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What should be the Flange Rating for LPG / Caustinc Service ???
2

What should be the Flange Rating for LPG / Caustinc Service ???

What should be the Flange Rating for LPG / Caustinc Service ???

(OP)
I am working on a LPG sweetening project in which I am using 2" Sch 80 pipe . The Design pressure is 16.6 barg and temperature is 60C.

My questions are :

1)  I am using Carbon Steel A106 pipe . Is carbon steel is suitable for LPG / caustic service ?

2) If carbon steel is acceptaable , then what will be the flange pressure rating . According to ANSI B16.5 150# rating , A105 flange can sustain 18 barg at 60C . Is there any particular requirement that for LPG srvice flange rating should be above 150 # ?

3) Is there will be a problem in welding a 2" Sch 80 pipe with 150 # rating .

Thankyou and Reagrds
Muhammad Assad Ahmed
Mechanical Engineer

RE: What should be the Flange Rating for LPG / Caustinc Service ???

1.) A106 OK for LPG.  Is this for sodium hydroxide or LPG?
2.) ANSI#150 is OK for your design pressure and temperature.  If there is a requirement for higher pressure, then you are using an incorrect piping design specification.  Apparently your piping design spec covers only systems that will be operating at <= 16.6 Barg and 60ÂșC.  You must find out if your system has a possibility to reach higher pressures.
3.) No problem welding 2" Sch 80 to compatible materials.

   Going the Big Inch! worm
http://virtualpipeline.spaces.msn.com

RE: What should be the Flange Rating for LPG / Caustinc Service ???

For carbon steel, consider stress relieving all welds to avoig stress corrosion cracking if your NAOH concentration is around or greater than 30% by weight or if you can expect temperatures above 60C with a 30% NAOH Concentration.  For lower NAOH concentrations the need to consider stress relieving decreases. For example, at 20% stress relieving should be considered for temperatures at or above 71C.  The relationship isn't linear and you should also factor in non-routine temperatures, say steaming out the line for maintenance.

My reference is a Corrosion Data Survey, 5th Edition, compiled by Norman E. Hamner, National Association of Corrosion engineers, Houston, Texas, 1974.

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