Combustible Dust: Five Critical Elements to a Thorough DHA

December 16, 2019

5 Critical Elements to a Thorough Dust Hazard Analysis

A safer workplace begins with a Dust Hazard Analysis.

A Dust Hazard Analysis (DHA) will not only determine if there is a significant amount of dust in your facility, but will systematically review and identify the potential for a fire, flash fire and explosion hazards associated with the presence of one or more combustible particulate solids arising from processes in your facilities.

Testing is necessary to know both if combustible dust is present in your business and what type of dust it is so that appropriate safety measures can be taken. That’s why performing a Dust Hazard Analysis, or DHA, of your worksite is critical to the future of your business.

A proper Dust Hazard Analysis does not merely report if dust is present in your workplace. Rather, it is a systematic review to identify and evaluate the potential for fire, flash fire and explosion hazards associated with the presence of one or more combustible particulate solids arising from your processes or present in your facilities.

Components of a DHA

There are five critical elements to a thorough Dust Hazard Analysis:

  • Methodology and scope
  • Material characterization
  • Process characterization
  • Hazard analysis and recommendations
  • Administrative controls and recommendations

Methodology and Scope

Methodology is important but there isn’t a specific process that works for every analysis. Frequently it’s a combination of methodologies.

One of the most common, and successful, is node-based methodology.

A node can be defined as an environment that has both oxygen and a combustible dust present. A site may have only one such node or it may have nodes reaching into the hundreds. A thorough Dust Hazard Analysis samples each one of these nodes looking for a credible ignition source and a dust concentration level that would support a combustible dust event.

This process is greatly assisted when the client has existing Process and Instrumentation Diagrams (P&IDs) or process flow diagrams.

Material Characterization

The second critical element to a DHA is material characterization - listing materials being handled and characterizing them in terms of combustible dust parameters such as maximal pressure (PMax) and rate of pressure rise. The list of materials needs to include manufacturers’ names, where the materials came from and how they’re received.

In the food industry, there are products like flour, sugars and starches whose parameters are well known. In the furniture handling industry, material could be anything from particleboard to a hybrid of wood and plastic. A proper DHA will take samples from the various nodes and decide whether a product needs to be tested further or whether the published data is sufficient to make a risk determination.

Process Characterization

Process characterization involves a variety of steps, including looking at the different nodes, the dust concentration levels that may be present, and the possibility of ignition sources in the different parts of the processes.

It should certainly include a site visit and thorough documentation of every part of the process that is handling combustible dust. The inspector then takes that information and closely examines the credible ignition sources for all those areas.

Hazard Analysis and Recommendations

In the end, the DHA needs to be more than a mere collection of generalized safety concepts. It must contain concrete information that spells out specific threats and identifies either a mitigation or consistent control strategy.

The language needs to be clear and simple. Information should be condensed and put it into a format that is readable by everyone from the production manager and workers in the plant to the engineering manager, plant manager, and even the director of the Environmental Health and Safety Group.

The report should have as its goal uniting everyone in a team effort to make the facility safer.

Administrative Controls and Recommendations

One aspect of a thorough DHA is an examination of housekeeping practices. In some cases, combustible dust may be building on ledges, building columns, building joists and above false ceilings.

Preventative maintenance recommendations should be a part of the final report. Preventative maintenance could reference filter bag changes on a dust collector or checking bearings on rotating equipment like screw conveyors, bucket elevators, rotary valves and grinding systems. Any one of these can be an ignition sources for combustible dust.

Finally, a complete DHA should also take a look at a company’s emergency planning response procedures. If there is an event, how do they handle that? How do they deal with a flash fire? If they have a dust collector that ruptures during an explosion, how do they deal with that?

If your business produces combustible dust, you can’t afford to ignore the hazards.