By Andrew Perks, FSAIRAC
You will all know by now that I am a firm advocate of joining IIAR (International Institute of All-Natural Refrigeration).
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Andrew Perks is a subject expert in ammonia refrigeration. Since undertaking his apprenticeship in Glasgow in the 1960s he has held positions of contracts engineer, project engineer, refrigeration design engineer, company director for a refrigeration contracting company and eventually owning his own contracting company and low temperature cold store. He is now involved in adding skills to the ammonia industry, is merSETA accredited and has written a variety of unit standards for SAQA that define the levels to be achieved in training in our industry. |
They really have jacked up their game and are presenting webinars with excellent content providing an invaluable educational service to the industry. There is much knowledge available, and I would like to talk about their latest webinar where they highlight lessons learned from past incidents.
We all know that accidents happen, but when you break it right down, there are three root causes: a lack of training (learning), competence (knowledge) and site maintenance (safe plants). Whenever there has been a root cause analysis of an incident it always points to these three criteria, with lack of maintenance being the prime factor. It is all about proactive learning.
If we think about our motor cars, if we don’t service them and they break down, we can attribute that to a lack of maintenance. But most often if we consider the problems, it is an operator error – us. Somebody needs to motivate the process. During the recent webinar, an incident at Fernie (British Columbia) in 2017 was a case study. We incorporate this event into our Site Incident Response training schedules as it is an interesting case. There are, as usual, many considerations, each one impacting the next and resulting in the death of three people.
I believe that a catastrophic incident is one where a seemingly incongruous combination of minor incidents reaches critical mass and then it all goes ‘pear shaped’. No incident on its own would have caused the Fernie catastrophe; but line them up together and watch out. In any situation, escalating incidents can change the risks quickly. The site’s emergency controller needs to be on his toes and consider escalating events.
The picture shown herein highlights that by looking at a situation from different perspectives, you get a different story. We need to stand back and fully analyse what is going on before we can arrive at a safe action plan. All about Risk Analysis as the event progresses, escalating circumstances will require different responses.
Let’s get back to the Fernie Incident. At the beginning of the skating and ice hockey season in Canada the cooling system for the Fernie ice rinks was switched on to build the rink ice. The ammonia refrigeration system had been running for less than a day when the ammonia alarm went off to say there were high levels of ammonia vapour in the plant room.
The emergency fire services were called, and it was found that ammonia was spilling out of the cooling brine balance tanks, increasing ammonia concentrations in the machinery plant room.
One of the plant operators closed the brine make up connection from the tanks to the brine pumps and switched off the refrigeration system, after which the firemen ventilated the room, reducing the ammonia level to an acceptable concentration.
This is where it starts to escalate. In order to save the rink’s ice, the manager told the rink operators to restart the plant.
This was a problem as the compressors were tripped on oil pressure. A refrigeration technician was called to work on the compressors and while three technicians were busy in the plant room, a section of the brine pipework failed, releasing a catastrophic mixture of brine and ammonia resulting in concentrations that were not survivable. Consequently, all three technicians perished.
When the incident was analysed, it was noted that a leak had developed in the brine chiller allowing ammonia to leak into the brine circuit. The chiller was over 30 years old and due for replacement.
This replacement should have happened during the off session. Now we are getting to the prime cause – lack of maintenance. That’s a given – but it’s the escalation thereafter that contributes to the fatal incident. What did I say before? It is the random factors that escalate an incident.
So yes, we had a leaking chiller but the operator who closed the initial brine make up valve set events in motion. With that valve closed and the plant standing, the ammonia leaks into the brine and builds up the pressure in the brine system to beyond the design pressures. This eventually ruptured a coupling, immersing the plant operators in a fatal release of ammonia.
Sadly no one foresaw these consequences.
So, let’s go back to the cause-and-effect scenario. It’s those three factors again, a lack of training (learning), competence (knowledge) and site maintenance (safe plants).
If you look at most incidents, these three elements are there with varying degrees of contribution. Risk assessments and standard operating procedures are a must. I can’t stress it enough, think through a safe procedure before you get involved. You know the story: there’s never enough time to do it right first time, but always enough time to fix it.
Stay safe