Combustible dust accidents reported by OHSA

This article presents examples from an OSHA report on ‘Combustible Dusts in Industry’ to illustrate the hazards of dust explosions, in relation to the current DSEAR requirements for hazard assessments.

The OSHA report entitled ‘Combustible Dust in Industry: Preventing and Mitigating the Effects of Fire and Explosions’ is a Safety and Health Information Bulletin (SHIB) that highlights the hazards associated with combustible dusts.

The examples are from actual accidents reported in the USA.

1) Organic Dust Fire and Explosion: Massachusetts (3 killed, 9 injured).

In February 1999, a deadly fire and explosion occurred in a foundry in Massachusetts.

The Occupational Safety Health Administration (OSHA) and state and local officials conducted a joint investigation of this incident.

The joint investigation report indicated that a fire initiated in a shell moulding machine from an unknown source and then extended into the ventilation system ducts by feeding on heavy deposits of phenol formaldehyde resin dust.

A small primary deflagration occurred within the ductwork, dislodging dust that had settled on the exterior of the ducts.

The ensuing dust cloud provided fuel for a secondary explosion which was powerful enough to lift the roof and cause wall failures.

Causal factors listed in the joint investigation report included inadequacies in the following areas: Housekeeping to control dust accumulations; Ventilation system design; Maintenance of ovens; and, Equipment safety devices.

2) Organic Dust Fire and Explosion: North Carolina (6 killed, 38 injured).

In January 2003, devastating fires and explosions destroyed a North Carolina pharmaceutical plant that manufactured rubber drug-delivery components.

Six employees were killed and 38 people, including two firefighters, were injured.

The U.S Chemical Safety and Hazard Investigation Board (CSB), an independent Federal agency charged with investigating chemical incidents, issued a final report concluding that an accumulation of a combustible polyethylene dust above the suspended ceilings fueled the explosion.

The CSB was unable to determine what ignited the initial fire or how the dust was dispersed to create the explosive cloud in the hidden ceiling space.

The explosion severely damaged the plant and caused minor damage to nearby businesses, a home, and a school.

The causes of the incident cited by CSB included inadequacies in: Hazard assessment; Hazard communication; and Engineering management.

The CSB recommended the application of provisions in National Fire Protection Association standard NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids, as well as the formal adoption of this standard by the State of North Carolina.

3) Organic Dust Fire and Explosion: Kentucky (7 killed, 37 injured).

In February 2003, a Kentucky acoustics insulation manufacturing plant was the site of another fatal dust explosion.

The CSB also investigated this incident.

Their report cited the likely ignition scenario as a small fire extending from an unattended oven which ignited a dust cloud created by nearby line cleaning.

This was followed by a deadly cascade of dust explosions throughout the plant.

The CSB identified several causes of ineffective dust control and explosion prevention/mitigation involving inadequacies in: Hazard assessment; Hazard communication; Maintenance procedures; Building design; and, Investigation of previous fires.

4) Metal Dust Fire and Explosion: Indiana (1 killed, 1 injured).

Finely dispersed airborne metallic dust can also be explosive when confined in a vessel or building.

In October 2003, an Indiana plant where auto wheels were machined experienced an incident which was also investigated by the CSB.

A report has not yet been issued, however, a CSB news release told a story similar to the previously discussed organic dust incidents: aluminium dust was involved in a primary explosion near a chip melting furnace, followed by a secondary blast in dust collection equipment.

5) Related Experience in the Grain Handling Industry.

In the late 1970s a series of devastating grain dust explosions in grain elevators left 59 people dead and 49 injured.

In response to these catastrophic events, OSHA issued a ‘Grain Elevator Industry Hazard Alert’ to provide employers, employees, and other officials with information on the safety and health hazards associated with the storage and distribution of grain.

In 1987, OSHA promulgated the Grain Handling Facilities standard (29 CFR 1910.272), which remains in effect.

This standard, other OSHA standards such as Emergency Action Plans (29 CFR 1910.38), and updated industry consensus standards all played an important role in reducing the occurrence of explosions in this industry, as well as mitigating their effects.

The lessons learned in the grain industry can be applied to other industries producing, generating, or using combustible dust.

Cooper Crouse-Hinds publish this report on their website, in relation to the supply of their equipment approved for use in such hazardous areas, particularly relating to the ATEX137 and DSEAR regulations recently introduced.

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