How To Effectively Control Combustible Dust

By Jason Reason CIH, CSP, CHMM
Senior Vice President of Safety and Health Services, Lewellyn Technology, LLC
with Scott Francis
Midwest Regional Market Manager, Westex by Milliken

The issue of combustible dust and its associated hazards (fire, deflagration, explosion) has always existed in several industries in one form or another. Only recently has the topic of combustible dust become one of the main concerns and focal points in safety and health. We have partnered with Lewellyn Technology to explore combustible dust hazards and how to control them leading up to ASSE Safety 2017.

In the past, most safety and health professionals perceived combustible dust hazards as low priority and low risk. This perception drastically changed after several high-profile combustible dust accidents and fatalities occurred, sparking an increased enforcement of combustible dust hazards by the OSHA.

High-Profile Combustible Dust Incidents

In the past decade, several highly publicized combustible dust accidents and fatalities have occurred including, but not limited to, these incidents:

  • On January 29, 2003, an explosion and fire destroyed the West Pharmaceutical Services plant in Kinston, North Carolina, causing six deaths, dozens of injuries, and hundreds of job losses. The facility produced rubber stoppers and other products for medical use. The explosion was fueled by a fine plastic powder, which accumulated above a suspended ceiling over a manufacturing area at the plant and ignited.1
  • On February 20, 2003, an explosion and fire damaged the CTA Acoustics manufacturing plant in Corbin, Kentucky, killing seven workers. The facility produced fiberglass insulation for the automotive industry. Chemical Safety Board (CSB) investigators determined the explosion was fueled by resin dust accumulated in a production area, likely ignited by flames from a malfunctioning oven. The resin involved was a phenolic binder used in producing fiberglass mats.2
  • On the evening of October 29, 2003, a series of explosions severely burned two employees, injured a third, and caused property damage to the Hayes Lemmerz manufacturing plant in Huntington, Indiana. One of the severely burned employees subsequently died. The Hayes Lemmerz plant manufactured cast aluminum automotive wheels, and the explosions were fueled by accumulated aluminum dust, a flammable by-product of the wheel production process.3

The most publicized and scrutinized combustible dust accident and fatality in the United States occurred on February 7, 2008, at the Imperial Sugar Company located in Port Wentworth, Georgia. The vast amounts of sugar dust accumulated throughout the facility caused fires and several violent explosions, which ultimately led to 14 deaths and 38 injuries. The explosion at Imperial Sugar caused all safety and health professionals in every industry to reexamine the potential hazards posed by combustible dust.

Cause for Alarm

Although combustible dust hazards are now more widely recognized, combustible dust accidents and fatalities continue to occur. On January 20, 2014, one or more grain dust explosions at the International Nutrition facility, located in Omaha, Nebraska, killed two employees and injured at least 10 employees.4 On August 2, 2015 one or more metal dust explosions at a wheel hub cleaning facility, located in Kunshan, China, killed 69 employees and injured at least 200 employees.5 These combustible dust accidents and fatalities will continue to occur because combustible dust hazards are frequently underestimated and poorly understood by both employers and employees.

OSHA’s National Emphasis Program

On October 18, 2007, OSHA initiated the Combustible Dust National Emphasis Program (CPL 03-00-006). On March 11, 2008, OSHA reissued the Combustible Dust National Emphasis Program (CPL 03-00-008) to increase its enforcement activities and to focus on specific industry groups who have experienced either frequent combustible dust incidents or combustible dust incidents with catastrophic consequences.6 Since its inception, OSHA’s Combustible Dust National Emphasis Program (NEP) has increased the number and severity of OSHA combustible dust citations. OSHA’s increased examination and enforcement of combustible dust hazards has not only surprised most employers, but also forced them to question how to adequately identify and address combustible dust hazards.

Myth: Sampling strategies are unnecessary for combustible dusts.

In order to properly assess and mitigate potential fire, deflagration, and/or explosion hazards, one must know the specific physical characteristics (particle size, moisture content, etc.) and properties (combustibility, ignition, etc.) associated with the combustible dust(s). Most facility operators know the importance of the Kst value and the maximum pressure (Pmax) value of a combustible dust. However, the properties of a combustible dust go far beyond how combustible a dust is (Kst value) or the amount of pressure released during a deflagration (Pmax value).

There is a common misconception stating historical data listed in consensus standards and other scientific sources can be used in lieu of testing specific samples of dust that are generated, conveyed, processed, etc., throughout facilities.

Myth: Explosion protection and prevention systems for enclosures are easily designed.

Deflagration and/or explosion hazards exist in several types of process machinery and equipment including, but not limited to, dust collectors, silos, pulverizers, mixers, and screeners (sieves). One of the most common ways to address these hazards is through explosion protection and/or prevention systems (i.e. engineering controls) such as deflagration venting or explosion suppression systems.

A common misconception is that any engineer, safety and health professional, equipment manufacturer, etc., can simply apply the requirements listed in specific standards (NFPA 68, NFPA 69, etc.) to design a system that will adequately control or eliminate the deflagration and explosion hazards associated with the specified combustible dust(s).

However, each of these combustible dust explosion protection and/or prevention systems is extremely difficult to design, install, and maintain correctly. Plus, the physical properties associated with a specific combustible dust are complex and cannot be fundamentally applied to one type of combustible dust. For example, Kst values for wood dusts vary widely and a standardized Kst value for all types of wood dusts does not exist. It is imperative that whoever tries to mitigate these deflagration or explosion hazards possesses a thorough knowledge of the properties and hazards associated with the specified combustible dust(s) and how to protect against those hazards.

Myth: Flash fires caused by combustible dust are the primary cause of catastrophic burn injury and fatalities.

When workplaces experience a flash fire due to combustible dust, non-FR clothing is often at fault for fatalities and catastrophic burn injuries, rather than the flash fire itself. The flash fire initiates the injury incident, but the resultant clothing fire of non-FR clothing causes the catastrophic and/or fatal body burn injuries.

The very science of a flame has three basic steps:

  1. The initial flame causes material to break down, or decompose, into smaller molecules, which then are vaporized into gaseous fuel.
  2. The fuel reacts with oxygen in the air to produce light, heat, and reactive molecules, called radicals.
  3. The produced heat and radicals lead to further decomposition of the material and the production of additional fuel – furthering the chain reaction of the fire triangle.

Everyday non-flame resistant workwear can ignite and fuel the flame, increasing the extent of injury.

PPE (Personal Protective Equipment) is truly the last line of defense in these situations. Proper FR (flame resistant) apparel does not act as fuel, will interrupt the flame chain reaction, and self-extinguish when the thermal source is removed and will significantly mitigate second and third degree body burns. A thorough and informed PPE program with trusted daily flame-resistant apparel is the most effective solution to protect workers from the hazard and remain OSHA-compliant.

Summary

The complex fire, deflagration, and explosion hazards associated with combustible dust are prevalent throughout many industries. Only a few of the common myths and mistakes associated with combustible dust were discussed in this article; many more exist. These myths cause inadequate and ineffective hazard identification, assessment, and mitigation, which could increase the severity and probability of combustible dust hazards and incidents.

It is vitally important to understand not only all of the characteristics and properties of a combustible dust, but also all of the techniques and methods that can be employed to control or eliminate combustible dust hazards.

To discover more about how to effectively control combustible dust at ASSE Safety 2017, visit Lewellyn Technology at Booth 745 and Westex by Milliken at Booth 1525.

In the meantime, download these additional resources for quick guides on combustible dust safety:


References

1. Chemical Safety Board. West Pharmaceutical Services Dust Explosion and Fire (http://www.csb.gov/investigations/detail.aspx?SID=36&Type=2&pg=1&F_AccidentTypeId=1)
2. Chemical Safety Board. CTA Acoustics Dust Explosion and Fire (http://www.csb.gov/investigations/detail.aspx?SID=35&Type=2&pg=1&F_AccidentTypeId=1)
3. Chemical Safety Board. Hayes Lemmerz Dust Explosion and Fire (http://www.csb.gov/investigations/detail.aspx?SID=33&Type=2&pg=1&F_AccidentTypeId=1)
4. Omaha World-Herald. “Evidence Suggests Blast Caused International Nutrition Accident” (http://www.omaha.com/article/20140126/NEWS/140128945/1707)
5. Fox News. “Dust Explosion at Car Parts Factory in Eastern China Kills 69 People, Injures Nearly 200” (http://www.foxnews.com/world/2014/08/03/dust-explosion-at-car-parts-factory-in-eastern-china-kills-6-people-injures/)
6. OSHA. Combustible Dust National Emphasis Program (CPL 03-00-008) (http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=DIRECTIVES&p_id=3830)

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