Repeat After Me: "Fire is Conveyable"

March 21, 2013
Poor housekeeping and shoddy conveyor maintenance can ignite the dust accumulating in your workplace.

The safe, efficient flow of product through a facility demands that manufacturers separate conveyable from non-conveyable items. Unfortunately, some companies don’t realize that fire is very conveyable. New England Wood Pellet LLC learned that lesson recently after OSHA discovered that workers at two of the company’s plants were exposed to fire generated by the combination of combustible wood dust and a poorly conceived conveyor system.

The fact that a similar fire occurred at one of the company’s other plants told OSHA inspectors this was a problem of poor management practices, consequently the company could be facing a fine as high as $50,000. Their mistake was failing to isolate the conveying systems to prevent fire and rapid combustion from spreading both upstream and downstream in critical process equipment. In environments like theirs, wood dust, sources of combustion and poor ventilation can combine to create fire. Adding fuel to this one was the fact that this company’s process equipment lacked containment, explosion venting and suppression to mitigate the hazards of rapid and explosive combustion. Lack of spark detection and extinguishing systems in the wood pellet processing system completed the formula for disaster.

According to literature from Martin Engineering, the fact that conveyor belting itself can burn amplifies the consequences of a conveyor belt fire. The length and movement of the belt can spread a fire over a great distance within a facility in a very short time, this supplier warns.

“Fires on conveyor belting are most commonly ignited by the heat generated from friction induced by a pulley turning against a stalled (or slipping) belt or by the belt moving over a seized idler,” it adds. Best practices for minimizing the fire risk of any conveyor belt include:

∙ Conducting regular belt examinations;
∙ Removing all accumulations of combustible materials along the conveyor belt; and
∙ Correcting potential sources of fire such as seized rollers, overheated bearings, or belt misalignment.

I’m bringing this up because several landmark combustible dust accidents have made news in recent years (remember the Imperial Sugar explosion?) and earlier this year Rep. George Miller (D-CA) introduced H.R. 691, the Worker Protection Against Combustible Dust Explosions and Fires Act. This bill would require the Secretary of Labor to promulgate an interim final standard regulating occupational exposure to combustible dust hazards. It applies to “manufacturing, processing, blending, conveying, repackaging, and handling of combustible particulate solids and their dusts.”  

The bill requires the management of such operations to:

∙ perform a hazard assessment identifying, evaluating, and controlling combustible dust hazards;

∙ have a written program that provides for hazardous dust inspection, testing, hot work, ignition control, and housekeeping;

∙ administer engineering controls, administrative controls, and operating procedures;

∙ implement good housekeeping to prevent accumulation of combustible dust in depths that can present explosion, deflagration, or other fire hazards; and

∙ provide safety and health information and annual training to managers and employees and their representatives.

Do conveyor fires happen very often? It’s hard to say how common they are because it’s the kind of incident that gets taken care of and goes unreported unless it turns into a catastrophe and gets OSHA attention. But the conditions are right for this happening anyplace that has old conveyors that haven’t been maintained regularly. That means poor lubrication, lousy bearings and lots of friction. And chances are, if conveyors aren’t maintained, housekeeping is probably also ignored—meaning significant dust accumulation. Those are the necessary ingredients for a conveyor fire.

But before shooting my blog off about this issue, I consulted my go-to expert on combustible dust to confirm it was worth bugging you about. That expert is John Astad, director and research analyst at the Combustible Dust Policy Institute in Santa Fe, Tex. I asked him what kinds of businesses could be kindling for a conveyor fire.

“Any business where equipment and materials can change, as well as your products’ dustiness, dryness or moisture content,” he said.

He cited the case of a sawmill in British Columbia that had originally been using green wood, but then started getting wood that was dried out and had a resin in it that increased its explosion severity. They didn’t recognize the fire hazard this represented.  

But you don’t have to be in the wood industry to resemble the kind of company where change is part of life. What about third party logistics companies that take on new clients and new products with which they have little experience?

For such companies—and any company that regularly handles a variety of dust-prone products that might be new to them—Astad recommends they do a hazard assessment—a walkthrough of their facility to identify all potential heat sources.

“You have to look at all your potential combustibles and have a written plan on how to prevent any kind of combustible from being ignited,” he said. “These are issues that are already in the OSHA standard. You need a written hazard assessment plan for any kind of operation. Any time you have workers at a facility you need to do a hazard assessment. OSHA wants to see written work. They want proof that you did a walkaround and identified all hazards—including slip, trip and fall hazards.”

Astad admits to being confused about how OSHA communicates its guidelines about hazard assessments. You have to know where to look, and even he didn’t know that up to now you had to look under personal protective equipment, or PPE (1910.132(d)). So imagine his confusion about why this new standard introduced by Rep. Miller must also include a guideline on hazard assessment.

“When you write a bill I would think you do it for stuff that isn’t already there,” he said. “You and I already know about hazard assessment, that’s stuck over in PPE. And this other requirement for a written program that includes provisions for hazardous dust inspection, ignition control and housekeeping. That’s in the fire prevention plan (1910.39) that OSHA requires for ignition control. I guess this is job security for people in the beltway.”

Be that as it may, there are worse problems than legislation written in duplicate and triplicate that bombards you with too much information. One of those problems is the housing of a hazard that you know nothing about.

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