Document ID: OSHA-2009-0023-0165
Agency: osha
Document Type: Supporting & Related Material
Title: 
Posted Date: 2010-08-23T04:00Z

Site Visits Related to Combustible Dust:

Facility V–Metal Manufacturer

	Prepared for:

U.S. Department of Labor

	Occupational Safety and Health 

Administration

	Directorate of Standards and Guidance

	

	Prepared by:

	Eastern Research Group, Inc.

Lexington, MA 02421

July 19, 2010

Table of Contents

  TOC \o "1-5" \h \z \u    HYPERLINK \l "_Toc262907794"  1	Project
Overview	  PAGEREF _Toc262907794 \h  1  

  HYPERLINK \l "_Toc262907795"  2	Facility Description	  PAGEREF
_Toc262907795 \h  2  

  HYPERLINK \l "_Toc262907796"  3	Process Descriptions	  PAGEREF
_Toc262907796 \h  4  

  HYPERLINK \l "_Toc262907797"  3.1.	Process Description	  PAGEREF
_Toc262907797 \h  4  

  HYPERLINK \l "_Toc262907798"  3.2.	Specific Issues Pertaining to
Combustible Dust	  PAGEREF _Toc262907798 \h  5  

  HYPERLINK \l "_Toc262907799"  3.2.1	Dust Accumulations	  PAGEREF
_Toc262907799 \h  5  

  HYPERLINK \l "_Toc262907800"  3.2.2	Housekeeping Practices	  PAGEREF
_Toc262907800 \h  6  

  HYPERLINK \l "_Toc262907801"  3.2.3	Oxidant Concentration Reduction	 
PAGEREF _Toc262907801 \h  7  

  HYPERLINK \l "_Toc262907802"  3.2.4	Dust Collectors	  PAGEREF
_Toc262907802 \h  8  

  HYPERLINK \l "_Toc262907803"  3.2.5	Fire Fighting	  PAGEREF
_Toc262907803 \h  10  

  HYPERLINK \l "_Toc262907804"  3.2.6	History of Fires and Other
Incidents	  PAGEREF _Toc262907804 \h  11  

  HYPERLINK \l "_Toc262907805"  3.2.7	Ignition Sources	  PAGEREF
_Toc262907805 \h  12  

  HYPERLINK \l "_Toc262907806"  4	Document Review	  PAGEREF
_Toc262907806 \h  12  

  HYPERLINK \l "_Toc262907807"  4.1.	Testing Data	  PAGEREF
_Toc262907807 \h  12  

  HYPERLINK \l "_Toc262907808"  4.1.1	Facility V’s Knowledge Base	 
PAGEREF _Toc262907808 \h  13  

  HYPERLINK \l "_Toc262907809"  4.1.2	OSHA’s Analyses of Samples
Collected During the Site Visit	  PAGEREF _Toc262907809 \h  13  

  HYPERLINK \l "_Toc262907810"  4.2.	Material Safety Data Sheets (MSDSs)
  PAGEREF _Toc262907810 \h  14  

  HYPERLINK \l "_Toc262907811"  4.3.	Written Safety Management
Procedures	  PAGEREF _Toc262907811 \h  15  

  HYPERLINK \l "_Toc262907812"  5	Training	  PAGEREF _Toc262907812 \h 
16  

  HYPERLINK \l "_Toc262907813"  6	Safety Programs	  PAGEREF
_Toc262907813 \h  17  

  HYPERLINK \l "_Toc262907814"  7	Main Findings	  PAGEREF _Toc262907814
\h  18  

  HYPERLINK \l "_Toc262907815"  8	Feedback to OSHA	  PAGEREF
_Toc262907815 \h  20  

  HYPERLINK \l "_Toc262907816"  9	References	  PAGEREF _Toc262907816 \h 
21  

 

Table 1			Testing Results for Samples Collected During the Site Visit

Figure 1		Photograph of Tiger Vacs

Figure 2		Photograph of Grinding Operation

Figure 3		Photograph of Control Panel for Argon Quench System 

Figure 4		Photograph of Dry Dust Collector

Figure 5		Photograph of Wet Dust Collector (RotoClone)

Figure 6		Photograph of Paper Filter Bed for Collecting Metal Fines in
Rinsate

Figure 7		Cylinder Used to Pour Salt on Fires

Attachment 1	Copy of Testing Results Provided by OSHA’s Analytical
Laboratory

Abbreviations

ERG		Eastern Research Group, Inc.

LOC		limiting oxidant concentration

MSDS		Material Safety Data Sheet

NFPA		National Fire Protection Association

OSHA		Occupational Safety and Health Administration

PPE		personal protective equipment

PSM 		process safety management

Definitions

argon quench	One of many different options for explosion prevention, an
argon quench prevents deflagrations by reducing the air concentration of
oxidants—one of the necessary elements for an explosion to occur. In
the context of this facility, certain manufacturing operations with a
high potential for deflagrations were operated in an atmosphere quenched
with argon, such that the oxygen concentration in the process equipment
was safely below the limiting oxidant concentration.

fines 	Fines is a general term used to refer to finely-divided
particulates (e.g., powders) formed in the manufacture of metal
products. Some consensus standards have established a specific particle
size cut-off when defining fines, but no such definition has been
developed for the metal that this facility processed. Examples of metal
fines at this facility include dusts and powders generated by the band
saws.

LOC	The limiting oxidant concentration (LOC) is the minimum
concentration of oxygen (displaced by an inert gas, such as argon)
capable of supporting combustion. Dust cloud explosions will not occur
in atmospheres having an oxygen concentration below the LOC.

“off-spec”	Off-spec is a term used in manufacturing industries to
refer to a material that does not meet standard requirements. In the
context of this facility, some metal materials generated at the facility
that did not meet quality control guidelines were designated as
“off-spec.” However, the various off-spec materials could still be
re-processed and made into viable products. 

pyrophoric 	A term used to describe a material that ignites
spontaneously when exposed to air. 

regulus	Refers to the metal mass that is formed when a metal-containing
ore is smelted or reduced. In the context of this facility, multiple
materials are placed in a retort furnace. After the furnace cycle is
complete, the furnace contained two solid products: the regulus (which
is the metal-enriched portion used for further processing) and a solid
byproduct that is removed and disposed of.

swarf 	Swarf refers to any fine metallic material generated by cutting
and grinding tools in the machining of metals. While the precise
distinction between swarf and “metal fines” was not always clear,
facility personnel generally suggested that swarf is coarser than metal
fines.   

 

Project Overview 

On June 18 and 19, 2009, Eastern Research Group, Inc. (ERG) conducted a
two-day site visit to a metal manufacturer (hereafter referred to as
“Facility V”). The site visitors included two ERG employees and one
consultant. The purpose of this site visit was to obtain
facility-specific information on combustible dust recognition,
prevention, and protection programs, and to relay notable findings and
other facility feedback to the Occupational Safety and Health
Administration (OSHA). Site visit activities included touring facility
operations, reviewing relevant documentation, collecting samples for
analysis by OSHA’s analytical laboratory, and interviewing employees
who work in areas with combustible dust. 

The purpose of this report is strictly to document observations made
during the site visit, which may not reflect facility conditions at
other times. The site visit was not designed to assess Facility V’s
compliance with OSHA regulations or adherence to National Fire
Protection Association (NFPA) consensus standards and therefore, should
not be used to make such assessments. The site visit focused on safety
issues pertaining to combustible dust and was not intended to be a
facilitywide evaluation of all OSHA regulations (e.g., means of egress,
fire protection, powered platforms). This report should not be viewed as
a comprehensive review of Facility V’s operations, because site
visitors toured only a subset of the facility’s processes; and not all
of the site visitors’ observations are documented in this report. The
remainder of this report is organized into the following sections:

Organization of Report

Section	Title	Contents

2	Facility Description	General information about Facility V, such as its
main products, operational history, and number of employees.

3	Process Descriptions	Descriptions of the production processes that ERG
toured, with a focus on combustible dust safety issues; section includes
information on process-specific controls, housekeeping practices, and
equipment cleaning procedures. 

4	Document Review	Summary of various facility documents pertaining to
combustible dust safety issues.

5	Training	Review of Facility V’s training programs.

6	Safety Programs	Summary of the extent to which combustible dust
factors into emergency response, confined space entry, and other safety
programs.

7	Main Findings	Key observations made by the site visit team. 

8	Feedback to OSHA	Feedback that Facility V representatives wished to
communicate to OSHA as it decides how to pursue combustible dust issues.

9	References	Full references for documents cited throughout the report. 

 

Facility Description

Facility V manufactures multiple metal products, with the main one being
a pyrophoric metal. The main metal product can readily ignite at room
temperature under certain conditions, as discussed later in this report.
This metal is separated and purified on site from a dry crystalline
chemical feedstock. The pure metal extracted from this feed is then
fabricated into various shapes and sizes to meet customer needs.
Facility V representatives suspected that the challenges they face in
controlling combustible dust hazards might be representative of those
experienced by other facilities that manufacture and process pyrophoric
metals. The site visit focused on potential combustible dust hazards
associated with manufacturing the main metal product. Facility V
manufactures other metal products, but those production lines were not
reviewed in detail and are not discussed further in this report. 

Facility V manufactures its primary metal product using a series of
operations—some conducted in batches but others continuously. Most
processes operate year round except for scheduled process down times,
but some processes are shut down for extended durations (months) for
maintenance. During the site visit, most of Facility V’s chemical
separation and purification steps were shut down, but the metal
fabrication processes were operating.  

Facility V was constructed approximately 30 years ago; and its main
production areas are located in buildings with a combined total floor
space of roughly 330,000 square feet. Approximately 480 employees work
at Facility V, with about 300 of these working in production areas. The
facility has approximately 30 in-house contractors who work primarily on
security and facility maintenance. Six full-time professionals—three
industrial hygienists and three environmental engineers—work in
Facility V’s safety department. All of these employees have had some
involvement with combustible dust safety issues, but no one works full
time on this topic. 

Facility V has its own fire brigade with approximately 40 members. The
facility also has a fire station, fire engine truck equipped with
various types of fire suppression agents and agent application devices,
hazardous materials response van, and other equipment needed to respond
to fires and other emergency events. Though Facility V has not
experienced an explosion resulting from combustible dusts in recent
years, employees frequently encounter fires and smoldering material (see
Section 3.2.6 for more details). Smoking is not allowed at Facility V;
site visitors noticed no evidence of smoking (e.g., discarded
cigarettes) in the production areas.

Site visitors asked the facility’s safety personnel to comment on the
roles that outside parties play in Facility V’s combustible dust
safety programs. A summary of those responses follows: 

Facility V is visited annually by the local fire marshal. However, the
local fire fighting force (a county fire department) reportedly has
limited specialized experience with combustible dust safety issues,
especially those associated with pyrophoric metals. The local fire
marshal does not require or suggest adherence to NFPA standards specific
to combustible dust. Per an internal company policy (see Section 4.3),
Facility V’s safety department informs the county fire department of
specific combustible dusts present at the facility and offers to share
testing results for these materials. 

Facility V’s insurance underwriter conducts annual site visits to
recommend actions to minimize property losses, but this company offers
limited specialized expertise in combustible dust safety issues.
Facility V has obtained and reviewed combustible dust safety guidance
documents prepared by other insurance underwriters (FM, 2009). 

Facility V has previously contracted with consultants and external
engineering and design firms to assist with designing and installing
dust controls during facility expansions, process upgrades, and other
changes to production equipment. However, consultation with external
parties occurred far less frequently at this facility when compared to
other facilities that ERG visited, apparently because Facility V and its
parent company have extensive in-house expertise for evaluating and
addressing safety issues for the metals produced.  

Facility V representatives have not consulted directly with OSHA on
combustible dust issues. Some facility personnel, however, actively
track OSHA’s ongoing activities pertaining to combustible dust. For
instance, some employees had already obtained and reviewed OSHA’s
Combustible Dust National Emphasis Program. Further, facility
representatives attended an OSHA presentation on combustible dust
issues, but the presentation was not specific to combustible metals. 

Facility personnel are actively engaged in relevant NFPA committees and
track and comment on proposed revisions to the most applicable
standards, primarily NFPA 484. 

For further insights on potential hazards, facility personnel maintain
communication with experts who conduct research on the same pyrophoric
metals and other companies that process these metals. As evidence of
this, Facility V recently hosted a symposium dedicated specifically to
the hazards posed by certain pyrophoric metal dusts. 

Process Descriptions

This section describes the process operations that the ERG site visitors
viewed at Facility V; Section 3.1 provides a very general overview of
Facility V’s production processes; and Section 3.2 summarizes site
visitors’ specific observations pertaining to dust accumulations,
housekeeping practices, control technologies, and other related issues.
All photographs referred to in this section appear at the end of this
report. 

Process Description

Facility V uses numerous unit operations to manufacture its metal
products. The unit operations used to manufacture the main metal product
fall under two general categories:

Chemical extraction. The various chemical extraction processes are used
to convert the dry crystalline feedstock into the pure form in a
physical state suitable for the metal fabrication procedures. The
feedstock is enriched with the metal of interest but also contains other
metals that must be separated. These separations occur when the
feedstock and other raw materials enter a series of reaction and
separation processes, which generate a chlorinated form of the metal as
an intermediate product. Facility V is subject to OSHA’s process
safety management standard due to the amount of certain highly hazardous
chemicals used in the separation processes. 

The chlorinated metal along with another metal are then placed into a
retort assembly, which is welded shut and heated in a reduction furnace.
The heat in the furnace (roughly 600 °C) drives inorganic reactions
that form the pure metal product in an unfinished solid form on the top
layer, as well as a solid byproduct beneath it. After the reaction is
complete, the retort is removed, its welds are broken, and the metal
product and byproducts are removed and physically separated. Combustible
dust is generally not an issue until the solid material is removed from
the furnace, and it remains an issue for all subsequent processing.  

The metal product at this stage is in a large, thick, disk-shaped
regulus. Employees remove surface impurities with needle guns and other
hand-held tools—a process that routinely causes sparks, hot spots, and
small fires that operators extinguish with salt (see Sections 3.2.5 and
3.2.6). The large unfinished metal disk is broken into smaller pieces
using a hydraulic press, after which the metal pieces are conveyed into
a grinder. The grinding operations are fully enclosed and crush the
metal into smaller pieces (typically not larger than 1 inch) more
suitable for further processing. Both the press and grinder operate
under inert atmospheres to prevent the pyrophoric metal from igniting
(see Section 3.2.3). Following a manual sorting process, where employees
remove rejected pieces from a picking conveyor by hand, the small pure
metal pieces are sent to the fabrication line. 

Throughout its processes, Facility V generates some scrap and off-spec
metal items that still hold value. These materials must first pass
through a recycling process to remove surface impurities before they can
be used in the other production lines. The recycling process involves
wet milling and drying. The dryer operates under an argon quench, but
has experienced several fires in recent years. Facility V developed
specialized approaches to applying suppression agents to address fires
in the recycling operation (see Section 3.2.5). 

Metal fabrication. Facility V’s metal fabrication processes form the
metal pieces generated by the chemical extraction and separation steps
into two categories of products: round items (e.g., tubes, rods, wires)
and flat items (e.g., sheets, plates). These products are formed through
a series of physical processing activities. First, the pure metal pieces
and alloying elements are placed in a 5,000-ton press that forms
briquettes. The briquettes are then assembled into an electrode, welded
together, re-melted in inert atmosphere vacuum arc furnaces, and cast
into ingots. 

Further processing activity of the ingots depends on the type of product
being made. For round items, a forge press shapes the ingots into long
logs, which are cut into smaller billets. The billets are extruded into
the rod shapes. For flat items, a forge press first shapes the ingot
into slabs, which then pass through a roller furnace and cold rolling
processes to form sheets of varying thickness. Various other activities
(e.g., annealing, conditioning, pickling, sanding, sawing, buffing,
polishing) are conducted when finishing both the round and flat
products. Metal chips, dusts, and fines are generated by many of these
physical processing operations, particularly the saws and sanders. 

Specific Issues Pertaining to Combustible Dust 

This section summarizes site visitors’ observations on several
specific issues regarding potential combustible dust hazards at Facility
V. These specific issues are documented here because they either
1) demonstrate unique challenges faced by this industry, 2) highlight
effective engineering solutions implemented by Facility V, or 3) point
to areas where improved combustible dust control measures could be
implemented. 

Dust Accumulations

Dust accumulations at Facility V were generally minimal but varied
across production areas and materials. Some of the most visible
accumulations were observed for materials that are not combustible
dusts, per laboratory tests conducted on selected samples. Examples
include petroleum coke with 0% smaller than 75 microns (see Table 1,
sample #4992) and metal oxide (see Table 1, sample #4993), both of which
had small localized accumulations in some production areas. 

For the main metal product, dust accumulations were minimal and limited
to areas where the metal was physically processed. These include several
production lines in the fabrication area, a metal recycling operation,
and the cleaning and grinding of large metal disks in the chemical
extraction area. The limited accumulations were consistent with a
facilitywide dust control philosophy of minimizing accumulations of
“fuels” (i.e., combustible metal dusts). Every operator interviewed
echoed this philosophy and cited internal guidelines limiting dust
accumulations. 

Facility policies specify maximum accumulations allowed for the most
high-risk materials (i.e., materials that ignite easily and burn
rapidly). For instance, these policies prohibit fine dusts found near
saw blades to be in mounds greater than the size of a baseball. For
lower risk materials (i.e., materials that do not ignite easily but will
burn if involved in an ongoing fire), accumulations near saw blades and
other localized areas were not to exceed the size of a basketball (see
Section 4.3). Operators appeared to understand and follow these
guidelines, possibly because they are communicated in terms that
employees can easily visualize (i.e., baseballs, basketballs) as opposed
to numerical descriptors that may be less transparent though more
precise (e.g., a cone no taller than 10 centimeters).  

Housekeeping Practices

Facility V’s housekeeping practices focus on minimizing accumulations
of metal dusts, especially finely divided material. In production areas
where the pyrophoric metal was machined and otherwise physically
processed, dust accumulations were removed from working surfaces
multiple times during a shift. For example, metal fines, dusts, and
threads were promptly moved to a 5-gallon metal bucket, typically stored
inside a fire resistant step can. Section 4.3 describes how these waste
buckets were consolidated and handled. 

Settled dust was typically removed with brooms and spark-free tools. Air
hoses are not permitted for removing dust accumulations, and site
visitors saw no evidence of their use. Facility V recently purchased
“Tiger vacs” (see Figure 1) that employees use to safely collect the
metal dusts. These vacuums have European and Canadian Standards
Association certification for operating in Class II Group E
environments: they are dust ignition proof or dust ingress proof,
static-dissipative, and have conductive hoses and attachments. Dusts
vacuumed by the Tiger vacs are submerged in water reservoirs internal to
the devices. Although these vacuum cleaners appear to have appropriate
certifications for use with combustible metals, some Facility V
employees have complained about lack of mobility when operating this
equipment and the need to clean water reservoirs after every use. 

In addition to the routine cleaning throughout the day, many production
areas at Facility V undergo more extensive “top-to-bottom” wipe
downs that remove dust accumulations not only from working surfaces, but
also from walls, overhead structures, and other inaccessible areas that
are not otherwise cleaned. The frequency of these more thorough
cleanings varies, and they occur monthly in production rooms with
greater potential for hidden accumulations of combustible dusts (e.g.,
in the room housing the grinder). 

Oxidant Concentration Reduction

Over the past 20 years, Facility V has retrofitted some processes to
operate inside enclosures under inert atmospheres. Examples include a
metal storage area, the grinding machine (see Figure 2), and the hopper
receiving metal pieces from the grinder—all of which use argon as the
inert agent. This control strategy was selected because formation of
metal dusts (particularly in the grinder and hopper) could not easily be
avoided, and limiting the oxidant concentration was the most effective
means for removing a required element for deflagrations. 

In the grinding operation, facility operating procedures require oxygen
concentrations to be below 10% for at least two minutes before the
machine can be energized; and the oxygen concentration must remain below
4% while metal is being crushed. A control panel in the grinding room
(see Figure 3) displayed oxygen concentrations inside the enclosures,
and the continuous oxygen measurements were interlocked with the metal
feed. 

Site visitors and facility representatives extensively discussed the
adequacy of this concentration threshold, given the significant
consequences associated with underestimating this value. Facility V
representatives indicated that the concentration threshold is based on
published values of the metal’s limiting oxidant concentration (LOC).
Documentation of this evaluation was not available for review at the
time of the visit, however. 

Site visitors encouraged facility personnel to ensure that the maximum
allowable oxygen concentration in the argon inerted grinder be derived
based on requirements outlined in NFPA 69 (“Standard on Explosion
Prevention Systems”), Section 7.7.2.5. Further, site visitors advised
that Facility V support its assessment with LOC measurements of the
metal in argon atmospheres, as determined by approved testing methods.
Such information would support the design for all facility operations in
argon atmospheres.  

Dust Collectors

Facility V operates various types of dry and wet dust collectors. Only
wet dust collectors are used to control dusts containing pyrophoric
metals. Site visitors’ observations on two specific dust collectors
are summarized below:

Dry dust collector. A large dry dust collector (see Figure 4) is located
outside Facility V’s general maintenance shop and controls welding
dusts and other materials generated by machining of tools, but no
pyrophoric metals are vented to this dust collector. Exhaust air from
the dust collector is returned to the workplace. No explosion isolation
systems are in place, however, to prevent deflagrations that might
originate in the dust collector from propagating into the building.
Facility V personnel can address the need for these and other controls
by testing a representative sample of collected dusts for combustibility
and explosibility parameters. 

Wet dust collector. In recent years, Facility V has installed several
wet dust collectors to control metal dusts generated during sanding,
sawing, and other fabrication processes. As an interesting and
representative case study, site visitors reviewed design and operation
considerations for a wet dust collector (similar to the one shown in
Figure 5) used to control dusts generated by a silicon carbide belt
sander. 

In earlier years, some belt sanding operations occurred without dust
control, which raised concern for both dust exposures and increased fire
and explosion risk. To address this issue, Facility V enclosed some belt
sanders, operated them under vacuum, and exhausted air to RotoClone wet
dust collectors. RotoClones were the preferred dust collector because:
1) collected airborne metal dusts are submerged in a water reservoir,
effectively eliminating fire and explosion risks, provided water levels
remain high, and 2) the only moving part is a fan impeller (as is the
case for most dust collectors), greatly reducing ignition sources from
friction and mechanical sparks. Every week, operators manually removed
sludge collected in the RotoClone and disposed of the material according
to the facility’s combustible dust procedure (see Section 4.3).
Enclosures containing the belt sanders are wiped down at the same time. 

Several wet dust collectors in the fabrication area vent the cleaned
exhaust air directly into the workplace. This design was selected for
various reasons. One facility representative noted that state
environmental regulations require industrial facilities to obtain air
permits before constructing any new vent from production areas to
outdoor air—a situation that presented a disincentive for venting the
wet dust collector exhaust to the ambient (outdoor) environment. Site
visitors also learned that Facility V had conducted industrial hygiene
testing to examine dust exposure potential due to the wet dust
collectors’ exhaust, and those results reportedly indicate that the
dust collector design does not present a health hazard. However, a site
visitor suggested that Facility V consider the possibility of unsafe
hydrogen gas levels in and near the wet dust collectors and their
ductwork, as hydrogen gas is produced following water-metal reactions in
the dust collectors. Assessment of this concern would require
measurements of hydrogen concentrations in the dust collectors’
exhaust. 

Site visitors identified several other notable design features for the
RotoClone wet dust collector systems. For instance, the devices have
water level controls that prevent the belt sander from operating if the
water reservoir levels are too low. Further, an interlock prevents the
belt sander from operating unless the RotoClone has been activated; and
a separate water spray in the sander cabinet must be activated before
the belt sander can operate. The flexible ductwork for some RotoClones
(see Figure 5) has many bends and areas of potential dust accumulation,
and some ductwork used on these devices consists of cylindrical plastic
tubing that is not conductive but seems to have a spiral wire insert for
ground connections. Dirty filters from the RotoClones are removed and
stored under water in drums prior to disposal.  

Facility V representatives said the cost to purchase and install a dust
collection system for the belt sander was approximately $60,000. These
costs included $18,000 for the RotoClone, $35,000 for ductwork and the
belt sander’s enclosure, and $7,000 for electrical equipment and other
peripherals. 

During interviews with Facility V employees, engineers and operators
both indicated that the implementation of dust control measures on the
belt sanders was a success. Previously, these operations emitted
uncontrolled metal dust, which would collect on walls and other
surfaces. Since installing the wet dust collectors and equipment
enclosures, fugitive emissions have decreased dramatically. The only
areas where dusts appear to collect are within the belt sander
enclosures, and these are removed periodically with wet rags. Facility V
shared other innovative strategies for ensuring that metal dusts
generated in the fabrication area are handled safely (see Figure 6). 

Fire Fighting

Facility V has its own fire brigade and hazardous materials response
team, and both groups have approximately 40 to 45 members. Fire brigade
members have been extensively trained on preferred fire fighting
measures, including field exercises conducted on the premises for
extinguishing metal fires. The facility has a fire house, fire engine,
fire water pump house, and hazardous materials response vehicle. 

Facility V’s safety engineers have tested a wide range of Class D
suppression agents (e.g., Met-L-X, sand) for metal fires before
concluding that table salt best meets their needs. All facility
personnel interviewed during the site visit—from senior employees to
new hires—were extremely knowledgeable about standard fire fighting
procedures for metal fires. For example, they knew when to use a Class D
suppression agent, and they emphasized the importance of not using water
or carbon dioxide because they can lead to violent reactions. Use of
other gaseous fire suppressants (e.g., argon) was considered but not
implemented due to concerns about employees encountering
oxygen-deficient atmospheres. One senior engineer stated that the table
salt is very effective for fires involving metal swarf and chips, but is
not as effective for extinguishing fires involving metal fines. 

The table salt used for fire suppression is stored in 55-gallon drums in
many production areas (see Figure 7). Operators used buckets, shovels,
or scoops to transfer table salt from the drums to their workplaces.
When they encountered small fires or smoldering material, employees
poured the table salt directly on top of the fire—a practice that
forced employees to stand very close to fires. Site visitors inquired
about the need for a system that allows employees to deliver salt to its
intended location, but from a safe distance. Facility personnel
responded that use of a pressurized stream to deliver the salt might
spread burning material, thus creating a potentially more hazardous
situation. One option investigated was to load salt in approximately
4-foot-long cylindrical plastic tubes (see Figure 7). This approach
helped keep employees several feet away from burning material and
enabled them to suppress fires in hard-to-reach areas of production
equipment; however, site visitors encouraged Facility V to investigate
the feasibility of using other materials for these tubes because the
plastic may deform or melt when in close proximity to intense heat. 

History of Fires and Other Incidents 

“Fires” appear to occur relatively frequently at Facility V, mostly
due to the fact that the facility processes pyrophoric metal. For the
purposes of this section, fires include a wide range of events, ranging
from glowing or smoldering material to flames of various height and
lateral extent. Certain operations at Facility V experience fires more
frequently (e.g., removing the reacted metal mixture from the retort
assembly, use of needle guns and other tools to clean surfaces of large
metal disks). In fact, site visitors inferred that fires in these
particular areas seem to be expected. 

While this situation was somewhat surprising, site visitors also noted
that every employee interviewed who worked in these areas was extremely
knowledgeable about the hazardous properties of the pyrophoric metal and
the appropriate fire fighting measures. The fact that Facility V had not
experienced a major fire or explosion in recent years due to these
activities was reassuring, but site visitors encouraged facility
representatives to continue to investigate engineering solutions to
reduce the hazard potential and ensure that employees do not develop a
sense of complacency about the metal dust fires. 

Facility representatives shared examples of other fires and incidents
that are noteworthy due to the actions taken to address them or the
lessons learned:

On more than one occasion, sparks emitted from belt sanders ignited
metal dusts and fines that had collected on the floor beneath the
equipment. On a few instances, flash fires occurred in or near the
sanders. As Section 3.2.4 describes, Facility V designed and installed
dust control measures that have largely addressed this problem. 

Facility V had previously experienced fires in a pickling hopper. To
address this issue, the hopper was enclosed, and oxygen concentration
monitors and temperature sensors were placed inside. The system was
designed to operate only when oxygen concentrations were lower than 4%
by volume. When air temperatures in the hopper exceed 150 °F, an argon
purge occurs for at least 30 minutes. Additionally, the hopper was
equipped with a vibrator, which helped operators remove loose material
and fines after the hopper was emptied. Fires have not occurred in the
hopper since these measures were implemented.

Fires have also occurred in and around the dryer used after washing
recycled material designated for further processing. The washing and
drying operation generates fines that are readily ignited because of the
pyrophoric nature of the metal. These operations have since been
modified to require water spray in the conveyors to the dryer and to
eliminate large horizontal surface areas where fines can accumulate.  

Facility representatives also shared the following account of a flash
fire or explosion caused by combustible metal dust in another facility.
Another company grinds and finishes metal products manufactured by
Facility V. Polishing is typically conducted in a process that captures
metal dusts in water. However, water controls in this process were not
functioning, causing accumulations of dry metal dust. An employee
subsequently attempted to remove the dry metal dust accumulation with a
commercial grade vacuum cleaner that was not rated for Class II Group E
materials nor was its hose grounded. Shortly after beginning this task,
a flash fire or explosion occurred inside the vacuum cleaner, and the
employee was badly burned. An investigation by the state OSHA office
found that hazards associated with handling the dry metal dusts were
well documented on Facility V’s material safety data sheet (MSDS), and
the company that polishes the metal products was fined. 

Ignition Sources

Potential ignition sources were discussed, particularly in the context
of sawing and sanding operations in the fabrication area. Facility V had
implemented several measures to minimize these ignition sources, such as
changing from dry sanding to wet sanding, using coolant on saw blades,
and frequently changing dull saw blades. The facility had also
eliminated its use of bucket elevators, which previously was a source of
mechanical sparking. 

Facility representatives seemed to appreciate the need for being
vigilant in identifying and eliminating these and other ignition
sources. Examples of areas of improvement include ensuring that 1) all
electrical equipment used in Class II locations is rated for those
applications and 2) equipment (e.g., flexible ductwork in the
RotoClones) is adequately grounded. 

Document Review

This section summarizes the documents pertaining to combustible dust
safety issues that Facility V made available to site visitors. This
section does not discuss every document that the site visitors reviewed,
but it focuses on documents that offered unique insights into
combustible dust safety issues and Facility V’s approaches for
controlling them. 

Testing Data

Testing data for materials that Facility V handles and produces were
available from two sources: Facility V shared its institutional
knowledge of the pyrophoric metal properties, and site visitors
collected three samples that were sent to OSHA’s laboratory for
analysis. This section summarizes both sources of information.

Facility V’s Knowledge Base

Facility V representatives did not share testing reports with site
visitors, but they summarized testing data during a presentation.
Insights about their main metal product’s combustibility and
explosibility came from tests conducted by the facility and information
published in the scientific literature. Overall, facility personnel
appeared to have a very strong command of the metal’s properties and
how they vary with chemical form and physical state. Examples of some
properties shared with site visitors include the following:

Metal dusts have deflagration indexes (Kst values) that vary with
particle size, but they can reach roughly 600 bar-m/s and the maximum
normalized rate of pressure rise for some samples was 65 psig. Particle
size information for the samples that led to these measurements was not
available. 

Very dry metal dusts (<3% moisture content) and very wet metal dusts
(>25% moisture content) have limited ignition potential, but the
ignition potential increases considerably for intermediate moisture
values. 

Facility representatives shared charts indicating how the minimum
ignition temperature increases as a function of particle size. Fine
metal dusts dispersed in air can spontaneously ignite at room
temperature, but this typically does not occur for particles larger than
50 microns. 

The ignition temperature for layered dust was reported to be as low as
100 °C. 

During employee interviews and the site tour, site visitors asked
several employees to describe the hazardous properties of the metal
dusts. Virtually every employee, including some who had worked at the
facility for only a few weeks, provided thorough qualitative (and
sometimes quantitative) descriptions of metal dust hazards and how they
vary with particle size and moisture content.

OSHA’s Analyses of Samples Collected During the Site Visit

As noted previously, site visitors collected three samples during the
site visit, with the permission and concurrence of Facility V
representatives. Copies of the laboratory testing results appear in this
report as Attachment 1; Table 1 summarizes the results. More information
on the samples collected and their findings follows:

Sample #4282: Metal Hydride. This metal hydride sample was a fine
material (i.e., 100% of the sample had particle size less than 75
microns) with 0% moisture content. The material was tested for
explosibility and did not react, indicating that the material is not
explosive under laboratory conditions. The material was also found to
not be a Class II dust.

Sample #4283: Petroleum Coke. This petroleum coke sample was much
coarser than the metal hydride sample (i.e., 0% of the petroleum coke
sample had particle size less than 75 microns). This sample had a 0%
moisture content and was found to not be explosive under the laboratory
conditions when testing occurred. 

Sample #4284: Metal Oxide. This metal oxide sample was the most coarse
of the three samples collected. Like the metal hydride sample, the metal
oxide had a 0% moisture content, was not found to be a Class II dust,
and was determined not to be explosive under laboratory conditions. 

As noted in the testing results, the data presented above should not be
used in designing or engineering protective safety equipment for various
reasons (e.g., the limited number of samples and tests might not
characterize the full hazard potential).  

Material Safety Data Sheets (MSDSs) 

Facility V provided copies of 14 MSDSs. These included MSDSs that
suppliers provided for raw materials and MSDSs that Facility V prepared
for selected intermediates and products. For the main metal produced by
Facility V, MSDSs were available for the metal in various chemical forms
(e.g., pure metal, metal oxide, metal chloride) and different physical
states (e.g., solid products, metal chips, metal fines, metal powder).
The MSDSs included specific information on fire and explosion risks in
the sections on hazard identification, fire fighting measures,
accidental release measures, and stability and reactivity. Examples of
precautionary language taken from multiple MSDSs include: 

***Emergency Overview*** Shiny, odorless, metal that presents little or
no unusual hazard if involved in a fire in its solid mass state. When in
a particle state, it can be flammable to pyrophoric depending on its
size, surface area, and if wet or damp.

Sources of ignition can start a fire on fine particle sizes. Layers of
3-micron diameter dust are susceptible to spontaneous ignition. [Metal]
burns with very little flame but with large quantity of heat. Do not
spray water on burning powder, fines, chips, or dust as violent
explosion may occur. This hazard increases with finer particles. If a
fire starts in a mass of wet metal fines, such as a drum of damp
machining chips, an explosion and a very high temperature flash
radiation may follow the initial fire. Therefore, when in doubt,
individuals should leave and not attempt to extinguish the fire and let
it burn out. Carbon dioxide is not effective in extinguishing burning
[metal] and will accelerate combustion. Fire extinguishers should not be
pointed directly at the burning material, so as not to stir up and
aggravate the fire.

Use extreme caution; do not air blow material or use a vacuum cleaner
during cleanup. Sweep up with non-sparking tools and put into dry metal
container no larger than 30 pound capacity. Have a supply of dry salt of
a Type D fire extinguisher immediately available prior to and during
cleanup.

Further, some MSDSs prepared by Facility V considered potential hazards
that might occur for a material’s anticipated future conditions of
use. For example, MSDSs for certain solid forms of the metal product
included the following precautionary language:

This metal in its present state is classified as an article and is not
OSHA regulated… However, manipulating this product, such as sawing,
grinding, welding, etc. may create a fire/health hazard and would then
be considered a regulated item. A new material safety data sheet would
have to be developed if the state of the product is changed in any way. 

Written Safety Management Procedures

Facility V shared two written safety management procedures with site
visitors. Details from these procedures follow:

“Handling of Flammable Metal Fines.” Facility V developed this
internal working procedure to “…establish guidelines for the safe
and proper handling of flammable metal fines, chips, and turnings.”
The procedures clearly define three different categories of metal
materials and specify how they should be handled. Examples of specific
requirements include: 

Type I flammable material includes any item that can ignite easily and
burn rapidly (e.g., saw fines, certain waste sludge, metal dusts, floor
sweeps). These materials pose the greatest fire and explosion potential.
The amount of Type I material allowed near the blade of a cutting tool
is to be minimal and generally not to exceed the size of a baseball,
when piled together. Only one 5-gallon accumulation container of Type I
material is permitted in a particular work area at a given time, and
Class D fire suppression agents must be readily available. Employees are
required to pour salt over every layer of metal fines added to these
containers. (Alternatively, fines added to waste containers can be
submerged in water.) 

At the end of every shift, or sooner if necessary, operators transfer
contents of the accumulation container to 55-gallon fines storage drums
kept in designated staging areas. No more than four of these drums can
be stored on a pallet at any given time, and the pallet must be placed
at least 25 feet from any building or structure. Any fire involving Type
I material triggers an investigation by a supervisor, who must prepare
an incident report. 

Type II flammable material includes any item capable of burning in a
fire, but not having the same ignition potential as Type I material.
Examples of Type II materials include turnings, chips, and scrap metal
foil. Accumulations of Type II material near cutting tools and other
operations are also required to be minimal and not to exceed the size of
a basketball, when piled together. Only one accumulation container of
Type II material is permitted in a given work area at a given time, and
it must be within 25 feet of Class D fire suppression agents. The
accumulation container for Type II materials can be a 55-gallon drum,
but there is no requirement for daily transfers of Type II material to
staging areas. Fires involving Type II materials also trigger
investigations and incident reports. 

Type III material includes metal items that are too large to sustain a
flame. Examples include wire, large chips, tube ends, and bar ends. The
only specific requirement for accumulated material is that Class D fire
suppression agents must be located within 50 feet.

Overall, site visitors found these material handling procedures to be
extremely thorough. Specifying accumulation thresholds in terms of
shapes (e.g., baseballs, basketballs) that operators can readily
recognize and visualize was useful. Also impressive was the fact that
employees seemed to be well aware of—and seemed to abide by—the
material handling procedures.

“Combustible Dusts.” In 2008, Facility V developed written
procedures with the objective of minimizing “…the occurrence of and
resulting damage from fire or explosion in areas where combustible
metals, metal dusts or non-metal dusts are handled, finished, produced,
processed, stored, and used.” These procedures were based on
information documented in multiple NFPA standards (i.e., NFPA 68, 69,
70, 77, 484, 499, and 654) and outline general considerations for
effective control of combustible dusts. For instance, the procedures
describe issues of concern for dust control, ignition control, damage
control, housekeeping, and training. These written procedures also
require that written hazard analyses be conducted when designing fire
and explosion safety measures, with the hazard analysis reviewed and
updated every five years. 

Training 

Facility V offers numerous training courses to its employees and
contractors. This section presents observations on the content of only
those training courses that facility personnel mentioned during the site
visit. Therefore, this is just a partial list of the training that
Facility V offers to its employees. 

Contractor training video. Site visitors watched a 30-minute video that
Facility V required visiting contractors to view before working in
onsite production areas. The training addresses a wide range of topics,
including plant security, emergency response, lockout/tagout, and
chemical and physical hazards. The training also specifically covers
unique hazards associated with working with a pyrophoric metal. 

Computer-based training series on general safety topics. Facility V
purchased a package of compact disks containing several computer-based
training courses. The individual courses addressed confined space entry,
forklift operation, hot work permits, lockout/tagout, and other general
safety topics. 

Initial training for operators. Every new employee received extensive
training on the hazards of pyrophoric metals, preferred methods for
suppressing metal fires, and relevant facility safety management
procedures (e.g., see Section 4.3). This training included computer
courses, videos (e.g., demonstrating effects of spraying water on metal
fires), and on-the-job training. One new employee interviewed by site
visitors indicated that his first three weeks on the job were spent
either in training courses or observing other operators. 

Safety Programs

This section typically reviews the site visitors’ observations of
selected facility safety programs, with a focus on the extent to which
combustible dust factored into these programs. When visiting Facility V,
site visitors had time to review two aspects of these safety programs: 

Management of change. Facility V’s written management of change
procedures, which were last updated in 2007, were apparently implemented
to comply with OSHA’s process safety management (PSM) standard, though
these procedures were also applied to changes in processes that did not
have chemical usage that triggered PSM applicability. The written
management of change procedures clearly defined “change” (e.g., all
changes to equipment, products, raw materials, production processes,
safety related equipment, control systems); it also defined exclusion
criteria and activities not considered to be “change” (e.g.,
replacements-in-kind). The procedures specified roles and
responsibilities for employees who propose and design changes and listed
minimum qualifications of employees who can authorize changes. Forms and
checklists must be completed and approved before most changes could be
implemented. Some questions in the checklists specifically address
potential combustible dust hazards: “Will the change increase the fire
hazard of accumulated or stored [metal] fines?” and “Will the change
create or increase existing fire or explosion hazards?”

Personal protective equipment and uniforms. All operators at Facility V
are required to wear hard hats, safety goggles, and steel-toed shoes in
most production areas. The facility also recently required its operators
to wear fire-resistant coveralls. Face shields and gloves are required
for certain operations, but primarily to protect against physical
hazards. 

Main Findings

During the closing meeting of the site visit, the ERG site visitors
shared several key findings. These represent observations raised by
three independent engineers and should not be viewed as a judgment on
Facility V’s compliance with OSHA regulations or adherence to NFPA
consensus standards. The main findings communicated to Facility V
representatives include: 

In most production areas, dust accumulations were minimal, which
appeared to result from 1) widespread employee recognition of hazards
posed by even small quantities of pyrophoric metals and 2) adherence to
Facility V’s materials handling procedures. Continued vigilance in
preventing unsafe accumulation of metal dusts and solids will help
prevent Facility V from experiencing a major fire or secondary dust
explosion. 

In recent years, Facility V implemented many effective and proactive
engineering solutions and administrative controls to prevent fires and
explosions or mitigate their consequences. Examples include installing
enhanced dust control systems and wet dust collectors on selected metal
fabrication lines, shifting from dry processes to wet processes,
developing a tube applicator for delivering salt to small metal fires,
limiting oxidant concentration in multiple operations, sealing off flat
surfaces that would otherwise accumulate dusts, and requiring employees
to wear fire-resistant clothing. 

Most employees interviewed at Facility V had an extremely high level of
awareness of combustible dust hazards, how to prevent fires, and how to
suppress a metal fire should one begin. This awareness is a testament to
the facility’s extensive education and training programs, which
consistently reinforce the need to control combustible dust hazards.
Expressing maximum allowable dust accumulations and other concepts in
terms that employees can visualize is an interesting approach and one
that might have also heightened understanding of the facility’s safety
management procedures. However, Facility V is encouraged to ensure (if
it has not done so already) that these visual representations are
related to quantitative measures of allowable dust accumulation based on
area explosion and fireball development hazard evaluations. 

Facility representatives seemed well aware of the specific workplace
activities that led to the greatest dust accumulations and caused the
most fires. Facility V is encouraged to seek engineering solutions or
implement administrative controls to mitigate the hazards associated
with these activities (e.g., cleaning surfaces of large metal disk
before crushing it, operations in the metal recycling room). Thoroughly
documenting and reviewing incident reports can also help prioritize
future hazard mitigation efforts. 

For some operations, small fires were commonplace, if not routine
occurrences (e.g., “we always have fires when conducting this
activity”). While employees generally knew the appropriate means for
suppressing metal fires, as noted above, site visitors were concerned
that some employees might be developing a sense of complacency about the
fires. 

Facility V should investigate engineering solutions to seek more
automated processing procedures for handling the more pyrophoric forms
of metals (such as the regulus from the retort) so that facility
personnel do not need to be in the immediate vicinity of these materials
when fires most frequently develop. Continued development of salt
applicators and determination of the limitations of manual salt
application for fire suppression are also encouraged. 

By multiple employee accounts, the dust control measures recently
installed in the fabrication area mark a considerable improvement over
previous conditions. Facility V should determine whether there are dust
accumulations in the wet dust collectors’ inlet ducting and verify
that the flexible plastic ductwork is adequately grounded. Measurements
should be made of possible hydrogen concentrations in the clean air
being returned from the wet collectors to the work area. Facility V
should also consider the need for (1) spark/ember detection and
extinguishing systems and (2) explosion isolation systems in the inlet
ducting to the large dry dust collector, if testing results of the
collected material indicate a potential for explosion propagation back
from the collector. 

Multiple processes at Facility V operate under inert atmospheres. This
operation can be highly effective at preventing fires or explosions, but
it is essential that the oxygen concentration limit be set below the LOC
with an acceptable margin of safety. Facility V is encouraged to ensure
that all aspects of these processes are consistent with specifications
in NFPA 69 and to document the LOC testing data used to establish the
maximum oxygen concentrations for these operations. 

Feedback to OSHA

At the end of the site visit, ERG asked representatives from Facility V
if they had any specific feedback to OSHA on combustible dust safety
issues. (Note: This site visit occurred before OSHA publicly announced
its intention to initiate a rulemaking on combustible dust [OSHA,
2009b]). Facility V representatives offered the following responses:

OSHA should be aware of the unique properties of certain metal dusts,
especially those for pyrophoric metals. Some requirements and guidelines
that may be acceptable for other facilities that process combustible
dust would not be acceptable if applied to certain pyrophoric metals.
For example, 1/8-inch accumulations might not be unsafe for agricultural
grain dust, but they would be extremely hazardous for a pyrophoric
metal. 

Facility V representatives noted difficulties associated with tracking
standards published by both OSHA and NFPA—an effort complicated by the
fact that NFPA revises its standards every few years. To simplify
matters, they encouraged OSHA to articulate its combustible dust
requirements as clearly as possible and to strive for consistency with
NFPA requirements, where appropriate.

Facility representatives responded positively to how NFPA 484 organizes
information into chapters for specific metals. This organization made it
much easier for facilities to quickly identify which requirements
pertain to their processes. They encouraged OSHA to consider a similar
approach when developing its combustible dust standard. 

Most facility representatives preferred that OSHA’s standard be
performance-based, rather than prescriptive. They also recommended that
OSHA consider designating agency experts on specific types of
combustible dusts (e.g., coal dusts, metal dusts, agricultural dusts)
and allowing these experts to provide technical consultation to the
regulated community. 

References

FM, 2009. FM (Factory Mutual) Global Data Sheet 7-76: Prevention and
Mitigation of Combustible Dust Explosion and Fire. March, 2009. 

OSHA, 2009b. U.S. Department of Labor’s OSHA announces rulemaking on
combustible dust hazards. U.S. Department of Labor, OSHA, Office of
Communications. National News Release: 09-475-NAT. April 29, 2009.

U.S. Bureau of Mines, 1965. Explosibility of Metal Powders. Available
online at:
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADB270510&Location=U2&doc=GetTRD
oc.pdf

 

Table 1. Testing Results for Samples Collected During the Site Visit

Parameter	Sample #4991	Sample #4992	Sample #4993

Description of material	Metal hydride	Petroleum coke	Metal oxide

Particle size information

	   % through 20 mesh	100%	99%	69%

   % through 40 mesh	100%	34%	49%

   % through 200 mesh	100%	0%	22%

Moisture content	0%	0%	0%

Resistivity 	694 ohm-cm	Not tested	50,400 ohm-cm

Explosive material?	No; did not react	No; did not react	No; did not
react

Class II dust? 	No	Not tested	No

Notes:	See Section 4.1 for a more detailed description of the sampled
materials and where they were collected.

Refer to Attachment 1 for the original reports from OSHA’s analytical
laboratory and important disclaimers about use of these data.

Figure 1. Photograph of Tiger Vacs

Note: 	This photograph shows two “explosion-proof/dust ignition-proof
vacuums” (Tiger vacs) that Facility V employees use to clean
combustible metal dusts. As Section 3.2.2 notes, the Tiger vacs have
helped employees collect metal dusts safely and effectively, though
employees have complained about limited mobility when operating these
devices and the need to remove the water reservoir of collected material
after every use. The Tiger vacs have Canadian Standards Association
certification for use in Class II Group E locations (see Section 3.2.6).

 

Figure 2. Photograph of Grinding Operation

Note: 	This photograph shows Facility V’s grinding machine. Large
chunks of the pure metal are fed at the top of the grinding machine and
are then crushed into smaller (roughly 1-inch) pieces in an argon
atmosphere. These pieces are conveyed to a hopper located in an adjacent
room. The hopper also operates under an argon atmosphere. 

Figure 3. Photograph of Control Panel for Argon Quench System

Note: 	This photograph shows the readout of oxygen measurements
continuously recorded in the hopper’s argon atmosphere. As Section
3.2.3 explains, the equipment can only operate when oxygen
concentrations are less than 4%—a concentration that was reportedly
derived from the metal’s LOC. Site visitors encouraged Facility V to
document the testing data and analyses used to establish this
concentration threshold. 

 

Figure 4. Photograph of Dry Dust Collector

Note: 	This photograph shows a dry dust collector used to control
operations in Facility V’s machining and maintenance shop. Dusts
generated in this operation do not contain pyrophoric metals. The
cleaned air from this dust collector returns to the workplace. However,
no fire detection/suppression or explosion isolation systems were in
place to prevent a deflagration that originated in the dust collector
from propagating directly into the workplace. 

Figure 5. Photograph of Wet Dust Collector (RotoClone)

Note: 	This photograph shows one of Facility V’s smaller wet dust
collectors located inside the metal fabrication building. Dusts removed
from the process air stream are submerged in water and eventually settle
in sludge, which operators periodically remove manually. The dust
collector’s exhaust air is vented directly into the workplace. The
flexible ductwork connecting the wet dust collectors has several bends
and areas of potential dust accumulation, which is inevitable with
flexible ducting, but did not appear to have sharp bends with small
radii of curvature.

Figure 6. Photograph of Paper Filter Bed for Collecting Metal Fines in
Rinsate

Note: 	This photograph depicts an innovative engineering solution that
Facility V employed when shifting from dry sanding to wet sanding
operations. Rinsate from the wet belt sander passes through the trough
before being collected in the larger vessel. By first passing the
rinsate through the filter paper, collected metal fines are removed from
the water stream, thus reducing potentially costly wastewater treatment
requirements. Operators remove the filter paper as needed, and the
collected material is placed in a water bath prior to disposal. Overall,
this engineering solution enables the facility to 1) reduce fugitive
dust emissions by changing from the dry sander to the wet sander and 2)
prevent metal fines from entering the facility’s wastewater. 

Figure 7. Photograph of Cylinder Used to Pour Salt on Fires 

Note: 	Facility V primarily used salt to extinguish metal fires. The
smaller photograph shows a 55-gallon drum of salt—many of which were
found throughout the facility’s production areas. Employees used
buckets, shovels, and scoops to transfer salt from the drums directly to
fires or other locations. The larger photograph shows a plastic cylinder
that some employees used when extinguishing metal fires with salt. This
practice had the advantage of allowing employees to extinguish metal
fires from a distance. It was unclear if this delivery method would be
effective for extinguishing intense fires, because the temperatures
could melt or deform the plastic cylinder. 

 

 

Attachment 1. Copy of Testing Results Provided by OSHA’s Analytical
Laboratory

Notes: 

Refer to Section 4.1.2 for information on the materials sampled and how
they were collected. 

Table 1 summarizes the sampling results; note that the “Sample
Numbers” across the top of the table correspond with the “Submission
Numbers” in this attachment. 

As acknowledged in OSHA’s testing results presented throughout this
attachment: “The results obtained from this equipment can not be used
in designing or engineering protective safety equipment.” Further, it
is possible that some materials that were tested exhibit lesser or
greater explosion hazards under different conditions. 

 Facility V representatives requested that this site visit report not
specify the identity of the main metal product.  

 When a material has an LOC less than 5%, NFPA 69 requires the oxygen
concentration to be less than 60% of the LOC (when the oxygen
concentrations is continuously monitored). A site visitor noted that an
earlier publication reports an LOC for the metal dust as 3% by volume
(U.S. Bureau of Mines, 1965). If this is a representative value, NFPA 69
would suggest that the oxygen concentration in these operations should
be less than 60% of the LOC, which would be 1.8% by volume.

  

 Facility V representatives referred to LOC testing data during the site
visit, but site visitors did not view the testing results and the
underlying testing methodology. 

 In production areas with many hard-to-reach areas, such as the inner
components of the grinding machine, equipment was operated under argon
atmospheres to prevent fires from occurring, rather than requiring
employees to suppress fires in inaccessible parts of large unit
operations. 

 

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Site Visits Related to Combustible Dust – Facility V 

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Site Visits Related to Combustible Dust – Facility V