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Up Topic Welding Industry / General Welding Discussion / Welding Air pipe
- - By Cumminsguy71 (*****) Date 01-03-2011 17:22
There is a job going on near me, some hvac guys are doing it so I'm out but they are running 4" Sch. 40 for the compressed air loops in this new factory. I was out talking with the construction manager seeing if there was something I could do and he said the hvac guys would be the ones to talk to. Anyhow, I asked what code the air pipe was being welded to....he was not sure but said the hvac guys had papers showing they were qualified.

My question is, what does pressurized air line fall under? I'm thinking it's gonna be in B31 somewhere and was just curious to feed my knowledge starved mind and for future reference. Other than calling the lab and pestering them I thought I'd pester you guys on here. LoL!

Shawn
Parent - By 803056 (*****) Date 01-03-2011 19:55
The Owner is responsible for determining which section of the code is applicable.

Now let's agree that the owner is the least likely entity to know what code is applicable. From there you can look into the building code to see what piping code is specified for the application. Assuming that is no help if you are working in an area that doesn't have a building code, then ask the contractor that is responsible for the installation.

I encountered a similar situation several years ago. I happened to be on-site for an unrelated problem when the TPI bounded into the office trailer and announced he had just rejected 90% of the pipe welds on the project. Knowing the inspector, I asked him what piping code was he inspecting to?

"Its just pipe." he responded.

"I know it is just pipe. It is process piping, so it should be B31.3, but what is the service category?" I asked.

"Its just pipe. How do I know what the service category is?" He snorted.

So, I turn to the Project Manager and ask him the same question.

"Its just pipe." was his response.

Since the contractor installing the pipe was one of my clients, I ventured on to the job site to hunt down the supervisor. When I found him I told him, "The inspector just rejected 90% of your pipe welds. What is the piping code and what is the service category?" I asked.

"Its just pipe Al." was the response.

"B31.3 is the piping code that is most likely specified, but the service category is going to make a major difference in the acceptance criteria." I told him.

"The project specification is in the desk over there." he said.

I rifled the desk and found the project specifications. It listed B31.3, category normal service. Only two of the 100 or so welded joint rejected by the inspector did not meet the VT acceptance criteria. However, the integrally reinforced branch fittings he did accept; none of them were welded right. In the middle of a (almost) stainless steel system, i.e., tanks, pipes, catwalks, ladders, etc., was a cast iron fitting. A cast iron fitting that was well rusted in the middle of an all stainless steel system didn't seem to bother the inspector in the least.

Gotta go do something useful.

Best regards - Al
Parent - - By G.S.Crisi (****) Date 01-03-2011 22:21
Compressed gases piping falls sometimes under other codes than ASME B31. Chlorine, for example, follows the rules of The Chlorine Institute.
It's possible, but I'm not sure, that compressed air piping is under CAGI (Compressed Air and Gas Institute). I'm going to check and come back to you.
Giovanni S. Crisi
Sao Paulo - Brazil
Parent - By G.S.Crisi (****) Date 01-06-2011 17:56
I've done a quick search on CAGI's website and found nothing regarding steel pipe for compressed air. They do have a recommendation on plastic piping for compressed air distribution.
If you're interested, enter CAGI's website www.cagi.org and write "compressed air piping" on the small search window that appears. 
Giovanni S. Crisi
Parent - - By sae350 (*) Date 01-04-2011 01:13 Edited 01-04-2011 01:15
It would probly be b31.1 section 9 which is pressure piping.
Parent - - By MBSims (****) Date 01-04-2011 04:12
That would be ASME B31.9, Building Services Piping.
Parent - - By ZCat (***) Date 01-06-2011 21:58
Its just pipe, weld it up and fill the pinholes up with paint!
Parent - - By G.S.Crisi (****) Date 01-07-2011 18:44
Back in my days of erector engineer (I'm talking of 40 to 50 years ago), compressed air piping was made of screwed galvanized steel. Pipe ends and fittings were threaded and the joints were made up by screwing. Pipe dope was used as sealant, until Teflon tape (tm of Dupont, I don't want to be put in jail for improper use of brand names) appeared.
Everything worked fine until they (who? I don't know) decided that compressed air piping must be welded. If it's so, welds have to be sound and well made. I'm sorry, but I don't agree with you in filling the pinholes with paint.
Parent - By ZCat (***) Date 01-08-2011 04:18
it was just a joke :(
Up Topic Welding Industry / General Welding Discussion / Welding Air pipe

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