Dear Vinod,
In my opinion there is no opportunity to repair undercuts in piping with only 2 mm wall thickness. By welding you will definitely damage the PTFE liner inside the piping.
Only possibility is to change weld geometry in such case that it will no longer be a sharp transition from weld to base material (if third party agrees).
You can do this by burr grinding but with such small wall thickness you will have the risk to remove too much material.
In this case I would propose to use high frequency hammering with a pin which have a radius at the front of min. 2 mm.
By this method you not removing any material but only changing welds profile. Beside that the loss of strength caused by the undercut will be compensated by the introduced compressive stresses in this area.
Met vriendelijke groeten / Best Regards
Herman Pieper
Pieper Quality Support & Inspection
Phone: +31 (0)521 380083
Fax: +31 (0)84 7539225
Cell: +31 (0)6 51691215
www.pieper-qsi.nl
Van: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] Namens Vinod Kataria
Verzonden: dinsdag 1 februari 2011 8:12
Aan: materials-welding@googlegroups.com
Onderwerp: [MW:9622] Weld Repair on PTFE lined vessel
Dear All,
Please see the attached photo for the undercut and advice if it is possible to repair this on PTEF lined vessel the vessel. The size is 2” NB and wall thickness is 2mm with inside PTFE lining of 4mm. We have imported this vessel from Germany but during 3rd party inspection it is rejected because of this undercut. The working pressure of this vessel is only 3.5 bar and its successful withstood a hydro test pressure of 10 bar.
Now I request all the expert to please advice if we can repair this undercut if yes than please provide me some guideline or some procedure to carry out this repairing.
Thanks in advance for your kind help.
With kind regards,
Vinod Kumar Kataria
GM - Operations
Bliss Anand Private Limited,
92B/93B Sector 5
IMT Manesar,Gurgaon,
National Capital Region Delhi.
India .
Phone : +91-124-4366000 (9 Lines)
Mobile Phone : +91-9560199004
Fax : +91-124-2290884
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