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

[massad]

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

 

[BigInch]

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 60ºC. 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!

http://virtualpipeline.spaces.msn.com

 

[dtn6770]

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.