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Lower Transformation Temperature

Lower Transformation Temperature

Lower Transformation Temperature

Our PWHT company exceeded the weld procedure for the PWHT temperature of 1300F to 1350F for a 49 pieces of 2", 4", 6" and 10" pipe spools. The materials were ASME SA 333 gr. 6 pipe and ASME SA 350 gr. LF2 flanges welded with E8013-C3 consumables. Our European customer will not accept the 1350F PWHT unless we can prove the 1350F is below the lowest transformation temperature for the materials used otherwise we must qualify another weld procedure with the higher temperature. Can someone tell me what the transformation temperature is or point me in the direction I can find this information?

RE: Lower Transformation Temperature

Go to ASME B31.1, look at Table 129.3.2 titled Approximate Lower Critical Temperatures. Lets see, for P-No 1 material;  1340 deg F. For P-No 3 material; 1350 deg F.

So, with that, you did indeed most likely exceed the lower critical transformation temperature that would require a second PWHT in the correct range below 1330 deg F using a new WPS/PQR reflecting having exceeded the lower critical followed by a second PWHT.

RE: Lower Transformation Temperature


Thanks for the response.

Unfortunately, the later is not an option for us when dealing with the EU welding procedures and additional PWHT to the existing equipment. The equipment has already been painted and would add tremendous amounts of cost to the project.

Our customer will allow us to re-qualify the existing procedure, as previously welded, but with a PWHT of 1350F. If it passes, they will then accept it as is. What I was trying to accomplish was to eliminate additonal costs associated with re-qualifying to EN 287 / 15614.

Another enteresting note is why the weld company we qualified chose to PWHT at 1300F when boiler code and B31.1 both state 1100F to 1200F for P1, group 2 materials.  

RE: Lower Transformation Temperature

The ASME B&PV Code and B31.1 Piping Code only provide minimum PWHT temperatures, while the maximum PWHT temperature is obviously the lower critical transformation temperature, so even 1300 deg F is OK for P-No 1 materials.

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