B31.3 'Stress Relief' of process piping
B31.3 'Stress Relief' of process piping
(OP)
Could someone with some experience in stress relieving carbon steel process piping give me some insight on the B31.3 code requirements for this process? Our customer's PID declares a number of pipe weldments to be stress relieved, but that's the only information they give. They have not specified any particular temperature, hold times, or processing requirements. All of the piping is to be done to B31.3.
In the mean time...I'll have my nose in the code. If I'm not back in 15 minutes, please notify my next of kin...
In the mean time...I'll have my nose in the code. If I'm not back in 15 minutes, please notify my next of kin...
Fitter, happier, more productive





RE: B31.3 'Stress Relief' of process piping
RE: B31.3 'Stress Relief' of process piping
to amend your reply with what i assume is an appropriate disclosure: 'unless specified by the customer'.
with the criteria spelled out in B31.3, i wonder why this customer is requiring this? we're talking about 150# class lines with sch 40 wall thickness carrying fluid not in excess of 500°F. Could this be a CYA thing? The runs aren't particularly long either...<40ft.
Fitter, happier, more productive
RE: B31.3 'Stress Relief' of process piping
RE: B31.3 'Stress Relief' of process piping
Although the code of construction (B31.x or VIII-x etc) may not explicitly require PWHT for a given design, most of them do require that the designer/owners engineer consider the situation as a whole, including the service application. It is not at all unusual to specify PWHT for a system which is in caustic, sour, or otherwise in some "metallurgically unfriendly" service based on good engineering judgment and lessons learned (by the process industry as a whole) from experience.
In the case of B31.3, there are at least a couple of references to this:
From the Introduction: The owner is also responsible for imposing requirements supplementary to those of the Code if necessary to assure safe piping for the proposed installation.
From 300(c)(5): The engineering design shall specify any unusual requirements for a particular service. Where service requirements necessitate measures beyond those required by this Code, such measures shall be specified by the engineering design. Where so specified, the Code requires that they be accomplished.
jt
RE: B31.3 'Stress Relief' of process piping
But not for the Code references he cites (they are way too damn vague)
Caustic service is an example of a process system where stress relief has been recommended and used for many years.
See Table 1 of this reference:
ht
Also Figure 7 of this fine text:
htt
Hydrofluric acid service (as a recall) might be another candidate (!!??)
Anyone care to repond ?
_MJC
RE: B31.3 'Stress Relief' of process piping
The Iranians/Shell oil require stress relief on carbon steel pipe bends that fail a paricular hardness limitation.
See section 2.3.2 of this document:
htt
I do not know if this requirement is from ASME B31.3 or it is understood as "good engineering practice"
It has long been my experience that the Shell Oil standards are industry state of the art
-MJC
RE: B31.3 'Stress Relief' of process piping