DSS 007: Dust Hazard Analysis and Explosion Prevention with Dr. Ashok Dastidar

In this episode of the Dust Safety Science podcast, we discuss dust hazard analysis and explosion prevention with Dr. Ashok Dastidar, Vice President, Dust and Flammability Testing and Consultancy services at Fauske & Associates.

In the past couple of episodes, we’ve extensively reviewed combustible dust incidents: how they happen, how many have occurred in the past year, and the U.S. Chemical Safety Board’s call to action for an improved understanding of both risk and perception of dust hazards.

Today we talk about performing a dust hazard analysis as one of the solutions.

Ashok has an extensive background in dust hazard analysis (DHA), being a member of several National Fire Protection Agency (NFPA) technical committees and the current chair of the ASTM E 27 committee on the hazard potential of chemicals. In this episode, he shares his knowledge and practical experience of DHAs and recommends ways that facilities can minimize their risk.

Dust Hazard Overview

A lot of time and resources are being dedicated to understanding combustible dust incidents, while the other side of the problem (prevention and protection) also needs to be examined. Specifically:

Measures to improve safety in industries handling combustible dust should be discussed
Resources that are currently available need to be identified and used
Training is needed on what inspectors and those employed in these industries should be looking for

Measuring Risk: the Process and the Challenges

Data from the U.S. Chemical Safety Board indicates that dust explosions are a hazard across multiple industries, from grain handling facilities to coal mines, waste handling plants, plastics factories, and more.

Many of the tools required to mitigate and prevent a dust explosion are already available and understood including:

Deflagration venting, suppression, and isolation
Electrical area classification
Effective housekeeping practices

However, awareness is needed to draw attention to these approaches.

An additional difficulty is that safety standards enforced by OSHA, the NFPA, and other regulatory bodies may not be updated to reflect new analysis and prevention wisdom and methods. NFPA 652 is the latest code that addresses the concept of DHAs but it’s not new

Many of the standards require a dust hazard analysis to be carried out on new processes being installed and older processes must be reviewed for dust hazards by 2020 or 2021, depending on the standard being used. This requirement alone can give a facility a reasonable idea of how exposed they may be to the hazards of a dust explosion.

Dust Hazard Analysis – Steps Explained

Fauske & Associates has a two-day course that covers dust explosion fundamentals and even offers accident case studies. Dr. Dastidar recommends that managers take the following steps to carry out a dust hazard analysis at their facility.

Collect All Relevant Data

The first step is collecting building and process data. This includes (but may not be limited to):

Process flow diagrams
Piping and instrumentation diagrams of the process
Up-to-date layered facility diagrams that cover all machinery
Diagram of all the electrical outlets, electrical utilities, and water utilities

A lot of companies have outdated data that is no longer relevant due to building or process changes, so step one calls for a current and accurate version of the above details.

Consider What is Being Handled

Step two is a close review of what materials are being handled at the facility, namely:

Particle size distribution
Moisture content
Variability: does it take one form at one part of the plant and become something entirely different at the end of the process?

Dust explosion potential, severity, and ease of ignition are greatly dependent on particle size distribution, particle morphology, moisture content, and chemistry. Testing for maximum pressure, rates of pressure rise, deflagration index, minimum ignition energy and other parameters may be completed at this stage.

Do a Walk-Through Assessment

Once a data package has been compiled, the third step is a walk-through assessment of the plant. Look at equipment such as dust collectors, spray dryers, and rotary drum drives and confirm that they comply with NFPA codes. Are there any gaps that need to be addressed?

In addition to reviewing historic data, events, and action remediation, facility managers should take a ‘what if?’ approach to tackle hypothetical situations. If a certain event does occur, are there any measures in place to tackle it?

Although the NFPA guideline recommends revisiting dust safety standards at a facility a minimum of every five years, any major changes should also call for a review. Examples of such changes include a new piece of equipment such as a dust collector or spray dryer or a change in suppliers.

Who Can Assess the Risk?

The NFPA states that a DHA must be carried out by a ‘qualified expert’ but is vague about what these qualifications are. An engineer or operator with a good background knowledge of combustible dust hazards and has had practical experience working with it in the field could be the right person.

In some states and Canadian provinces, a Professional Engineer is required to do a start-up review. However, not all engineers have taken a combustible dust course or a hazard loss prevention course in their formal education, so the best solution is a team approach. In addition to the qualified person referenced in local regulations, a comprehensive DHA should have input from personnel who work in maintenance, production, and procurement. Everyone can brainstorm gaps and mitigation steps to make the DHA more effective.

Conclusion

A team approach to dust hazard analysis can proactively identify and be used to prevent combustible dust incidents at facilities. Many managers and experienced employees have probably conduct a mental DHA (in their head) but the procedure simply hasn’t been documented and systematized. Both formalizing the process and involving third-party experts can result in steps forward to prevent incidents, thereby increasing their risk prevention strategy.