NH3 - Weld Cracking

[shipmate]

A colleague advised that a simple pressure vessel, constructed without post weld heat treatment, in which ammonia was used was found with substantial weld cracking. Tests on the material prior to construction indicated the material was sound, and the vessel was constructed by a quality company following good procedures.
Any ideas on whether there is a phenomenum associated with ammonia?

 

[arto]

check this out:

http://www.nationalboard.org/Classics/classic8.html

 

[PVRV]

http://www.nationalboard.org/Classics/classic28.html

 

[MJCronin]

shipmate,

Some things to note about cracking induced in carbon-steel pressure vessels by ammonia.....

1) It only happens with anhydrous ammonia (NH3)contained in carbon steel pressure vessels..... do not confuse ammonium hydroxide (also called aqua-ammonia) with anyhdrous ammonia

2)This phenomena has been thoroughly studied and there are several measures that can be taken to safely store anyhdrous ammonia in carbon steel vessels. Carbon steel vessels can still be safely used if the considerations of ANSI K61.1-1981, (Safety Requirements for the Storage and Handling of Anhydrous Ammonia) are considered. OSHA mandates adherence to K61.1

3) Even the slightest amount of water contained in the anhydrous ammonia will inhibit the cracking. Heat treating the welds also inhibits cracking

4) See some of the following websites for related info:

http://www.tfi.org/Meetings/anhydrous ammonia.pdf

http://www.nh3.org

http://www.ncedaust.org/peter3.htm

http://www.appliedinspection.com/ammoniatanks.htm

http://www.hghouston.com/pvessel.html

http://hansontank.us/ammoniastoragetanks.html

http://asmepressurevessels.com/ammonia/N1000.jpg

( read the notes on the drawings)


Hope that this helps

MJC

 

[Shmulik]

Hi,
You may find relevant info at the following: thread794-17433