Hi,

Can any body tell me why allowable stresses of materials are started from -29 degreeC in ASME Sec. II-D.? Even in the flange rating deciding criteria in B16.5, temperature is started from -29 degreeC.
Is there any benchmark that has been decided by ASME or is there any something else reason?

Please reply me ASAP.

I "think" that it is because standard ASME B16.5 flanges are good as default to -20°F (-29°C). I doubt if there are are many DESIGN condition where the design temperature (I am not talking about MDMT) is < -29°C without using special materials.

Do not challenge me. I just said "I think."