Deluge system for a spherical pressure vessel of anhydrous ammonia

[fabuara]

I need size a deluge system for a spherical pressure vessel of anhydrous ammonia of about 820 m3 wich should to be protected by water spray, but I can not get the right information on the design of such systems. I consulted NFPA 55 but understood that it is limited to "occupancies" and in my case it is an external installation. Could someone help me with some info? Thanks in advance.

 

[stookeyfpe]

See NFPA 15 for design and construction requirements for a water spray system. See CGA/ANSI K61.1 for safety requirements for the storage and handling NH₃. You will need to purchase these standards and they should be part of your engineering specifications.

 

[MJCronin]

Why is a spherical storage vessel being used for storage of Anhydrous Ammonia ? (I do, of course, understand how that this type of storage makes sense for refrigerated liquid ammonia service)

This seems like a lot of unnecessary expense ....spherical vessels are much more expensive than the common "bullet tank" storage.

Was the vessel being reused from another service ? What was the original service ?

If so, what is the MAWP of this reused vessel ?

It is important to note that, if indeed this is bulk storage of ambient temperature anhydrous ammonia, no deluge system is necessary

MJCronin
Sr. Process Engineer

 

[fabuara]

Thanks Stooketfpe. I'll provide these standards.

 

[fabuara]

Thanks for reply MJCronin.
I guess I was not clear enought. In fact, it treats of an existing pressure vessel that has a spraying system with 2 HV-45 sprays at the top and 2 more at the bottom of the vessel (if no cooling system is required for the sphere, may be it was designed to fight eventual ammonia clouds in the valves only).
Currently the fire hydrant system and spraying systems of the plant are supplyed by an external source and will be disconnected from it. Since I do not have the documentation, I need to premisse the values of flow and pressure in order to be able to size a new tank and water pumping system for the site.
Note: My interpretation of 55:6.10.2.1 led me to believe that a sprinkler system would be required for the case in question. Please correct me if my interpretation was wrong: "Where sprinkler protection is required, the area in which compressed gases or cryogenic fluids are stored or used shal be protected with a sprinkler system designed to be not less than that required by 11.2.3.1.1 of NFPA 13 for Ordinary Hazard Group 2 density/area curve. "