DSS034: Understanding the Dust Explosion Risk Reduction Toolkit with Keith Plumb

In this episode of the DustSafetyScience Podcast, we interview Keith Plumb, owner and director at Integral Pharmacy Services, about the dust explosion risk reduction toolkit and how to best understand and implement it.

In addition to his position at Integral Pharmacy Services, Keith is a lecturer in pharmaceutical engineering at the University of Chester in the UK. He has over 40 years of experience in pharmaceuticals, biopharma, fine chemicals, and allied process industries and is on the board of trustees with the Institute of Chemical Engineers.

In late 2016, Dr. Chris Cloney came across a video featuring Keith, who was talking about his evolving dust explosion risk reduction toolkit. Keith mentioned a paper that Dr. Cloney published in 2013 with several coauthors, Development of an organizational framework for studying dust explosion phenomena, it included the phrase ‘unwrapping the dust explosion pentagon.’

What is the Concept Behind Unwrapping the Pentagon?

Dr. Cloney’s research focused on the concept that dust explosions occur when you have dust, oxidizer, and a process, namely:

The dust is dispersed and ignited
Once it’s dispersed and the flame propagates, the confinement allows it to accelerate or build pressure

Keith took the observation that the pentagon is a process, zoomed in on different pieces from an industry perspective, and used it as a framework for prevention of and protection from dust explosions. In 2017, HazardEx gave his group an award for the framework and its contribution to safety.

Keith said that the reason for developing the framework was that there was more methodology than science involved in dust explosion safety, which made it impossible to draw sound conclusions. He took the concept of unwrapping the pentagon and was able to immediately relate it to the steps involved in approaching industrial problems.

What Are The Steps in the Risk Reduction Toolkit?

Keith took the process of unwrapping the pentagon and initially broke it down into steps.

Step One: The probability of creating a combustible dust cloud. Is there a fuel present?
Step Two: Can the fuel be replaced by non-combustible material? If not, can the inventory be reduced?

Step Three: Is there a dispersion mechanism, such as pneumatic conveying or powder leaks and spillage?

Step Four: Carry out a Hazardous Area Classification using EN 60079-10-2 or similar.

Step Five: Minimize sources of ignition.

Step Six: Assess the severity and potential consequences of the hazard. Is the explosion unconfined, partially confined, or fully contained?

Step Seven: Reduce the risk using simple measures like housekeeping and inventory reduction.

Step Eight: Determine whether the residual risk is acceptable.

Step Nine: Determine whether the oxidant can be excluded.

Step Ten: If the oxidant can be excluded, provide a system for doing so.

Step Eleven: Take steps to mitigate consequences.

What Are the Challenges Involves in Creating a Systematic Approach?

Keith commented that very few of the people working in dust-handling pharmaceutical factories are educated and informed on the danger associated with what they’re doing. When something happens, all that results is a lot of finger-pointing and no lessons are learned. It’s an issue that was discussed by Dr. Ivan Pupulidy in Episode #11.

It is also difficult getting people to agree on what a combustible dust cloud is, especially in the pharmaceutical industry. Looking at the question from a numbers perspective, a dust cloud needs to be something like 30 to 60 grams per cubic meter before it comes into the flammable range. From operational exposure, these numbers are measured in micrograms or nanograms per cubic meter.

Keith explained that there was a fundamental difference because the pharmaceutical industry wanted to ensure that it doesn’t have a cloud of powder outside the equipment, but they’re not grasping the fact that inside the equipment, the measurement is likely to be in the grams per meter cube scale. The greater urgency lies in what is inside the equipment.

The source of the problem appears to be the fact that when it comes to explosion hazards, the industry is more familiar with gases, vapors, and leaks than dust. Keith recalled that when he started working in the chemical industry, the emphasis was on hazardous area classification. It was the responsibility of the electrical department because the area of concern was electrical equipment. If there was no electrical engineering component in the hazard, the engineers didn’t focus on it because it was outside their scope. So it raises a question: who is paying attention to dust hazards inside the equipment?

With ISO and IEC standards, they refer to the grade of release, or what comes out of the equipment. “But in the dust world, that doesn’t matter,” Keith insisted. “It’s what is usually inside the equipment that matters. The fundamental thing we need to think about is that number three on the unwrapped pentagon, which is a dispersion mechanism. And until we’ve got clear in our heads that wherever there’s a dispersion mechanism we’ve got a potential problem, we’re not going to move forward on this.”

How Can the Dust Explosion Risk Reduction Toolkit Be Implemented?

Keith said that the first question should be, “Is there a fuel in a facility?” Some industries, like pharmaceuticals and food, try to keep dust inside for hygiene reasons while others, like lumber, leave a lot of dust lying around. This was one of the issues with the Imperial Sugar incident. With West Pharmaceuticals, the dust issue wasn’t obvious because it was hidden.

Another question is: is the product the fuel? (Dr. Chris Bloore raised a similar question in Episode #31.) When the product being made is the dust hazard, which is common in pharmaceuticals, it’s difficult to change the situation. When the fuel is a byproduct, such as lumber processing creating wood dust, it’s easier to address.

Keith explained that in the European approach to risk assessments, the number one priority is to eliminate the fuel. If the fuel is the product, the next logical step is to see if it’s possible to produce a different product that isn’t so dangerous.

“What you find in the pharmaceutical industry is that in many cases, the active part of the product has a very high dust explosion risk for a few reasons, one of which is its small particle size. The second point that is they often have very low minimum ignition energies,” he explained. “So part of your risk reduction is: what can I only handle? Can I only handle the high-ignition substances in the minimum amount so that the risk of an explosion is reduced?

“So even if you can’t get rid of it because it’s the product, it doesn’t mean you can’t go to number two on the priority list, which is finding some way of reducing the risk without getting rid of the actual explosive material.”

Some industries are changing the way they operate to reduce the hazard. An example could be in the wood pellet industry, where some facilities are not building storage silos. Instead they are improving the timing of the arrival of raw material so it doesn’t have to be stored.

The U.S. Chemical Safety Board report on the 2012 US Ink fire, which involved material build-up in a dust collector, found that the company did not design their equipment to the required NFPA standard. In that case, ink dust had settled throughout the whole ducting system all the way up to the dust collector and turned into a sludgy mixture due to incoming vapours.

Although the explosion happened in a roof dust collector, the unit’s suppression parameters were not designed for that KST. Eventually the fire travelled back through the dust collector venting to where workers had gathered. Dr. Cloney talked about challenges to dust fire responses in Episode #30, and this was a perfect example.

Noticing that the ducting was melting and flex hoses were catching fire, the workers grabbed fire extinguishers, but eventually, an elbow blew off one of the tanks, dispersing the dust with the sludge and creating a giant flash fire that injured the workers.

This incident raises questions whose answers could result in a safer process:

Should employees be trying to putt out these fires?
Should flex hoses be used if they can melt during a fire in the system?

“The whole process could have been completely redesigned in such a way that you may not have had a dust collector at all,” Keith said. “And that’s got to be a major improvement.”

Conclusion

All facility inspections and reviews should involve a hard question: has enough been done to make a situation safer or is the risk still too high to be acceptable? If something has a reasonable chance of exploding, what other protection methods might be needed? For example, do you need nitrogen inertion or a suppression system? How can you reasonably make a facility as safe as possible?

As Dr. Trevor Kletz said, “What you don’t have can’t explode.” Hazard elimination should be the primary goal of anyone using the dust explosion risk reduction toolkit, but if the industry makes that infeasible, a strong system of controls can still make a valuable difference.

If you would like to discuss further, leave your thoughts in the comments section below.

You can also reach Keith Plumb directly:
Email: [email protected]
LinkedIn: https://www.linkedin.com/in/eur-ing-keith-plumb-b482797/ Website: https://www.integpharma.com/

If you have questions about the contents of this or any other podcast episode, you can go to our ‘Questions from the Community’ page and submit a text message or video recording. We will then bring someone on to answer these questions in a future episode.