DSS023: Applying the Hierarchy of Controls to Combustible Dust Safety with Jeff Nichols

In this episode of the Dust Safety Science Podcast, we interview Jeff Nichols, managing partner at Industrial Fire Prevention, about applying the hierarchy of controls to combustible dust safety.

Jeff has over 30 years of experience in combustible dust and fire and explosion safety. He’s also the facilitator of the Combustible Dust Policy Institute group on LinkedIn and the author of a book titled The Ultimate Guide To Fire And Explosion Prevention: How to keep your plant from blowing up and burning down.

Industrial Fire Prevention was the first sponsor for the DustSafetyScience newsletter. Along with our other early supporters, Jeff made us feel that what we were doing had real value and encouraged us to create the combustible dust incident database, this podcast, and other tools for spreading awareness about combustible dust hazards.

Jeff has also supported us by writing guest articles for DustSafetyScience. In one article he referenced the hierarchy of controls, which is the process of ranking different solutions, equipment, and control methods in order of effectiveness in a processing facility. In this episode, he talked about applying the hierarchy of controls to support combustible dust safety.

The Hierarchy of Controls Explained

Although his main function today is a manufacturer’s rep, Jeff’s focus in on making people aware of combustible dust hazards in their facilities and presenting solutions designed to prevent fires and explosions.

One measure he uses is the hierarchy of controls, which is a system designed to minimize or eliminate exposure to hazards. It consists of the following sections/stages.

Elimination: physically remove the hazard
Substitution: replace the hazard
Engineering Controls: isolate people from the hazard
Administrative Controls: change the way people work
Personal Protective Equipment (PPE): protect the worker with protective equipment

The goal is to reduce the probability of occurrence and the severity of the consequences by starting with the most effective type of control and proceeding to the least effective. For example:

Trevor Kletz once said, “What you don’t have, can’t leak.” That quote can be applied in an explosion context. Does the facility need to have a silo storing raw material or can the process be made more efficient so that the backup isn’t needed?
Can a larger particle size distribution be used? A less volatile or reactive material?
Can a non-combustible dust be used in the process instead?

The problem is that when these controls are applied, most people think in the opposite direction: they take the ‘least effective to most effective’ approach.

Trevor Kletz’s autobiography, By Accident… A Life Preventing Them in Industry, includes a picture of a big acetylene tank and an engineer who’s sitting on a one-legged stool so that he doesn’t fall asleep while watching the gauges. This is an administrative control. An example of substitution in the same situation could be having a smaller tank. Elimination would be not needing to have that sort of tank involved in the process anymore, or automating the process instead of having a human monitoring it.

How Safe is Your Building?

According to Jeff, you could have a modern and attractive factory designed by an efficiency expert, but how safe is the design? In many cases, the building may have been constructed by the lowest bidder, with inherent safety not being a primary focus.

Another problem that Jeff sees in a lot of industries is technology transfer. The particle board and fiberboard industries have been working with wood dust, particles, and chips since the 1970 but when biomass plants were built, the technology transfer was not there, and he found combustible dust hazards and ignition hazards in these facilities as a result.

He said that he sees more of a reactive approach to combustible dust safety in these facilities. The managers notice that dust is collecting on the joists and ask him how they can avoid it. Do they cover the joists, keep an air barrier maintained up there to drive the dust down low, or do they increase the efficiency of their dust collection systems?

Ignition source handling fits into the engineering controls area of the hierarchy of controls. For example, a hammer mill sitting on a large plenum may be dropping material into a screw down below. But in the middle is a plenum full of combustible dust and the dust collector might be mounted at the end.

Jeff referred to this type of system as a “bomb” and said that he sees it inside biomass plants all the time when an inherently safer design would be to move the dust collector outside and protect the individual. Spark protection and extinguishment explosion protection would still be in place on the plenum itself, where anything coming out and dropping into the material is being detected, along with anything coming in and being pulled through the air stream.

How is the Hierarchy of Controls Applied?

Using a coffee grinding operation as a theoretical example, how can the hierarchy of controls be applied?

If a dust fire occurs, water can’t be used as effiectively in a grinding or roasting application. It also causes problems like bacteria and mold. The plant has to be designed with an understanding of where and how combustible dust is being created and where the possible spark sources are located.

Spark traps or diverters can be used to eliminate sparks from the operation and then suppress them or send them to a safer place to process. Jeff said that in most cases, hazards are diverted using resources like high-speed diverting gates. The goal is to avoid affecting production unless there is an upset condition like a fire.

There are different ways to address this hazard, depending on the operation. Examples include:

Suppressing it with water or CO2
Diverting the process to a dumpster and letting it go into wet sand
Suppressing it in the duct

Jeff recently did a dust hazard analysis at a hardwood flooring plant. They were proud of the fact that their process was automated and efficient, but he saw that exhaust from the robots handling the wood material was blowing combustible dust everywhere. There was a film of dust on the ceiling, ductwork, and on the wiring cable trays. They were also cycling dust in the HVAC system and blowing it out in the exhaust, leaving traces on the walks and the exhaust vents.

Upon going outside, Jeff saw that the facility was dumping the contents of its dust collection system into a bin. There was a truck being loaded underneath, and combustible dust was everywhere. When he asked if the truck was running, they didn’t know.

When asked how such a situation should be handled to minimize risk, Jeff said that appropriate steps could include:

Shutting the truck off during loading
Placing curtains to ensure that the dust was contained to the truck bin
Putting in a suction system to pull the dust out as it was being loaded and put it back into the dust collector

Jeff explained that when he’s walking through these plants, he creates a risk matrix that examines the possibility of an event occurring versus the severity of the potential consequences. The truck situation had both combustible dust and an ignition source, making it a serious risk.

Open Challenges in Combustible Dust Safety

In its 2006 study on combustible dust safety, the U.S. Chemical Safety Board found that people weren’t sufficiently aware of the hazards or how to address them. Jeff said that this problem exists today. People change, processes changes, and product mixes change, but this change is not properly managed.

Housekeeping issues are also an ongoing problem. Jeff has used a simple infrared temperature gun to detect bearings that have become excessively hot or a dryer system elbow that’s too cool, suggesting that material has built up. The facility managers don’t take these steps to detect hazards, although they have called Jeff to ask if he knows anyone who can put out a storage fire.

These fires can be dangerous to extinguish. Jeff pointed out that in rural areas, many of the fire departments are volunteer ones. They are not trained in combustible dust safety and can accidentally cause a flash fire when entering storage bins to put out the flames. One excellent resource for first responders in this situation is Henry Perssons’ Silo Fires: Fire extinguishing and preventive and preparatory measure.

Conclusion

Applying the hierarchy of controls can create layers of valuable protection in facilities that were more hazardous than the managers realized. Education and awareness are also essential to making these workplaces safer by reducing the possibility of risk and the severity of consequences.

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

You can also reach Jeff Nichols directly and ask for a free copy of his book:
Email: [email protected]
Company Website: https://industrialfireprevention.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.