PWHT

[QC7]

Hi,

I have some query related with Local PWHT of piping spool as per B31.3.

1)Throught out heat tratment cyclce (resticted range) the temperature differential bewteen thermocouples registering peak temperatures shall be within limit of + or - 40degree celsius as per ASME Sec VIII , However what about as per B 31.3, 31.4 & 31.8 ?

2)As per B 31.3, 31.4 & 31.8 what will be the restricted temperature range for P1 and other materials ? And where it has specified in code ? (Genarally resticted temperature range, 300degree celsius following in site)

3)During Pwht heating or cooling rate not maintained as per WPS requirment,then whether re-pwht can apply on same joint ,How many times can do re -pwht on one particular weld joint as per the B31.3 ,B31.4 & B31.8 ?


QC7

 

[weldstan]

1. There is no definition of permitted deviation of T/C measurements during heating - only the minimum/maximum PWHT temps.
2. Restrictive temps are also provided in ASME IX. You need to ;look at the requirements of both the piping codes and ASME IX.
3. There a no restriction r4egarding number of times one can perform PWHT on a weld not subject to PWHT. When impact testinfg is required, ASME Section IX provides the limits on aggregate time at temp.