Multiple PWHT allowed

[Lahane]

I had a PQR(P1G1 TO P1G2)done with 2 Hrs soaking time.I build a spool(CS, A105/A 106 Gr B) which has gone for 2 Hrs soaking time as well.Now customer wants me to weld a mounting on the spool.As per customer spec PWHT is needed for Min 2 Hrs.Service is sour.NACE MR0175 is applicable & max production hardness allowed is 200HB.

What I will need to do now?
Shall I weld the mounting on spool & do a localized PWHT for 2 Hrs again.By this way, one of the portion of spool will have a pwht for 4 Hrs.Will my existing PQR with 2 Hrs PWHT will support this?I have never done pwht beyond the PQR time earlier.
As NACE MR 0175 is involved i heard that production piece should go for same pwht cycle as that of original PQR coupon. is it true?

 

[weldtek]

lahane,
Is your PQR qualified in accordance with ASME Sec IX?
Is the WPS impact qualified?

 

[Lahane]

Yes, PQR is qualified with ASME SEC IX & ASME B 31.3.
The PQR is also qualfied with impact test.But the spool piece here does nor require imapact test.

 

[weldtek]

lahane,
If impacts are not required for this application, your PQR will support a WPS with additional PWHT cycles.
I don't believe the additional PWHT will conflict with NACE MR0175.

 

[Lahane]

Is there any limit for additional PWHT time for cs material beyond PQR time if imact is not involved.

 

[weldtek]

For non impact tested applications, Sec IX does not limit the time at PWHT when that PWHT is performed at a temperature below the lower transformation temperature.

Remember this is a minimum requirement and should not be construed to indicate that PWHT is not a crtical process. Your customer may have more stringent requirements.

 

[Lahane]

I agree that PWHT is a essential variable.but why code has not kept any time constraints on PWHT below lower critical temp when impact is not involved.Then by this way if my PQR is qualified with 2 Hrs soaking time i can go for multiple PWHT cycles and my total soaking time of all cycles may go beyond 6 Hrs also. what impact it will have on material property then?