Generally it depends on the WPS, being used. If WPS specify the pre-heating (at certain temperature) then it is mandatory to carry out preheat on next day morning prior to any strike.
As a Good engineering practice, and most of the client specification call for completing Hot pass prior to stop the welding. If you are stopping before ½ thickness deposition or hot pass, need to examine the root pass for defect by PT/MT to ensure that it is free from any cracking.
Regards.
C. K. Purohit
General Manager - QC
KNM Process Systems Sdn Bhd -
HP No. : 6016-3376448
From:
Sent: Monday, February 09, 2009 1:16 AM
To:
Subject: [MW:1518] Significance of HOT PASS
Please let me know for A 106 B 16'' dia 12.7 mm thik pipe to pipe butt joint, if after root pass joint is left as it is for overnight and next morning welder wants to continue with hot pass, can he do welding without any pre heating..
Regards
Rafique
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