In today’s episode of the Dust Safety Science podcast, we talk to Kayleigh Rayner Brown from OBEX Risk about the application of bow tie analysis and inherently safer design in Canadian wood pellet mills.
This is a follow-up to some earlier episodes related to the WorkSafe BC Innovation at Work project: Inherently Safer Bow Ties for Dust Hazard Analysis. In this particular case, WorkSafe BC funded the project, which was put together by the project partners BC Forest Safety Council, Wood Pellet Association of Canada, Dalhousie University and OBEX Risk and Dust Safety Science.
The previous episodes were:
- DSS131: History of the Wood Pellet Association of Canada with Gordon Murray
- DSS132: Identifying and Implementing Critical Controls in Wood Pellet Facilities with Cherie Whelan
- DSS133: Inherently Safer Design using Bow Tie Analysis for Combustible Dust Hazards with Dr. Paul Amyotte
Today we cover some of the findings that came out of this research and were published in the research report.
An Overview of Inherently Safer Design (ISD)
Inherently Safer Design (ISD) includes things like minimization, substitution, moderating or modifying the hazards and simplifying the hazards.
Elimination can be thought of as the ultimate minimization. There are ways to reduce and actually eliminate the hazards from a process safety or combustible dust standpoint, instead of adding engineering solutions or administrative controls.
Kayleigh Rayner Brown got involved with process safety almost 4 years ago. She has a Chemical Engineering degree and a lot of experience in Environment, Health & Safety. After finishing her Master’s in Applied Science with Dr. Paul Amyotte at Dalhousie University, she launched OBEX Risk.
When asked about Inherently Safer Design, or ISD, Kayleigh explained, “Inherently Safer Design, or ISD, focuses on the treatment or elimination of hazards rather than only relying on add-on safety equipment or procedures or administrative controls. It is based on 4 principles: Minimization, Substitution, Moderation and Simplification.”
She proceeded to give some examples of each one:
- Minimization would be sealing off areas where combustible dust can accumulate, such as horizontal surfaces.
- Substitution could be substituting the correct electrical equipment for the hazardous area that the electrical equipment is being used in.
- Moderation could be locating certain types of equipment, such as a vessel with explosion venting, away from personnel so they aren’t hurt if the explosion vent were to rupture.
- Simplification would be redesigning processes or human-machine interfaces or procedures.
Because ISD is hazard-specific, Kayleigh recommended checklist questions that promote brainstorming. For example:
- Is there a way that we could minimize hazardous material?
- Can we replace one process with one that is less hazardous?
- Can we simplify something to make it less prone to human error?
- Could we change the conditions around the hazard to reduce the severity or likelihood of an incident if that were to occur?
Her research was published in Process Safety & Environmental Protection in 2021.
How Are the Hierarchy of Controls and Critical Controls Developed?
Kayleigh pointed out that when we talk about Inherently Safer Design and the hierarchy of controls for combustible dust risk management, you use all four types of controls. ISD should work in conjunction with those passive and active-engineered controls as well as safe work procedures.
“So in terms of the protocol for incorporating ISD, we’re just encouraging users to first think about adding in and identifying ways that you could incorporate Inherently Safer Design into your safety barriers, measures and systems that you are currently using at your facility or designing into a facility. We also encourage you to incorporate ISD prior to those add-on engineered and procedural controls.
“In the protocol, you should first identify the stage of your facility’s lifecycle. Are you at the design stage? Or are you operating? Because Inherently Safer Design is most beneficial when incorporated at the design stage. Not that there aren’t opportunities for later implementation, but the lifecycle stage may affect the feasibility of some recommendations.”
Once you identify the lifecycle stage, the next step is to do a bow tie analysis.
“This involves identifying the top event- the negative or the undesirable incident that you’re looking to prevent. What kind of conditions or scenarios can exist that could lead to that top event? What consequences would you want to mitigate or prevent? And what barriers or safety measures do we have in place? That could be your explosion venting, deflagration isolation, hot work programs, so on and so forth.”
Once these questions are answered, you should examine all these barriers and determine whether Inherently Safer Design is being used. Have you minimized inventory in the silos, for example? Did you relocate hazardous equipment away from personnel? Once your ISD principles are identified, the next step is to consider whether you should implement any additional engineered or procedural controls.
“At the end of the protocol, you would just look at the different recommendations,” Kayleigh says. “Look at what ISD options were identified and consider what is feasible and how you want to move forward.”
Bow Tie Analysis and ISD in Wood Pellet Mills
Kayleigh recalled that the full-on engagement with the BC Forest Safety Council and WPAC for the first Innovation at Work Project began on October 1st, 2020.
“The first step was to develop these bow ties with the wood pellet operations. So it really began with that stakeholder engagement. These are the bow tie workshops that we’re going to do. This is what the process will be like. This is what bow tie analysis is. Here’s the terminology. Here’s the methodology that we’re going to apply.
“So we did two bow tie workshop pilots and developed the bow tie analyses with two initial facilities. Those were for the primary process units in the wood pellet plants: your pelletizer, your hammer mill, dryer, conveyance systems, cyclones or baghouses, etc. These analyses were used as benchmarks for subsequent bow tie validation.
“During these validation activities, they could look at the bow tie and say, “We already have these controls in this bow tie or we don’t have them so we’ll exclude those from our analysis. But we have these other controls instead, so we could add those to our bow tie.” So using that as a baseline, the Operations were able to go through and identify their critical controls. The key activities around CCM were identifying responsibilities, roles, and accountabilities to help ensure that those controls deemed critical would be more reliable.”
What Were Some of the Main Takeaways for the Hierarchy of Controls in These Facilities?
“It was really interesting to find that all of the facilities did have some ISD barriers and controls already in place.” Kayleigh recalls. “One of the things that I find particularly interesting from the protocol application and the development of the bow ties is looking at the diversity in the types of controls that we employ.”
She pointed out that in some cases and some bow ties there were some threat lines that were primarily administrative controls.
“Getting some more diversity, incorporating some engineered controls and ISD barriers as much as possible would be a really key point to focus on because when you have, for example, all administrative controls, and then you go that next level and find that for the degradation factors and the degradation factor controls when those are also administrative, I think that that’s really challenging because you have inherently weaker administrative barriers. Then the only controls that you have in place to help ensure that those barriers would be less likely to be defeated are also administrative. It’s a bit of a double whammy if you will.
“There’s also an opportunity to apply the protocol and look at that next level of the bow tie, and looking at those degradation factor controls and say, “Can we automate something instead of having someone manually check it? Can we add an alarm or an active engineered system here? Again, just removing that human element and moving as high up as you can on the hierarchy – I think that that would bring a lot of value to the operations.”
Conclusion
Kayleigh concluded the discussion by stating, “ Even if you’re having a hard time incorporating true Inherently Safer Design, I would encourage operations and end users to think about ways to incorporate the ISD principles into some of those more administrative controls. So if we’re using a safe work procedure, well, how clear is it to understand? Is it well written? Can it be easily interpreted? So on and so forth.
“I would still encourage administrative with ISD overtones if you will. There are some barriers that [meet that definition]. A good example of that is your combustible dust housekeeping program. Even though your program itself is administrative, it is achieving ISD through minimization of fuel loadings. So you’re reducing the combustible dust fuel loading through administrative means. Just considering how you can explicitly consider ISD principles in the operations can bring a lot of value.”
If you would like to discuss further, leave your thoughts in the comments section below. You can also reach Kayleigh Rayner Brown directly:
Email: [email protected]
LinkedIn: https://www.linkedin.com/in/kayleigh-rayner-brown/
Website: https://www.obexrisk.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.
Resources mentioned
Dust Safety Science
Combustible Dust Incident Database
Dust Safety Science Podcast
Questions from the Community
Dust Safety Academy
Dust Safety Professionals
Dust Safety Share
Companies
OBEX Risk
Organizations
WorkSafe BC
BC Forest Safety Council
Wood Pellet Association of Canada
Dalhousie University
Publications
Kayleigh Rayner Brown, Michele Hastie, Faisal I. Khan, Paul R. Amyotte, Inherently safer design protocol for process hazard analysis, Process Safety and Environmental Protection, Volume 149, 2021, Pages 199-211,
The role of inherently safer design in process safety
Previous Episodes
DSS131: History of the Wood Pellet Association of Canada with Gordon Murray
DSS132: Identifying and Implementing Critical Controls in Wood Pellet Facilities with Cherie Whelan
DSS133: Inherently Safer Design using Bow Tie Analysis for Combustible Dust Hazards with Dr. Paul Amyotte
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