DSS031: Reconciling Hygiene with Explosion Safety in Food Industries with Dr. Chris Bloore

In this episode of the DustSafetyScience Podcast, we interview Dr. Chris Bloore in New Zealand about how to reconcile hygiene with explosion safety in food industries. Chris, who has a Ph.D. in spray drying applications from Massey University in New Zealand, has a wealth of experience that includes 19 years with the New Zealand Dairy Research Institute and almost 30 years as a self-employed consultant focusing on explosion protection and explosion safety training and education throughout the world.

Chris became passionate about explosion protection and safety after a 1989 incident in a spray dryer at a milk powder plant in Northland, New Zealand. The explosion ruptured the drying chamber, wrenched the dryer out of its mounting, and blew about half the cladding off the building. Neither of the two people in the building at the time was hurt, but one of them had just walked past a hatch that subsequently blew off.

The dairy industry, New Zealand Insurance Council, the Department of Labor, the Dairy Board, and the Dairy Research Institute subsequently developed a code of practice for the dairy industry spray drying plants. Chris edited the final draft, which was issued in 1990 and subsequently reissued in 1992.

Combustible Dust Safety in the Food Industry

Chris identified two major situations regarding combustible dust safety in the food industry.

The first is where dust is a byproduct of handling food. Examples include grain silos, where grain movement creates dust through attrition as it is conveyed, stored and packed. Equipment is available to handle these granular products with minimal attrition and avoid dust emission. There are also techniques to mitigate the effect of an explosion should it take place.

The second is where the foodstuffs themselves are combustible dust. Examples include:

Milk powder
Powdered sugar
Instant coffee

When these products are being mingled, sifted, conveyed, or dried, combustible dust is an inherent part of the process. Some of these foods are also capable of self-ignition if they’re allowed to accumulate in warm places.

U.S. Chemical Safety Board reports have often mentioned the hygiene versus explosion safety issue. A well-known example is the Imperial Sugar refinery, where changes were made to address hygiene issues. One change was enclosing the conveying system so that foreign materials didn’t fall into the stream. It led to (along with other things) the catastrophic explosion.

The refinery had been inspected a few months before and given a top hygiene rating. After the explosion, the Chemical Safety Board interviewed the inspectors, who said that they had been trained on combustible dust issues. The overall question was: why hadn’t they said anything about the astronomical levels of combustible dust?

Chris recalled a presentation he did a few years ago in Reno, Nevada, at a conference run by the Dairy Producers Institute. A number of cheese factory managers were in the audience. Whey is a combustible byproduct of cheese making, so Chris told them that if he walked in their plants and could see his footprints in the dust, there was enough dust to destroy their plant and kill everyone if it got dispersed and ignited.

Six or seven managers rushed up to him for more information during the coffee break, but the fact remains that more education is needed. Dry material like sugar is seen as less of a microbial hazard, so it tends to be overlooked by the hygiene people. However, from a dust explosion safety point of view, it’s a massive hazard.

“Everybody says, Well, we’re not likely to have a sudden dispersion of dust and that ignition source happening at the same time,” Chris stated. “And that’s perfectly true right up until it happens.”

The Dangers of Complacency

People become complacent about combustible dust hazards. During their first day on the job, they may notice accumulated dust and become uneasy, but by the time they retire 40 years later, they’ve gotten so used to it that they don’t see it anymore. This presents a challenge because sugar lying around on the floor is not a hygiene problem, which is a major concern at a food plant, but it certainly is a dust hazard.

One issue continues to present itself in this situation: not all individuals who work on the hygiene side understand the risks of combustible dust and there are combustible dust professionals who don’t know anything about hygiene in facilities. There is a need for each side of the coin to understand the other.

Recommendations for Improvement

When asked if he had any tips for improvement, Chris had the following recommendations.

More Extensive Training

“Fire is quite bad but explosions or deflagrations are significantly worse,” he said. He referred to a YouTube video that had been linked in an earlier DustSafetyScience newsletter. It showed three firefighters being engulfed by a fireball after they tackled a sawdust fire with hoses. Chris stated that dust spillage needs to be cleaned up using an approved vacuum cleaner or by physically scooping it up.

Awareness of the Self-Ignition Danger

“The other issue I would want to emphasize is that a lot of powders do self ignite,” he said. “We need to keep them warm so that they are dry and don’t stick to things and build up a layer which will light itself.”

Chris also advised that those working with spray dryers should heat the vent ducting so that there are no cold spots inside the dryer that can let powder attach and accumulate. He added that electric heaters should not be used to heat the vent.

“We had a case in New Zealand where this actually triggered an explosion in the vent duct,” he said. “It blew back into the dryer, which then blew the dryer out through the vent. So that’s an example of using an inappropriate technique to do a very worthwhile job.”

One video depicts a coal dust fire on a boat arriving in Hong Kong. The coal self-ignited, which is quite common. In Episode 10 of the podcast, Alan Tyldesley said that a vast majority of wood pellet shipments received in the UK are smoldering on arrival, and the same thing happened with this shipment of coal. As the shipping containers were being moved around, doors opened and dust fell out, so there were three days of flash fires.

Whenever practicable, Chris encourages local first responders to attend his seminars so that they can understand the difference between a dust fire and a powder product and all the other kinds of dust that they used to fighting.

“I’m an engineer and there a couple of lessons I was taught while very young,” he said. “Never open anything you can’t close quickly. Never close anything you can’t open quickly. If you look at some of the videos of people fighting fires in dust collectors and sawdust bins and the like, you’ll realize that if you’ve shut something or opened it and you can’t reverse that action swiftly and without hazard, then you really need to think about what you’re doing.”

Addressing the issue of using foam to fight fires, he acknowledged that there were quality firefighting foams available, but they weren’t suitable for dust fires. “If you put a foam blanket over a powder product that’s on fire, it will suppress the dust, which is a valuable thing, but do not for one moment imagine it’s going to put the fire out. That fire will burn for a week or two underneath.”

He recommended gentle low-pressure soaking that could take longer to put the fire out but is a better alternative to a faster event that could harm people.

Open Challenges

For Chris, the biggest open challenge is raising awareness. Once the problem is recognized, the next step is to apply appropriate mitigating or coping strategies. For example, aluminum fan components can’t be used in the dairy industry because caustic soda dissolves aluminum and produces hydrogen, which is an explosion hazard in its own right. Flexible connectors are another issue because they are places where a flash fire or a deflagration could emerge. The regulatory authorities need to be educated so they can be part of the solution.

Conclusion

One of the difficulties in many countries is that there is an inherent antipathy between people building and operating plants and the regulators, and it is often caused by liability issues. If the insurers, the equipment manufacturers, equipment purchasers, and regulatory authorities can agree on a way to tackle safety situations, everyone wins.

“Joint collaborative action (is better) than keeping everything secret within each individual competing company,” Chris said. “Otherwise, they end up all running hazardously when in fact they could have all run safely.”

If you would like to discuss further, leave your thoughts in the comments section below. You can also reach Chris Bloore directly:
Email: [email protected]
LinkedIn: https://www.linkedin.com/in/chrisbloore/

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.