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Ammonia as Refrigerant

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The events in Fernie where three people lost their lives due to exposure to high levels of ammonia refrigerant have caught our attention. The facility is for recreation; skating, curling. Ammonia is commonly used in these facilities so the public rightfully asks whether these places are safe. Why is this toxic gas used at all? Is it handled safely?

Technical BC Fernie Incident is a link to the Technical BC analysis of the incident. Their focus is the technical and mechanical details that led to the incident. WorksafeBC will be releasing their report with the focus on worker safety.

Ammonia is used as a refrigerant because it has higher energy efficiency compared to the alternatives, 3-10% better. It is less expensive to install as well. It is rated as a B2 refrigerant, meaning moderately toxic and moderately flammable. Because of this there are codes for mechanical rooms that are designed to prevent the public and workers from being exposed.

In an ice rink, the code essentially establishes a way to maintain two layers of separation between the public and the ammonia refrigerant. Vessels containing the refrigerant are either outside or enclosed in a sealed fire proof room. The refrigerant is not circulated in the floor, but typically a calcium chloride salt brine is circulated in piping under the ice, and through a heat exchanger where the refrigeration system removes the energy. If there is a leak of the brine, there is little hazard. If there is a leak of ammonia, it is either contained and vented in a controlled way from the enclosure, or it leaks into the brine, dissolves in the water and is contained within the brine piping system.

All these safeguards are designed to buy time. An arena full of people would not be exposed to ammonia, and there would be time to safely evacuate everyone in the event of a leak.

The workers who are in the mechanical rooms working on the equipment are required by WorksafeBC to wear protective gear, and each situation being analyzed for the appropriate level of precaution. Up to 35 ppm is safe, annoying but safe. Above that to 300 ppm a respirator and face mask is required. Ammonia dissolves in water, we are mostly made of water, so it dissolves in our tears, sweat, sinuses, etc. At high concentrations above 300 ppm there is not adequate oxygen available and a full self contained breathing apparatus is required.

It is widely used in food preparation in BC. The fruit industry, fish packing and preservation both on shore and on the boats, cold storage, warehouse freezers all use ammonia refrigerant.

The Paris Accord dealing with greenhouse gas emissions encourages industry to move towards refrigerants with a lower greenhouse gas potential. Ammonia has no greenhouse gas potential, along with other natural refrigerants such as hydrocarbons and CO2. Hence we likely will see more ammonia used as refrigerant in the future.

Incidents like Fernie teach us harshly how to work with this stuff safely. The link above to the Technical BC site details how the accident happened. There were a series of decisions made that led to the accident. WorksafeBC and Technical BC is in process of going to all facilities who use this refrigerant to make sure that it is handled safely from the standpoint of the public and the workers. WorksafeBC has a program with four phases; first the ice rink facilities were visited and procedures examined. Then the refrigeration contractors who install and maintain these sites. We have been involved and have developed safe work procedures for all the circumstances we would run into. Then food preparation facilities, then other refrigerant installations will be examined. I will have another blog post on the fourth phase and what that means.

What I got out of the incident report are two things. First the detailed technical descriptions clarified what happened. In my experience this stuff doesn’t just fall apart like that, and indeed it didn’t just fall apart. A series of technical decisions were made that exacerbated the problem. Second, and this is of interest more generally, each decision made the necessary level of knowledge and understanding higher to deal with the next situation that would arise. Let me explain.

First, in 2012 or so, the age of the chiller barrel reached is expected life span. 25 years. The city started the budget allocation process for replacement. The contractor had given them this information, a budget number and from then on it was up to the city to do what it knows how to do; allocate money, find a contractor qualified for the work, and run the project to replace the thing. It was all within the capabilities and skills of the participants.

Then the budget proposal fell off the list for some reason. The necessity of replacing this unit was lost in the many things needing done. The level of understanding required to recognize the priority of replacing this chiller was higher; in fact other consultants missed it. The manager of the facility didn’t know either. It didn’t happen, it wasn’t advanced in the budget process.

Toward the end of the 2016-2017 winter season ammonia was detected in the calcium chloride brine, both by smell and by analysis. This new information required a decision whether to run the plant the next year. During the year prices were acquired for replacement, but the money wasn’t budgeted and the chiller was started for the 2017-2018 winter season. This decision made everything that proceeded afterwards likely and extremely difficult to deal with safely.

In the report there are indications that the severity of the problem wasn’t clear to either the contractor, the city or the plant operators. There wasn’t enough information; how large was the leak, was it going to get worse, how fast would it deteriorate.

Nassim Taleb talks about making decisions under uncertainty. The important information isn’t the details or likelihood, but the consequences. I know that these things can fail slowly or quickly, and it is unpredictable. Precise analysis can be made, but in this situation the thing needed changing. The consequences of the decisions made at this point were catastrophic.

Shortly after startup, the leak got worse. One night the ammonia detector alarmed, the monitoring company called the fire department, they attended the site along with the operator. They had high levels of ammonia in the room, and the surge tanks were banging and vibrating. Let me explain. The water and salt mixture is pumped through the floor and the chiller barrel. It is open at the top, in a surge tank. The ammonia was escaping from the chiller barrel, through the brine piping and out the surge tank. The vibration and banging was indicative of a serious leak.

This situation required a high level of technical knowledge. The fire department is not trained at this level, and cannot be, and the rink operator didn’t have the knowledge either. So the decision was made to isolate the leak by closing valves on the brine system, essentially making it part of the pressure vessel. But the piping wasn’t designed to handle the pressure.

That made a sudden release just a matter of time.

The next step is of personal interest, because this is typically the situation where I show up. When reading the report I asked myself what I would have done in the situation with what I know and could have known. A refrigeration mechanic was dispatched from Calgary, and either didn’t know what he was walking into, or didn’t have the understanding to recognize the situation.

I would guess that of all the refrigeration mechanics in the province who would respond to such a call, maybe 1/4 of them would recognize what the situation was. The situation had developed to a point where a very high level of technical expertise was required to survive. Not only technical; it was unsafe to walk into the room, so getting information from the operator was critical. What do you mean you isolated the leak in the chiller barrel? That is impossible. Then having the wherewithal to recognize and convince everyone that it was a potential catastrophe, and lay out a course of action that would diffuse the situation without loss of life.

But no, the three of them were doing a routine maintenance task when the piping came apart, releasing the ammonia brine mixture and giving them seconds to find a way out of the room while blinded and coughing. They didn’t make it.

Further mistakes and problems with the installation became apparent over the next days.

I suspect I am not the only one who feels angry, disgusted, sad and afraid. We make a living dealing with these and other situations, and plan to retire and get a sun tan on the beach, not at work. There are two conclusions I have come to.

  1. Decisions made early are easy. The situation is not going to get better, so make a decision. It will only get more complicated and expensive. Clear communication with the client as to the situation and potential consequences is necessary.
  2. Uncertainty is the rule. There is no way of knowing what is going to happen. All we know are the negative consequences. In all installations, either ammonia or HFC refrigerants, the consequences of failure are easy to figure out. Those are the important facts upon which to base a decision.

Written by Kite Refrigeration

July 31, 2018 at 12:33 am

Posted in Uncategorized

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