankSeparator
Separator
SeparatorSand Filter
Catalyst BedsDemin Water
CausticAcid O2 ScavengerArea 1: tank farm Area 2 Area 3Hx’s
US
50
US
52US
53
US
54US
57US
55
US
59US
56
US
58
Figure 18.11 Positioning of utilit y stations in a plant based on the plot plan.AS WN ASW
Figure 18.10 P&ID presen tation of utility stations. |
Piping and Instrumentation Diagram Development
152
of process and instrument nozzles are related to
instruments. They are nozzles that are installed on a container to attach sensors to a container. The sensors could be level sensors or temperature sensors.
Nozzles can also be classified as operating nozzles and
spare nozzles. Operating nozzles are the ones currently in use. Spare nozzles are implemented for future poten-tial use.
Table 9.6 summarizes the name and purpose of several
container nozzles.
The size and the number of spare nozzles could be
specified by the client. Otherwise the process engineer can use his judgment. For process spare nozzles he/she can use a rough number of 10–20% of operating process nozzles, with sizes in the mid‐range of existing process operating sizes. For instrument spare nozzles several 2″ and 3″ nozzles can be provided.
9.9.2
Nozzle L
ocations
It is important to know that the location of nozzles on
containers in the P&ID never ever represent their real location on containers. The real location of nozzles on each container can be found in the container datasheet. The nozzle symbols are drawn on the container symbol just wherever there is enough room around the container.
Table 9.6 Duties of no zzles.
Nozzle name Explanation
Process fluid nozzles Process nozzles are nozzles that process fluid goes through for entering the container fluid or exiting the
container fluid
Instrument nozzles Instrument nozzles are the nozzles for installation of different sensors to the containers
Manway Manways are not only for quality control or maintenance personnel to enter. Manways are used for operator
entrance and also entering or exiting container internals. They are generally used in large containers, ones with a diameter more than one meter
Overflow nozzle Overflow nozzles provide a release route when the liquid level in a tank keeps increasing and is going to fill
the container
Thief hatch Thief hatches used to be called dip hatches. They are nozzles with easy‐to‐open lids and are installed on the top of liquid containers (for example on the tank roof) for the purpose of taking samples from the container liquid. This sampling is done by sending down (dipping) a small jar to the liquid. In older times, these nozzles were used by thieves to steal oil products from tanks. This is the reason their name gradually changed from dip hatch to thief hatch
Pressure protection nozzleThis is a nozzle (or nozzles) that releases fluid out of the container to protect it against high pressure. Basically, this nozzle is for the installation of a PSV
Vacuum protection nozzleThis is the nozzle (or nozzles) that provide contort release of fluid out of the container to protect it against high vacuum. Basically, this nozzle is for the installation of a VSV
Free vent nozzle Free vent nozzles can be necessary for non‐flooded containers. They are installed mainly on atmospheric tanks. These are used to provide an opening for tank “breathing. ” “Breathing” will be discussed in Section 9.11
Clean‐out doors Clean‐out doors are generally larger nozzles of mainly rectangular shape that are placed on large containers
(large tanks) to provide capability of sending machine to the tank. For a plenty of cases, these machines are for sludge removal from the bottom of the tank.
Drain nozzles Drain nozzles are the nozzles used to drain liquid from a container for the purpose of taking out the
container from normal operation.
Hand holes Hand holes are nozzles on smaller containers that are too small for an operator to be able to enter into. Hand holes are used only for inserting a hand to check the inside of container. They are used for smaller containers instead of manways.
Drain and vent size For draining and venting the container
Sting nozzle For cleaning during the operation
Steam‐out nozzle For off‐line cleaningPurge nozzle For off‐line cleaning and making safe the internal atmosphere
View or inspection
portFor monitoring by the operator
Media adding/removal For adding or removing media such as sand or resin beads during rejuvenation
Cathodic protection For corrosion protection |
297
11.13 INCIDENT INVESTIGATION
As with PHA and MOC, the use of IS checklists and guidewords based on
the four IS strategies can be used in investigation activities, root cause
analysis, and in the formulation of recommendations. The overall
incident investigation process and where IS guidewords and checklists
can be used in it is shown in Figure 11.4 (Ref 11.16 Kletz 2010).
The formal investigation of in cidents and near misses also
represents an opportunity to ch allenge and possibly eliminate the
hazards that caused the events in the fi rst place. This is the goal of root
cause analysis, which is a common prac tice during an incident/near miss
investigation. The elimination or reduction of ignition sources or
potential leak points as a result of an investigation, as described for
emergency response plans is an example of the use of the IS strategy of Minimization. Another example of this IS strategy is as follows: if an
investigation is conducted pursuant t o a n i n j u r y c a u s e d d u r i n g a
sampling operation, this is an opport unity to question why the sample is
required in the first place.
11.14 MEASUREMENTS AND ME TRICS/AUDITING/MANAGEMENT
REVIEW AND CONTINUOUS IMPROVEMENT
The three elements of PSM/RBPS wh ere the process safety program are
measured and formally evaluated represent opportunities to use IS
strategies.
Minimization of a large list of process safety metrics to a small and
more manageable list that is easier to collect and analyze is a preferred
practice. This will allow a focus on the key issues that affect the process safety risk rather than diluting a ttention and time with a large number
of KPIs. Also, a metric could be crea ted that provides a measure of how
many times (divided by the number of opportunities) that IS strategies were used in both the design and op eration of the facility (including its
equipment and its chemicals), and in the modification of the PSM/RBPS
program policies, practices, and proced ures. It is not probably necessary
to report this KPI at the same fr equency as other PSM/RBPS program
metrics, but having the PSM Manager keep track of these IS uses and
opportunities will provide some useful data on how the facility and its
PSM/RBPS program reflect the state-of-the-art. |
•Mansfield, D.P. and Cassidy, K. (1994). Inherently safer
approaches to plant design: The be nefits of an inherently safer
approach and how this can be bu ilt into the design process.
Presentation at IChemE Hazards XII—European Advances in Process Safety, April 19-21, 1994, UMIST, Manchester, UK. AEA/CS/HSE/R1016, HSE Books/HMSO, August 1994, ISBN 0853564159.
•Sanders, R.E. (2003). “Designs that lacked inherent safety: case histories.” Journal of Hazardou s Materials, 104, 1-3, 149-161.
15.10 REFERENCES
15.1 American Industrial Hygiene Association, Emergency
Response Planning Guidelines: Chlorine . Akron, OH: American Industrial
Hygiene Association, April 20, 1988.
15.2 Carrithers, G.W., Dowell, A.M., and Hendershot, D.C., It’s
never too late for inherent safety. In International Conference and
Workshop on Process Safety Ma nagement and Inherently Safer
Processes, October 8-11, 1996, Orlando, FL (pp. 227-241). New York:
American Institute of Chemical Engineers, 1996.
15.3 Center for Chemical Process Safety (CCPS), Guidelines for
Engineering Design for Process Safety . New York: American Institute of
Chemical Engineers, 1993.
15.4 Crowl, D.A., and Louvar, J.F., Chemical Process Safety
Fundamentals With Applications (pp. 14-15). Englewood Cliffs, NJ:
Prentice Hall, 1990 and 2002.
15.5 Det Norske Veritas (DNV) - PHAST® (Process Hazard
Analysis Software Tool) is a compreh ensive hazard analysis software
tool broadly used in the chemical and petroleum industries developed
and marketed by DNV Software, th e commercial software house of
DNV.
15.6 Dow Chemical Company, Dow's Chemical Exposure Index
Guide, 1st Edition . New York: American Institute of Chemical Engineers,
1994a. 431 |
B Major accident case studies
B.1 Texas City Refinery explosion, 2005
The 2005 Texas City refinery explosion, shown in Figure B-1, occurred during the
start-up of the isomerization (ISOM) unit, killing 15 people and injuring 180 [16].
The unit was being restarted after main tenance. The raffinate splitter tower
was overfilled. The raffinate flowed from th e tower through a set of pressure safety
relief valves to a blowdown drum and stac k, from which it was released into the
atmosphere and likely ignited by a nearby truck engine.
The CSB produced a video of this incident [14].
Figure B-1 Texas City Refinery Explosion
(from www.csb.gov)
The steps leading to this accident are as follows:
• The ISOM raffinate section start-up began during the night shift and
stopped with the tower level control valve closed (this was unusual). The
operator did not use the start-up checklist and did not log his actions.
When the day shift started work, they had no record of the start-up.
• The bottom of the tower had been filled to 99%, which was not unusual
but was not consistent with the start- up procedures. Over time, this had
become an accepted deviation to the procedures. A high-level alarm set
at 72% activated and alarmed throughout the incident. A 78% high-high
level alarm did not activate.
• A poor shift handover meant the day shift was unaware that heat
exchangers, piping and other equipment had been filled in addition to
Human Factors Handbook For Process Plant Operations: Improving Process Safety and System
Performance CCPS.
© 2022 CCPS. Published 2022 The American Institute of Chemical Engineers. |
232 Human Factors Handbook
• Implementation of error prevention techniques may increase the
duration of tasks completion, until the individuals had developed the required skills. Pressuring a team for faster performance during the initial stages of skills development, may have the opposite effect and
increases likelihood of error.
• Effective strategies to detect, manage, and recover from error include:
o Error Management Training and coaching.
o Building resilience from error recovery.
o Creating a psychologically safe environment.
o Task verification, such as Human Based Checking.
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5.2 Learning Models for Individuals | 59
5.2.3. Dynamic Learning
In the digital age, classroom-based training and online slide decks are a thing
of the past. New cloud-based digital learning experiences are flexible,
personalizable, effective, and good for the bottom line (Willyard 2016).
As with the Career Architect model, employees and their managers work
together to identify learning and development needs. Then, development is
supplemented with dynamic novel online tools, including:
• micro-learning. Short lessons, typically three minutes or less, reflect the
trend in today’s society toward consuming information as short videos or
social media posts. Micro-learning is best when applied to very concise
learning opportunities, for example to tackle an unfamiliar task in a new
assignment, or as a periodic refresher. It may also be used to segment
longer courses into manageable bites.
• self-serve learning. E-learning is available on demand when the employee
needs it.
• learning as entertainment. Digital games, virtual reality, interactive
presentations, and competitions are effective learning tools—and have
special appeal for younger workers.
• social learning. Online collaboration platforms make it easy for employees
to share and collaborate.
• user-generated content. Content doesn’t have to be polished to be effective.
Students today are eager to develop their own content—presentations,
videos, signs, and more—and to learn from other students.
Like Gardner’s Multiple Intelligences Model, the Dynamic Learning Model
fits primarily in box III (Check) of Figure 5.1 but should be extremely useful in
box IV (Act). Dynamic Learning serves as a reminder that our toolbox for
communicating learning experiences is larger than the classroom—and likely
to keep expanding. When we review internal and external incidents, we should
look beyond reports and videos, and when institutionalizing the learning, we
should not limit the way we communicate.
5.2.4 Ancient Sanskrit
An ancient Sanskrit shloka states (Surya Rao 2019; Joshi 2009):
One gains ¼ of the knowledge from the
Acharya (the teacher), ¼ from his own
self-study and intellect, ¼ from co-learners
and the balance out of experience.
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187
Although it is usually difficult to modify the process chemistry and
operating conditions during the op erations and maintenance stage of
process life, there may be opportuniti es to make partial changes that
have profound process safety impa cts. It may not be possible to
substitute chemicals, but it may be possible to use them in more
moderate conditions. Examples: even a small adjustment in pH may
have a significant effect on the rate of corrosion; small adjustments in
flow may reduce erosion problems in certain components. Larger scale projects later in life, such as debo ttlenecking, may offer the opportunity
to change heat and mass transfer equipment to simpler, more inherently robust, and more IS friend ly designs (see Chapters 6 and 7).
8.7.2 Inherent Safety - Continuous Improvement
At a minimum, a facility with a proc ess safety program will perform PHAs
or similar studies at least once ev ery five years. Many companies and
facilities also perform PHAs as part of projects. During these studies,
each safety device or procedure should be evaluated to see if it can be
eliminated or modified by applying inherently safer principles of
Simplification . These include the use of:
Valve designs that offer a visual in dication of actual position and
not the commanded position.
Mechanical connections (or disconnections) for blanking,
draining, cleaning, and purging connections so that maintenance activities cannot be started without first disconnecting lines that might add hazardous materials to the equipment. One example
is to route a nitrogen line across or through a manway, so the vessel cannot be entered withou t disconnecting the nitrogen
line.
Accessible valves and piping to minimize errors.
Adequate spacing to avoi d crowded vessel access.
For operability and maintainability, minimize the complexity of any instrumented protection layers, where possible (Ref 8.23 CCPS 2016b).
Logical numbering of a group of equipment. Figure 8.5 is an example of poor assignment of equipment numbers for pumps.
Logical control panel arrangements. Figure 8.6 is an illogical arrangement of burner controls on a kitchen stove. |
292 INVESTIGATING PROCESS SAFETY INCIDENTS
Figure 12.4 Example Recommendatio ns and Assessment Strategies
(ABS, 2001)
|
170 INVESTIGATING PROCESS SAFETY INCIDENTS
On the other extreme, a field operat or’s observations and actions may
be less precise. “Sometime around noon,” or “right after the 10:00 AM
morning break,” may expre ss these approximations.
Figure 8.6 is an example of a simple timeline using imprecise data from
the field operator. This timeline uses a portion of the approximate data from
the incident example discussed in detail in Appendix D.
Figure 8.6 Timeline Example Based on Approximate Data
Normally the investigator is pres ented with a combination of both
precise and imprecise data. Mixing th ese significantly different data often
proves to be a challenge—a challeng e, however, that can be overcome
simply by understanding the source an d precision of the data and the use of
appropriate graphing techniques. On e such technique involves using a line
with timing marks as th e common boundary between the two different types
of data. On one side of the line, the known precise data is logged against the
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188
Organized and complete technical information (i.e., the process
safety information) for the process equipment that includes not
only the basic design informatio n, data, and specifications, but
also additional information that will thoroughly support operations and maintenance activities, such as maintenance materials, vulnerabilities of the materials of construction to corrosion and damage mechanisms (often referred to as Corrosion Control Documents or CCDs), lubricants, packing materials, etc.
During PHAs and at other opportunities when operating procedures
undergo review, they should be reviewed using inherently safer
principles for the following safer provisions:
Using checklists in operator rounds.
Using a second person to doub le-check certain log entries.
Scheduling to minimize cross-contamination and clean-ups.
Recording a value for a process variable rather than just a check mark.
Reformatting procedures to make them more user-friendly. For example, placing an easily recognized tab at the page containing the emergency procedures. See Chapter 6 for further discussion of human factors.
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EQUIPMENT FAILURE 197
Table 11.2. Common failure modes and design considerations for heat exchangers
Failure
Mode Causes Consequences Design Considerations
Leak from
heat
transfer
surface Corrosion from
contaminants in the
process fluids, and cooling
fluids, and/or loss of
treatment chemicals.
Anaerobic attack under
sediments and scale.
Thermal stress (e.g.
extreme heat/cold) Loss of
containment
Inadvertent
mixing and
contamination of
low pressure
side, potential
reactions, (HIRA
needed) Periodic inspection
Choice of materials of construction
Choice of heat transfer fluid
Shell expansion joints
Non shell and tube design
Control of introduction of process
fluids during startup and shutdown
Monitoring of low pressure side fluid
Toxic fluids in tubes, monitor shell
side.
Treatment chemicals
Rupture
from heat
transfer
surface Corrosion
Thermal stress (e.g.
extreme heat/cold)
Operation out of design
temperature range
resulting in stress cracking,
improvement, weakening
of tubes or tubesheet (see
loss of cooling or heating
load)
Blocking in one fluid side
during operation Potential rupture
of heat
exchanger
Loss of
containment Emergency relief device
Control of introduction of process
fluids during startup and shutdown
Loss of
cooling or
heating
fluid Loss from supply
Control system
malfunction
Pluggage or Misalignment
of valves Loss of process
control (HIRA
needed)
High pressure Alarms / interlocks on low flow or
pressure of heat transfer medium
High or low temperature alarms on
process side
Inadequate
heat
transfer Fouling
Accumulation of non-
condensable gases (mostly
condensers) Loss of process
control (HIRA
needed)
High pressure Ability to clean
High or low temperature alarms on
process side
Mass Transfer: Distillation, Leachi ng and Extraction, Absorption
Overview. Mass transfer operations are used to se parate materials, purify products, and
detoxify waste streams. Knowledge of the properties of the materials being handled is
necessary to assess the hazards of the potential failures of mass transfer equipment. |
HUMAN FACTORS 363
Figure 16.6. Human failure types
(HSE a)
Figure 16.6 identifies the types of human error and violations.
Skill-based errors include slips such as cond ucting an action too soon in a sequence
or lapses such as forgetting to perform a task.
Mistakes occur when someone does the wrong thing, believing it to be appropriate.
This includes rule-based mistakes such as conducting a procedure differently than
written or knowledge-based mistakes su ch as responding based on knowledge
which is incomplete in this instance.
Violations are intentional. These failures can be routine in that it is the way a task is
conducted (despite what the procedure says); situational or exceptional in that the
operator, in that situation, thought it was appropriate to perform the task that way.
Workload challenges. Workload is the amount of mental effort used to process
information. Problem solving, decision maki ng, and thinking cause workload. The more
attention required, the higher the workload. Su stained high workload is associated with
increased errors, fatigue, and stress.
Multi-tasking causes competition between task s for mental attention. Communicating and
conducting a manual operation at the same time is an example. Although this sounds easy,
the two tasks compete for the same brain space and this can result in poor performance of
one or both tasks.
Reducing the difficulty of the task, the number of tasks running in parallel, the number of
tasks in a series, and time constraints all serve to minimize workload challenge.
Surprise and startle. This is related to the hum an fight or flight response. In this situation
all mental capacity becomes focused on the threat and/or the escape from it. In a fight or flight
state, time is key to survival. Today, that is seen in an urge to be engaged in the active solution.
To act fast, the brain requires a quick underst anding of the problem that doesn’t require
problem solving. Providing very clear instruction on what to do and when to do it is helpful in
this situation.
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REACTIVE CHEMICAL HAZARDS 91
The CSB identified three reactive hazard type s: chemical incompatibility, runaway reaction,
and impact or thermally sensitive materials. (CBS 2002) Chemical reactivity can occur by design
(e.g. in a chemical reactor) or accidentally (e.g. inadvertent mixing of incompatible materials,
storage or handling).
Reactive chemical incidents typically involve:
inadequate hazard identification & evaluation,
inadequate procedures and training for storage and handling of reactive chemicals,
and
inadequate process design for reactive hazards.
Important definitions and terminology related to reactive chemistry include
Endothermic and exothermic reactions can gene rate gaseous or highly volatile products.
Exothermic reactions have the potential for a runaway reaction leading to a dramatic increase
in temperature, pressure (if the reaction is contained) and reaction rate.
Chemical reactions can occur throughout a proc ess facility including in the storage of raw
materials, in process streams, as the products , or in the process waste streams. Particular
attention should be paid to waste streams wher e many chemicals can come together in ways
that may not be identified unless specifically an alyzed. Chemical reactivity types are listed in
Table 5.1 and several reactive function al groups are listed in Table 5.2.
Chemical Reactivity - The tendency of substances to
undergo chemical change. (CCPS Glossary)
Exothermic Chemical Reaction - A reaction involving one
or more chemicals resulting in one or more new chemical
species and the evolution of heat. (CCPS Glossary)
Endothermic Chemical Reaction - A reaction involving
one or more chemicals resulting in one or more new
chemical species and the absorption of heat. (CCPS
Glossary) |