Temperature derating factor
Temperature derating factor
(OP)
HI,
Why "Temperature derating factor" not considered in calculating linepipe wall thickness as per ASME B31.4?
Regards,
rizpet23467
Why "Temperature derating factor" not considered in calculating linepipe wall thickness as per ASME B31.4?
Regards,
rizpet23467





RE: Temperature derating factor
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RE: Temperature derating factor
See 400.1.2 is a little bit more specific stating that the code was not developed for use outside the temperatures range of -20F (-30C) to 250F (120C), however actual temperature limits of the code are not specifically stated.
In the above and in Table 403.2.1-1 you see that B31.4 does not set allowable stresses at various temperatures as does B31.3. The temperatures encountered in pipeline work seldom reach outside the codes stated applicability range 4012.3.7. Inside the B31.4 stated temperature range, no adjustment of material properties, ie. yield stress for temperatures different from those given at 100F is necessary (404.1.2). When (if) designing for temperatures outside of the above range you would first adjust yield stress for the higher temperature, then calculate the allowable stress from that. At lower temperatures you would take caution in regard to potential for brittle fracture.
RE: Temperature derating factor
I know the valve stations, pig stations, etc are short, but they would go lower in the colder climes.
RE: Temperature derating factor
RE: Temperature derating factor
The materials listed are all basically carbon steels of one form or another and I would have no issue with that, but beware temperature yield de-rating would apply for other steels such as stainless or duplex.
For pipe exposed to metal temperatures below -30, then as the notes in the attached thread say, you really need low temperature pipe material and test it accordingly.
31.4 isn't very clear about what you do outside of -30 to +120 or how to use different pipe, at least as far as I can see other than to say in note a of table 403.3.1-1 that Sy = SMYS of the pipe material. The inference is that outside of the temperature range or the materials listed, you use SMYS at the design temperatures you have.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.