Flange System for low temp gas stream 1

[green1959]

I am involved in a project to design pressure equipment handling either Nitrogen, Hydrogen, Oxygen or a mixture of these - all at very low temperatures. These will all be in gaseous form within the equipment and in the connecting piping. The design temperature of the equipment and piping is -257C/-430F. Design Pressure is 20 barg. The equipment will be made from Stainless Steel.

Regarding the connections to the equipment: Can anyone please suggest an appropriate "flange system" for these conditions. Is there a standard I can refer to? Whats the minimum allowable temp for ASME B15.5 flanges?

Any help pointing me in the right direction would be appreciated.

 

[PAN]

I understand that you refer to ASME B16.5 (not B15.5).
B16.5 does not mention about minimum temperature service of stainless steel flange.

 

[NozzleTwister]

You might refer to the piping code for your system. ASME B31.3, for example, does establish minimum temperatures for flange and bolting materials.

NozzleTwister
Houston, Texas

 

[Ashereng]

Try calling Air Liquide, Praxair, or one of the gas manufactures and asked them what they use.

If anyone knows, the manufacturers of the gases should.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[Montemayor]

green1959:

Do you have a special reason for flanging absolutely clean gases at cryogenic levels? I have to assume that the gases originate from either a vaporizer of cryogenic liquid (Cryo Storage Tank) or from an Air Separation Plant. In either case, these fluids are the cleanest of all the clean fluids found on the planet. The stuff has had to go through extensive scrubbing, adsorption, filtration, and liquefaction prior to it getting to the gaseous state you are describing. This stuff is so clean that I never flanged it. I either welded or brazed all my piping because I have never found a reason to ever get into the piping or to remove it for maintenance. Besides being costly, flanges constitute a leak and stress weak point as well as a hinderance to critical cold insulation and its specific needs for perfect vapor seal on the insulation.

You say you have to flange to Stainless equipment? Then I would only employ Stainless flanges at that point and weld the rest of the piping. You don't mention the piping material and I have to assume you are going with Stainless there also - or do you propose to employ Cryogenic level Carbon Steel? I wouldn't do that. For 20 BarG you'll find the Low Temp Carbon Steel more expensive as piping material.

I believe that checking with PraxAir will confirm what I say. Keep us posted.

 

[JLSeagull]

I too am watching the responses. I noticed that the flange tables start at -29 degree F. However, I have installed flanged stainless steel on equipment rated to -150 degree C.