Now that the necessary steps have been taken to prepare the Dust Hazard Analysis, it’s time to methodically complete the process of identifying problem areas and exploring possible solutions by following the steps below:

List of Equipment to Evaluate

By using a process flow diagram or touring the plant, all areas in which a hazard could occur (and cannot occur) is evaluated.
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Inspecting Equipment for Dust Hazards

Once the hazardous areas of the plant have been identified, the question of how an explosion or fire may occur in these areas must be answered.
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Identifying Credible Ignition Sources

Combustion cannot occur without an ignition source. By identifying these hazards, they may then be added into the action plan to prevent an explosion.
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Reviewing Existing Safeguards

It shouldn’t be assumed that installed safety systems will work as intended. These systems must be investigated to ensure their reliability.
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Inspecting Rooms and Buildings for Dust Hazards

Deflagration hazards can exist outside of the process equipment. Therefore, fugitive dusts and other hazards outside of a process must be reviewed.
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Developing a List of Equipment to Evaluate

The first step to conducting a Dust Hazard Analysis is to determine where potential explosion or fire hazards could exist.

The first method to identify these prospective hazard areas is to view a process flow diagram of the facility’s process. Areas of the process requiring further evaluation include equipment which:

  • handles dust in a way that may create a dust cloud
  • may introduce an ignition source into the process
  • has various “states” of operation and variables to consider

If a process flow diagram isn’t available, a tour of the plant by the internal team or an external DHA expert is required.

Not only is this part of the process intended to identify where hazards may exist, but it’s also intended to identify where hazards don’t exist, and therefore the areas which can be ignored during the rest of the DHA. For example, areas where the material is all liquid or the packaged product is all formed goods, neither have the ability to produce dust clouds or ignition sources and wouldn’t require further evaluation.

Do you need the guidance of a combustible dust safety expert to tour your facility?


Inspecting Equipment for Dust Hazards

How might an explosion or fire occur within the process? To answer this question, the following must be determined:

  • How is the material within the equipment being handled and conveyed?
  • What are the explosibility characteristics of the material?
  • Is there enough room to create a dust cloud?
  • Could the equipment create or support conditions for an explosion or fire?
  • Do solid materials exist which may not have the potential to explode but could catch fire?

Answers to these questions are often obtained from the internal team. For example, a team member such as a maintenance manager who periodically inspects a vessel or pipe should be able to disclose whether he or she finds dust clinging to the walls. An engineer can provide information for exactly how an area of the process is designed. Or a machine operator may be aware of a leak or upset in the process when it is turned on, and likely can describe the different states of the process.

Therefore, relying on institutional knowledge and documentation will usually provide enough information to understand where problem areas exist.

When necessary, certain tests may be required. For example, a particle size test can help determine how much dust separates from a material when it enters a specific part of the process, which of course will affect its combustibility.

Do you need help identifying dust hazards within your process?


Identifying Credible Ignition Sources

As observed in the dust explosion pentagon, combustion can only occur if an ignition source is present. Thus, identifying potential ignition sources throughout a process is imperative to not just the DHA but to the safety and overall understanding of the plant.

Possible ignition sources to identify and document include:

Open Flames or Heat
from welding, cutting, matches and cigarette butts

Hot Surfaces
from combustion equipment, heated processes, motors, and lights

Frictional Heat
from overheated bearings or other malfunctioning equipment

Mechanical Sparks
from impact or broken piece in mechanical equipment

Electrical Sparks
from when a high-voltage device fails or cable ruptures

Electrostatic Discharges
from equipment, personnel, and containers not grounded properly

Smoldering Material
which slowly combusts internally as long as oxygen is present

Rogue Objects
such as a bolt entering the system and creating friction

Non-Isolated Explosions
from connected equipment that creates secondary explosions

With so many types of ignition sources, it may initially seem difficult or even impossible to consider all the possible hazards. This is where the team’s institutional knowledge and documentation is invaluable to rule out certain possibilities.

For instance, if the handled dust has a minimum ignition energy (MIE) of more than 1 joule, most electrostatic discharges won’t have enough energy to ignite the dust. Therefore, electrostatic discharges might be removed from the list of possible ignition sources.

Need further help identifying potential ignition sources throughout your facility?


Reviewing the Safeguards

Safety systems which detect and eliminate ignition sources or protect against fires and explosions must also be evaluated to ensure they are being used properly and are still compliant with the latest codes and testing standards.

Safeguards that should be reviewed include:

Temperature monitoring
Are these systems accurately reading temperature irregularities?

Spark detection and suppression
Have these systems been periodically inspected to ensure reliable performance?

Automatic sprinkler systems
If a fire were to occur, is it certain the sprinkler systems will activate quickly enough and have the ability to reach the fire?

Chemical agent suppression systems
Is the current agent still allowed by the EPA and NFPA, and does a more effective agent exist?

Explosion vent panels
Do the panels themselves appear to be in good condition? And if a deflagration did cause them to burst, would the flame be directed away from walkways and other parts of the process?

Explosion suppression systems
Do the suppression units have the appropriate amount of agent?

Explosion isolation valves
Have they been maintained and are they free of dust buildup?

Do you need help with the status of an existing safeguard in your facility?


Inspecting Rooms and Buildings for External Hazards

Dust hazards don’t only exist within process equipment, and the areas outside of the process must also be inspected for dust accumulation. In fact, some of the deadliest explosions occurred from the deflagration escaping from the process and igniting externally accumulated dust.

Within the DHA, areas which may accumulate dust outside of the process must be documented, including:

On the ground
Overhead surfaces
Light fixtures
Conveying ducts atop electrical panels
Roof of machine operating center

Furthermore, identify any processes which may create upset conditions. For example, when changing the hopper of a dust filter, does dust escape and accumulate outside of the process? Or are there any areas of the process which leak small amounts of dust which accumulate over time?

These external dust hazards must be identified in the DHA, and this may be used for future housekeeping efforts or process improvements.

Interested in learning more about good housekeeping around your facility?