Liquid Nitrogen Storage Rooms Require Rating?

1/18/2021

Do liquid nitrogen storage rooms need to be fire-resistance rated?

According to NFPA 55 (2016 Edition) Section 6.4.4, gas storage rooms need to be 1-hour fire rated, but it just seems odd since nitrogen can be used as an extinguishing agent.

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7 Comments

Jonathan Sullivan

1/18/2021 08:09:12 am

You'll want to check out the compressed gas definition in 3.3.5.1. Liquified gases with a boiling point of 68 F or less at 14.7 psi are considered compressible for the purposes of NFPA 55 (and IFC too).

Glenn Berger

1/18/2021 09:29:15 am

The quantity of stored liquid nitrogen can be factor in determining if fire rating is required. Is it just being stored, or is it a part of a closed loop system?

Michael Knott

1/18/2021 09:37:32 am

I believe they are just liquid nitrogen dewars being stored and not connected to a closed loop system. I am unsure of how much they are storing as of now.

CJ Bonczyk

1/18/2021 09:31:24 am

NFPA 13 2019 26.11 provides sprinkler criteria similar to as outlined below.

NFPA 55 6.11 * Fire Protection Systems.Except as provided in 6.11.1, buildings or portions thereof required to comply with
Protection Levels 1 through 5 shall be protected by an approved automatic fire sprinkler system complying with NFPA 13.

NFPA 55 6.11.1
Rooms or areas that are of noncombustible construction with wholly noncombustible contents shall not be required to be protected by an automatic fire sprinkler system.

NFPA 55 6.11.2 Sprinkler System Design.

6.11.2.1
Where sprinkler protection is required, the area in which compressed gases or cryogenic fluids are stored or used shall be protected with a sprinkler system designed to be not less than that required by 11.2.3.1.1 of NFPA 13 for the Ordinary Hazard Group 2 density/area curve.

6.11.2.2
Where sprinkler protection is required, the area in which the flammable or pyrophoric compressed gases or cryogenic fluids are stored or used shall be protected with a sprinkler system designed to be not less than that required by 11.2.3.1.1 of NFPA 13 for the Extra Hazard Group 1 density/area curve.

Liquid Nitrogen Gas is commonly stored in in pressurized cylinder/or tanks. The purpose is to prevent the bottle under pressure being exposed to extreme heat causing failure of the cylinder since its under pressure and can cause damage to the surrounding area. If you look up a typical SDS sheet of liquid nitrogen it does not have flammability issues but you are trying to prevent the bottle/cylinders from failing creating danger for the surrounding area essentially. Under normal conditions of storage and use, hazardous reactions will not occur. The cut off room basically allows the sprinkler protection to be omitted since its fire rated limiting exposure. SDS sheets require to store in accordance with local regulations. Typical SDS sheets also
state to store in a segregated and approved area.Store in a dry, cool and well-ventilated area, away from incompatible materials. Cylinders should be stored upright, with valve protection cap in place, and firmly secured to prevent falling or being knocked over. Cylinder temperatures should not exceed 52 °C (125 °F). Keep containers tightly closed and sealed until ready for use.

Michael Knott

1/18/2021 09:42:49 am

Makes sense. Thanks for the input!

robert kluck

1/18/2021 02:04:04 pm

If you look at the parent of that code section, 55.6.4, it is stating that "Where a gas room is used to the threshold quantity for a gas requiring special provisions...the room shall meet the requirements for 6.4.1 to 6.4.5. As an inert gas, table 55.6.3.1.1 does not set a requirement for Nitrogen, based on that parentage, I would argue that the clause 55.6.4.4 would not apply.

Serious consideration of gas detection for O2 levels may be wise, depending on the details of the location. Many deaths have occurred in locations where gas storage leaks develop and displace the air in the room.

Franck

1/19/2021 11:36:55 am

Just one small comment on the following sentence (for the rest of the technical conversation, it was well detailed above, in particular by CJ BONCZYK):
"but it just seems odd since nitrogen can be used as an extinguishing agent"
It is true that nitrogen is used as an extinguishing agent and is not combustible.
But even nitrogen bottles used for fire extinguishment need to be stored outside the room it protects (and not exposed by surrounding fires).
In your case, if there is absolutely no combustible load and no fire hazard exposing your tank (including construction, other equipment, possible storage during outages...), then there is no need for fire protection and no need for specific fire rating of the room.
But if your room may be exposed by adjacent fire hazards (including hazard in adjacent rooms), then you need to provide a fire separation and/or a fixed fire protection system.
The purpose is to avoid that an adjacent fire will heat the tank and overpressure the nitrogen inside: limited volume - if you heat the tank, liquid will become gas and pressure will increase... (with in addition possible collapse, leakage... as possible direct mechanical damages)

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Liquid Nitrogen Storage Rooms Require Rating?

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