Class 150 flange temperature limitations
Class 150 flange temperature limitations
(OP)
I'm currently working on a project with 18" class 150 HVGO suction piping from the vacuum tower to the pumps. Operating temperature can be from 530F up to 600F and class 150 flanges meets the design pressure and temperature requirement. We are reviewing whether class 150 flanges should be used or should be use class 300 flanges?
I'm aware of section 2.4.2 in B16.5 which talks about the tendency for class 150 carbon steel flanges over 400F to relax and develop leaks if exposed to severe thermal cycles and/or external loads and the need to check bolt tightness.
One of our engineers recalls seeing a section (he thought it was in B16.5) recommending/suggesting minimum class 300 flanges be used when operating temperatures were over 400F. While it's similar to section 2.4.2, he thought it specifically suggested class 300 flanges.
Does this ring a bell with anyone? I've gone through B16.5 and B31.3 and can't seem to find such a recommendation.
I'm aware of section 2.4.2 in B16.5 which talks about the tendency for class 150 carbon steel flanges over 400F to relax and develop leaks if exposed to severe thermal cycles and/or external loads and the need to check bolt tightness.
One of our engineers recalls seeing a section (he thought it was in B16.5) recommending/suggesting minimum class 300 flanges be used when operating temperatures were over 400F. While it's similar to section 2.4.2, he thought it specifically suggested class 300 flanges.
Does this ring a bell with anyone? I've gone through B16.5 and B31.3 and can't seem to find such a recommendation.





RE: Class 150 flange temperature limitations
Our specification crossed over at 300°F mainly due to getting the gasket seating stresses for the higher temperature gaskets required.
We have some areas where the piping specs calls out all Class 300 C/S flanges due to the recognized problems with the 3" and 8" flanges if used with spiral wound gaskets.
S/S was all Class 300 above 150 PSIG and/or 300°F.
RE: Class 150 flange temperature limitations