Site Visits Related to Combustible Dust:

Facility R–Cereal 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

 (March 30, 2010)

Table of Contents

  TOC \o "1-5" \h \z \u    HYPERLINK \l "_Toc257713397"  1	Project
Overview	  PAGEREF _Toc257713397 \h  3  

  HYPERLINK \l "_Toc257713398"  2	Facility Description	  PAGEREF
_Toc257713398 \h  3  

  HYPERLINK \l "_Toc257713399"  3	Process Descriptions	  PAGEREF
_Toc257713399 \h  3  

  HYPERLINK \l "_Toc257713400"  3.1.	Overview of Common Operations	 
PAGEREF _Toc257713400 \h  3  

  HYPERLINK \l "_Toc257713401"  3.2.	Specific Issues Pertaining to
Combustible Dust	  PAGEREF _Toc257713401 \h  3  

  HYPERLINK \l "_Toc257713402"  4	Document Review	  PAGEREF
_Toc257713402 \h  3  

  HYPERLINK \l "_Toc257713403"  4.1.	Testing Data	  PAGEREF
_Toc257713403 \h  3  

  HYPERLINK \l "_Toc257713404"  4.1.1.	Facility R’s Testing Data	 
PAGEREF _Toc257713404 \h  3  

  HYPERLINK \l "_Toc257713405"  4.1.2.	OSHA’s Analyses of Samples
Collected during the Site Visit	  PAGEREF _Toc257713405 \h  3  

  HYPERLINK \l "_Toc257713406"  4.2.	Material Safety Data Sheets (MSDSs)
  PAGEREF _Toc257713406 \h  3  

  HYPERLINK \l "_Toc257713407"  4.3.	Decision Tree for New Equipment
Installations	  PAGEREF _Toc257713407 \h  3  

  HYPERLINK \l "_Toc257713408"  4.4.	Prioritization Tool for Existing
Equipment	  PAGEREF _Toc257713408 \h  3  

  HYPERLINK \l "_Toc257713409"  4.5.	Analysis of Costs to Comply with
NFPA Combustible Dust Standards	  PAGEREF _Toc257713409 \h  3  

  HYPERLINK \l "_Toc257713410"  5	Training	  PAGEREF _Toc257713410 \h  3
 

  HYPERLINK \l "_Toc257713411"  6	Safety Programs	  PAGEREF
_Toc257713411 \h  3  

  HYPERLINK \l "_Toc257713412"  6.1.	Confined Space Entry	  PAGEREF
_Toc257713412 \h  3  

  HYPERLINK \l "_Toc257713413"  6.2.	“Hot Work” Permits	  PAGEREF
_Toc257713413 \h  3  

  HYPERLINK \l "_Toc257713414"  6.3.	Management of Change	  PAGEREF
_Toc257713414 \h  3  

  HYPERLINK \l "_Toc257713415"  6.4.	Personal Protective Equipment and
Uniforms	  PAGEREF _Toc257713415 \h  3  

  HYPERLINK \l "_Toc257713416"  7	Main Findings	  PAGEREF _Toc257713416
\h  3  

  HYPERLINK \l "_Toc257713417"  8	Feedback to OSHA	  PAGEREF
_Toc257713417 \h  3  

  HYPERLINK \l "_Toc257713418"  9	References	  PAGEREF _Toc257713418 \h 
3  

 

Table 1			Testing Results for Samples Collected During the Site Visit

Figure 1		Photograph of Dust Collectors for Raw Commodity Bins

Figure 2		Photograph of Vibratory Conveyor Line

Figure 3		Photograph of Compressed Air and Central Vacuum Connections

Figure 4		Photograph of Baghouse With Flameless Explosion Vent

Figure 5		Photograph of Explosion Suppression System on Waste Material
Storage Silo

Figure 6		Photograph of Pneumatic Conveying Line in Mixing Room

Figure 7		Photograph of Ducting in Packaging Area

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

Acronyms and Abbreviations

cfm			cubic feet per minute

ERG		Eastern Research Group, Inc.

MEC		minimum explosible concentration

MIE		minimum ignition energy

MSDS		Material Safety Data Sheet

NFPA		National Fire Protection Association

OSHA
伉捣灵瑡潩慮⁬慓敦祴愠摮䠠慥瑬⁨摁業楮瑳慲楴湯倍
䕐उ数獲湯污瀠潲整瑣癩⁥煥極浰湥൴䍓䵆उ瑳湡慤摲
挠扵捩映敥⁴数⁲業畮整

μm			micron (or micrometer) 

Project Overview 

On April 27 and 28, 2009, Eastern Research Group, Inc. (ERG) conducted a
two-day site visit to a cereal manufacturer (hereafter referred to as
“Facility R”). 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 R’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
facility-wide 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 R’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 R, 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 R’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 R 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 R manufactures multiple “ready-to-eat” (or cold) cereal
products from a wide range of raw material feeds, including, but not
limited to, whole grain rice, whole grain corn, whole wheat berries,
flours, sugars, starches, and other additives. Facility R
representatives indicated that the basic production equipment and
processes used throughout the cereal manufacturing industry are fairly
standard and suspected that the challenges the facility experiences are
likely reasonably representative of those experienced by other companies
in this industry. 

Facility R has multiple cereal manufacturing production lines; ERG site
visitors toured a representative subset of these processes, including
some of the facility’s older and newer processes. Most of Facility
R’s production lines operate continuously, except for process down
times, though some specific operations are conducted in semi-continuous
batches. 

Facility R’s main production areas are located in buildings with a
combined total floor space of approximately 1 million square feet.
Several hundred employees work at Facility R, and at least 70% of them
are operators or maintenance personnel. The operators typically work
12-hour shifts. Some contractors work at the facility on specialized
tasks, such as metal working, plumbing, and mechanical support. Smoking
is not allowed at Facility R, except in isolated shelters located
outside and separate from the main production lines; no evidence of
smoking (e.g., discarded cigarettes) was observed in the production
areas. The smoking areas were well-marked, and “no smoking” signs
were posted at various locations throughout the facility. Though
Facility R representatives noted that they have never experienced an
explosion resulting from combustible dusts, several minor fires have
occurred, typically in dryers (see Section 3 for more details). 

Two employees at Facility R work full time on the facility’s various
safety and health programs. Additional employees at the facility work on
safety and health programs but have shared responsibility for other
facilities owned by the parent company. Overall, these employees spend
approximately 15% of their time working on combustible dust safety
issues. ERG asked the facility’s safety personnel to comment on the
roles that outside parties play in Facility R’s combustible dust
safety programs. A summary of those responses follows: 

Facility R periodically offers site tours to local fire fighters.
However, the local fire fighting force provides the facility with
virtually no information or unique insights on combustible dust and does
not require or suggest adherence to NFPA standards specific to
combustible dust. 

Facility R has previously contracted with consultants and external
engineering and design firms to characterize various materials (see
Section 4.1) and to design dust controls during facility expansions,
process upgrades, and other changes to production equipment. Facility R
sometimes uses outside firms to get second opinions on judgments made
internally about code compliance and dust controls. 

Facility representatives have not consulted directly with OSHA on
combustible dust issues. Before the site visit was scheduled, however,
the facility had already obtained and reviewed OSHA’s Combustible Dust
National Emphasis Program, and facility representatives also had
attended a conference hosted by their state-OSHA program on combustible
dust safety issues. Facility personnel subscribe to an online service
that informs members of OSHA regulatory activity.

Facility R’s insurance underwriter (Factory Mutual) is reportedly very
actively engaged in, and extremely knowledgeable of, combustible dust
safety issues. The insurance underwriter visits Facility R annually and
conducts more frequent facility inspections. Factory Mutual has
developed extensive property loss prevention guidelines specific to
combustible dust (FM, 2009) and requires its policyholders to meet these
guidelines. In fact, Factory Mutual personnel will review design
specifications for major process changes before they are implemented.
Facility R representatives noted that Factory Mutual is one of their
most trusted resources for reliable information on combustible dust
safety issues. 

The company that owns Facility R is a member of a trade association
(Grocery Manufacturers Association), but the trade association offers
limited insight on combustible dust safety issues.  The company also has
representatives that are members of the National Fire Protection
Association. 

Process Descriptions

This section describes the process operations that the ERG site visitors
viewed at Facility R. Section 3.1 provides a very general overview of
the common operations across Facility R’s production lines, 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

ERG toured multiple cereal production lines manufacturing various
products. Though these production lines all had unique characteristics,
they also shared several common processing steps. This section presents
a very general overview of the activities involved in nearly every
production line toured. The operations do not always occur in the
sequence listed below and may occur at multiple stages in a particular
production line. Further, many additional operations occur at Facility R
other than those listed below. 

Materials receipt and handling. Facility R receives its largest
shipments of bulk raw materials via railcar, with the material
transferred pneumatically to large storage silos. Multiple magnets are
placed along the conveyor lines to remove any tramp metal from the
incoming goods. Facility R has dozens of large storage silos, all of
which have exhaust air vented to baghouses (see Figure 4) or bin vent
filters to capture combustible dusts generated by the receipt and
handling of large quantities of dry goods. The silo (commodity bin)
areas are unmanned and are located indoors.  The silos have weak-seam
roofs to relieve excessive pressure; this design would help provide a
pathway for resulting pressure and fireball during an explosion. These
areas are also in rooms equipped with explosion vent panels. Later
sections of this report identify additional measures in place to prevent
explosions from occurring in the storage silos. 

Cleaning. Some bulk ingredients pass through a water or steam washing
step to remove foreign material, such as stems and dust. For these
commodities,  the process materials have a high moisture content and
virtually no dust present following this cleaning step. Most commodities
are not cleaned or washed and any foreign material is removed with metal
detection, magnets, or through screening. 

Baking, cooking, heating, or drying. Facility R uses many different unit
operations to bake, cook, heat, and subsequently dry its cereal
ingredients. Every production line had either ovens or dryers to reduce
the moisture content of the formed cereal product from 30 to 50% down to
less than 5%. Facility R currently operates a variety of steam dryers
and gas-fired dryers and the operating temperatures of these devices
vary from roughly 200 to 400 oF. Much of Facility R’s gas-fired
equipment is now equipped with steam suppression to extinguish possible
fires. As noted later in this section, Facility R has experienced some
fires in its drying operations, some of which have propagated into air
exhaust systems. 

Forming. Various types of processing (e.g., extrusion) occur to change
the physical appearance of the cereal product. 

Coating. At different stages in the process, various materials—both in
dry and wet forms—are added to the surface of the cereal product.
Examples include sugar (some of which is milled at Facility R), honey,
cinnamon, nutrients, spices, and other additives. Site visitors noted
that production areas with dry coating operations tended to have the
greatest dust accumulations of the areas toured during the two-day site
visit. In some cases, freshly-coated cereal product was transferred at
the facility along vibratory conveyors (see Figure 6), which also
appeared to be a source of dust accumulation in the workspace. 

Packaging. In the final step of the process, manufactured cereal product
is packaged before being shipped to distributors. 

Specific Issues Pertaining to Combustible Dust 

This section summarizes site visitors’ observations on several
specific issues regarding potential combustible dust hazards at Facility
R: 

Testing. Facility R representatives used two general means for
characterizing explosibility and combustibility of various materials: 1)
the facility sent several materials to an external laboratory to be
tested for explosibility parameters, and 2) the facility referred to
data published in peer-reviewed literature for some commonly used
ingredients in the cereal manufacturing process. Section 4.1 provides
more detailed information on the testing data Facility R shared with the
site visitors. 

Dust accumulations. Site visitors noted that dust accumulations in
Facility R’s production areas were generally minimal and appeared to
be removed frequently, with few exceptions. The areas with the most
notable accumulations were production rooms where finely powdered
materials were processed. Examples included a room containing a hammer
mill to generate powdered sugar; a room where a dry coating was applied
to a cereal product; and a room where a recently coated cereal product
passed along a vibratory conveyor (see Figure 6). Facility R
representatives were already investigating dust control solutions for
some of these production areas. 

Housekeeping practices. Facility R’s housekeeping procedures are
motivated by the need to reduce hazardous accumulations of combustible
dust and by the need for a clean, food grade production environment for
manufacturing cereal products. Though housekeeping requirements vary
from one production area to the next, they generally share some common
elements:

Routine activities. Larger and localized dust accumulations are removed
immediately, typically through the combined use of brooms, vacuums, and
shovels. In addition, most production areas have requirements to remove
dust accumulations greater than ¼-inch at the end of a production run.
The procedures require employees to use vacuums or brooms, where
possible, to remove accumulations. Wash water and selected cleaning
chemicals are also used regularly to remove accumulations from inside
certain equipment and clean production areas, but usually only when
equipment is down.

The procedures allow for use of compressed air to remove dust
accumulations from areas that cannot easily be cleaned by other means
(e.g., crevices in certain equipment). These procedures specify that
compressed air can only be used after other means are used to remove
bulk accumulations.  However, during interviews with site visitors some
employees said they used compressed air to remove dust accumulations in
locations where use of brooms and vacuums would likely have sufficed.
Compressed air connection lines were found throughout the production
areas (see Figure 3), even in locations where use of compressed air for
cleaning did not appear to be necessary. 

The amount of time employees spend on routine housekeeping activities
varies. One employee estimated that he spends approximately 45 minutes
every day removing dust accumulations from the process he operates. 

Weekly or monthly housekeeping responsibilities. More thorough cleaning
of production areas occurs weekly to monthly, with the preferred
frequency for a given area depending on the extent of accumulations.
This more extensive cleaning includes sweeping and washing floors,
cleaning ledges, and blowing down equipment. Production equipment is not
operating during these weekly or monthly cleaning campaigns. 

Quarterly or annual housekeeping responsibilities. Production areas also
included requirements for cleaning at quarterly or annual frequencies.
Specific activities for this cleaning are similar to those conducted
weekly or monthly, but also include brushing down and cleaning walls,
pipes, and overhead surfaces.

For the weekly, monthly, quarterly, and annual housekeeping activities,
employees are required to document their efforts on checklists.
Following the facility’s written good manufacturing practices, a
quality assurance officer from Facility R conducts monthly or quarterly
audits of housekeeping practices in production areas

Dust collectors. Facility R operates hundreds of various types of dust
collectors, all of which are located inside the main production
buildings and ultimately vent exhaust both indoors and outdoors. For
example, Facility R operates approximately 150-200 cyclones to remove
dusts from air streams. Almost all (>95%) of these cyclones have
capacities of less than 100 cubic feet (ft3). The facility also operates
100-150 baghouses of varying design. Approximately half of these also
have capacities of less than 100 ft3; and the remaining half have
capacities of between 100 and 500 ft3. Of these baghouses, eight have
some form of explosion protection (e.g., explosion panels with flame
arrestors). However, safety engineers at Facility R were actively
seeking means for improving the explosion protection, such as installing
additional flameless explosion vents on dust collectors for which
conventional explosion venting is not an option due to the location of
the devices within the building (see Figure 4). 

Explosion suppression systems. Some large silos at Facility R were
equipped with explosion suppression systems (see Figure 5). These
systems were designed to suppress explosions by injecting large volumes
of a sodium bicarbonate based suppression agent into the silos upon
detection of elevated pressures. Facility representatives noted that
pressure transducers continuously monitor the system and would activate
the suppression system if pressures were to exceed 0.75 pounds per
square inch. The facility noted that each of these systems cost
approximately $100,000 to install in a large silo. To date, none of
these systems has been activated to suppress an explosion event.

Though facility representatives had confidence in the systems’
effectiveness, they also voiced some reservations about the technology.
For example, the facility currently pays approximately $8,000 per year
to train employees to inspect and maintain these explosion suppression
systems. While these costs are substantially lower than the initial
purchase and installation costs of the deflagration suppression systems,
the facility noted that the cumulative long-term maintenance costs can
be significant. Further, the facility was concerned about the
possibility of “false trips” that can contaminate storage vessels
and large quantities of raw materials, even if the system uses an inert
agent. (Note: The particular suppression agent used in this case was
compatible with U.S. Food and Drug Administration requirements for food
additives, which helped address concerns for food manufacturing
facilities.) 

Ignition control. Facility R has various measures in place to control
potential ignition sources that might trigger combustible dust events.
For instance, the facility currently employs internal and external
bonding and grounding of many pneumatic lines to dissipate electrostatic
charge that could otherwise be generated while transporting dry
materials (see Figure 2). All pneumatic couplings have an internal
bonding strap that maintains continuity in the system. External bonding
is used as a redundant installation on selected conveying lines to
prevent the buildup of static electricity should the internal strap
fail. Facility R representatives said they implement their most
stringent electrostatic controls on pneumatic conveying lines believed
to transport material with the greatest hazard potential (i.e.,
combustible dusts smaller than 420 microns). Pneumatic conveying lines
that transport larger particles have internal bonding straps, but
typically do not have secondary bonding. Site visitors noted that larger
particles can still retain and later discharge electrostatic charges,
but the significance of this issue for plant materials could not be
addressed without Minimum Ignition Energy testing data.   

Maintenance and equipment cleaning. During employee interviews, site
visitors asked operators and maintenance employees to describe the
procedures they followed when cleaning or servicing the interior of
various process equipment (e.g., dryers, enrobers, baghouses). Typical
procedures followed varied considerably across the types of equipment
that were cleaned. For dryers, employees sometimes used compressed air
to remove accumulated material. One employee noted that the accumulated
material occasionally showed evidence of charring, which suggested that
the dryers may be a source of potential fires or that charred material
may move from dryers into bins or dust collectors. 

Hazardous locations. Facility R designated multiple areas as Class II
hazardous locations due to the presence of combustible dust. These
locations included areas surrounding the bottom and top of the large
bulk commodity bins, some rooms with mixing operations and milling
operations, and hose switch rooms near the commodity bins. Some of the
dust collectors in Class II locations had no explosion controls. 

Fire history and protection. Facility R has experienced a few fires,
mostly associated with gas-fired dryers and ovens. These were typically
small pan fires in open-pan dryers, though some fires spread to exhaust
stacks. The fire department responded to some of these incidents, as
Facility R does not have its own fire brigade. Facility R has
implemented several changes (e.g., steam suppression systems, manual
“fire stop” systems to stop the material feed after fires have been
detected) that have reduced the frequency and severity of these events. 

Other. Some of Facility R’s dryers were originally designed with
explosion venting latches to relieve unanticipated overpressures.
Facility R representatives noted that this particular design was
compliant with NFPA requirements at the time the dryers were installed,
but is not compliant with the most recent version of NFPA 86, which now
requires use of “approved” explosion-relief hardware. However, the
venting latches on the dryers were not approved by Factory Mutual or
some other independent certifying organization.

Document Review

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

Testing Data

Testing data for materials that Facility R handles and produces were
available from two sources: Facility R made selected testing results
available to site visitors for review, and the site visitors collected
three samples, which were sent to OSHA’s laboratory for analysis. This
section summarizes both sets of testing data.

In addition, Facility R representatives noted that they had obtained and
reviewed testing data published in the scientific literature for some of
their raw materials (e.g., corn starch, wheat starch, sugar). Those
published testing results were used primarily to assess the relative
explosion potential for certain classes of raw materials that Facility R
had not tested itself. References for the published data were not
requested. 

Facility R’s Testing Data

Facility R provided site visitors with copies of two reports documenting
testing results for various materials processed at the facility. The
testing generated some explosibility parameters, but no data were
available on other parameters useful for evaluating combustible dust
safety hazards (e.g., minimum ignition energy). A brief summary of those
testing data follows:

Corn grits testing. Facility R provided copies of corn grits sampling
results. The samples were collected by another facility within the same
company as Facility R and submitted to an external laboratory for
analysis. The documentation reviewed by site visitors did not specify
the process locations (at the other facility) where the samples were
collected. The corn grits had a moisture content of 8.8%, but no
information on particle size distribution was recorded. Testing for
explosibility parameters followed ASTM Standard E1226 (“Standard Test
Method for Pressure and Rate of Pressure Rise for Combustible Dusts”).
The laboratory reported the following results, which were tested on the
sample as received (i.e., not sieved or dried):

Maximum explosion pressure (pmax) = 5.32 bar

Maximum rate of pressure rise [(dp/dt)max] = 188 bar/second

Deflagration index (Kst) = 51 bar-meter/second

Since the Kst value was less than 200 bar-m/s, the laboratory concluded
that the corn grits sample had an explosion hazard category of “Class
St. 1.” 

Testing of multiple materials. Facility R also provided a copy of an
external consultant’s analysis of 12 different materials sampled from
dryers, “puffer/toasters,” and dust collector filters. The
consultant ran Hartmann tube tests on the materials and, based on the
observations from these tests, assigned a “rating index” and
provided qualitative comments characterizing the level of concern for
potential explosions. The consultant’s report noted that a rating
greater than 6 is of potential concern for explosions unless the vessels
from which the samples were collected were equipped with some form of
explosion protection. Seven of the materials tested were assigned
ratings below 6, and five the materials tested were assigned ratings
above 6. 

Facility R sent three of the materials considered by the consultant to
pose a potential explosion hazard to a different laboratory, which
analyzed the samples as received (i.e., not dried or sieved to less than
200 mesh). The laboratory followed ASTM Standard E1226 and reported the
following results:

Sample #6

Unknown material that consultant assigned a rating index of 1

Maximum explosion pressure (pmax) = 6.4 bar

Maximum rate of pressure rise [(dp/dt)max] = 502 bar/second

Deflagration index (Kst) = 136 bar-meter/second

Particle size information = 12% of material less than 75 microns

Moisture content = 0%

Sample #8

Unknown material that consultant assigned a rating index of 10

Maximum explosion pressure (pmax) = 8.2 bar

Maximum rate of pressure rise [(dp/dt)max] = 697 bar/second

Deflagration index (Kst) = 189 bar-meter/second 

Particle size information = 33% of material less than 75 microns

Moisture content = 0.7%

Sample #18

Unknown material for which consultant did not assign a rating index

Maximum explosion pressure (pmax) = 7.1 bar

Maximum rate of pressure rise [(dp/dt)max] = 425 bar/second

Deflagration index (Kst) = 115 bar-meter/second 

Particle size information = 24% of material less than 75 microns

Moisture content = 0%

These laboratory results—particularly for sample #6—suggest a much
greater explosion potential than implied by the consultant’s scoring
scheme. It is not clear, however, if the discrepancy results from the
use of different testing methods or possibly from differences in the
physical properties of the material (e.g., moisture content, particle
size distribution) that was sent to the consultant and the second
laboratory. Another possibility is that the consultant’s rating scheme
may not have been valid for the materials that were tested. 

OSHA’s Analyses of Samples Collected during the Site Visit

As noted previously, ERG collected three samples during the site visit,
with the permission and concurrence of Facility R representatives. A
fourth sample of milled sugar was also collected, but not enough
material was obtained to conduct the laboratory analyses. 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: Wheat Starch. This wheat starch was sampled from a dust
collector that controls the bulk material receiving area. According to a
product data sheet, the wheat starch has bulk density ranging from 32 to
45 pounds per cubic foot and a moisture content of 10.2% (which is
comparable to the moisture content reported in Table 1). Eighty one
percent of the sample was smaller than 75 micrometers. Laboratory
analysis of this sample concluded that it was explosive, with an OSHA
measured Kst value of 46.4 bar-m/s.

Sample #4283: Mixed Ingredients. This mixture was sampled from a dust
collector in Facility R’s dry enrobing room. The sample is a mixture
of cinnamon, sugar, spices, and some additives. Only 3.9 % of the sample
(by weight) was smaller than 75 micrometers. The material had a negative
test for explosibility. As noted on the testing report, however,
“…it is possible that the material is hazardous under different
conditions.” Note that the material that was sampled came from a dust
collector that likely captured larger airborne particles generated in
the dry enrobing process. It is possible that a finer distribution of
this same material (e.g., the fine dusts that were not captured by the
dust collector or that settled onto surfaces and overhead structures)
would exhibit different explosibility characteristics.

Sample #4284: Baghouse Dust. This material was collected from a dust
collector that controlled multiple operations in Facility R’s cereal
packaging area. Therefore, the material contains a mixture of
ingredients commonly found in cereal products. It is likely a
combination of flours, starches, sugars, grains, and selected additives.
Laboratory testing of this sample, which was 13% (by weight) less than
75 micrometer particles, concluded that it was explosive, with an OSHA
measured Kst value of 17.24 bar-m/s.

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 Kst and Pmax determinations were not made using ASTM
methods, the limited number of samples does not characterize the full
hazard potential). 

Material Safety Data Sheets (MSDSs) 

Facility R provided copies of 57 material safety data sheets (MSDSs) for
a number of different materials, including various types of sugars,
flours, starches, and brans. In addition, site visitors reviewed
contents of nine “product data sheets” and two letters that
suppliers provided in lieu of MSDSs. The extent of documentation of
potential combustible dust safety hazards varied greatly across the
MSDSs that ERG reviewed. In cases where MSDSs acknowledged and
characterized combustible dust safety hazards, relevant information was
typically found in sections on firefighting measures, accidental release
measures, handling and storage, and stability and reactivity. Following
are several general observations about the MSDSs that the site visitors
reviewed:

Quantitative information. MSDSs exhibit great variability in terms of
quantifying combustibility and explosibility; some MSDSs presented only
qualitative descriptors of hazards, while others included quantitative
data on various parameters. Of the 57 MSDSs reviewed, 35 provided some
type of quantitative information regarding combustibility or
explosibility. The parameters that were most frequently quantified were
minimum explosible concentration (MEC), sometimes called lower explosive
limit, and cloud ignition temperature. Following is an excerpt from the
MSDS that included the most detailed quantitative information (in this
case, for a modified food starch):

Lower explosive limit: 	60 g/m3

Starch is a class St1 dust at normal moisture level

Minimum ignition energy (MIE): > 30 mJ at normal moisture level

Pmax: 9.5 bar

Kst: 170 bar-m/s

Layer ignition temperature: > 450 oC

Auto ignition temperature: 170 oC. (Above this temperature starch will
self-heat.)

Qualitative information. A much greater proportion (52 out of 57) of the
MSDSs that ERG reviewed had some qualitative characterization of
potential fire and explosion hazards, though the level of detail varied
widely. At one extreme, certain MSDSs included very generic information
(e.g., “avoid dusty conditions”) without acknowledging the full
range of hazards and how they can be minimized or controlled. At the
other extreme, some MSDSs offered much more detailed and thorough
characterization of the potential hazards and means for controlling
them. The MSDSs that included no quantitative or qualitative information
on potential combustible dust hazards were for sugar, rice flour, yellow
corn flour, and “dry corn ingredient.” 

Inclusion of hazards for “normal conditions of use.” According to
OSHA’s recent guidance on hazard communication for combustible dusts
(OSHA, 2009c), suppliers and importers must consider the potential
hazards of materials “that may occur under normal conditions of use”
and address known hazards on MSDSs. Such information appeared to be
lacking on some MSDSs that ERG reviewed, especially for food items sold
in bulk but subsequently milled at Facility R. To illustrate this point,
one supplier’s MSDS included the following statement: “…we cannot
predict the uses of [wheat flour] and deny any liability for injuries or
illnesses that might be occasioned by unanticipated or non-normal
uses.” This particular MSDS provided very limited information on this
material’s potential hazards.

Regulatory interpretations. Facility R received two letters from a
supplier of rice flour indicating that MSDSs need not be provided
because food products are exempted from OSHA’s Hazard Communication
standard. The letters were received in 1998 and 2001. Direct quotes from
these two letters follow:

(1) Food grade products intended for edible uses do not require Material
Safety Data Sheets (MSDS) to comply with OSHA regulation 29 CFR
1910.1200 (The Hazard Communication standard). Under the standard, MSDSs
are only required for hazardous chemicals. Hazardous chemicals are
defined as any chemical which is a physical or health hazard. Physical
or health hazards are further defined and Appendix B of the standard
describes criteria used to determine whether or not a chemical is to be
considered hazardous. Foods regulated under The Food, Drug, and Cosmetic
Act (which all of our foods and food ingredients are) do not meet any of
the criteria which require them to be listed as hazardous. Therefore,
our rices and rice by-products do not require MSDSs.

(2) [Company] believes its wheat flour and other milled wheat products,
for human consumption, are not hazardous materials according to the OSHA
Hazard Communication standard (29 CFR 1910.1200). These products are
labeled according to the Federal Food, Drug, and Cosmetic Act and are
exempt from further OSHA or EPA labeling requirements.

These interpretations are included in this report to inform OSHA of
circumstances by which facilities may not be fully informed of potential
combustible dust hazards. It is outside the scope of this project to
comment on whether these suppliers’ regulatory interpretations are
correct.

Decision Tree for New Equipment Installations 

Facility R prepared a written program—“Dust Explosion Protection
Hazard Analysis Criteria”—to determine what specific controls may be
warranted on all newly installed equipment. The criteria were organized
into a decision tree that asked a series of questions (e.g., Is dust
combustible? Is equipment confined? Is the particle size less than 420
microns? Are ignition sources present? Has explosibility testing been
conducted? If not, should testing be conducted?). Based on answers to
these and other questions, the decision tree indicates whether equipment
explosion protection is required, whether fire protection options are
necessary, the extent of technical review required of the proposed
installation, and other design considerations. 

A second tier of questions then provides additional specificity on the
preferred explosion protection technologies. For instance, if the first
tier of questions indicates that equipment explosion protection is
needed, the second tier of questions determines what type of protection
is most appropriate, including equipment explosion protection (i.e.,
explosion venting, flameless explosion venting, or explosion
suppression), room explosion protection, explosion isolation systems,
and ignition control. In short, this facility’s hazard analysis
criteria walked safety engineers through the process of determining
whether protection is required and, if so, what type of protection is
preferred. Responses also determine whether hazard analyses are required
for new equipment installations. 

Facility R’s decision tree helped ensure that combustible dust safety
issues were considered for all new equipment installations. While site
visitors reviewed the series of questions incorporated into the decision
tree, they were not tasked with reaching conclusions on the adequacy of
the approach for addressing combustible dust safety issues (e.g.,
whether Kst cut-off values used for certain decision points were
appropriate). 

Prioritization Tool for Existing Equipment 

Facility R also developed a spreadsheet-based approach to prioritize its
resources for retrofitting existing processes with controls to minimize
combustible dust hazards. Facility R voluntarily developed this scoring
approach to help prioritize capital spending projects and to define
overall facility risk, and not in fulfillment of any external mandate. 

In its prioritization tool spreadsheet, Facility R representatives have
scored individual unit operations according to several factors, and the
outcome of the scoring activity is a list of equipment that should have
the highest priority for safety controls. The following factors are
considered in the scoring scheme, with each factor receiving a score
between 1 and 10:

Fuel issues. Provides information regarding the type of fuel (e.g.,
starch, flour), the quantity of fuel, the particle size (e.g., based on
cut-offs established by Facility R), and how easily combustible dusts
can be suspended. 

Equipment. Scores are assigned based on whether dusts are in confined
areas and whether operating temperatures exceed certain
facility-specified cut-offs.

Ignition sources. Assigns additional scores based on the presence of
potential ignition sources, including static electricity, mechanical
friction, arcing, “hot work,” and direct gas-fired equipment. 

Other factors. Provides information on other relevant factors such as
proximity of equipment to employees; level of existing explosion
protection; and history of fires, explosions, and near misses. 

The outcome of this scoring scheme is a composite rank that
qualitatively indicates each unit operation’s combustible dust hazard.
Though not tasked with commenting on the specific assumptions in the
scoring spreadsheet (e.g., whether particle size cut-offs were
appropriate), ERG site visitors found this “risk assessment”
approach to be a useful tool in ranking hazards and prioritizing
upgrades for existing equipment.    

Analysis of Costs to Comply with NFPA Combustible Dust Standards

Facility R representatives had previously conducted an internal
assessment of the estimated costs to bring the facility’s dust
collectors into compliance with NFPA standards pertaining to combustible
dust. The facility considered costs for upgrading their dust collectors,
most of which currently have no explosion protection features. In this
analysis, facility representatives assumed that some equipment would be
replaced and other equipment retrofitted with explosion suppression
systems, isolation devices, and other control features. The facility’s
initial analysis suggested that the total up-front costs associated with
purchasing and installing new equipment would likely fall in the range
of $10 million to $28 million. OSHA should note the following when
interpreting these figures:

These costs focus exclusively on bringing dust collectors up to NFPA
standards and did not consider costs for upgrading other devices at
Facility R that may be regulated under a new combustible dust standard
(e.g., dryers, mixers, commodity bins). 

These projected costs address the up-front purchase and installation
costs of new equipment and do not reflect the in-use operations and
maintenance expenses. Facility R representatives noted that many types
of explosion control measures require periodic maintenance, which could
amount to between 2,400 and 4,800 hours of staff time per year,
depending on the types of controls installed. In other words, Facility R
would likely have to dedicate one or two full-time employees to
maintaining explosion protection systems (particularly if explosion
suppression is employed). Use of explosion suppression systems has
additional costs associated with having maintenance staff attend
training courses offered by the equipment manufacturer to ensure staff
are qualified (and certified where necessary) to maintain the equipment.


One representative from Facility R indicated that the range of estimated
costs ($10 million to $28 million) may understate the actual costs
associated with ensuring that the dust collectors comply with NFPA
standards, especially if new versions of applicable NFPA standards have
requirements beyond those considered in Facility R’s initial analysis.


Training 

This section describes various safety training courses that Facility R
offers to its employees and to contractors, focusing on the extent to
which combustible dust concepts are covered in the courses. Facility R
offers numerous safety training courses to its employees. Some courses
were developed in fulfillment of specific OSHA requirements (e.g.,
confined space entry, “hot work”), but others were developed
voluntarily to address important safety issues. The training addresses
combustible dust issues to varying degrees, as described below. Site
visitors noted that Facility R made a concerted effort to ensure that
all employees and “resident contractors” received adequate training,
but it was not as clear whether specialty contractors received the same
level of training. 

Facility R’s safety training courses include, but are not limited to,
the following:

Facility R offers two-day orientation training to operators on general
facility hazards, including those specific to combustible dust. 

During their first quarter of employment and biannually thereafter
(unless a specific type of training is required annually to meet
regulatory requirements). Operators also receive supplemental safety
training from the environmental health and safety manager. Topics
covered include “hot work” permits, confined space entry, and
combustible dust safety issues.

During the first six months of employment, employees must take a series
of computer-based training courses, which are self-paced and include
proficiency tests. Training modules address various topics, and an ERG
site visitor viewed the two modules most relevant to combustible dust
safety hazards:

The “fire and explosion safety” module covers many concepts. The
module introduces operators to the necessary elements for fires and
explosions and identifies the various materials at Facility R that
present potential combustible dust hazards. The module also describes
potential ignition sources (including buildup of static electricity) and
measures that should be taken to prevent ignition of dust clouds. The
training also covers preferred housekeeping methodologies (e.g., use of
vacuums, brooms, and water) and instructs employees to not use
compressed air to remove dust accumulations. 

The “explosion suppression” module presents technical information on
Facility R’s explosion suppression systems. The module explains that
explosion suppression has been used in cases where explosion venting and
flame arrestors are not viable options. The module then describes how
the facility’s explosion suppression system works (i.e., injection of
large volumes of sodium bicarbonate into a vessel upon detection of
elevated pressures) and indicates where these systems are located. The
module presents general information on lockout considerations to ensure
that the suppression system is not inadvertently triggered when workers
are inside vessels. 

Operators and contractors view a 30-minute video as part of their
orientation, and this video addresses many different health and safety
issues. The video also covers hazards posed by combustible dusts (e.g.,
fires, explosions) and how to prevent and respond to these hazards.

All operators receive on-the-job training from their supervisors. 

Employees responsible for maintaining the explosion suppression systems
must attend specialized training sessions offered by the manufacturer. 

Safety Programs

This section reviews the site visitors’ observations of selected
safety programs implemented at Facility R, with a focus on the extent to
which combustible dust issues are factored into these programs. 

Confined Space Entry

Facility R has written confined space entry procedures, with slightly
different procedures prepared for the various types of vessels that
workers enter (e.g., dryers, silos, baghouses). These written procedures
include many standard elements of confined space entry programs: a
written permit must be obtained before the work begins; energy sources
must be locked out; the confined space must be adequately ventilated;
and the atmosphere must be tested. In addition, the procedures require
employees to remove excess dust from the workspace, to the extent
feasible. All employees who are expected to enter confined spaces
receive initial training on confined space entry and annual refresher
training on rescue procedures. 

“Hot Work” Permits

Facility R has a written “hot work” policy, which includes specific
guidelines for “hot work” activities in hazardous locations due to
the presence of combustible dust. Examples of the policy’s provisions
include, but are not limited to: 

A project manager must be physically present before the “hot work”
begins.

Employees must verify that sprinklers are operational and not down for
maintenance or otherwise not functioning, and a fire extinguisher must
be present in the working area. 

Combustible material must be either moved at least 35 feet from the work
site or shielded.

A fire watch must be present throughout the activity, and for four hours
after the activity if conducted in an area where a combustible material
was present and could not be removed.

Contractors conduct some of the “hot work” performed at Facility R,
and they receive training beforehand on general food safety issues, the
facility’s manufacturing processes, and unique hazards, such as those
posed by combustible dust. Facility R representatives stated that they
are considering enhancing their contractor training to more explicitly
address hazards of combustible dust. 

Management of Change

Facility R has documented management of change procedures. These
procedures were implemented approximately eight months before the site
visit, and Facility R representatives noted that some operators and
maintenance staff were still becoming familiar with the written
requirements. 

As outlined in the procedures, an internal panel of six managers
(engineers and safety professionals) holds weekly meetings to discuss
and evaluate certain changes to the manufacturing processes. Briefly,
“replacements-in-kind” are evaluated but do not require formal
approval from the panel to implement; however, more substantive process
changes must undergo some form of review and receive written approval
before being made. While site visitors found these procedures to be very
thorough and useful for preventing hazards associated with equipment
changes, they noted one instance where process operators did not follow
the facility’s management of change procedures: In the product
packaging area, operators recently began using a new type of gasket to
provide an improved seal in connections between flexible ductwork (see
Figure 7). However, facility personnel who typically review such changes
(according to the facility’s written procedures) were unaware that
this change had been made. 

Personal Protective Equipment and Uniforms

Operators at Facility R are required to wear uniforms, hard hats, safety
goggles, hair and beard nets, and steel-toed shoes in most production
areas. Some of these requirements are motivated by safety reasons and
others by hygiene demands for food production facilities. Operators are
not required to wear flame-resistant clothing anywhere at the facility. 


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 R’s compliance with OSHA regulations or adherence to NFPA
consensus standards. The main findings communicated to facility
representatives include: 

Site visitors commended Facility R for developing its spreadsheet-based
risk assessment for establishing priorities on future capital projects
and its decision tree for determining what types of protection are
needed on new processes. However, site visitors were not tasked with
reviewing the finer details of these tools.

In most processing areas, dust accumulations were minimal. Facility
representatives seemed well aware of the production areas that had the
greatest dust accumulations (e.g., the dry enrobing process, areas with
vibratory conveying of cereals that had just been coated with sugars,
sugar milling operations) and were in the process of considering
engineering solutions to minimize or control dust releases for some of
these areas. Facility R’s written housekeeping procedures are
extremely thorough, though site visitors noted minor discrepancies
between written procedures, specifications in training programs, and
actual work practices; the discrepancies were most evident for the use
of compressed air for removing dust accumulations.

Facility R shared testing data with site visitors that provided
important insights on several of the materials used throughout the
manufacturing process. However, the adequacy of Facility R’s
engineering controls could not be fully evaluated due to the lack of
testing data on a full set of parameters. For example, without testing
data on certain parameters, site visitors could not evaluate if Facility
R classified hazardous areas correctly, whether adequate electrostatic
prevention measures were in place, and whether dust collectors were
adequately grounded. Additional testing would be necessary to provide a
more complete evaluation of these and other issues. 

Facility R has taken proactive measures to retrofit existing equipment
with explosion suppression systems. However, the majority of dust
collectors at Facility R have no explosion protection or explosion
isolation systems, with some of these unprotected dust collectors found
in Class II locations. It should be noted that all Class II locations
are located in unmanned areas that are not frequented by building
personnel. By applying its prioritization tool (see Section 4.4),
Facility R can systematically implement controls in areas that pose the
greatest potential for damaging explosions. Consideration should be
given to both device-specific explosion protection measures as well as
isolation devices that would prevent an explosion or fire from
propagating to other parts of the manufacturing processes. 

From the information currently available, it was unclear if Facility
R’s mixers and dryers had adequate protection for combustible dust
hazards. None of the large mixers had explosion protection, though
mechanical friction from their moving parts may present an ignition
source. Similarly, some dryers and ovens at Facility R have a history of
fires. Facility R may be able to better characterize the risk of these
fires and establish “safe” temperature ranges for these devices
through additional testing (e.g., hot air flow over layer ignition
temperature, and self-heating onset temperature). Fires can also be
avoided by using monitoring devices (e.g., flame sensors, spark/ember
detection systems) that might detect the presence of a fire that outlet
temperature monitoring equipment might otherwise fail to detect.

Facility R currently employs internal and external bonding and grounding
of many pneumatic lines to dissipate electrostatic charge that could
otherwise be generated while transporting dry materials. 

Feedback to OSHA

At the end of the site visit, ERG asked representatives from Facility R
if they had any specific feedback for 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 R representatives offered the following responses:

Facility R representatives expressed concern about the burden that older
facilities like theirs might face if OSHA were to promulgate a
combustible dust standard, especially if that standard were to reference
the various NFPA standards pertaining to combustible dust without
retroactivity considerations. With manufacturing processes designed over
multiple decades, during which building codes and NFPA standards were
frequently changing, Facility R would likely face significant hurdles if
OSHA were to require facilities to “retrofit” process equipment to
be compliant with the must current codes and standards. Facility R’s
concerns addressed timing, resources, and costs:

For a large facility with many production lines, like Facility R and
many other facilities in the food manufacturing industry, it could take
several years to upgrade all processes to be fully NFPA-compliant.
Facility R representatives encouraged OSHA to implement a standard that
gives facilities a realistic and ample timeframe to come into compliance
and allows facilities to phase in compliance over several years or allow
for grandfathering of existing installations.

Facility R representatives suspected that few industrial facilities have
in-house expertise on combustible dust safety issues and noted that
relatively few consultants and engineering and design companies have
experience in this field. As a result, the facility personnel were
concerned that this limited pool of expertise would be insufficient to
handle the anticipated need for engineering and design services that
might follow promulgation of a new combustible dust safety standard.
They asked that OSHA, when developing its combustible dust standard, be
mindful of the potential backlog among experts helping facilities comply
with new regulations. 

Facility R has already determined that it would face substantial costs
to comply fully with NFPA standards regarding combustible dusts. The
total upfront purchase and installation costs associated with upgrading
or replacing Facility R’s dust collectors that currently do not have
explosion protection was estimated to be in the range of $10 million to
$28 million. 

Facility R representatives noted that their property insurer takes a
very proactive approach to implementing combustible dust safety
programs. However, they feared that industrial facilities located in
small communities without an actively engaged fire marshal and insured
by a less knowledgeable underwriter might be relatively unaware of the
nature and extent of combustible dust hazards.

Facility R representatives have already accessed numerous resources for
gaining insights on combustible dust safety hazards and how to prevent
them. These resources include workshops hosted by state OSHA programs
and consulting and design firms; publications issued by OSHA, the
Chemical Safety Board, and other entities; and articles in the
peer-reviewed literature (primarily for testing data). Facility R
recommended that OSHA consolidate information from these resources into
more comprehensive guidance or compliance assistance that facilities can
use for “one-stop shopping” on combustible dust technical
information. Facility R has also made extensive use out of publications
and literature from the Center for Chemical Process Safety (CCPS),
Society of Fire Protection Engineers (SFPE), and the National Fire
Protection Association (NFPA). 

When evaluating costs of compliance, OSHA should note that certain
industries may face greater costs than others, even when implementing
the same level of control. For instance, Facility R will have to install
equipment that is food-grade compatible and use food safe installation
methods—an incremental cost that certain other industries may not
incur. 

Facility R representatives noted that the periodic revision of the NFPA
standards may complicate matters if OSHA’s combustible dust regulation
cites the NFPA standards. For example, will OSHA’s regulation mean
that NFPA standards would apply retroactively? Meaning, if a facility
installed processes two decades ago that were fully compliant with the
NFPA standards of the time, would the facility be required to ensure
that those processes comply with the current NFPA requirements? And
would this same facility have to periodically update their processes in
order to comply with all future changes to NFPA standards? 

References

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

NFPA, 2008. NFPA 61: Standard for the Prevention of Fires and Dust
Explosions in Agricultural and Food Processing Facilities. 2008 Edition.
National Fire Protection Association. 

OSHA, 2009a. Hazard Communication Guidance for Combustible Dusts. OSHA
3371-08. 2009.
<http://www.osha.gov/Publications/3371combustible-dust.html>

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.

 

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

Parameter	Sample #4282	Sample #4283	Sample #4284

Description of material	Wheat starch	Mixed ingredients	Baghouse dust

Particle size information



	   % through 20 mesh	100 %	95 %	67 %

   % through 40 mesh	100 %	65 %	63 %

   % through 200 mesh	81 %	3.9 %	13 %

Moisture content	9.7 %	0.3 %	2.6 %

Kst *	46.4 bar-m/s	Negative test	17.24 bar-m/s

Explosive material?	Yes	No	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.

* Kst refers to the deflagration index for combustible dust. Since the
OSHA Kst test does not follow the ASTM E1226 testing procedures, these
values are not equivalent to those obtained using ASTM E1226 testing.

Samples with moisture content greater than 5% were dried prior to
testing. Figure 1. Photograph of Dust Collectors for Raw Commodity Bins

Note: 	This photograph shows three dust collectors used to control dusts
generated during material loading operations at Facility R’s large
storage silos. The dust collectors are located indoors and are not
equipped with explosion protection technologies. 

Figure 2. Photograph of Vibratory Conveyor Line

 

Note: 	This photograph shows a production area where a cereal product
that was coated with a sugar mixture passed along a vibratory conveying
system to the packaging operations. The photograph was taken shortly
after the area was cleaned (using the cleaning equipment visible along
the back wall in the photograph). A similar area that site visitors
toured exhibited very fine dust accumulation on the floor and all
horizontal surfaces. 

 Figure 3. Photograph of Compressed Air and Central Vacuum Connections 

 

Note: 	This photograph shows connections, hoses, and nozzles for central
vacuum and compressed air found in a production room. Several production
areas had similar set-ups. Although Facility R had written housekeeping
procedures that clearly delineated when use of compressed air was and
was not acceptable, some employees were not fully aware of these
requirements. Site visitors observed one employee using compressed air
to remove dust accumulations, but this was only observed in a production
area where the equipment was not operating. 

 

 Figure 4. Photograph of Baghouse With Flameless Explosion Vent

 

Note: 	This photograph depicts a dust collector that is fixed to the
wall and ceiling of a hallway used by facility personnel, primarily
operations and maintenance staff. The dust collector is controlling
dusts generated in processes on the other side of the wall shown in the
photograph. Explosion venting to the outdoors was not feasible in this
case, as the dust collector is not located near the building exterior.
The dust collector is equipped with a flameless explosion vent, which
prevents any potential explosions from reaching their maximum pressures
and does not result in a flame exiting the dust collector.

Figure 5. Photograph of Explosion Suppression System on Waste Material
Storage Silo

 

Note: 	This photograph shows a component of the explosion suppression
system that Facility R had installed on a storage silo used to collect
dusts and other dry materials from the facility’s central vacuum
system. Specifically, the elbow in the photograph is the suppression
agent’s pressurized storage container. The storage silo is the large
vessel shown on the right-hand side of the photograph. The explosion
suppression system was installed in 2006 and includes a pressure
transducer that monitors pressures within the storage silo. When
pressures exceed 0.75 pounds per square inch, the system injects a
sodium bicarbonate based suppression agent into the silo. The system has
not been triggered to date. 

 Figure 6. Photograph of Pneumatic Conveying Line in Mixing Room

Note: 	This photograph shows a pneumatic conveying line found in a
mixing room where fine dust accumulations were present. The flexible
boot on this conveying line had been a source of static building.
Facility personnel researched the matter immediately and implemented
corrective action shortly after this issue was identified. 

 Figure 7. Photograph of Ducting in Packaging Area

 

Note: 	This photograph depicts ductwork that vents dusts generated in a
product packaging operation (not visible in the photograph) to a
baghouse. During the site visit, operators stated that a gasket (visible
in the photograph) previously did not provide a leak-proof seal between
the ductwork and the baghouse. The operators corrected the problem by
installing a different gasket. While this effort corrected the problem,
safety officials were unaware of the change and noted that the repairs
did not follow Facility R’s management of change procedures (see
Section 6.3). Attachment 1. Copy of Testing Results Provided by
OSHA’s Analytical Laboratory

Notes: 

Refer to Section 4.2 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. 

 Most production areas had hose connections to Facility R’s central
vacuum system (see Figure 3). The material vacuumed by this central
system was collected in a large silo, which was one of the silos that
Facility R equipped with an explosion suppression system. 

 This concern about contaminating material applied mainly to the
possibility of installing explosion suppression systems on raw material
storage silos. The concern did not apply to the suppression system
installed on the silo that received dust and waste material from the
facility’s central vacuum system.

 During the site visit, Facility R representatives noted that many other
cereal manufacturing companies would experience similar challenges if a
new OSHA standard were to require facilities to retrofit their processes
according to current codes and standards. 

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 PAGE   38 

Site Visits Related to Combustible Dust – Facility R 

 

