Document ID: OSHA-2009-0023-0166
Agency: osha
Document Type: Supporting & Related Material
Title: 
Posted Date: 2010-08-23T04:00Z

Site Visits Related to Combustible Dust:

Facility Y–Titanium Recycler

	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

 (June 22, 2010)

Table of Contents

  TOC \o "1-5" \h \z \u   HYPERLINK \l "_Toc258772484" 1	Project
Overview	  PAGEREF _Toc258772484 \h  1  

 HYPERLINK \l "_Toc258772485" 2	Facility Description	  PAGEREF
_Toc258772485 \h  2  

 HYPERLINK \l "_Toc258772486" 3	Process Descriptions	  PAGEREF
_Toc258772486 \h  4  

 HYPERLINK \l "_Toc258772487" 3.1	Overview of Common Operations	 
PAGEREF _Toc258772487 \h  4  

 HYPERLINK \l "_Toc258772488" 3.1.1	Raw Materials Handling and
Processing	  PAGEREF _Toc258772488 \h  4  

 HYPERLINK \l "_Toc258772489" 3.1.2	Melting and Re-melting	  PAGEREF
_Toc258772489 \h  5  

 HYPERLINK \l "_Toc258772490" 3.2	Specific Issues Pertaining to
Combustible Dust	  PAGEREF _Toc258772490 \h  6  

 HYPERLINK \l "_Toc258772491" 3.2.1	Dust Accumulations	  PAGEREF
_Toc258772491 \h  6  

 HYPERLINK \l "_Toc258772492" 3.2.2	Housekeeping Practices	  PAGEREF
_Toc258772492 \h  7  

 HYPERLINK \l "_Toc258772493" 3.2.3	Dust Collectors	  PAGEREF
_Toc258772493 \h  8  

 HYPERLINK \l "_Toc258772494" 3.2.4	Classification of Hazardous
Locations	  PAGEREF _Toc258772494 \h  10  

 HYPERLINK \l "_Toc258772495" 3.2.5	Fire History and Suppression	 
PAGEREF _Toc258772495 \h  10  

 HYPERLINK \l "_Toc258772496" 3.2.6	Building Insulation and Insulation
Facing	  PAGEREF _Toc258772496 \h  11  

 HYPERLINK \l "_Toc258772497" 4	Document Review	  PAGEREF _Toc258772497
\h  12  

 HYPERLINK \l "_Toc258772498" 4.1	Testing Data	  PAGEREF _Toc258772498
\h  12  

 HYPERLINK \l "_Toc258772499" 4.1.1	Facility Y’s Testing Data	 
PAGEREF _Toc258772499 \h  12  

 HYPERLINK \l "_Toc258772500" 4.1.2	OSHA’s Analyses of Samples
Collected During the Site Visit	  PAGEREF _Toc258772500 \h  13  

 HYPERLINK \l "_Toc258772501" 4.1.3	Published Information	  PAGEREF
_Toc258772501 \h  13  

 HYPERLINK \l "_Toc258772502" 4.2	Material Safety Data Sheets (MSDSs)	 
PAGEREF _Toc258772502 \h  14  

 HYPERLINK \l "_Toc258772503" 4.3	Risk Assessment of Dust Fires and
Explosions	  PAGEREF _Toc258772503 \h  15  

 HYPERLINK \l "_Toc258772504" 5	Training and Safety Programs	  PAGEREF
_Toc258772504 \h  15  

 HYPERLINK \l "_Toc258772505" 6	Main Findings	  PAGEREF _Toc258772505 \h
 16  

 HYPERLINK \l "_Toc258772506" 7	Feedback to OSHA	  PAGEREF _Toc258772506
\h  18  

 HYPERLINK \l "_Toc258772507" 8	References	  PAGEREF _Toc258772507 \h 
19  

 

Table 1 		Titanium Dust Testing Results Provided by Facility Y

Table 2			Testing Results for Samples Collected During the Site Visit

Figure 1		Photograph of Titanium Chips Storage Area

Figure 2		Photograph of Rotary Drum Blender

Figure 3		Photograph of Employee Removing Metal Condensate From Slab 

Figure 4		Photograph of Dusts and Turnings Collected by a Tiger Vac

Figure 5 	 	Photograph of Two Dry Dust Collectors

Figure 6		Photograph of Dry Dust Collector

Figure 7		Photograph of Wet Dust Collector and Insulation Facing

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

Abbreviations

cfm			cubic feet per minute

CO2		carbon dioxide

EB			electron beam

ERG		Eastern Research Group, Inc.

MEC		minimum explosible concentration

MIE		minimum ignition energy 

MIT		minimum ignition temperature

MSDS		Material Safety Data Sheet

NFPA		National Fire Protection Association

OSHA		Occupational Safety and Health Administration

VAR		vacuum arc remeltProject Overview 

On June 29 and 30, 2009, Eastern Research Group, Inc. (ERG) conducted a
two-day site visit to a titanium recycling facility (hereafter referred
to as “Facility Y”). The site visit was conducted by an ERG employee
and a consultant. Its purpose 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 Y’s
compliance with OSHA regulations or adherence to National Fire
Protection Association (NFPA) consensus standards; it 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 Y’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 Y, 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 and Safety Programs	Review of Facility Y’s training
programs and summary of the extent to which combustible dust factors
into other safety programs.

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

7	Feedback to OSHA	Feedback that Facility Y representatives wished to
communicate to OSHA as it proceeds with its combustible dust rulemaking
effort.

8	References	Full references for documents cited throughout the report. 

 

Facility Description

Facility Y is a titanium recycling facility. It receives titanium-rich
material in various shapes, sizes, and alloys. The raw materials are
cleaned, sized, and blended before being melted (and sometimes
re-melted) in furnaces. Titanium products generated by the furnaces are
sent to customers as large electrodes, smaller ingots, or slabs; the
customers then further process this material in different shapes and
forms. Facility Y representatives suspected that their potential
combustible dust hazards are likely reasonably representative of those
experienced by other titanium recyclers. 

Facility Y operates a large material handling area and multiple melting
furnaces; ERG site visitors toured a representative subset of these
furnaces, including the facility’s oldest and newest ones. The
facility operates continuously throughout the year, though some
individual operations (e.g., certain furnace melts) are batch processes.
The oldest furnace at Facility Y is approximately 30 years old, and the
newest was installed two years ago.  

Facility Y’s main production areas are located in buildings with a
combined total floor space of roughly 450,000 square feet. Approximately
350 employees work at Facility Y, and around 275 of these work in
locations where combustible dusts might be found. The facility hires
contractors primarily for specialized services, like welding, plumbing,
and electrical work. Contractors are also used to perform various
equipment and process maintenance activities. 

Facility Y does not have its own fire brigade, but several employees are
trained in all aspects of emergency response, including fire fighting.
The facility has installed several “safety islands” throughout the
production areas where employees can readily access fire extinguishers
and other emergency response equipment. Section 3.2.5 documents the
facility’s recent history of fires attributed to combustible dust.
Smoking is not allowed in or near Facility Y’s production areas; site
visitors noticed no evidence of smoking (e.g., discarded cigarettes) in
the production areas, with the exception of a testing report (see
Section 4.1.1) that indicated the presence of a cigarette butt in a
sample. 

Three full-time employees work in Facility Y’s safety department, and
these employees estimated that they spend no more than 20% of their
collective time on combustible dust safety issues. The company that owns
Facility Y has a corporate safety practice, but local and regional
safety personnel conduct most of their own facility-specific safety and
engineering evaluations, without extensive input from corporate safety
officials. 

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

Facility Y is located in a township served by a volunteer fire company.
Once every year or two, facility representatives invite the local fire
marshal to tour Facility Y to discuss process safety, firefighting
measures for metal fires, and emergency response issues. The local fire
company does not require or suggest adherence to NFPA standards specific
to combustible dust, and Facility Y tends to teach the fire company
about unique combustible dust safety hazards, rather than the other way
around.  

Facility Y’s insurance underwriter conducts inspections once every
year or two. Facility representatives noted that one inspector is very
knowledgeable about combustible dust safety issues. However, this person
does not conduct every inspection. The facility has also contracted with
Global Risk Consultants to conduct independent loss prevention analyses.

Approximately once every three years, Facility Y hires external
consultants to conduct comprehensive reviews of the facility’s health
and safety programs. These reviews evaluate many different general
health and safety issues (e.g., confined space entry, means of egress,
emergency response, and personal protective equipment) and do not focus
specifically on combustible dust. 

Facility Y’s regional safety manager has accessed various reference
materials that OSHA posted to its combustible dust Web site. He has also
attended a technical presentation on combustible dust given by the
Assistant Director of a nearby OSHA Area Office. Facility Y was
inspected as part of OSHA’s combustible dust National Emphasis
Program. 

Facility Y is a member of the International Titanium Association, which
provides its members a wide range of services. However, the trade
association has not yet offered detailed technical guidance on
combustible dust safety hazards. The trade association is currently
preparing a manual that describes safe practices for using and handling
titanium, and facility representatives are assisting the trade
association with that effort. 

The company that owns Facility Y has recently formed a corporate
combustible dust safety team, but this team has not developed any
technical guidance for the company’s titanium recyclers and
manufacturers.

Facility representatives have accessed all NFPA standards applicable to
combustible dust issues and are very actively engaged in the process of
revising NFPA’s combustible metals standard (NFPA 484). 

Process Descriptions

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

Overview of Common Operations

This section presents a very general overview of the production lines
that the site visitors toured. Housekeeping procedures are described
here and discussed in greater detail in Section 3.2. Many operations
occur at Facility Y in addition to those listed below. 

Raw Materials Handling and Processing

Facility Y receives scrap titanium in various shapes and sizes. The
material arrives in bales, boxes, crates, bins, super-sacks, and other
containers. The scrap is stored in many locations, including open bays
(see Figure 1). Only four of the specific processing steps in the
materials handling area are reviewed here. Taken together, these and
other operations are conducted to prepare scrap before it is sent to a
furnace for melting (see Section 3.1.2). 

One of the first processing steps is to remove fine surface layers of
oxidized material from the titanium scrap. This is accomplished by
feeding scrap through an abrasive blasting operation with a steel shot
blasting material (see Section 4.2 for further information on the
properties of the steel shot). Dusts generated in this operation are
controlled by a wet dust collector on the shop floor (see Section
3.2.3). 

Some scrap material (e.g., turnings) is crushed in a ring mill to for
size reduction. Dust-laden air streams generated in the ring mill pass
through a wet dust collector, with the exhaust vented into the
workplace. Interlocks prevent the ring mill from operating without a
sufficient water supply. 

Further processing occurs in a wash line, where processed scrap is
washed, rinsed, centrifuged, and then dried at temperatures up to
325°F. The wash line does not perform additional size reduction, but
removes trace surface contamination from the processed titanium scrap.
Titanium fines that settle from the dryer are collected and sold as a
product. Airborne dusts generated in this operation are controlled by a
cyclone located outside the building (see Section 3.2.3). The dryer has
interlocks that prevent it from operating unless the exhaust fan is
activated. 

A final stage before melting involves blending mixtures of the processed
scrap titanium metal. In this step, a tote of titanium scrap is loaded
into a rotary drum blender (see Figure 2), which is flushed with argon.
After each blending cycle, the mixed material is unloaded into a bin
beneath the rotary drum opening. The loading and unloading operations
are uncontrolled sources of fugitive metal dust. 

At many locations throughout the materials handling area, employees can
activate a manual emergency stop (e-stop) shutdown. These e-stops are
labeled “Fire alarm/argon suppression.” E-stop activation causes 1)
exhaust fans to stop, thus reducing the risk of burning material
spreading through production equipment, and 2) argon flush of individual
production equipment (e.g., ring mill, dryer, cyclone) via hose
connections to extinguish burning material. 

The wash-line duct from the dryer to the cyclone outside is equipped
with a spark detection system. It provides a local alarm upon detection
of a burning ember in the duct.

Melting and Re-melting

Facility Y operates both electron beam (EB) furnaces and vacuum arc
remelt (VAR) furnaces. The EB furnaces manufacture large titanium
products: electrodes, slabs, and other products. Some electrodes are
sold to customers without further processing; others are used as a raw
material for the VAR furnaces, which re-melt the electrodes to form
ingots. The VAR furnaces that site visitors toured were relatively new
and exhibited less evidence of combustible dust accumulations.
Accordingly, this section focuses on site visitors’ observations in
the EB furnace rooms. 

Processed titanium scrap was fed by vibratory conveyor and other means
into the EB furnace, which operates under vacuum. After the furnace is
charged, a steel lid (approximately 12 feet wide) is secured on top and
melting begins. At the end of a campaign, which is a series of
consecutive melts, the lid is lifted and combustible material at the top
of the chamber begins to burn once air (oxygen) enters the furnace. This
controlled burn can last for a few hours, after which the titanium
product is removed from the furnace. 

The titanium melt process causes the underside of the lid to be coated
with metallic “condensate.” Before the lid can be reused, this
condensate must be removed by one of the following two processes:

For some lids, employees remove metal condensate with a pneumatic chisel
(see Figure 3). This operation takes place in a designated area, and
dusts generated during the chiseling vent to a wet dust collector
located inside the furnace building, which exhausts outdoors. Note that
metal condensate dust from this area was sampled (see Table 2) and found
to be a Class II dust. 

For other lids, employees remove the metal condensate using a backhoe
scraper that travels around the lid’s perimeter. This operation takes
place in a portable blast enclosure, in which employees must don
supplied air respirators when operating the motorized backhoe. Metal
dusts generated during this activity are collected and vented to a wet
dust collector—the same dust collector that controls dusts released by
a furnace. Operators manually engage a gate valve in the ductwork to
ensure that dust from the condensate cleaning vents to the wet dust
collector (see Section 3.2.3 for further details). 

EB furnace loading, unloading, and continuous casting of titanium did
not occur while site visitors were touring the furnace rooms. To avoid
dangerous over-pressures, all furnaces have either been designed with or
retrofit with pressure relief systems. Site visitors encouraged facility
representatives to ensure that this design is consistent with NFPA
484’s guidelines and requirements and other published guidelines for
safe operation of titanium furnaces (e.g., Poulsen, 2000). 

Specific Issues Pertaining to Combustible Dust 

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

Dust Accumulations

The nature and extent of dust accumulations at Facility Y varied across
the different production areas. In the materials handling area,
localized fine accumulations were observed near size reduction and
materials handling and transfer operations (e.g., centrifuge, ring mill,
dryer, presses, blenders). As Section 3.2.2 discusses, these localized
accumulations were removed at least once per shift. However, the
fugitive releases from these operations apparently contributed to
accumulations on equipment surfaces and elevated overhead structures. A
facility representative collected a settled dust sample from an
unspecified location in the materials handling area, and the laboratory
concluded that the sampled material was a Class II dust (see Table 2). 

Dust accumulations observed in the furnace rooms varied across buildings
and production areas within buildings. As noted previously, limited
evidence of dust accumulations was observed in the newer VAR furnace,
except for highly localized accumulations near the electrode sawing
operation. In contrast, dust accumulations were evident at selected
locations in the EB furnace building. Site visitors did not tour the
entire operation, but noted that dusts had settled on pipes, beams,
electrical boxes, and other horizontal and vertical surfaces. These
dusts most likely originated from processes inside the EB furnace room,
but the relative contribution from different sources was not known.
Chemical analysis of the settled dusts might indicate which specific
operations account for dust accumulations (e.g., excess iron content
might suggest a greater contribution from abrasive blasting) in this
part of the facility—an insight that would be useful for determining
which operations require enhanced dust control. 

Housekeeping Practices

A wide range of housekeeping practices have been developed for Facility
Y’s individual production areas. This section reviews selected
observations made by site visitors, which fall into two general
categories:

Current practices and the need for a written program. Facility Y does
not have a written housekeeping program, but has a Fire Prevention
Program that includes housekeeping requirements. However, during the
facility tour, site visitors learned of numerous routine and non-routine
housekeeping practices and procedures. For instance, in the materials
handling area, settled dust on the floors in the sorting area was
removed every shift using some combination of Tiger vacs (see below),
brooms, aluminum pans, and other non-spark-producing tools.
Accumulations around the wash line and ring mill are also reportedly
removed every shift. 

Some other housekeeping (and equipment cleaning) practices in the
materials handling area occur at other frequencies. For example, the
entire wash line undergoes weekly cleaning, which includes removal of
accumulated material from inside the dryer and ductwork. This cleaning
can take two employees up to eight hours to complete. Finally,
“top-to-bottom” cleaning occurs every six months in the area with
rotary blenders and every two years in other materials handling areas.
This extensive cleaning involves vacuuming of dusts and other materials
from walls, rafters, beams, and other surfaces. Materials handling
operations generally do not shut down during the “top-to-bottom”
cleaning. 

By developing and implementing a written housekeeping program, facility
representatives can have a single resource documenting preferred
housekeeping procedures and frequencies for each production area.
Effective housekeeping programs identify roles and responsibilities,
include housekeeping checklists for process operators, record amounts of
dust collected, and require periodic inspections and audits to ensure
that the required housekeeping activities are being conducted. 

Use of “Tiger vacs.” As an example of Facility Y’s attempts to
minimize hazards from combustible dusts, facility personnel recently
purchased approximately 50 stainless steel “Tiger vacs” (see Figure
4) to replace nearly every conventional electric vacuum cleaner used in
production areas. According to the Tiger vac manufacturer’s
literature, the Tiger vacs used most widely at Facility Y are explosion
proof, dust ignition proof, and certified for use with Group E, F, and G
Class II materials. This certification is notable given that samples
collected during the site visit confirm that settled dust from the
materials handling area is a Class II dust (see Sample #7115 in Table
2). 

The vacuums are equipped with non-sparking wheels and static conductive
hoses, and have an internal storage capacity for 10 gallons of collected
dry material. Dust capture efficiencies are reportedly greater than
99.99% for the filters internal to the equipment. It was not clear how
frequently collected material was removed from the Tiger vacs, and site
visitors encouraged facility safety personnel to establish a removal
frequency consistent with NFPA 484 requirements and ensure that
employees abide by the established guideline. 

In 2008, the cost for purchasing a single Tiger vac unit with several
hose and wand attachments was quoted as $4,000. The quote did not
include costs for replacement parts (e.g., additional filters) and
optional components (e.g., grounding reels and cable). Facility Y likely
received a volume discount when purchasing multiple units, but invoices
documenting the magnitude of the discount were not available. 

Dust Collectors

Facility Y operates dry and wet dust collectors that vary considerably
in terms of design and measures for preventing fires and explosions.
Site visitors’ observations on several selected dust collectors
follow: 

Wet dust collector for abrasive blasting unit. Dusts generated from the
steel shot abrasive blasting operation vent to this wet dust collector,
located on the shop floor in the middle of the materials handling area.
The dust laden air from the abrasive blasting operation flows through a
pool of water and the formerly airborne metal dust settles as sludge in
the water reservoir. Exhaust air from the dust collector passes through
a high-efficiency particulate arresting filter before venting into the
workplace. (For every other dust collector viewed by site visitors,
cleaned air was vented to the outdoor, ambient environment.) Facility
personnel remove sludge from the dust collector on a weekly basis. The
dust collector does not have a water level sensor interlocked to the
abrasive blasting equipment. Facility Y paid approximately $40,000 to
purchase and install this dust collector from a used equipment vendor. 

Two dry dust collectors. Dusts generated from welding, torch cutting,
and selected other operations are vented to two adjacent dry dust
collectors located outside the materials handling area (see Figure 5).
The dust collectors (baghouses) remove metal dusts and fines before
venting the cleaned exhaust air to the outdoor environment. Both dust
collectors are equipped with linear heat detectors that would trigger
argon quench systems should temperatures approach levels indicative of
fires or smoldering material. Collected material is periodically removed
in 55-gallon drums placed beneath the devices. 

Cyclone. Also located outside the materials handling building, another
dry dust collector (see Figure 6) controls dusts generated in the dryer
on the wash line. Two spark detection systems have been installed in
this process: one in the ductwork connecting the dryer and the cyclone
and the other at the cyclone’s outlet. Detection of sparks or embers
activates an audible alarm and strobe. When these are observed,
employees are instructed to visually inspect the process and cyclone and
manually activate an argon suppression system if hazardous conditions
are observed. While this procedure might prove to be effective in some
instances, explosions would propagate faster than the time needed for
employees to activate controls. Thus, installation of an explosion
isolation system at the inlet of the cyclone would help ensure that an
explosion originating in the cyclone does not propagate back into the
production area. Grounding straps are visible in the photograph, though
site visitors encouraged facility representatives to ensure that
connecting segments of flexible ductwork are adequately bonded.

Dust collector for “rough cleaning area.” Operation of pneumatic
chisels in the enclosed “rough cleaning area” generates small clouds
of metal dusts, which vent through ductwork to an adjacent wet dust
collector (“RotoClone”). The RotoClone has a water level sensor
interlocked with the power: meaning, the RotoClone cannot operate unless
the water reservoir is filled above a designated level. However, the
RotoClone and blasting room are not interlocked: an employee can operate
the pneumatic chisel without the dust control measures activated.
Nonetheless, employees noted that their standard operating procedure is
to first activate the RotoClone before entering the blasting room to
operate the pneumatic chisel. The RotoClone has a 950-gallon water
reservoir, and employees remove roughly three 55-gallon drums of sludge
material from the device every six months. Accumulation of metal dusts
in the ductwork is believed to be minimal, most likely due to the
system’s air flow rate, which is typically more than 12,000 cubic feet
per minute. 

Dust collected in EB furnace room. A smaller RotoClone is located in the
furnace room. It controls dusts generated in multiple operations: the
portable blasting enclosure and at least one of the EB furnaces. The
position of a gate valve in the ductwork determines which particular
equipment is being controlled at a given time. For instance, before
working in the portable blasting enclosure, the operator must first set
the gate valve position such that dusts from this operation can blow
through the ductwork into the dust collector. Failure to set the gate
valve in the correct position would result in dusts not being vented to
the RotoClone; however, no interlock is in place between the gate valve
and the other operations to prevent dusts from being generated unless
the valve is in the correct position.  

Standard operating procedures call for the RotoClone to be activated
before dust-generating processes begin and to continue operating after
the dust-generating processes end, but no interlocks are in place to
ensure that these procedures are followed. However, an interlock does
prevent operators from activating the RotoClone if the water reservoir
does not reach a minimum water level. There has been a fire in this dust
collector, attributed to a gradual buildup of collected material that
dried following a long period of inactivity; this material apparently
ignited when the RotoClone was reactivated. A heat detector that
triggers an alarm and argon suppression has since been added to the
system to prevent future fires. The facility paid a vendor $68,500 to
purchase and install this RotoClone. 

Classification of Hazardous Locations

No information on Class II locations is available, though dust sampling
suggests that some settled materials at Facility Y are Class II dusts.
According to an employee interview, dust-tight electrical enclosures
showed some evidence of accumulated material inside; this was believed
to result from employees not securely engaging the clamps when shutting
the enclosures. Site visitors were not able to determine whether the
enclosures had the dust ingress protection rating needed for Class II
classified locations.

Fire History and Suppression

Facility Y keeps a log of all fires that occur in production areas, and
site visitors reviewed a copy of the log that documented approximately
85 events between January 2004 and March 2006. Individual entries varied
in severity: some events were a series of sparks or smoldering material,
and other events were fires that required suppression and, in a few
cases, employee injury. No general trends could be gleaned from the log,
and fires occurred in various production areas. However, certain events
appear to have occurred in Class II hazardous locations, when employees
operated equipment not rated for these locations. These examples include
fires in forklift tailpipes and a fire in the motor of a pump at the
briquetting press. 

One more damaging fire has occurred since 2006. An employee was cleaning
ductwork and process equipment on the titanium wash line, when the wash
line was configured differently: a “transition box” was placed
downstream of a dust collector (which at the time was indoors) and the
ductwork venting to the atmosphere. The employee was removing
accumulated dust from the transition box with a vacuum cleaner not rated
for Class II locations, and this operation led to a flash fire that
injured the employee and damaged process equipment. After that incident,
the portable vacuum cleaners have been replaced by the Tiger Vacs
described in Section 3.2.2.

As Section 3.1.2 notes, metal condensate fires are reportedly fairly
common when operators remove lids from furnace crucibles. These fires
eventually burn out, with smoke collected by dust collectors. However,
facility representatives are taking proactive measures to investigate
options for using other Class D fire suppression agents and other means
to minimize the severity of these fires. Other Class D agents used to
extinguish metal fires elsewhere at the facility include Met-L-X powder
and salt. 

Building Insulation and Insulation Facing

When touring Facility Y, site visitors noted that some production
buildings had building insulation along walls and ceilings that was
covered with insulation facing—a material that had the appearance of a
white plastic coating. (The insulation facing is visible in the
background of Figure 7.) Given the proximity of the facing to titanium
metal dust accumulations, site visitors asked about the potential for
the material to burn and delaminate, drip, or melt. Compounding the
concern was the fact that 1) some insulation facing had tears and holes,
potentially allowing titanium metal dusts to accumulate behind the
facing in certain localized areas, and 2) extinguishing fires on the
walls and ceilings might be complicated, because the facility production
areas are not equipped with sprinklers due to the incompatibility of
water and titanium dusts. 

Site visitors reviewed a product data sheet for the insulation facing
(“Lamtec Corporation WMP-50”), which indicated that the
polypropylene-based material has a flame spread rating of 5 (which is
relatively low) and a smoke developed rating of 30, as determined by
tests conducted following ASTM method E84. Facility personnel are
encouraged to compare these measurements to their applicable building
code requirements, which will depend on the locality and building
occupancy designation.  

Similarly, site visitors reviewed a product data sheet for the
fiberglass building insulation used at most of Facility Y’s metal
structures. This insulation is placed on walls and ceilings, and then
covered with the insulation facing. According to Owens Corning product
specifications, Facility Y’s building insulation is non-combustible
(as determined by ASTM method E136) and found to have a flame spread
rating of 25 and a smoke developed rating of 50. Efforts should be made
to ensure that titanium dusts cannot accumulate behind the insulation
facing and in the insulation itself. This can be achieved by
periodically replacing damaged insulation facing. 

 

Document Review

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

Testing Data

Testing data for materials that Facility Y handles and produces were
available from two sources: Facility Y representatives let site visitors
review testing data that they had recently collected, and site visitors
collected four samples that were sent to OSHA’s laboratory for
testing. This section summarizes both data sets, as well as information
published by other researchers. 

Facility Y’s Testing Data

Facility Y has recently conducted extensive testing on the
combustibility and explosibility of titanium dusts. In 2007 and 2008,
for instance, facility representatives sent four titanium dust samples
to be tested in a laboratory for particle size distribution and for one
or more explosibility parameters. Three of the four samples were tested
for minimum ignition temperature (MIT) of a dust cloud and MIT of a dust
layer; the fourth sample was tested for minimum ignition energy (MIE)
and minimum explosible concentration (MEC). The samples not only varied
in physical characteristics, but may also have varied in chemical
composition. Table 1 presents the sampling results, which indicate that
MIT of a dust cloud ranged from 285 to 470°C and MIT of a dust layer
ranged from 260°C to 650°C. Facility Y paid approximately $2,000 to
have a single sample analyzed for particle size distribution and the two
MIT values. Table 1 also indicates that a titanium dust sample had an
MIE of 180 mJ.

Facility representatives shared more recent testing results for three
additional titanium dust samples. The sample with the finest particle
size distribution (93.1% smaller than 75 microns) was found to have a
deflagration index (Kst) of 184 bar-m/s and minimum ignition energy less
than 9 mJ. Samples with larger particle sizes (and probably different
oxidation levels or alloy composition) had lower Kst values and higher
MIE values. The small particulate sample was labeled “RM dust,”
while the two larger particulate samples were labeled “EB MS dust”
and chamber booth dust.

OSHA’s Analyses of Samples Collected During the Site Visit

Site visitors collected four samples during the site visit, with the
permission and concurrence of Facility Y representatives. Site visitors
requested that every sample be subject to a “Class II test” at
OSHA’s laboratory. Table 2 summarizes the testing results, and
Attachment 1 of this report presents copies of the testing data, as
reported by the laboratory. More information on the samples collected
and the test results follows:

Sample #7112: Tiger vac dusts. This sample is a mixture of titanium
dusts, turnings, and dirt that had settled onto the floor in the
materials handling area and been collected by a Tiger vac. Facility
representatives estimated that the alloy dust composition was comparable
to “6-4 Titanium”: 90% titanium, 6% aluminum, and 4% vanadium. A
Class II test was requested but could not be performed because the
material was too coarse. The laboratory instead tested the sample for
explosibility and concluded that the material tested was not explosive. 

Sample #7113: Metal condensate. This sample is metal condensate, which
is generated inside the furnace; in the rough cleaning area, employees
use pneumatic chisels to remove the condensate from the surface of the
metal product. The condensate is composed primarily of titanium and
contains much lesser quantities of iron, aluminum, and vanadium. The
laboratory concluded that this sample is a Class II dust. 

Sample #7114: Dryer fines. This sample contains fine metal dust
collected from bins beneath dryers on the metal wash line. The
composition was estimated to be comparable to 6-4 Titanium. A Class II
test was requested but could not be performed because the material was
too coarse. The laboratory instead tested the sample for explosibility
and concluded that the material tested was not explosive.

Sample #7115: Settled dust. This metal sample was collected from
elevated horizontal surfaces in the milling processes in the materials
handling area. It also was estimated to have composition comparable to
6-4 Titanium. The laboratory concluded that this sample is a Class II
dust.

As noted in the testing results (see Attachment 1), the information
presented above should not be used in designing or engineering
protective safety equipment.

Published Information

Site visitors reviewed several scientific publications on titanium’s
fire and explosion hazards before visiting Facility Y (e.g., Poulsen,
2000; DOE, 1994). Findings from these publications echoed insights that
facility representatives shared during the site visit. For instance, the
U.S. Department of Energy reports that titanium dust, turnings, and
other small particles readily ignite and release large quantities of
heat once burning; further, the MIT for titanium dust clouds are between
330°C and 590°C (DOE, 1994). Titanium dust layers can ignite at
similar temperature ranges (380°C to 510°C) (DOE, 1994). Some tests
indicate that finely divided titanium powder’s MIE is as low as 25 mJ
(Poulsen, 2000). The publications also state that molten titanium reacts
violently with water, as facility representatives noted throughout the
visit (Poulsen, 2000).

Material Safety Data Sheets (MSDSs) 

Facility Y representatives provided site visitors several MSDSs for
review. Three of these MSDSs pertained to materials that can generate
combustible dusts, whether at Facility Y or at one of its customers’
facilities: 

Steel shot. Facility Y conducts abrasive blasting in the materials
handling area to remove oxide layers from raw materials. Site visitors
reviewed the MSDS for the steel shot used in the blasting operation. The
MSDS reports that: “Cast steel shot and grit are non-hazardous as
received. Fine metallic dust is generated as the abrasive breaks down
from impact and wear during normal use…the fine steel dust created can
be a mild explosion hazard.” Later sections of the MSDS indicate that
fires should be extinguished with Class D agents or sand, and not with
water, other liquids, or foam. The MSDS does not include quantitative
data on combustibility or explosibility. 

Titanium product #1. Site visitors reviewed a copy of an MSDS that
Facility Y issued in 2006 for its commercially pure titanium (99%)
product. The MSDS clearly identifies health hazards and environmental
concerns associated with formation of titanium dusts. For instance, the
MSDS indicates: “chronic overexposure to dust and fumes may cause
respiratory irritation…” and “if significant amounts of dust are
created, these may have impacts on the air and water quality.”
However, the MSDS is not as explicit when acknowledging fire and
explosion risks associated with dusts that may occur under normal
conditions of use. The MSDS states that salt, sand, or Class D agents
should be used when fighting titanium fires, but does not identify or
describe any unusual fire or explosion hazards. 

Titanium product #2. Site visitors reviewed a copy of an MSDS that
Facility Y issued in 2003 for a titanium product that included aluminum
and vanadium alloys. This MSDS had virtually the same content as that
for the commercially pure product. 

Risk Assessment of Dust Fires and Explosions

A Facility Y contractor recently conducted a risk assessment project to
evaluate all potential combustible dust hazards and to prioritize them
according to hazard potential. The facility developed a
spreadsheet-based ranking tool, in which dozens of potentially hazardous
situations are evaluated and scored based on two factors: 

Probability of occurrence. Every potentially hazardous situation is
assigned a score for its likelihood of occurring, with risk values
ranging from 1 for “no likelihood” to 6 for “almost certain.”

Severity of event. This category also assigns scores between 1 and 6. A
score of 1 refers to an event with no injury, illness, or property
damage; a score of 6 is assigned to events expected to cause a fatality,
disabling injury, or property damage that takes at least two weeks to
repair. 

For each operation or employee activity, a composite rank between 1 and
36 was calculated by multiplying the two aforementioned scores. Facility
representatives then assign “hazard ratings” based on the composite
ranks. For instance, a composite rank between 30 and 36 is considered to
be an operation or activity with “extreme risk;” and a composite
rank between 1 and 5 is considered a “minor risk.” By this ranking
scheme, a few operations and employee activities—all in the materials
handling area—fell in the “high risk” or “extreme risk”
categories. For these and other activities, the risk assessment document
not only ranked potential hazards, but offered recommendations for
mitigating them. 

Though not tasked with commenting on the specific assumptions in the
scoring spreadsheet (i.e., whether the specific criteria, scenarios, and
scores assigned were appropriate), site visitors found this
spreadsheet-based hazard ranking scheme to provide useful insights into
how Facility Y prioritizes future work to reduce combustible dust safety
hazards.  

Training and Safety Programs 

Site visitors and facility representatives briefly discussed employee
training efforts and other safety programs (e.g., confined space entry,
lockout/tagout, hot work permits), but had limited time to conduct
thorough evaluations of these topics. Observations for selected general
issues follow:

Contractor and visitor training video. Site visitors watched a 10-minute
safety video that Facility Y required contractors and other visitors to
view before entering production areas. The training addresses a wide
range of topics, including emergency response, lockout/tagout, operation
of overhead cranes, and confined space entry. The video mentions
Facility Y’s requirement that contractors provide MSDSs for all
hazardous materials brought to the workplace. The video does not mention
any unique fire or explosion hazards associated with titanium dusts. 

Personal protective equipment. All operators and maintenance staff at
Facility Y are required to wear hard hats, safety goggles, and
steel-toed shoes in most production areas. Face shields, gloves, and
respiratory protection are also required for selected operations. Site
visitors noted that employees wore cotton uniforms (see Figure 3) when
removing condensate from furnace lids and during other operations that
generate atmospheres of Class II metal dusts. In these cases, cotton
uniforms might not offer adequate protection against potential fire
hazards. Facility representatives were encouraged to consider
information presented in NFPA 484 (e.g., Section A.13.3.4) and elsewhere
to investigate the need for employees to wear fire-resistant clothing
while performing certain operations. 

Work in oxygen-deficient atmospheres. Several of Facility Y’s
processes are equipped with argon suppression systems that fires will
trigger. In these cases, employees who respond to these incidents might
come into direct contact with argon atmospheres, especially when
responding to fires or doing other work at floor level and below the
argon-air interface. Because people can lose consciousness within
seconds of entering argon atmospheres, Facility Y should consider
providing oxygen sensors to response teams that work in areas expected
to have argon purges. 

Main Findings

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

Site visitors commended Facility Y for developing its “Risk Assessment
of Dust Fires and Explosion” as one approach to identifying high
priority combustible dust safety issues. They also commended the
facility for systematically tracking past fire incidents, no matter how
minor, and taking measures for preventing their recurrence. 

Facility and regional safety personnel have clearly taken the initiative
to exchange information about combustible dusts, whether by attending
informational workshops, attending technical presentations at the local
OSHA Area Office, actively tracking and participating in the revision of
applicable NFPA standards, or participating in trade association efforts
to develop guidance on combustible dust safety issues. 

Site visitors noted many outward signs of a strong emphasis on
occupational safety and health: numerous employees wore clothing with
safety slogans; several banners and posters were hanging in and near
production areas with important safety messages; and signage in some
parts of the facility clearly described safe working practices and
conditions to avoid. 

Facility representatives seemed well aware of the specific workplace
activities that released metal dusts and caused the most fires.
Engineering solutions have already been pursued to minimize or eliminate
hazards in many process areas. Further consideration should be given to
manual operations that either 1) cause uncontrolled emissions of
fugitive metal dusts (e.g., transfer of material between containers) or
2) require employees to work in potentially unsafe operations (e.g.,
cleaning of spray shields and furnace lids). Development and evaluation
of new Class D fire extinguishing agent dispensers and delivery systems
are also encouraged to allow agent application without endangering
personnel doing the application. Facility Y should investigate the need
for employees performing high risk operations, such as cleaning furnace
lids and unloading the blender, to be outfitted with flame-resistive
clothing, per NFPA 2113, “Standard on Selection, Care, Use, and
Maintenance of Flame-Resistant Garments for Protection of Industrial
Personnel Against Flash Fire,” 2007 Edition. 

Facility Y employees perform many different routine and non-routine
housekeeping duties, ranging from daily removal of localized dust
accumulations to annual “top-to-bottom” cleaning of entire
buildings. The recent shift to Tiger vacs should reduce the potential of
fires during housekeeping activities, provided that collected material
is removed at set frequencies. Facility Y can best ensure ongoing safe
and effective housekeeping practices by developing and implementing a
written housekeeping plan. Effective plans establish housekeeping
procedures and cleaning frequencies based on observed dust accumulation
rates and specify roles and responsibilities for operators, supervisors,
and management. One objective to consider in the written plan is to
minimize dust accumulations so as to avoid the need for Class II
hazardous locations (see next finding) and building deflagration
venting. 

Testing data provided by Facility Y and sampling results from the site
visit indicate that titanium dusts from various production areas are
considered Class II dusts. Moreover, some past fires at Facility Y
appeared to result from use of electrical equipment that was not rated
for Class II environments. While the recently purchased Tiger vacs
appear to be rated for Class II environments, it is not clear if other
electrical and fuel-fired equipment (e.g., forklifts, motors) used in
the presence of Class II dusts carry the same rating, and metal dusts
had settled in some electrical boxes in these areas. Facility Y is
encouraged to systematically evaluate its hazardous locations and ensure
that appropriately rated electrical equipment is used.

Efficient operation of ductwork and dust collectors is critical to
ensuring that combustible metal dusts are handled appropriately and in a
manner that does not allow for hidden, unsafe accumulations. Several
opportunities exist to ensure that Facility Y’s dust collectors are
not the source of a future combustible dust incident, but generally
involve ensuring that design and operation of dust collectors are
consistent with specifications outline in NFPA 484. Specific examples of
potential enhancements include: use of additional interlocks to prevent
dust-generating processes from starting unless dust collectors are
operating with gate valves set in correct positions and verification of
air flow in the exhaust duct; installation of explosion isolation
measures in ducts for dry dust collectors handling titanium dusts; and
ensuring that connecting segments of flexible ductwork are adequately
bonded. 

Facility Y should consider converting from manual initiation of argon
suppression agents into process equipment to fire detector actuated
discharge of the agent. This conversion would allow earlier agent
application and would reduce the need for personnel to be in an area
where argon is discharged and fires may be spreading. Facility
representatives are encouraged to refer to NFPA 484 to identify
additional opportunities for safe operations (e.g., adequacy of
protective clothing, furnace operations, use of coolants). 

Although it is not directly a combustible dust issue, the use of
petroleum-based hydraulic oils and cutting oils poses a spray fire
hazard that could eventually involve titanium particulates.  Therefore,
consideration of the feasibility of replacing these oils with less
flammable oils would provide an opportunity for potential fire hazard
reduction.

Feedback to OSHA

At the end of the site visit, ERG asked representatives from Facility Y
if they had any specific feedback for OSHA on combustible dust safety
issues. (Note that this site visit occurred after OSHA publicly
announced its intention to initiate a rulemaking on combustible dust
[OSHA, 2009], but before the agency convened its stakeholder meetings).
They offered the following responses: 

Facility representatives voiced concern about having to understand and
comply with multiple consensus and regulatory standards all pertaining
to combustible dust (e.g., NFPA standards, insurance guidelines, OSHA
regulations). They recommended that OSHA consider referencing some
existing standards, rather than developing entirely new requirements. By
this approach, facilities that already have invested considerable
resources to meet applicable NFPA standards would not have to invest
additional resources to evaluate specific requirements in OSHA’s
pending rulemaking.

Noting that larger companies tend to have extensive internal resources
for researching new safety regulations and ensuring compliance, facility
representatives expressed concern that smaller businesses—including
many that receive and process Facility Y’s products—do not have the
necessary resources to research, comprehend, and comply with highly
technical combustible dust safety standards. 

Facility Y representatives noted that its furnaces (as with those at
other titanium manufacturers) are major capital investments. These
facilities may face a considerable economic burden should OSHA’s
combustible dust rulemaking effectively require replacement of, or
significant retrofit to, this equipment. 

References

DOE, 1994. Primer on spontaneous heating and pyrophoricity. U.S.
Department of Energy, Washington, DC. DOE-HDBK-1081-94. December, 1994.

OSHA, 2009. 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.

Poulsen, E., 2000. Safety-related problems in the titanium industry in
the last 50 years. Journal of Occupational Medicine, 52(5):13-17. 

 

Table 1. Titanium Dust Testing Results Provided by Facility Y 

Parameter	Sample 1	Sample 2	Sample 3	Sample 4

Particle size data 

   % on 40 mesh	Not tested	Not tested	30.6%	0.0%

   % on 70 mesh	2.1%	15.1%	7.0%	0.1%

   % on 100 mesh	0.6%	10.2%	2.8%	0.1%

   % on 200 mesh	3.9%	11.2%	9.7%	0.1%

   % in pan	93.4%	63.5%	49.9%	99.4%

Moisture content	0.6%	1.6%	1.0%	1.0%

MIT (cloud) (°C)	380	650	470	Not tested

MIT (surface) (°C)	285	285	260	Not tested

MEC (g/cm3)	Not tested	Not tested	Not tested	120

MIE (mJ)	Not tested	Not tested	Not tested	180

Notes:	See Section 4.1 for a more detailed description of Facility Y’s
testing data.

	All measurements shown in the table were made using standard ASTM
methods. 

MIT (cloud) = minimum ignition temperature of a dust cloud 

MIT (surface) = minimum ignition temperature of a dust layer 

MEC = minimum explosible concentration

MIE = minimum ignition energy

Notes in the testing report indicate that a cigarette butt was found
within Sample 2.

Testing results also documented data for two reference materials:

Pittsburgh Steam Coal: MIT (cloud) = 585°C; MIT (surface) = 235°C; MEC
= 65 g/cm3; and MIE = 110 mJ. 

Lycopodium spores: MIT (cloud) = 430°C; MIT (surface) = 245°C; MEC =
30 g/cm3; and MIE = 17 mJ.

Table 2. Testing Results for Samples Collected During the Site Visit

Parameter	Sample #7112	Sample #7113	Sample #7114	Sample #7115

Description of material	Tiger vac dusts	Metal condensate	Dryer fines
Settled dust

Particle size data 

   % through 20 mesh	52%	78%	52%	94%

   % through 40 mesh	38%	58%	9.7%	91%

   % through 200 mesh	13%	11%	0.2%	66%

Moisture content	Not tested (<5%)	0.1%	Not tested (<5%)	1.2%

Explosive material?	No	Not tested	No	Not tested

Class II dust?	Not tested	Yes	Not tested	Yes

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 (e.g.,
“it is possible that the material is hazardous under different
conditions; the results obtained from this equipment can not be used in
designing or engineering protective safety equipment”).



Figure 1. Photograph of Titanium Chips Storage Area

Note: 	This photograph shows a bay in which small titanium chips were
stored before processing. The materials handling area at Facility Y
included many different storage areas, many of which are not enclosed. 

Figure 2. Photograph of Rotary Drum Blender

Note: 	This photograph shows a rotary drum blender used to mix processed
titanium chips and pieces into a homogeneous blend, before they are fed
to the furnace. This vessel is charged with titanium material, purged
with argon, and then spun to achieve the desired mixing. The mixed
material is then poured into a vessel (visible in photograph)—an
activity that was not viewed during the site visit but reportedly is a
source of fugitive dusts. Grounding straps were applied to this blender.

Figure 3. Photograph of Employee Removing Metal Condensate From Slab

Note: 	The photograph above shows an employee operating a pneumatic
chisel to remove metal condensate from a slab. Metal dusts are visible
on the floor around this operation. 

The photograph at right is a close-up of the broken-up metal condensate,
which has the appearance of a coarse metal dust. Site visitors submitted
a sample of this material to OSHA’s laboratory for testing. The
testing concluded that the material is a Class II dust. Refer to Section
4.1.2, Table 2, and Attachment 1 for additional information on the
testing results and associated caveats.  

Figure 4. Photograph of Dusts and Turnings Collected by a Tiger Vac

Note: 	This photograph shows the collected material within an
explosion-proof and dust-ignition-proof Tiger vac. The collected
material appeared to be a mixture of dirt, metal dusts, and fine metal
shavings and turnings—all removed from the floor of the materials
handling area. Site visitors submitted a sample of this material to
OSHA’s laboratory for testing. The testing concluded that the material
in this particular sample was not explosive. Refer to Section 4.1.2,
Table 2, and Attachment 1 for additional information on the testing
results and associated caveats. 

Figure 5. Photograph of Two Dry Dust Collectors

Note: 	This photograph shows two dust collectors located outside
Facility Y’s materials handling area. The dust collectors are
baghouses that control dusts from welding operations. Cleaned exhaust
air from both dust collectors vents to the ambient air and not returned
to the workplace. Both dust collectors are equipped with continuous heat
detectors that trigger argon quenches if temperatures exceed action
levels. Facility representatives reported no history of fires in these
dust collectors. 

Figure 6. Photograph of Dry Dust Collector

Note: 	This photograph shows a dust collector (cyclone) that controls
airborne dusts from a dryer on Facility Y’s “wash line.” Exhaust
air from the dust collector is vented to the ambient air and not
returned to the workplace. A spark detection sensor is placed on the
exhaust end of the cyclone, and another is located in the ductwork
inside the building. These sensors trigger a strobe and horn alarm in
the process control area for the “wash line.” When the alarm is
activated, operators are instructed to go outdoors and assess whether a
fire is taking place; if so, the employees press a button (not visible
in the photograph) to engage an argon suppression system. To date, no
fires have occurred in this dust collector, nor have employees been
required to activate the argon suppression system. 

 

Figure 7. Photograph of Wet Dust Collector and Insulation Facing

Note: 	This photograph shows a new RotoClone dust collector installed in
a furnace room. The insulation facing, discussed extensively in Section
3.2.6, is visible on the wall behind the dust collector. Some of the
insulation facing at Facility Y had holes and tears, raising concern
about combustible dusts accumulating behind the facing, though no holes
or tears were evident at this location. 

 

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 to 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. 

 The next edition of NFPA 484 has a method to use the amounts of metal
dust accumulated to determine the possible need for (1) building
explosion venting or (2) employee fire-resistant personal protective
equipment.

 These values are consistent with data reported in Table 4.5.2 of NFPA
499 for pure titanium, which indicates that MIT for a titanium dust
cloud is 330°C. 

 Note that MIE is very sensitive to particle size and oxidation state.
As evidence of this, data provided by Facility Y indicated that MIE for
one titanium dust sample was < 9 mJ.

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Site Visits Related to Combustible Dust – Facility Y 

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Site Visits Related to Combustible Dust – Facility Y