Ammonia Refrigeration Req' Explosion Control?

9/24/2020

We have a closed ammonia refrigeration system for a large cooler/freezer. The refrigeration equipment is located in a separate mechanical room. Total amount of ammonia is less than 10,000 lbs.

My question is explosion control per Section 911 of the International Fire Code required for the refrigeration mechanical room?

I am reading different interpretations on whether ammonia is considered a flammable gas, most say it is technically not a flammable gas but can burn and/or explode.

I'm interested in hearing everyone's take. Thanks.

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3 Comments

Daniel Bustamante

9/24/2020 10:38:37 am

It depends really on the AHJ in my projects installing ammonia closed cycle it was never requested any explosion protection, however the code CSA requested that ammonia equipment be in a separated room than thermal equipment

Franck

9/24/2020 10:53:29 am

Ammonia in the gas form is definitely explosive. The LEL is 16% approx.

Ventilation is a good practice for the area housing the unit with a continuous mechanical ventilation of 1 cu ft/min of exhaust air for each sq ft of room area.

Electrical shut down of electrical equipment should be set at 50% of LEL (the Lower Explosion Limit for ammonia is 16%, so auto shutdown at 8% ammonia detected in the room)

Normally, no sprinkler protection is required for a separate room if no combustible storage, or combustible construction, or other equipment is present.

You may have a look at FM data sheet 7.13 Mechanical refrigeration (freely available on fm global website)

John R. Sternitzke, PE FPE CxA link

9/24/2020 03:06:22 pm

IIAR, ASHRAE, and IMC codes address R717 and things change based on machine room design and the lbs of charge. Typically Explosion control NFPA 68 Is not required in the design of these spaces.
IIAR has Guidelines for PSHA Process Safety Hazard Analysis... etc. My AHJ holds ammonia days.. and as a community with over 50 cold storage spaces we take this serious. RM and MM Relay and monitor modules are always tied to the System and picked up on the FA...

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