Dust Hazard Analysis-DHA is a foundational component of continuous hazard management for combustible dust safety. Ideally, a DHA should be a proactive hazard management exercise rather than a reactive compliance exercise. There are many elements that can be explosive in the form of dust, fire and explosion dangers are prevalent in the majority of sectors that produce, handle, or generate combustible particulate solids.

According to NFPA 652, a Dust Hazard Analysis (DHA) is a systematic procedure for determining and assessing the fire, deflagration, and explosion risks connected to dust and particulate solids in your plant. A dust hazard analysis is required to recognize, evaluate, and reduce the risks of fires, deflagrations, and explosions caused by combustible particulate particles wherever these hazards are present. The dust hazard analysis gives suggestions for controlling these risks.

Why is Dust Hazard Analysis Important?

 Dust testing is a common practice at a DHA to assess the relative dangers of any present dusts. 

A comprehensive examination to discover and evaluate any potential fire, flash fire, and explosion risks related to the presence of one or more combustible solids in a process or facility that are in the form of particles. 

Locating safe operating limits and suitable protections, as well as identifying the hazards for each process, facility, and component. 

Data gathering for system and performance criteria, including testing for dust hazards, giving counsel on managing flammable particulate solids, and keeping records of all findings for the dust hazard analysis.

Doing a dust hazard analysis is one of the most crucial measures towards explosion safety since it will help to:

• Assure that the workplace is safe for Employees.
• Avoid fires and explosions to maintain company continuity.
• Observe additional dust regulations as well as NFPA 652
• Prevent possible OSHA penalties or temporary stoppages.
• Implement the rules set forth by the local authorities.

Getting started with Dust Hazard Analysis

 Begin by collecting relevant process, equipment, and operating data, for example:

• Process flow diagrams
• Piping and Instrumentation Diagrams
• General Arrangement Drawings (GAs)
• Building Plans
• Equipment Manufacturer Drawings, Data Sheets, Manuals, etc.
• Electrical Drawings

Field Survey & Research:- Site Visits and Field survey are necessary to adequately document the facilities, machinery, and processes to make the analysis easier. It is also necessary to record and comprehend the materials used in the process, as well as their characteristics at each stage. The main objective is to take every step of the procedure into account, identify potential risks, and decide what steps should be taken to reduce those risks.

When considering combustible dusts,  pay special attention to:

• Particle Size
• Size Distribution
• Moisture Content

Dust test reports :- If any testing has been conducted, this information should also be collected. These tests are also referred to as Ignition Sensitivity Tests.

• Go / No-Go Test– This is the basic test or premise where one begins with combustible dust to understand if the dust will explode or no , from there on you start with actual DHA
• Kst: Kst stands for a dust cloud’s deflagration index. The speed of an explosion is measured in Kst. The faster the pressure for an explosion builds, the greater the Kst value.
• Pmax: According to NFPA68, the highest pressure created in a contained deflagration of an ideal mixture serves as a general indicator of the strength of the explosion.
• Minimum explosible concentration (MEC). The MEC is the minimum concentration of dust in the air that will explode if ignited.
• MIE: The MIE (Minimum Ignition Energy) is the bare minimum energy needed to start a flame when it is delivered at a specific location within a dust cloud. This value is mostly used to determine how sensitive the dust is to static electricity discharge as a source of fire. With a smaller (lower energy) spark, it is simpler to ignite dusts with lower MIEs.
• Minimum Ignition Temp. (MIT): the lowest temperature that will ignite the dust, both when suspended in air and layered on a surface (hot bearings, oven hood, or motors).
• LIT: Layer Ignition Temperature
• HSIT : Hot Surface Ignition Temperature

It is essential to detect, comprehend, and effectively mitigate the threats in your facility. Getting your combustible dust analyzed will reveal significant aspects of your particular dust. How severe an explosion might be is defined by Kst and Pmax. MIE enables you to identify the process steps or facility locations that may provide a risk and to specify the steps that must be taken to lessen that risk.

Execute: 

• Site Visits and Detailed Surveys
• Check what NFPA Standards are applicable to your facility.
• Check the dust test reports.
• Evaluate Hazards and Compliance
• Prioritize Each Hazard
• Address, Remove, and Mitigate All Hazards
• Document
• Repeat

If changes are made to your institution, the DHA needs to be reviewed and updated. This involves modifying the operational parameters of your current processes, utilizing novel or alternative ingredients or materials, installing new machinery or methods, etc.

Industries that handle combustible dusts include:

• Agriculture
• Chemicals
• Coal dust in coal handling and processing facilities
• Food products
• Metal processing
• Pharmaceuticals
• Textiles
• WoodWorking

Check what NFPA standards are applicable to you:

• NFPA 652: Standard on the Fundamentals of Combustible Dust
• NFPA 61: Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities
• NFPA 655: Standard for Prevention of Sulphur Fires and Explosions
• NFPA 484: Standard for Combustible Metals
• NFPA 654: Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids
• NFPA 664: Standard for the Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities