Changes In the 2012 Edition of ASME B31.3

Bryon,

If you use Equation 1b, the result can be as high as 414 MPa when SL = 0 and f = 1.2.

Sa = f [1.25(138 + 138) - 0] = 414 MPa max.

Have fun!

Don Frikken

I'm not familiar enough with ASME B&PV Code Section IX to know if there is an exception to the rule you describe. If the material is not sufficiently ductile to withstand the bend test, it may not be suitable for use as a piping material, at least is some applications. Note that the material might still be used for piping without welding according to ASME B31.3 if it can be otherwise qualified.

Thank you for this prompt reply. These specific materials are used for petrochem furnace, due to good properties for creep resistance and also oxydation resistance.
The design code of these furnaces is mainly API 530 referring to ASME B31.3. Before the revision 2012, I was able to achieve the PQR with the bend tests by stating the para 328.2.1 of ASME B31.3 (prior to 2012 edition) to pass the PQR. I'm now very confused about that! These possibility was also stated in ASTM A488 (casting products). I cannot find any information about the changement of ASME B31.3.

That revision was made as part of a general update to para. 328. I’m pretty sure no one recognized the problem with the deletion of the provision. I will recommend that the committee consider reinstating the old para. 328.2.1(b), but if it is approved, it won’t appear until the 2016 or 2018 editions. Two approaches you can take for now: 1) Many people do not consider the piping you describe as being within the scope of B31.3. If you can take that approach, then you could write your own rules for welder qualification. 2) You can use the rule described in para. 300(c)(3) to justify qualification by the old requirement.

Thank you for your help. I think temporary both solutions can help myself. Do you know how explain my request to the committee?

I sent the request to the committee. I already have a response from Phil Flenner. He says:
The test bend requirements of Section IX is actually slightly less restrictive than the requirements that were in 328 for bends. If the base materials have a ductility less than 20%, QW-466.1 allows an adjustment for the bends per Note 1 that was somewhat less restrictive than 328 bend test requirements.

High strength steels have about the same fatigue resistance as low strength steels, especially for low cycle fatigue. Using the higher values of Sc and Sh when calculating SA gave higher allowable stress ranges for the high strength steels than the materials were capable of accepting. Limiting Sc and Sh to 20,000 psi corrects this problem.

Thanks for your reply. I am still not clear on,
1. Why to consider fatigue when in general the displacement stress range is with the consideration of shake down to elastic cycling
2. This can be valid if f>1(Sc & Sh be limited to 20000psi)
3. Most of the plant is designed for f

Even when the stress range is less than two times yield, the materials cannot be cycled forever without failure. That is why the Code has the stress range factor, f, as part of the equaiton. Figure 302.3.5 illustrates this point.
When f is greater than one, the limit on Sc and Sh applies as you say.,
I agree that, in general, 90 plus percent of piping in process plants has f greater than or equal to 1.

Limiting Sc and Sh to 138 MPa applies no matter what the value of f is. Without this limit, the allowable stress range could be higher than 414 MPa for high strength steels when f = 1.0 or less. For example, SA could be as high as 617 MPa for X80 material.