Anhydrous Ammonia Bottles; Are PRV's Required?

[stolzbrad]

Just a little confused about the requirements for a PRV on Anhydrous Ammonia bottles. These are relatively small bottles (150 lb) and are marked with DOT numbers.

ANSI K61.1 says that PRV's are not required when the bottle holds less than 165 lbs.

However, 49 CFR Ch.1, Section 178 says that "Each portable tank... MUST be fitted" with a primary PRV... (emphasis mine)

Does 49 CFR outweigh the ANSI standard in this case? Anybody know? I know the bottles have been manufactured for many years without PRV's, but it appears that perhaps they should be installed.

Thanks,
Stolzbrad

 

[JLSeagull]

It sounds like you are in the DOT area and relief valves are required. My bits and pieces of stored information apply to LPG and I have not looked into ammonia. The LPG cylinder regulations require DOT cylinder safety relief devices; and they must be tested for leaks before the filled cylinder is tested. The safety relief valves have a tolerance better than -10% and +0% of the test pressure. I don't have copies but the following are among the applicable DOT cylinder regulations

49 CFR § 107.805 Approval of cylinder requalifiers
49 CFR § 173.301 General requirements for shipment of compressed gases in cylinders…
49 CFR § 180.203 Definitions
49 CFR § 180.205 General requirements for requalification of cylinders
49 CFR § 180.209 Requirements for requalification of specification cylinders
49 CFR § 180.209 Requalification markings
49 CFR § 180.215 Requirements for requalification of specification cylinders

All of these standards are available on the web. This should provide a starting point for your search.

 

[stolzbrad]

JLSeagull: That is my thought, as well. DOT should govern, whereas ANSI is a recommendation, right?

Anyone else?

 

[CHD01]

My recollection is that K61.1 applies for API tanks below 15 psig; I don't believe it also applies for pressure vessels. Anyone have K61.1 available for review? High pressure cylinders and DOT applicable vessels require a relief valve. I support you previous responders.

The more you learn, the less you are certain of.