· Check the project client specifications to see if PWHT is mandatory. It is unlikely.
· The international standard pipeline design/installation codes would not require PWHT for a pipeline of this diameter and wall thickness.
· The main reason why you may need to apply PWHT is to meet the required hardness limit which the client specification will inevitably require. That is to say if you fail to meet the specified maximum hardness during welding procedure qualification then PWHT would be one way of changing that situation, but not the best way for production reasons. Alternatively your welding engineer should know how to manage this issue by other means, avoiding PWHT, for example by applying more preheat, controlling the sequence of weld passes or by increasing the thermal input during welding.
· The reason for the hardness limit is to avoid sulphide stress corrosion cracking caused by the H2S in the sour condensate. Contrary to what others have said hardness control does not affect hydrogen induced cracking susceptibility, which will occur if the linepipe is susceptible to it and there is H2S in the product. You have to have pipe which has been shown not to be susceptible to HIC.
Alan Denney
AKD Materials Consulting Ltd
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of zhy370137@gmail.com
Sent: 14 September 2016 15:59
To: Materials & Welding <materials-welding@googlegroups.com>
Subject: [MW:25392] PWHT
Dear sir
good day
pls hlep us confirm whether we need apply PWHT for every girth weld according to your experience.
pipe ：API 5 L X60 HIC resistant pipe
welding method: CRC automatic
pipeline diameter and thickness:20inch 0.4inch(10MM)
medium：sour condensate
pressure:960psi
pipeline distance：164km between two gas plant in saudi （safaniya plant to berris gas plant)
client：saudi aramco
CNPC daqing saudi
QAQC
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The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.
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