Dear all, I too agree to the fact that Mr. Bapat has mentioned. Peening the weld in steam service has higher risk level especially pressure vessel. In case of low pressure steam service try to arrest the leak with the help of online sealing as a temporary measure, provided its an emergency. Later on as mentioned by Mr. Bapat, go for complete UT and find the leak path. |
From: Ramesh Bapat <rbapat@hotmail.com>;
To: <materials-welding@googlegroups.com>;
Subject: [MW:21248] RE: 21247] peening as a temporary repair
Sent: Wed, Jun 25, 2014 2:05:14 AM
I suggest against it in an existing vessel in steam service. Peening may take care of a surface indication or stop up a pin hole leakage, but one has no idea if the root cause may or may not be a lot bigger than what can visually be detected. Steam is erosive. It will eat metal away fast. Also if steam flashes, it can hammer, which will result in the possibility of high stress concentrations at points of stress risers in such as nozzle to shell welds (corner joints) which over time, can cause stress cracking. I suggest you to take this vessel out of service, perform a UT examination at the location of the indication (Try to discover the path of failure), remove the defective weld to sound metal by grinding, PT examine the repair area, re-weld it, PT the cover pass, perform local PWHT if required by code, and re-hydro test it. I would not risk the possibility of blowing a nozzle off the vessel wall for a quick fix of a leaky weld in steam service. Thanks
Ramesh Bapat
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Adriaan Stoltz
Good day valued members.
Has any of you gentlemen had any experience in temporary repairs on carbon steel pressure vessel by means of mechanical peening? A steam leak was discovered on a Low pressure Heater (300Kpa) at a nozzle to vessel shell weld interface. It seems to be a pinhole through the weld. Is mechanical peening of the defect area considered to be an acceptable means of closing up the leak temporarily until a proper weld repair can be carried out? And if so, is this type of repair documented in any of the in service inspection and repair standards? Your input is greatly appreciated.
Riaan Stoltz RITC Inspection 083 6405909 021 556 4884
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