Tuesday, December 20, 2022

Industrial Ammonia Accident Kills One

Very well written article over on MSN.com about an industrial refrigeration accident in Norwood, MA yesterday that killed one contractor and severely injured another. Preliminary news from the article indicates that there might be an industrial control system issue that aggravated the situation, but we will have to wait for more information after the building is finally cleared of ammonia fumes and investigators are allowed into the building. There is no indication at this point that the Chemical Safety Board is planning on being part of the investigation, though this is certainly a reportable release of ammonia from the point of view of CSB regulations.

The industrial refrigeration system used at the facility uses ammonia as the cooling fluid, very common in large industrial applications, particularly food processing plants. In this case there is reportedly a 21,000-lb anhydrous ammonia storage tank at the facility that supplies the refrigeration system. Apparently during work unrelated to that system, an ammonia line was breached. It is not clear from the article (and may not be known yet) if it was a feed line (liquid ammonia) or a return line (gaseous ammonia), but liquid ammonia quickly turns to gas when released to the atmosphere, so either could be the source of ammonia in the building.

The potential control system issue is briefly mentioned in the article:

“"It's a 21,000 pound tank that was leaking, we have no idea how much leaked," the fire chief explained. "There's no valves, basically all electronics in the area stopped working very quickly so we didn't have any of the controls."”

Ammonia is very corrosive, so if the gas got into any of the control system components, you would expect that there could be damage to those components. I would have expected most of those components (beyond perhaps operator controls) to be in atmospherically tight cabinets, but I come from a chemical manufacturing background where such things are standard.

It sounds like the system refrigeration system employed at this facility did not have a high-flow cutoff valve on the ammonia tank. When you have a line break, the flow rate of ammonia out of the system is typically much higher than seen in normal use. A high-flow cutoff system senses that unusual flow and turns off the main outflow valve of the tank to minimize the potential loss from the system. It would seem that such a system would have mitigated the problem seen in Norwood. It does not seem if it would have prevented the death and injury (they apparently occurred at the initial point of release), but it would have allowed the building to be cleared much more quickly.

Finally, it sounds like the facility had a good evacuation program in place. With a massive leak such as this, to get all of the employees out of the building with minimal exposure is impressive.

It will be interesting to see what the investigation turns up. Unfortunately, without a CSB investigation, it is unlikely that the results will be widely shared.

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