Preheat and inter pass temperature as per ISO 15614-1 : 2017 A-2019

Clause no. 8.4.8 and 8.4.9 are talking about the reduction is maxi. 50 Deg.C and addition of 50 Deg.C for preheat and inter pass temperature. Suppose, I would like to qualify a WPS and the welding test temperature is say 40 Deg. C(Ambient) for a thickness of 10 mm thick butt joint and the inter pass temperature was 200 Deg.C . In this case, what will be the range for preheat and inter pass temperature to be written in WPS.

Best regards,

Satish Keskar


  • min preheat: -10 deg. C
  • max interpass: 250 deg C

Your question should follow topic

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Thanks for your prompt response…

Can you please explain why the values of preheat and inter pass temperature are 10 Deg C and 250 Deg C…

The rule of - 50 Deg C in preheat and +50 Deg C in inter pass why can not be applied as a rule of standard.

Best regards

10 deg. C is min preheat temperature follows construction code. You can not down lower than construction code.

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I am not familiar with BSEN but in general the variables that recorded on PQR shall be actual variable no matter whether it is essential or non essential.
In your question your test coupon welded in an ambient temperature of 40C with a Max interpass temp of 200 C .
Since your PQR qualified with an ambient (Preheat temp) of 40C you can go down upto -10C with out requalification.
And increase in interpass temperature upto 50 C is allowable that means u can go up to 250C without requalification as per ASME interpass is a supplimenary essential variable (Not sure about BSEN) and u only have to worry about it when there is an impact requirement .

Bien is right like always .

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Okay. Fine. Even though, ISO 15614-1 provides ranges for preheat and interpass temperature, we need to follow construction code.

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