KEM RUSSELL

In most cases, experience is something we build upon. It allows us to take advantage of the things we’ve learned, and hopefully, remember those lessons when they matter most. But sometimes, no matter how important the lesson, it can get overlooked.

In visits to several ammonia refrigeration facilities and ongoing talks with managers and operators of these systems, there’s one recurring lesson that sticks out, precisely because it’s the one lesson that is seemingly never learned. Here are a few examples:

In our first scenario, an experienced refrigeration operator was called to the process area because of a complaint of an ammonia smell. He quickly found the source, which was one of the hoses on a low temperature plate freezer.

The leak was a slow drip of liquid from a failed portion of a plate hose. He isolated the liquid and hot gas inlet to the plate freezer, and with a new hose began the replacement. As he was working the pressure slowly began to rise in the plate freezer and, being by himself, he was faced with a problem: how to stop (or greatly slow) the leak, while reaching for the replacement hose, which just happened to be at the limit of his fully extended arm. The process people in the area watched, from a safe distance, wondering . . . what is going to happen to this guy?

Similarly, in another facility, repair work was to be done on a suction pressure control assembly. The work would require isolation of the ammonia line and control assembly. Two refrigeration maintenance men were assigned the task.

Having some experience as well as having observed other experienced operators perform maintenance; they were reluctant to wear full-face ammonia masks, as required by their SOP (Standard Operating Procedure). Nevertheless, they complied, even though they knew from past experience that putting on an ammonia mask may not be necessary.

As they proceeded with the work, isolating the assembly, and checking the control valve pressure gauge, everything seemed to be in order to proceed with removal of the valve flange bolts. As the fl anges parted, ammonia pressure trapped on the outlet side of the control valve (apparently due to a stuck piston in the control valve) was released into the faces of the operator parting the fl anges and the other man standing close by to assist.

Finally, at yet another facility, one commonly performed task was to drain oil from an oil pot located in the machine room. The facility had an SOP for this task that clearly stated the steps to be followed in the procedure. The refrigeration maintenance person doing this particular task had become very experienced and quite comfortable with the procedure and had started to skip two of the required steps in the SOP.

How long this slightly altered procedure had been occurring is unknown, but it just so happened that a regulator came to the facility to specifically review the Process Safety Management program, and observe some of the field applications of the program. The regulator, having briefly reviewed the oil draining SOP, was in the machine room with the facility manager when he noticed two things associated with the oil pot.

One; the oil drain hose was still connected to the oil drain outlet valve, and two; there was no plug in the oil drain valve (since the hose was connected). Both removal of the hose and re-installing the steel plug were procedural steps identified in the SOP.

So what are we learning here in all three cases? I’m sure that you’ve either heard of or have been directly involved in ammonia accidents or near misses that involved experienced people doing things they should not have been doing. As an industry and as individuals we rely on experience. However, this reliance is a double-edged sword. We need experience to properly carry out the required tasks, but with experience a person often becomes complacent in following proper procedures.

From the above three incidents, we can see that one lesson that can have a real, positive, effect on the outcome is the use of a “buddy system,” especially when the task involves opening the system.

In the first example, the somewhat routine work of changing a plate freezer hose very nearly became a critical situation. There was no other appropriately trained person present to assistant. This other person could have both helped with the work, and have been another set of eyes to see the things the experienced operator may have missed or not realized.

In the second example, the two men had learned from watching other experienced personnel do work on the ammonia system, and those personnel they learned from did not follow proper protective procedures. No incidents had occurred over months (and sometimes years) of ammonia maintenance.

This complacency based on experience could have led to a serious harmful effect on these two maintenance men had they not, albeit reluctantly, put on full-face ammonia masks. From this particular event these two operators suddenly realized how important it is to wear the proper personal protective equipment (PPE). They continued to relate this experience to other maintenance personnel for months afterward.

In the third example, we again see complacency in experience leading to the skipping of important steps in a procedure. In this case, no release had occurred, but there was certainly the potential of a significant release.

Again, due to the experience of performing this procedure with no adverse impact, the maintenance person became lax in completing each required step. In addition, the visiting regulator asked “Has this refrigeration maintenance person been trained to do the oil draining procedure? Prove it.” There was an SOP that was clearly not being followed. Unfortunately, there was no specific documentation showing the maintenance person had been trained to do this procedure and that he had acknowledged that training.

Anhydrous ammonia is an extremely important chemical in maintaining our life style. Besides being a natural refrigerant, it has great properties that make it efficient to use in many refrigeration applications. Its pungent smell is also very helpful. It can be detected at very low levels, long before it may be harmful.

In addition the guidelines developed by IIAR have helped improve the design, construction, and maintenance of ammonia refrigeration systems so that these systems are not only reliable, but safe.

These are important and necessary resources, but operational safety still comes down to the ability of experienced personnel to properly operate and maintain systems in a manner that will not result in injury to themselves, other employees, the public or the environment.

Do not become complacent due to your experience with ammonia. Treat it with the constant vigilance and respect that it requires, and constantly question the merits of making a decision based on your own “experience.”