Re: Amnonia pipe minimum wall thickness

From: <Gary>
Date: Mon Apr 19 2004 - 18:11:00 EDT

Hi Arturo, I have used tables in the ammonia refrigeration industry for so long that I often forget that the pipe thickness can be calculated. In our industry we use schedule 80 for 1-1/2" and below, schedule 40 for 2" thru 10" and standard weight for 12" and above. Most of the criteria for the pipe thickness was derived from B31.5 refrigeration piping standard.

I believe that price drives this thinking on the 14" standard pipe. Last time I priced 14" standard pipe was cheaper than 14" schedule 30 because schedule 30 was not stocked.

Anyways, I found a new table that was published by the International Institute of Ammonia Refrigeration (IIAR) www.IIAR.org that is similiar to the table I use an is more official. The table is from the IIAR Ammonia Refrigeration Piping Handbook, Table 1-21 and it states that a "corrosion allowance is included for threaded or welded piping, equal to the depth of a pipe thread". The IIAR piping handbook is an excellent source of information and I would suggest it as a first buy book for anyone sizing ammonia refrigeration systems.

Gary Gneiting

"Arturo M." <amurillo@t-visa.com.mx> wrote:

Hello all.

There is an Ammonia Industrial Refrigeration system, with a low pressure side (Receiver and evaporator) and works about at 200 psi, we specified a 14" seamless STD pipe carbon steel A-106 gr X42 ( wall 0.375" ) .

Someone is argued that a minimum of Schedule 40 pipe is needed at ( wall 0.438" ), temperature pressure is not a problem he said , Corrosion is the thing to watch out.

So the question is, where can I find the standard norm for correction for corrosion for industrial ammonia for the pipe wall? ( the factor I used was 1/64" ) .

Thank you.

Arturo Murillo.

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Received on Mon Apr 19 18:11:00 2004