In this episode of the Dust Safety Science podcast, we interview UK explosion safety consultant Alan Tyldesley. We talk biomass fire and explosion hazards and the regulatory approaches used in the UK to deal with dangerous substances and explosive atmospheres.
During his 21-year career with the UK Health and Safety Executive, Alan spent nearly 15 of those years as a dust explosion specialist. And for the past 13 years, he has been running his own firm, Tyldesley Explosion Consulting, providing professional advice regarding dust explosions, chemical warehousing, and hazardous area classification.
During this interview, we asked Alan:
- What are some of the biggest fire and explosion hazards in the biomass sector?
- How do biomass storage methods affect fire protection?
- How have fire and explosion safety regulations evolved in Europe and internationally?
- How can we best move towards a global standard for combustible dust safety?
Our focus for 2019 is to better understand combustible dust as a global problem and come up with global solutions. To support this goal, we are interviewing experts from around the world to gain a better understanding of what’s working in combustible safety within these regions and their these industries. One such combustible hazard is biomass material.
Biomass Fire & Explosion Safety
Biomass is organic material used as a fuel, frequently to generate electricity in power stations. One of the most common sources is dried wood pellets made from cultivated trees and shipped from North America to Europe and other parts of the globe. The loads are so large that self-heating can be a problem: by the time a ship arrives at the dock, a pellet fire may already be in progress.
Biomass material like wood pellets are typically unloaded from ships and transferred to an interim storage site using belt conveyors. These conveying systems are enclosed because they trail dust, but the problem is that dust accumulates. If an explosion occurs, it or the resulting fire could run the whole length of the conveyor.
Storage Methods
Wood pellets are stored in bulk at the dock terminal after unloading or at the power station. Storage is typically in a large silo: one of the biggest is the 80,000 ton-structure at the Drax power station in the UK.
There are two primary types of storage systems, both of which have their benefits and challenges:
- Silos, or cylindrical storage units. Larger ones can be challenging because they limit what you can do in terms of fire protection, as determining whether you’ve actually got burning inside the silo can be quite tricky.
- Flat-floor storage, which consists of warehouses that allow you to go in with long lances and probe the temperature deep inside the pile to detect localized heating. The challenge with this storage method is that people are in the storage area, which is always a danger.
Ignition Sources
With wood pellets, common ignition sources include:
- Self-heating during transit
- Dust trapped between fast-moving parts on the conveyor system
- Metallic objects such as screws and nails, which can also jam the machinery
It can be difficult to catch a fast-moving, burning clump of material and prevent it from dropping into the system because these belt conveyors can’t be suddenly shut down. With so much momentum built up, suddenly slamming the motor could cause the material to spill over, get dispersed in the air, and cause an explosion or flash fire.
These dust explosions have the ability to interrupt power supply (which is why some of the UK’s biggest users have requested two different boats to bring in product) and even disrupt the national economy if the event occurs at a major shipping port.
Equipment Safety Regulations in Europe
There has been an ongoing effort in Europe to harmonize equipment design standards. The movement began in the 1940s and 50s, when it was recognized that the flame-proof motors used in the mining industry should be the same whether the mine was in Germany, France, or the UK.
Progress was slow until 1994, when the European Union passed a directive called ATEX, which established common standards for a wide range of electrical equipment. It expanded into mechanical equipment and explosion protection devices. However, this 1994 directive did not become mandatory until 2003.
Almost all of these standards were European. DIN, the German Institute for Standardization, then proposed to turn them into international standards. Most of them are now ISO standards.
Standards were also developed to protect the end user. In the UK, the Dangerous Substances and Explosive Atmospheres Regulations (DSEAR) addresses fire risks, explosion and similar events arising from dangerous substances used or present in the workplace.
Alan recommended that we watch the North American insurance industry guidelines for direction on how to evolve safety standards even further. Factory Mutual has codes for safety considerations that do not appear to be covered by other bodies.
Moving Towards a Global Standard
Alan discussed the differences that exist between some national regulatory bodies. For example, the National Fire Protection Association (NFPA) in the U.S. has a standard for fire protection in belt conveyors, but Europe does not.
When asked about the best approach to create a global community with unified safety standards, Alan stated that it was a matter of “endless education.” For example:
- Each new generation of engineers needs to appreciate that what looks like fairly harmless sawdust or flour or sugar dust can be incredibly destructive if mishandled.
- Workers need to understand that smaller plant fires need to be taken seriously, especially if they happen frequently. A series of minor incidents may one day result in a catastrophic loss.
Conclusion
Alan mentioned that during his time at HSE UK, he acquired a booklet titled “Prevention of dust explosions in grain elevators–an achievable
The goal of this publication, which came out in 1980, is similar to the goal of Dust Safety Science and its tools, the Combustible Dust Incident Database and the Dust Safety Science Podcast: to understand combustible dust safety as a worldwide problem and develop worldwide solutions.
Resources Mentioned
Dust Safety Science:
Combustible Dust Incident Database
Dust Safety Science Podcast
Alan Tyldesley’s Consultancy:
Tyldesley Explosion Consulting
Organizations:
Health and Safety Executive UK
National Fire Protection Association (NFPA)
Standards:
International Organization for Standardization (ISO)
DIN – German Institute for Standardization
Dangerous Substances and Explosive Atmospheres Regulations (DSEAR)
Publications:
United States. Department of Agriculture. Office of the Special Coordinator for Grain Elevator Safety and Security
Power Stations:
Drax Power Station
Previous Podcast Episodes:
DSS 009: DSS009: Understanding Combustible Dust as a Global Challenge and Developing Global Solutions (Our 2019 Dust Safety Focus Area)
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Download the Episode
DSS 010: Biomass Fire & Explosion Hazards and UK regulations with Alan Tyldesley