ASME B31.8.1.4 2

[JmanTexas]

The above referenced code, Paragraph (b) states that "when pipe that has been cold worked for meeting the specified minimum yield strength is subsequently heated to a temperature higher than 900 degrees F (482 degrees C) for any period of time or over 600 degrees F (316 degrees C) for more than 1 hr, the maximum allowable pressure at which it can be used shall not exceed 75% of the value obtained by use of the steel pipe design formula given in para. 841.1.1."

Based on the foregoing, I have to stress relieve a pre-fabricated header in its entirety which includes API 5L X65 x 42" x 0.938 WT line pipe. In my experience, this line pipe is not "...cold worked for meeting the specified minimum yield...". While it is cold rolled and expanded some for tube sizing, this, in my opinion, does not tie me to the ASME B31.8 841.1.4 para. requiring me to reduce the max. allowable pressure. Please advise of any concrete evidence either supporting or opposing my opinion.

 

[salmon2]

X65 should have been hot flat rolled into the final thickness and then spirally welded to tube format. So you are right that you are exempt from that paragraph because it was never cold worked.

 

[metengr]

You are referring to ASME B31.8, section 841.1 Steel Piping Design Requirements. Subsection 841.112 you mention refers to determining the specified minimum yield strength for pipe that is not new pipe purchased under a specification approved by B31.8, so there are options (a) through (c). As stated (b) is what it is and indicates for pipe that has been cold worked you cannot take credit for the higher yield strength because exposure to stress relief or elevated temperature service reduces the benefit of remnant cold work. Look at (a) or (c).

 

[JmanTexas]

metengr - thanks for your replu.

How do I know that the pipe was not "cold worked"? It is purchased from an approved mill from the client I am working for, however, it was purchased from the secondary market. Although we have the MTR's and all checks out fine, the client is still asking about cold working - - I did not think pipe manufacturers performed any cold working specifically to meet a specified minimum yield strength for X60-X65 pipe.

 

[blacksmith37]

I expect that strength level is a "control rolled / microalloyed" steel. Look for Nb/Cb, V, Ti in the chemistry :in which case it was finished at a "high" temp like 1200F and ppt hardened as it cooled in the coil. My experirnce with these steels was that they were very resistant to softening at temps up to 900F.
To make the customer happy ,heat treat samples at a couple temps and tensile test (hardness tests are not good for yield strength).

 

[salmon2]

With this strength level, you can get it either by normalizing heat treatment or thermomechanically rolled HSLA steel, both of them are not related to cold work.

You should be able to confirm none cold work by MTR. I don't have a MTR about line pipe on hand, but I got one ASTM A519 right here and it says seamless hot rolled. Another way to prove it has no cold work effect is to get a metallographic picture showing grain structures on a longitudinal direction. Cold work will give you elongated grain structure.