QW-403.6

I have a low temp carbon steel impact tested PQR with a PWHT range of 600 10 . Is this condition giving an exemption for me on QW-403.6 to prepare a wps with maximum interpass temprature of 200 degree , maximun interpass temperature observed during specimen welding=140 Degree

PWHT is an essential variable as per Sec-IX. Please look under any table from QW-252 onwards.

 

To summarize based on the PQR data(max interpass 1400C), on paper max interpass allowed would be 1950C ( when there’s impact requirement), welds shall be subject to PWHT. If you want to refer this PQR for case where PWHT is to be performed but No impact Requirement, you may increase interpass temperature to 2000C.

Per QW-406.3 WPS maximum permitted is PQR value + 55C.  Therefore WPS IP max = 140C + 55C  =  195C

According to ASME IX, QW-406.3, when the Preheat is a supplementary essential variable, an increase of more than 55 degC in the max Interpass temperature requires requalification.

I would suggest you read carefully QW 406.1 to 406.3

Maximum Interpass

Regarding the  max interpass clause QW-406.3, An increase of more than 100°F (55°C) in the maximum interpass temperature recorded on the PQR is considered to be a supplemental essential variable. This does not apply if the PWHT is for C.S is above upper transformation temperature (723⁰C) or for austenitic S.S , when soln annealed.

As the PWHT in your case  is 600⁰±10⁰C. the  max interpass temperature clause as above will apply, second clause as above will not apply.

To summarize based on the PQR data(max interpass 140⁰C), on paper max interpass allowed would be 195⁰C ( when there’s impact requirement), welds shall be subject to PWHT. If you want to refer this PQR for case where PWHT is to be performed but No impact Requirement, you may increase interpass 

temperature to 200⁰C