Hello KCR,
The prime acceptance criteria for any tube bends is good workmanship.Tube bends shall be free from cracks or dent marks as above and the wall thinning should be within the limits set forth by PG-19 & PG-20.See table PG-19 and PG-20 (for P91 alloys) as guidance.
Given a choice these superheater tubes shall not be accepted for a new boiler is as it is condition..These damaged areas would cause premature failures, though,corrosion fatigue or any other form of service induced failures where those external dents could act as serious stress raisers. Superheaters operate at extreme high pressure and temperature regime and failures of supreheaters could mean costly both in terms of repair an outages(shutdowns).
What're the materials of construction? Are they austenetic stainless steels or P-91/P-92 alloys.
If the damages are local, it may be repaired after discussion with client. Most preferred welding methods would be GTAW (pulsed) or GMAW (STT). It would be advisable to develop are repair procedure/ mock-up to keep the suggested welding parameters under control. Austenitc S.S may not be stress relieved following repair but P-91/P-92 alloys must be subject to PWHT following repair.
Let me know if it helps.
Thanks.
Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist & Consultant
Ontario,Canada.
Email-pgoswami@sympatico.ca,
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of kcrtechnical
Sent: Saturday, September 03, 2011 5:28 AM
To: materials-welding@googlegroups.com
Subject: [MW:12335] Boiler Super heater U TUbe Bend_Kink_Reg.,
Dear Friends,
We like to know what is the acceptance critaria on SuperHeater U Tube bends kink as shown in Photo. Construction code ASME Section I
Best regards
K C R
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