Document ID: OSHA-2009-0023-0176
Agency: osha
Document Type: Supporting & Related Material
Title: 
Posted Date: 2011-08-04T04:00Z

Site Visits Related to Combustible Dust:
Facility D - Wet Corn Milling 

                                                                               
                                                                 	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 27, 2011
                               Table of Contents
                                       
1	Project Overview	1
2	Facility Description	2
3	Process Descriptions	4
3.1	Corn Kernel Receiving and Handling	4
3.2	Hammer Mills	6
3.3	Dryers	9
3.4	Product Load-out	10
3.5	Dust Accumulations and Product Bulk Storage	11
3.6	Housekeeping Practices	12
3.7	Baghouses	13
3.8	Other	14
4	Document Review	16
4.1	Testing Data	16
4.1.1	Facility D's Testing Data	16
4.1.2	OSHA's Test Data for Samples Collected During the Site Visit	16
4.2	Material Safety Data Sheets (MSDSs)	17
5	Training	18
6	Main Findings	18
7	Feedback for OSHA	21
8	References	22

Table 1			Testing Results for Samples Collected During the Site Visit
Figure 1		Photograph of Truck Unloading
Figure 2 		Photograph of a Bucket Elevator and Storage Silo
Figure 3  	 	Photograph of Newer Installation Hammer Mills
Figure 4		Photograph of Older Installation Hammer Mills 
Figure 5		Photograph of Dust Accumulations at the Product Load-out Area
Figure 6		Photograph of Product Storage Piles in a Storage Warehouse
Figure 7 		Photograph of a Dust Collector
Attachment 1	Copy of Testing Results Provided by OSHA's Laboratory

Acronyms and Abbreviations

ERG		Eastern Research Group, Inc.
LOC		limiting oxidant concentration
MSDS		Material Safety Data Sheet
NFPA		National Fire Protection Association
OSHA		Occupational Safety and Health Administration
PSM		process safety management 
 
Project Overview 
On December 1 and 2, 2010, Eastern Research Group, Inc. (ERG) conducted a two-day site visit to a facility with wet corn milling operations (hereafter referred to as "Facility D"). The site visit was conducted by two ERG employees and a 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 D's compliance with OSHA regulations or adherence to National Fire Protection Association (NFPA) consensus standards and therefore, should not be used to make such assessments. The site visit focused on safety issues pertaining to combustible dust and was not intended to be a facilitywide evaluation of all OSHA regulations (e.g., means of egress, fire protection, powered platforms). This report should not be viewed as a comprehensive review of Facility D'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 D, 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 D's training programs.
                                       6
                                 Main Findings
Key observations made by the site visit team. 
                                       7
                               Feedback to OSHA
Feedback that Facility D 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. 
                                  Attachments
Testing results provided by OSHA's laboratory
 Facility Description
Facility D uses wet corn milling operations to manufacture multiple products from kernel corn. Wet corn milling refers to a sequence of unit operations (e.g., cleaning, steeping, milling, drying) designed to separate corn kernels into different materials more suitable for further processing. The various production streams tend to be enriched in different components of kernel corn: starch, germ, fiber, and protein (CRA, 2010). More information on typical wet corn milling operations can be found in other references (e.g., Schroeder, 2010). 
The site visit focused on facility processes where combustible dusts are most likely to be present, which included receipt and processing of corn kernels and manufacture of dry animal feed products. In addition to the wet corn milling process, some operations at Facility D, such as the facility's coal-fired boiler, involve combustible dusts. Site visitors toured some, but not all, of the operations involving dry materials. They did not tour or evaluate facility operations involving liquid process streams that do not present combustible dust hazards. 
Most processes at Facility D are continuous or semi-continuous, but some operations (e.g., steeping) occur in batches. At capacity, the facility can process approximately 105,000 bushels of corn kernels daily. Facility representatives said their annual throughput is relatively large for wet corn milling facilities, but they added that their basic wet corn milling unit operations are fairly standard, even though other facilities might be designed to manufacture different products (e.g., corn syrup, ethanol). Smoking is not allowed at Facility D; site visitors noticed no evidence of smoking (e.g., discarded cigarettes) in or near the production areas.
Approximately 195 employees work at Facility D. The facility does not have any regularly contracted personnel but uses contractors for new construction, equipment retrofits, and other activities. The number of contractors working at Facility D on any given day can range from a few to more than 100. Two full-time employees work in Facility D's safety department and support a wide range of safety programs, including process safety management (PSM). Facility D does not have its own fire brigade. 
Site visitors asked the facility's safety personnel to comment on the roles that outside parties play in Facility D's combustible dust safety programs. A summary of those responses follows: 
   # Facility D is located in a small city served by a fire department with approximately 50 career firefighters who work at three stations, one of which is located within a five-minute drive of the facility. Representatives from the fire department tour Facility D annually and have previously provided feedback on safe operation of grain elevators and other topics. However, the fire department neither requires nor encourages adherence to NFPA standards specific to combustible dust. Nonetheless, the fire department is reportedly very experienced in responding to fires and explosions involving grain dust and coal dust because several of these incidents have occurred over the past few decades at the many different industrial facilities in its jurisdiction. 
   # Facility D is insured by one company for property losses and workers' compensation claims. Representatives from this company and from the insurance broker both tour the plant annually and recommend action items to address potential safety hazards. These annual reviews focus largely on the facility's PSM-covered processes, but the insurance representatives have previously made recommendations pertaining to general housekeeping and explosion protection on grain elevators. 
   # Facility D is a member of multiple trade associations, including the National Grain and Feed Association and the Grain Elevator and Processing Society. One of these trade associations is actively engaged in combustible dust regulatory developments and participated in OSHA's combustible dust stakeholder meetings. This trade association also sponsors a safety committee that has compiled for its members some technical information on combustible dust issues. Another trade association to which the facility belongs offers similar services; this second trade association has a regional office located near Facility D. Facility representatives have attended presentations on combustible dust safety issues delivered by the association's regional director of safety, health, and environmental services. This association also provides guidance on OSHA's Grain Handling Facilities standard. 
   # The company that owns Facility D also owns other wet corn milling facilities; some of these are operating and some are under construction. Facility D's two safety professionals periodically consult with safety professionals from other facilities run by the company that owns Facility D. However, the company that owns Facility D does not offer corporate technical support on combustible dust safety programs. 
   # Facility representatives said they have attended symposia and presentations offered by experts (e.g., academics from Kansas State University's Grain Science and Industry program) to learn about combustible dust safety issues associated with their industry. 
   # Facility D representatives have not consulted directly with OSHA on combustible dust safety issues, nor have they tracked relevant publications issued by the agency (e.g., the National Emphasis Program and its status reports). OSHA officials did not visit Facility D as part of the National Emphasis Program.  

Process Descriptions
This section describes selected process operations and production activities that site visitors viewed at Facility D. The specific issues discussed in this section were selected for more detailed summaries because 1) they demonstrate unique challenges faced by this facility or industry, 2) they highlight effective engineering or administrative solutions implemented by Facility J, or 3) they pertain to specific safety issues OSHA might be considering in its rulemaking effort. 
Corn Kernel Receiving and Handling
The first sequence of unit operations at Facility D is designed to transfer corn kernels from trucks to temporary storage silos and clean the kernels before feeding them into the production process. This section reviews the various operations involved in these preliminary receiving and handling steps.
   # Truck unloading. Facility D processes corn kernels delivered by local elevators and farms. The corn kernels arrive by truck. Drivers pull their trucks into the unloading station and park above a series of grates, through which they pour their corn kernel loads (see Figure 1). The corn kernels fall through chutes to a pit leading to an underground belt conveyor system. Corn dust and fine dirt particles become airborne during the unloading process. Most airborne dust enters a dust collection system dedicated to the truck unloading station (see Section 3.7 for further details), but some of the dust forms a cloud that will typically disperse to the outdoor air or possibly enter the unloading station when the door is open. The rest of the dust settles to the ground, where employees remove accumulations following standard housekeeping procedures (see Section 3.6). 
   # Conveying. Belt, drag, and screw conveyors are used throughout Facility D's corn kernel receiving and handling operations. One system transfers corn kernels from the truck unloading station to the bucket elevators that lift the materials into the facility's largest storage silo. Other systems transfer corn kernels to various production buildings and equipment. The bearings on the conveyors are continuously monitored for temperature and sensors verify rotation. Some are equipped with dedicated oil lines for automated lubrication. The belt itself is monitored for speed and signs of misalignment.
      Display panels in some of Facility D's newer control rooms pinpoint precisely which bearings are overheating, but in older control rooms, the displays merely indicate detection of an overheated bearing, and operators must then determine which bearings are experiencing problems. Facility representatives were encouraged to ensure that this monitoring meets specifications outlined in Section7 of NFPA 61. Some bearing sensors are interlocked with the belt motors such that detection of an overheated bearing will automatically shut down the corn kernel flow rate and trigger a shutdown of the primary material feed. 
   # Bucket elevators and storage silos. Facility D operated numerous bucket elevators and storage silos and bins of different capacities. The following paragraphs review observations about the subset of these operations that site visitors evaluated during the facility tour.
      Most bucket elevators at Facility D were located outdoors. Figure 2 is a photograph of the tallest elevator, which delivered incoming corn kernels to the facility's largest silo. As the photograph shows, this particular elevator was equipped with explosion venting panels at regular intervals along the casings, and these panels were placed on both sides of the casings. The burst pressure on these vents was reportedly between 1 and 2 pounds per square inch. Boot and head bearings had motion and temperature sensors. This construction appears to be consistent with design specifications outlined in NFPA 61. 
      In contrast, site visitors observed four bucket elevators used in the wet milling process that were located indoors, without explosion venting panels or explosion suppression systems. These elevators -- some of the oldest at the facility -- did not appear to meet the explosion protection specifications in NFPA 61, but site visitors could not fully evaluate this issue without knowing the elevators' belt speed. Facility representatives had already considered replacing these four indoor elevators with new elevators of comparable capacity, but with an upgraded design and sited outdoors. This project would involve a substantial renovation to the wet corn milling process and operation building, estimated to cost $1.2 million. Facility D had not yet decided if this renovation would take place. 
      Additional engineering controls were installed on some, but not all, of the facility's bucket elevators. At least one indoor bucket elevator, for example, was equipped with an "X-PAC" explosion suppression system manufactured by Fenwal Protection Systems. These systems inject suppression agents within milliseconds of detecting abnormal pressure increases. Magnetic separators were installed at the inlet of other bucket elevators, particularly those that transfer unprocessed corn kernels. 
      Facility D's design and control of storage silos and bins also varied. The facility's largest concrete storage silo is equipped with multiple internal temperature sensors to detect burning material at different depths, but several of the facility's smaller silos do not have these sensors. However, facility representatives noted that corn kernels and intermediate products had much shorter residence times in the smaller silos, thus reducing the likelihood of self heating. 
   # Corn cleaning process. Cob fragments, dirt, and other coarse foreign materials are present in corn kernel shipments arriving at Facility D. The facility employs two different "corn cleaning" operations to remove as much of these undesired materials as possible before the corn kernels enter the steeping process. The cleaning is not a liquid wash but rather occurs by use of either a rotary scalper or a vibratory screener, both of which help separate corn kernels from other solid materials. The scalper reportedly is not a major source of fugitive dust emissions unless it gets choked because of inadequate dust collection draft  -- an observation that was consistent with the minimal dust accumulations observed around this unit operation during the site tour. (Note: The scalper was not operating during the time site visitors toured this production area.) However, the vibratory screeners in the older production line appeared to have greater fugitive dust emissions during the site tour, which might be better controlled by identifying and sealing gaps in the screeners and assessing the effectiveness of the screeners' dust collection systems. 
Hammer Mills
Facility D operates two sets of hammer mills that differ in terms of engineering design and combustible dust safety controls. The feed to the two sets of hammer mills also differs in terms of composition, moisture level, and particle size. The following table identifies design features and safety controls found on the two different hammer mill installations. The older installation, known as the wet mill, was equipped with greater safety controls than the newer one, most likely because the older one was viewed as a higher risk operation. However, it was unclear why the newer installation had such limited controls, especially considering that it processes the more explosible feed, due to its higher starch content. The wet mills are in an open area near one of the dryers in one of main production buildings, whereas the newer installations are in a separate building with only the rotary scalper.
                                   Parameter
                              Newer Installation
                              Older Installation
Description
                            Three mills in parallel
                             Two mills in parallel
Magnets on inlet
                                      Yes
                                      Yes
Explosion suppression
                                      No
                                      Yes
Spark/ember detection and suppression in ducting
                                      No
                                      Yes
Steam injection for fire suppression
                                      No
                                      Yes
Additional notes
                            See Figure #3 for photo
                            See Figure #4 for photo
More detailed information on the various design features follows: 
   # Magnets. Both sets of hammer mills are equipped with strong magnets designed to remove tramp metal from the inlet feed. The magnets do not have a self-cleaning design. Rather, when a given hammer mill is ready for servicing (typically weekly), employees de-energize the magnet and remove any collected materials before bringing the mill back online. 
   # Explosion suppression. Both older installation hammer mills are equipped with explosion suppression systems manufactured and installed by Fenwal Protection Systems. (Note: The hammer mills also had steam injection capability for fire suppression.) The explosion suppression systems inject large quantities of halon gases upon detection of a potentially unsafe increase in pressure. The systems are designed to inject suppression agent inside the mill itself and in ductwork on both the inlet and outlet, which should help ensure that events initiated within the mill are effectively isolated. Facility representatives noted that the explosion suppression systems have been actuated a few times in the past, and they always performed as expected. Original purchase and installation costs were not available for the explosion suppression systems, but the systems have ongoing operations and maintenance costs: representatives from Fenwal Protection Systems conduct quarterly maintenance, and the facility previously paid approximately $10,000 every time the suppression agent had to be recharged. 
      Site visitors also reviewed the facility's written operating procedures for engaging and disarming the explosion suppression systems. These were developed to avoid accidental actuation of the systems while maintenance employees work on the hammer mills, to ensure that maintenance employees do not inadvertently damage pressure sensors and other equipment critical for the suppression systems, and to ensure that these employees remember to arm the systems after completing their work. 
   # Spark/ember detection and suppression system. Dust pickups from the wet hammer mills next to the rotary dryers are connected via ductwork to a dust collection system. To prevent burning material generated in the mills from entering the dust collectors, Facility D installed a spark/ember detection and suppression system in the interconnecting ductwork. The system was manufactured and installed by GreCon, Inc. and is reportedly approved by Factory Mutual. This system continuously monitors for sparks and embers at a fixed point in the ductwork. Upon detection, the system immediately releases a fine mist of water at a downstream location. The system allows for controls of potential ignition sources without interrupting the process when suppression is activated. 
      Facility representatives noted that suppression is rarely activated at this particular device. While the infrequent suppression activity could reflect a limited amount of sparks/embers in this ductwork, it could also suggest an improperly functioning detection system. Site visitors noted that dust build-up on the infrared detectors is a documented cause of detector malfunction, and they encouraged facility representatives to ensure that their spark/ember detection and suppression system is operated and maintained according to the manufacturer's recommendations (Barnum, 2007) and FM approval. Maintenance activities should ensure that the GreCon system's detection and suppression features are functioning properly. All maintenance of these systems is currently conducted by a local fire protection contractor. 
   # Other. Site visitors made additional observations regarding the hammer mills. First, motors were installed in very close proximity to the hammer mills, and it was unclear if this equipment was rated for Class II, Division 2 hazardous locations (i.e. Totally Enclosed Fan Cooled). Second, with multiple hammer mills in parallel, facility personnel could shut down individual mills while leaving the others operating. This enabled maintenance employees to service and clean individual mills without shutting down production. The facility was encouraged to minimize the amount of time that maintenance personnel spend servicing hammer mills when adjacent mills were operating. Third, according to facility representatives, bearing temperatures were continuously monitored on the newer hammer mill installations, and high alarm readings reportedly shut down the mills. 
Dryers
Facility D's processes separate corn kernels into many components. An outcome of the steeping process is multiple intermediate product streams with high moisture content. Facility D operated numerous rotary dryers to reduce the moisture content of the main production streams. This section first presents a detailed review of the newer dryer installations and then offers additional observations regarding the older dryer installations. (Note: Facility D also operated a spray dryer on one of its production lines, but that unit operation is not reviewed here.)
   # Rotary dryers: newer installations. In Facility D's newest production area, reduction in moisture content is achieved by passing inlet material through two rotary dryers, operated in series. The first dryer is a co-current, direct contact, gas-fired dryer that reduces the feed's moisture content from more than 60% to approximately 35%. The second dryer is of similar design and further reduces the moisture content to approximately 12%. Exhaust gases from both dryers vent to separate banks of cyclones located inside the production building.
      Both rotary dryers are equipped with multiple sensors, interlocks, and controls to promptly detect evidence of potentially unsafe operating conditions and to implement automated corrective actions. For example, temperature is continuously monitored at the inlet and outlet of both dryers to indicate burning or smoldering material in the dryer. Two temperature sensors were installed at each monitoring location to account for the possibility of malfunctioning equipment. Low-alarm and high-alarm settings are programmed into the dryer controls, and these conditions automatically trigger different actions (e.g., steam suppression, water suppression, feed cut-off). The steam suppression system has been activated a few times over the past five years, mostly during power outages and subsequent start-up, but water suppression has yet to be triggered. 
      Other parameters monitored on the dryers include rotational speed and input feed rates. These are important to monitor to ensure that the processed corn materials do not remain in dryers for unexpectedly long durations, or after the dryer is shutdown. All process controls for these dryers are automated and do not require operator action, though designated operators have the authority to override certain responses.  
   # Rotary dryers: older installations. Site visitors observed nine rotary dryers in the older processes at Facility D. These included co-current direct contact dryers fired by natural gas and non-contact shell and tube dryers. In the latter dryer type, steam circulates through the tubes, and the material to be dried tumbles over the outside of the warm tubes, thus providing the desired heat exchange. Site visitors reviewed a subset of these dryers, all of which were equipped with continuous temperature monitors designed to identify higher than intended operating temperatures potentially leading to a dryer or duct fire. However, dryer outlet temperature sensors would probably not detect the burning of small embers in the outlet flow.
      A major difference between the older and newer installations, however, was the nature of the response when measurements exceeded alarm settings: the newer installations generally had automated corrective actions (e.g., fire suppression actuation and feed cut-off), but most of the older installations triggered audible and visible alarms in control rooms, without automatically activating controls. Upon noticing alarm conditions in these older installations, operators had to evaluate the nature of the alarms and manually implement controls following standard operating procedures. While manual response to alarm conditions has proven to be effective to date, reliance on administrative controls runs the risk of operator error, such as not noticing alarm conditions or failing to apply the appropriate corrective actions. Facility representatives were encouraged to implement automated controls, where feasible. 
Product Load-out
Facility D's primary dry corn products are transferred via overhead belt conveyors to two dedicated "product load-out" areas. The facility is capable of pouring its products into both trucks and railcars. Product load-out operations, like most material transfers involving dry powders, are well-known sources of fugitive dust. The magnitude of dust emissions depends on material-specific properties (e.g., particle-size distribution) and engineering design of the transfer location (e.g., the chutes and spouts). Site visitors noted different dust control issues associated with the two load-out areas. 
One load-out area is located adjacent to the main wet corn milling production building, where several different co-products are poured into trucks and railcars. Facility engineers have reportedly tested multiple load-out options and spout designs in attempt to minimize dust formation. These include using plastic curtains to completely enshroud trucks during the load-out process. Despite these and other efforts, dust releases still occur, as demonstrated by settled dust accumulations observed on many horizontal surfaces in the load-out building (see Figure 5). Further evaluation of the load-out operations, such as testing the effect of the vertical distance between the downspout and the receiving truck or railcar, investigating the effect of different downspout geometries on dust formation, and using enclosures for load-out to railcars, was encouraged. 
The second load-out area is used exclusively for transferring the protein-rich co-product and is used almost entirely for loading the co-product into railcars. Compared to the load-out area described in the previous paragraph, the second load-out area had fewer horizontal surfaces onto which combustible dusts could settle, which led to notably lower dust accumulations observed during the facility tour. Although both load-out areas had similar dust control challenges, the railcar load-out had a special issue. Since the loaded railcars are not allowed to leave the load-out area with product (dust) on top of the railcar, the load-out operator has to blow off the dust using compressed air. Refer to Section 3.6 for site visitors' observations regarding housekeeping practices used in the second load-out area.  
Dust Accumulations and Product Bulk Storage
Settled dust thicknesses varied from one production area to the next, and accumulations observed during the site visit might not be representative of those experienced over the long term. Nonetheless, site visitors either saw or heard of three specific production areas that had the greatest dust accumulations: 
   # The production area with the greatest dust accumulations was the large (42 foot high ceiling) warehouse that served as a temporary bulk storage area for the protein-rich co-product. The yellow material enters this warehouse on an elevated drag conveyor, from which it falls onto large cone-shaped piles (see Figure 6). As Section 4.1.2 indicates, this particular co-product was found to be explosible and had the highest deflagration index of the three dust samples that site visitors collected. 
      According to facility representatives, the powder co-product must "cure" in the piles for at least 20 hours in order to facilitate subsequent handling and prevent "setting up" in the railcar. The typical product residence time in the warehouse is 48 hours. After the co-product finishes curing, operators use front-end loaders to push the co-product over metal grating, where the material falls into a pit and eventually is transferred to a product load-out station (see Section 3.4). 
      Usually the product pile height in the warehouse is about half the ceiling height (i.e., about 20 feet). However, on the day of the site visit, the two conical piles of co-product had peaks over 30 feet tall. The falling material led to dust accumulations on horizontal surfaces (e.g., I-beams) throughout the warehouse. The facility previously installed coverings on some I-beams in order to minimize the area of horizontal surfaces on which dust could collect. However, this control strategy was eventually abandoned when operators noted considerable amounts of settled dust accumulating behind the coverings. Site visitors encouraged further evaluations of these controls, given that other facilities have reported success in designing and installing downward-sloping wall structure ledge coverings to minimize dust accumulations.
      Given the presence of combustible dust throughout the warehouse, facility representatives were encouraged to identify and eliminate potential ignition sources. It was unclear whether the lights, other electrical fixtures, and front-end loaders were rated for Class II, Division 2 environments -- an issue that the facility was encouraged to evaluate. According to some employee accounts, smoldering co-product material is sometimes noticed (usually by smell) in the warehouse and on front-end loader engines. Some employees reported removing smoldering material to outdoor locations and spraying the burning pile with water hoses. However, employees are instructed to call the municipal fire department rather than attempt suppression of moderate-to-large burning piles. It would be helpful to provide more detailed instructions on distinguishing moderate fires from "hot spots" and developing standard operating procedures for locating and dealing with these hot spots. Given that hot spots can quickly develop into fires, it would be prudent to contact the fire department any time a hot spot or fire of any size is discovered.
   # Dust releases also reportedly occurred through leaks in ductwork and at certain elevators. Holes (probably caused by corrosion) and leaks in ductwork were typically sealed upon detection (see Section 3.8). However, two older bucket elevators were known to have small leaks that were chronic sources of fugitive dust: one was located in the wet milling process near the older installation hammer mills, and the other was used for transferring coal to storage bunkers. Facility representatives were already researching options for replacing older elevators. In the mean time, greater emphasis should be placed on identifying and repairing leaking elevators and ducting, and more frequent housekeeping might be necessary to remove settled dusts until the leaks are fixed. 
   # Several control rooms at Facility D were located adjacent to operations with fugitive sources of combustible dust. To minimize dust accumulations in control rooms, entry doors should remain closed whenever possible, and the rooms should operate under positive pressure. Additionally, facility representatives were encouraged to look for evidence of hidden dust accumulations, especially above the control rooms' drop ceilings. 
Housekeeping Practices
Time constraints prevented site visitors from conducting a complete evaluation of Facility D's housekeeping practices in all production areas. However, written housekeeping procedures reviewed for certain processes were generally consistent with the employees' actual housekeeping practices. The primary housekeeping activities involved using manual cleaning methods, such as brooms, sweeps, and shovels. Water wash-downs also occurred, but not in places where sub-freezing temperatures occurred during winter months. Vacuuming was rarely used to remove dust accumulations. Housekeeping activities included daily removal of dust accumulations and less frequent (intervals varied from weekly to several months) "top-to-bottom" cleaning of certain production equipment. 
Compressed air is reportedly used in limited circumstances for removing dust accumulations. As noted previously, much of Facility D's products are loaded into railcars for shipment to customers. Although the load-out process efficiently poured powder materials into railcars, some dusts settled atop railcars, and local transit authorities require that settled dusts be removed from railcar surfaces before trains leave facility grounds. Brooms and other hand-held housekeeping tools were not effective at removing dust accumulations from all surfaces on large railcars, and employees instead used compressed air (roughly 80 to 90 pounds per square inch) to remove these settled dusts. Blowing settled dust off the exterior of a single railcar typically took less than 10 minutes, and designated employees reportedly performed this activity several times daily. During these blow-downs, employees temporarily worked in the presence of combustible dust clouds, which quickly dissipated after the compressed air was disengaged. Employees who perform compressed air blow-downs would be better protected against potential risks from flash fires, if they wore flame-resistant garments. 
Though site visitors were assured that compressed air was typically not used for housekeeping activities, they observed compressed air connections at several locations throughout the facility. Use of compressed air could be effectively eliminated in these locations by removing any ancillary equipment (e.g., hoses, wands) needed to operate the systems.  
Baghouses
This section documents the site visitors' observations regarding multiple baghouses that were viewed during the facility tour. Facility D might operate additional baghouses beyond those that were observed. Note that the facility operates other types of dust collectors (e.g., numerous cyclones), but this section focuses on baghouse design and explosion protection features. 
The observed baghouses varied in terms of design and explosion protection features. Every baghouse was located outdoors. Some were at ground level, and others were atop production buildings. Dust-laden inlet air originated in multiple processes, and clean exhaust air was almost always vented to the outdoor environment and not returned to production buildings. Collected dust at almost every baghouse was still considered a viable ingredient for animal feed products and was therefore eventually returned to other process locations rather than handled as waste. Some dust collectors showed evidence of corrosion, with a few having holes visible on the exterior walls and other surfaces. Facility representatives were encouraged to address these corrosion issues to prevent potential sources of fugitive dusts. 
The baghouses also varied in terms of the number and size of filtering bags. Smaller baghouses contained between 25 and 45 bags, and larger ones had as many as 400. Generally, bags were changed once or twice per year in all parts of the facility, and more frequently when magnehelic sensors recorded increased pressure drop across the filter media. Maintenance personnel noted that dusts collected on the bags tended to have a "caked" appearance, but charred and smoldering dusts were reportedly never observed during the bag changeouts. 
Every baghouse that site visitors observed was equipped with explosion venting panels (see Figure 7). It was unclear what consensus standard and dust explosibility data were originally used when determining the size and placement of these panels. Site visitors noted that NFPA 68 provides prescriptions on these design features based on the explosibility of the collected dusts, but these testing data were not available. 
Facility D did not operate any spark/ember detection and suppression systems in the inlets to its dust collectors. Site visitors noted that these systems might be worth considering for baghouses that control air exhaust streams from dryers, because of the higher likelihood that smoldering dusts might be conveyed from a dryer to the dust collector. None of Facility D's dust collector ducting was equipped with explosion isolation systems that meet the design specifications of NFPA 69. Isolation systems would be particularly beneficial in cases where dust collectors connect directly to storage bins and elevators as well as dryers and hammer mills. 
Other
The remainder of this section documents various additional observations not summarized in the earlier discussion: 
   # Classification of hazardous locations. It was unclear to site visitors if Facility D had systematically classified its hazardous locations per the National Electrical Code Article 502 and NFPA 499. Observations made during the site visit suggested that some production areas likely meet the criteria for Class II, Division 2 designations due to the presence of combustible dusts during routine operations. Some electrical fixtures and other equipment (e.g., front-end loaders) operating in these production areas did not appear to be suitable for Class II environments. However, a full review of Facility D's electrical classifications and use of rated equipment was not conducted during the site visit. 
   # Ductwork maintenance. Some ductwork at Facility D had extensive patchwork, which included use of metal patches, duct tape, and polymeric sealants. In isolated areas, more than half of the visible ductwork consisted of patches rather than the original material. Excessive patchwork was particularly evident in ducting at the highest floors near the indoor elevators. Corroding and leaking metal equipment was also observed in some dust collectors and reported for selected elevators. While patching temporarily sealed leaking ducts, standard operating procedures should be developed to help maintenance personnel decide when individual ductwork segments should be patched or replaced with new ducting. 
   # Coal-fired boiler. Facility D burns approximately 200,000 tons of bituminous coal per year. Coal arrives at the facility primarily by truck and is poured through grates to a belt conveyor system, which transfers incoming coal to temporary storage silos. The coal is eventually fed to a pulverizer, and the crushed coal is burned in onsite boilers. The silos are not equipped with temperature sensors, and the pulverizer is not equipped with an automated fire or explosion suppression system or inerting system. Because the purpose of this site visit was to evaluate the wet corn milling process, site visitors spent limited time evaluating coal-dust issues. However, some observations were noted and are documented here.
      Site visitors discussed the formation of coal dust deposits that occurs during receipt, transfer, and conveying of coal. The coal handling operation is equipped with a dust control system, but the facility routinely operates coal handling and transferring with the control system disengaged and instead opts for coal-dust suppression. Facility representatives noted that they only address coal-dust releases during the summer months due to the lower moisture content in the coal and the higher ambient temperatures. To mitigate fugitive dust releases during this time, a foam suppression agent is sprayed on the coal along parts of the belt conveyors and at other process locations. This procedure is not implemented during fall, winter, or spring. Settled coal dust in the conveyor tunnel is reportedly cleaned out daily, using brooms, shovels, and wash water. These activities were not observed during the site visit because the coal conveyor was down at the time of the facility tour. 
      An interior bucket elevator is eventually used to lift coal from ground level to storage silos, from which the coal feeds directly to pulverizers. Site visitors noted some coal-dust accumulations along the base of the elevator. Consistent with this observation, facility personnel confirmed that the elevator has some leaks and is a significant source of fugitive coal-dust releases and is the area where housekeeping activity is most time-consuming. Facility representatives said they were planning to replace this bucket elevator within a year. 

Document Review
This section summarizes documents pertaining to combustible dust safety issues that Facility D 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 D's approaches for controlling them. 
Testing Data
This section describes testing data for materials that Facility D handles and produces, focusing primarily on results from three samples that site visitors collected and sent to OSHA's laboratory for testing. 
Facility D's Testing Data
Facility D did not have any combustibility or explosibility testing data available for review. Without this information, site visitors could not evaluate the adequacy of the facility's engineering controls. Although, it is possible that the engineering and design firm that constructed the facility's process had access to relevant testing data on corn dust and co-products from previous work conducted at other facilities, site-specific data should be obtained to confirm the data used as a basis for dust explosion protection designs.
OSHA's Test Data for Samples Collected During the Site Visit
As noted previously, site visitors collected three samples during the site visit, with the permission and concurrence of Facility D representatives. Copies of the laboratory testing results appear in this report as Attachment 1; Table 1 summarizes the results. More information on the samples collected and the test results follows:
   # Sample #9121: Protein-rich co-product. One of Facility D's co-products is a finely milled protein-rich animal feed. The facility temporarily stores this co-product in piles inside a large warehouse before shipping the material to customers (see Figure 6). This sample was collected from horizontal I-beams along the walls in the storage area. Of the three samples collected during the site visit, this material was the finest (54% passing through a 200 mesh screen), driest (3.3% moisture), and had the highest deflagration index (OSHA Tech Center Kst = 35.29 bar-meter/second). The relatively high Kst value indicates that this dust had a faster rate of combustion than the other three dusts the site visitors had tested, and therefore requires the largest explosion vent areas on a given size baghouse or other enclosure. 
   # Sample #9122: Fiber-rich fines. The wet corn milling process is used to manufacture multiple products enriched in different components of corn kernels. One co-product is enriched in fiber, which originates primarily from the kernels' outer hull. This sample was collected from a dust collector that controls particle-laden exhaust streams from a dryer and hammer mill used to manufacture the fiber-rich co-product. The original sample had a moisture content of 13%, and 41% of the sample passed through a 200 mesh screen. The dried sample was found to be explosible (OSHA Tech Center Kst =18.29 bar-meter/second). 
   # Sample #9125: Corn meal co-product. Facility D also manufactures a fine, yellow, gluten-rich powder referred to in this report as "corn meal co-product." The finished corn meal co-product is eventually poured through a downspout into railcars. This dust sample was collected from horizontal surfaces in the product load-out area (see Figure 5). The material had a moisture content of 9.6%; 15% of the sample passed through a 200 mesh screen; and the dust was found to be explosible (OSHA Tech Center Kst = 16.01 bar-meter/second). 
As noted in the testing results (see Attachment 1), the data presented above should not be used in designing or engineering protective safety equipment since the OSHA Tech Center testing procedures are not the same as the ASTM standard tests needed for KST values for explosion venting and isolation designs. The testing results reflect the conditions of materials collected during the time of the site visit, which might not be representative of the full range of combustible dusts at Facility D. 
Material Safety Data Sheets (MSDSs) 
Facility D maintains an inventory of MSDSs for the various materials used and processed, and site visitors reviewed three MSDSs and four product specification sheets. The three MSDSs were for animal feed products, and the only information that all three sheets presented on combustible dust hazards was: "Unusual Fire and Explosion Hazards: Airborne concentrations of dust greater than 20 grams/cubic meter with sources of ignition." The MSDSs had fields for conditions to avoid, special firefighting procedures, or procedures for cleaning spills, but no detailed information was included documenting potential combustible dust safety hazards. 
The four production specification sheets were for different grades of pet food ingredients. None of these sheets presented any information on potential combustible dust safety hazards. However, it was not clear if these product specification sheets were intended to comply with OSHA's hazard communication requirements. 

Training 
Facility D offers multiple initial and refresher training courses to its employees, with the type and frequency of training depending on each employee's job duties. Due to time constraints, site visitors could only review one of the facility's training courses: "Elevator Training Program." Every employee who works with elevators must take this training annually, and new employees must take the course before they begin working on elevators. This training provides extensive information on combustible dust safety issues, including maximum allowable dust accumulations, cleaning procedures, and ignition sources to avoid. The training requires elevator operators to immediately remove dust accumulations greater than 1/8 inch observed within a 35-foot radius of bucket elevators -- a requirement that is consistent with OSHA's Grain Handling Facilities standard (29 CFR 1910.272). The training materials indicate that housekeeping should be performed using brooms and shovels, though employees are permitted to use water hoses in certain areas. The training materials are silent on the use of compressed air for housekeeping activity: this cleaning technique is neither advocated nor prohibited. The specific ignition sources mentioned in the training were smoking (which is prohibited at Facility D) and overheated bearings, and the training addressed procedures for responding to indicators of overheated bearings. 
 
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 D's compliance with OSHA regulations or adherence to NFPA consensus standards. The main findings communicated to Facility D representatives included: 
   # The employees that met with site visitors exhibited strong awareness of combustible dust safety issues, and the facility's safety professionals appeared to be committed to preventing dust-related fires and explosions. Facility representatives were encouraged to enhance their awareness by evaluating their operations in light of specifications in the current edition of NFPA 61. 
   # Because Facility D did not have testing data available characterizing the combustibility and explosibility of various dusts, the adequacy of the facility's various engineering controls could not be fully evaluated. Site visitors shared several examples of how the facility could incorporate material-specific testing data into safety controls: 1) alarm settings in dryers should be based on an evaluation of the ignition temperatures of the feed materials (e.g., hot air over layer temperatures); 2) whether flexible hose connections and the super sacks used for certain products are potential sources of static electrical discharge should be based on the corresponding materials' minimum ignition energy; and 3) the placement and sizing of explosion vent panels on dust collectors should be based on the materials' deflagration indexes. 
   # Facility D uses many operations (e.g., bearings, drive belts, conveyors, bucket elevators, dryers, silos) for which NFPA 61 has published recommended controls. The instrumentation used in the newer production lines included sophisticated process controls that allowed operators to readily pinpoint potentially unsafe operating conditions, such as overheating bearings. However, several opportunities were identified for enhancing controls, such as using more temperature sensors in storage silos. Facility representatives were encouraged to evaluate the facility's existing monitoring systems, engineering controls, and equipment design with respect to the various specifications outlined in Sections 7 and 8 of NFPA 61. Not enough information was available to site visitors to fully evaluate adherence to these standards, particularly for the indoor elevators. 
   # The warehouse used to temporarily store the facility's protein-rich powdered co-product exhibited large quantities of settled combustible dust in addition to the storage piles themselves. The following opportunities were identified for reducing the risks of dust-related fires and explosions: 1) installing building explosion venting panels per NFPA 68; 2) classifying the hazardous location per OSHA standards (29 CFR 1910.207) and ensuring that all electrical fixtures and mechanical equipment (e.g., front-end loaders) are rated for use in the assigned classification; 3) developing and implementing consistent procedures for identifying and extinguishing small fires that originate in the warehouse, whether in the dust piles or on the equipment used to move the co-product; 4) installing downward-sloping coverings on horizontal structural steel surfaces to minimize dust accumulations; and 5) considering the acquisition of large ceiling fans with downward directed air flow to prevent accumulations on elevated surfaces. 
   # Facility D uses multiple rotary dryers to reduce moisture content in process streams. The newest installations have sophisticated controls with numerous interlocks, sensors, alarms, and automated corrective actions designed to prevent fires and explosions. The older installations have some similar features, but alarm conditions do not trigger automated responses. Effective operating procedures are critically important in cases where operators manually address alarm conditions. For the older dryer installations, written operating procedures should ensure prompt and effective manual responses to alarm conditions (see Section 3.3). Further, dryer outlet streams have the potential to carry smoldering material to other unit operations, including some storage silos; use of additional spark/ember detection and suppression systems on dryer outlets would help ensure that the dryers do not pose a fire or explosion hazard to downstream operations. 
   # The new installation hammer mills should be equipped with explosion suppression and isolation systems since hammer mills are often a frequent site for frictional and impact ignition sources (due to tramp metal, broken hammers, and torn outlet screens) and the generation of combustible dust clouds is probably a normal operating condition.
   # The dust collectors that site visitors observed varied considerably in terms of design and operation. Every baghouse dust collector viewed during the site visit was located outdoors and was equipped with explosion venting panels. The evaluation of the adequacy of the placement and sizing of the panels was beyond the scope of the visit. Future evaluations by others will require the ASTM standard explosibility testing data (e.g., Kst values) that are currently not available. Opportunities for minimizing hazards in the dust control system include: 1) installing additional spark/ember detection and suppression systems, especially in ductwork connecting known ignition sources (e.g., hammer mills, dryers) to dust collectors; 2) installing explosion isolation systems in pneumatic conveying locations found to present a significant risk for deflagrations propagating to other equipment (e.g., baghouse inlet lines); and 3) promptly repairing holes identified in filter media and in the dust collector housing. 
   # A critical element in preventing combustible dust incidents is effective maintenance of equipment and controls. Site visitors observed two instances where maintenance programs could be enhanced. First, excessive patchwork was noted in some of Facility D's ductwork, especially near the top levels of the indoor elevators. More careful consideration should be given to whether individual segments of ductwork should be replaced or patched. Second, facility representatives should ensure that the spark/ember detection and suppression systems are properly operated (check detector setting and signal fault monitoring) and maintained by the outside fire protection contractor, because the infrequent activation of suppression could be a sign that the detection system is coated with dust or otherwise malfunctioning. 
   # The MSDSs made available to site visitors included limited information about combustible dust safety hazards, and the product specification sheets for the pet food ingredients had no information on this topic. Facility representative were encouraged to include more explicit acknowledgement of potential combustible dust safety hazards on MSDSs for their various solid products (see Section 4.2).
   # Facility D's written housekeeping procedures were consistent with the employees' actual housekeeping practices. Compressed air is reportedly used in limited circumstances for removing dust accumulations; however, connections to compressed air at 80 - 90 pounds per square inch pressure were observed at locations throughout the plant. Site visitors encouraged facility representatives to monitor use of compressed air and consider providing flash fire-resistant personal protective equipment per NFPA 2112 specifications for personnel who use compressed air during housekeeping activities or work in the bulk product storage warehouse, or other areas with significant dust accumulations greater than those specified in the NFPA 654 2011 Tentative Interim Amendment. 
   # Site visitors briefly reviewed combustible dust safety issues associated with Facility D's coal receipt, handling, and burning processes. They encouraged the facility to ensure that these operations are consistent with specifications in applicable NFPA codes and recommended practices, such as the "Recommended Practice for Fire Protection for Electric Generating Plants and High Voltage Direct Current Converter Stations" (NFPA 850). The current practice of operating coal conveyors and transfer points during the colder months without any form of dust suppression or collection was not advised. Refer to Section 3.8 of this report for additional feedback provided by the site visitors. 

Feedback for OSHA
At the end of the site visit, ERG asked representatives from Facility D if they had any specific feedback for OSHA on combustible dust safety issues. (Note: This site visit occurred after OSHA had publicly announced its intention to initiate a rulemaking on combustible dust [OSHA, 2009] and convened its stakeholder meetings). Facility D representatives offered the following responses: 
   # If a new combustible dust standard is promulgated, facility representatives recommended that OSHA place a greater emphasis on providing compliance assistance to the regulated community (especially in the first few years following promulgation), with a lower emphasis on enforcement. 
   # Many industrial facilities like Facility D have limited financial and personnel resources available to implement new programs to comply with new safety standards. The two safety professionals who work full time to ensure compliance with existing regulations, including OSHA's PSM standard, had concerns about not having enough time available to comply with an additional combustible dust standard. To illustrate their concern, facility representatives noted that an employee would have to invest an extensive amount of time just to become well versed on the various NFPA standards that could apply to their facility (e.g., NFPA 61, 69, 654, 850). 

References

Barnum, B, 2007. Spark Detection: Maintain Spark Detection/Extinguishment Systems to Ensure Effectiveness. Bob Barnum, GreCon. In: Modern Woodworking. September, 1997. Document available online at: http://www.grecon-us.com/pdfs/maintain.pdf. 

Corn Refiners Association (CRA), 2010. The Corn Refining Process. Document available online at: http://www.corn.org/wp-content/uploads/2009/11/CornRefiningProcess.pdf. 

OSHA, 2008. Combustible Dust National Emphasis Program (Reissued). U.S. Department of Labor, Occupational Safety and Health Administration. March 11, 2008. 

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.
 
Schroeder, JW, 2010. Corn Gluten Feed: Composition, Storage, Handling, Feeding and Value. North Dakota State University, Extension Service. Publication AS-1127. Document available online at: http://www.ag.ndsu.edu/pubs/ansci/dairy/as1127.pdf. 

     Table 1. Testing Results for Samples Collected During the Site Visit
                                   Parameter
                                 Sample #9121
                                 Sample #9122
                                 Sample #9125
Description of material
                            Protein-rich co-product
                               Fiber-rich fines
                             Corn meal co-product
Particle-size data 
                                       
                                       
                                       
   % through 20 mesh
                                     100%
                                      81%
                                      95%
   % through 40 mesh
                                     100%
                                      65%
                                      73%
   % through 200 mesh
                                      54%
                                      41%
                                      15%
Moisture content
                                     3.3%
                                      13%
                                     9.6%
Explosive material?
                                      Yes
                                      Yes
                                      Yes
Kst (bar-meters/second)
                                     35.29
                                     18.29
                                     16.01
Pressure ratio
                                      7.5
                                      6.7
                                     6.72

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 testing 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 cannot be used in designing or engineering protective safety equipment").
      Samples with moisture content greater than 5% were dried prior to testing, following the laboratory's standard protocols.
      Kst = maximum normalized rate of pressure rise (or deflagration index); values are provided only for explosive materials.
                                       

                    Figure 1. Photograph of Truck Unloading
                                       
Note: 	This photograph is a close-up picture of a truck delivering corn kernels to Facility D. After pulling into the unloading area, the driver opened a sliding gate beneath the truck, which allowed corn kernels to flow through the metal grates down to belt conveyors that transferred the corn to other facility operations. The unloading process generates airborne dust, which is primarily a mixture of corn dusts and dirt. These dusts either enter a dedicated dust collection system (see Figure 7 for a photograph of the dust collector) or settle to the ground where employees eventually remove dusts during standard housekeeping activities. Some corn kernels falling from the trucks initially do not pass through the metal grates shown in the photograph. After trucks leave the unloading area, employees sweep these kernels into the grates for further processing. 
          Figure 2. Photograph of a Bucket Elevator and Storage Silo
                                       
                                       

Note: 	This photograph shows part of the facility's largest concrete storage silo (left) and the elevator that lifts corn kernels to the top of the silo. An enclosed belt conveyor delivers the corn kernels to the elevator base, where a magnetic separator removes metallic impurities from the incoming raw materials. The elevator is equipped with explosion venting panels at regular intervals along both sides of the casings, and three panels are visible in the photograph. The burst pressure on these vents was reportedly between 1 and 2 pounds per square inch.
            Figure 3. Photograph of Newer Installation Hammer Mills
                                       
                                       

Note: 	This photograph shows two of Facility D's three newer hammer mills that operate in parallel. Magnetic separators at the top of the mills remove tramp metal from the inlet stream of cleaned corn kernels. The hammer mills then crush the corn kernels to sizes that pass through size 8 mesh screens. These hammer mills were not equipped with explosion suppression systems, and the inlet and outlet ductwork had no isolation systems or spark/ember detection and suppression systems. Each hammer mill was equipped with a 300 horsepower motor. 

            Figure 4. Photograph of Older Installation Hammer Mills
                                       
                                       
                                       
Note: 	This photograph shows the two older hammer mills operating at Facility D. These mills are located on the floor of a main production area adjacent to a rotary dryer, which is visible in the background. The hammer mills are equipped with explosion suppression systems, and the outlet ductwork has spark/ember detection and suppression systems. 
                                        
                                       
    Figure 5. Photograph of Dust Accumulations at the Product Load-Out Area
                                       
                                       

Note: 	This photograph is an overhead view of one of Facility D's product load-out areas, where corn co-products are poured into trucks or railcars for shipment to customers. The photograph shows settled dust accumulations of a corn co-product atop an elevated horizontal surface. Refer to sample #9125 in Table 1 for explosibility testing results conducted by OSHA's laboratory.
 
 
      Figure 6. Photograph of Product Storage Piles in a Storage Warehouse
                                       
                                       
                                       
Note: 	This photograph was taken inside the warehouse used to temporarily store Facility D's protein-rich co-product. Newly manufactured material drops from an overhead conveyor onto the piles. The two conical piles shown were approximately 20 feet tall. Settled dust accumulated on all horizontal surfaces in the building, such as the I-beam wall supports visible at the back of the building. Operators used front-end loaders to move this co-product to floor openings, where the material was transferred to the product load-out area. Refer to Section 3.5 for site visitors' observations about this operation and potential risk mitigation strategies; and refer to sample #9121 in Table 1 for explosibility testing results conducted by OSHA's laboratory. 
                                        
                    Figure 7. Photograph of a Dust Collector
                                       
                                       

Note: 	This photograph shows the dust collector (baghouse) used to control dusts generated at the truck unloading station. One of two explosion panels is visible in the photograph. The explosion panels were placed relatively high on the dust collector, raising questions about whether they would effectively vent deflagrations originating in the baghouse. Collected dusts pass through a rotary valve at the base of the baghouse and are conveyed back to other process streams. The baghouse was not equipped with any suppression systems or explosion isolation controls. 

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 cannot 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 sampling date and sample shipping date in the attached documentation are incorrectly listed as September 18, 2010. The actual sampling date and sample shipping date were November 18, 2010.