Mitigating Combustible Dust Risks in Powder Processing

By -

From our Friends at: Donaldson Filtration Solutions

Mitigating Combustible Dust Risks in 

Powder Processing

Combustible dust is common in many bulk solid manufacturing processes and can have serious consequences. It’s important to review your risks and determine a mitigation strategy. In that strategy, consider implementing both prevention and protection options.

Here are three steps to get started.

Step 1: Determine and Understand Your Regulatory Standards

Review the standards that may apply to your industry, specifically those addressing combustible dusts.

The most broadly applicable standards governing combustion hazards are NFPA 652: Standard on the Fundamentals of Combustible Dust, and NFPA 654: Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids. NFPA 652 also provides guidance on the process of conducting a DHA. Also be sure to consult the NFPA website to identify any additional standards required for your specific industry.

Although the NFPA has no enforcement authority of its own, OSHA inspectors and many AHJs (authorities having jurisdiction) consider these standards to be the benchmark of safety and cite them when levying fines or reviewing permits. To meet your DHA requirements and minimize fire and explosion risks in your operations, follow these further steps:

Step 2: Assess Your Dust and Process Risks

Next, identify whether or not the dust in your facility is combustible (can ignite in a pile or layer), explosible (can ignite in a cloud), or neither. You can use historical or published data to help you characterize your dust. But if you are at all uncertain about how well that data matches your dust and your processes, you need to have a fully representative dust sample tested by a qualified lab.

Next, review whether any of your processes create the possibility of a combustion risk. Do you have processes that generate sparks or processes that mix incompatible materials? Every facility will have slightly different risks; therefore, every plant owner is responsible for fully reviewing the operation’s unique risks and constraints.

Step 3. Develop Your Risk Mitigation Plan

Effective mitigation for combustible dust hazards should consist of two focus areas: prevention to minimize the likelihood of a combustion event; and protection to minimize the extent of damage if an event occurs. Both areas are equally important.

Prevention Strategies: Ignition Source Control

The key to preventing a fire is to remove one of the three elements required for combustion: a fuel source (in this case, dust), ignition or heat source, or oxygen. An explosion requires two additional factors: dust dispersion and confinement.

Ignition Control can be the easiest way to reduce fire risk. Common options to prevent ignition sources entering the dust collector include the following:

  • Keep the capture hood and the dust collector as far apart as possible. Increased distance may allow a spark to extinguish before it reaches a possible fuel source.
  • Install an active spark abatement system to extinguish a spark before it reaches the collector.
  • Install a passive spark abatement device, which creates turbulence in the dust collection duct to extinguish sparks before they reach the dust collector.
Protection Strategies: Limit and Extinguish

Fire protection techniques include sprinkler systems or fire suppression systems using CO2 or argon. Each style of system has pros and cons that you should review to determine the best method for your facility.

Explosion protection focuses on both reducing the damage of a deflagration and helping to decrease the risk of a secondary explosion. Common options include the following:

  • Explosion vents that intentionally create weak points in a dust collector to direct an explosion through a designated pathway
  • Chemical suppression systems inject a chemical into the dust collector to absorb the heat and interrupt flame propagation.  Although typically more expensive, it is very effective at reducing the risk of a post-deflagration fire and minimizing clean-up.
  • Isolation devices (either active or passive) in your dust collector help keep the flames and pressure generated from a combustion event from propagating through the ducts or hopper discharge.  Isolation should also be considered if you return filtered air back into the facility rather than discharge it outside.

With risks identified and mitigation strategies in place, you are on your way to completing your DHA. Be sure to walk through your facility with your draft plan and review it for gaps. For an example DHA, see Annex B of NFPA 652.

As a process owner, it is wise to consider the costs of effective mitigation against the potential costs of downtime and injury. Ultimately, addressing and managing your combustion risks is a worthwhile investment in your operation.

Comments

Post a Comment

Popular posts from this blog

The Fire Triangle, Fire Tetrahedron and Dust Explosion Pentagon

By -
Image
Fire Triangle From Wikipedia, the free encyclopedia Jump to: navigation , search The fire triangle. The fire triangle or combustion triangle is a simple model for understanding the ingredients necessary for most fires . [1] It has been replaced in the fire fighting and protection industry partially by the fire tetrahedron (see below). The triangle illustrates a fire requires three elements: heat , fuel , and an oxidizing agent (usually oxygen ). The fire is prevented or extinguished by removing any one of them. A fire naturally occurs when the elements are combined in the right mixture. Without sufficient heat , a fire cannot begin, and it cannot continue. Heat can be removed by the application of a substance which reduces the amount of heat available to the fire reaction. This is often water, which requires heat for phase change from water to steam. Introducing sufficient quantities and types of powder or gas in the flame reduces the amount of heat available for t...
Read more

Are Spices Flammable?

By -
Image
Is Cinnamon Flammable? - Science - ChefSteps Made from the dried bark of Cinnamomum verum , a tree indigenous to Sri Lanka, cinnamon's exotic perfume and subtle flavor come from its two major components: cinnamaldehyde and eugenol. These two chemicals are volatile, meaning they readily vaporize at temperatures comfortable to humans, which is in fact why cinnamon is so fragrant. But those same vapors are also highly combustible (indeed, combustion only happens in the presence of vapors), making cinnamon a highly flammable material under the right conditions. Now a cloud of cinnamon dust isn’t the kind of thing most people would consider dangerous, but add enough heat and you’ll quickly have an expanding ball of fire known as a dust explosion. For dealing with this situation, we can only recommend a good pair of running shoes. In fact, the federal Occupational Safety and Health Administration issues warnings about cinnamon explosions in food manufacturing plants....
Read more

Functional Safety Audit vs. Functional Safety Assessment

By -
From Chemical Processing Don’t Confuse a Functional Safety Audit with a Functional Safety Assessment Understand the critical differences between the two essential evaluations By John Walkington, ABB Safety Lead Competency Centre Apr 19, 2017 Many people working in safety instrumented system (SIS) project development, execution, operation and maintenance treat a functional safety audit (FS Audit) and a functional safety assessment (FSA) as one and the same. So, based on this assumption, they simply ensure that such an activity is undertaken and perhaps signify the need to perform this evaluation at some point when it appears as a milestone on the project schedule. Moreover, often they call upon someone working on the project, who may or may not have had some previous experience in quality auditing, to deliver this audit/assessment. However, this is not a reasonable approach because the concepts for the audit and assessment markedly differ. An FS Audit provides...
Read more