[MW:9652] RE: 9641] RE: 9622] Weld Repair on PTFE lined vessel

As an alternative to Herman’s recommendations, you might consider undertaking an Engineering Critical Assessment (ECA).  I realize that the toe geometry probably fails to meet code requirements, but if it can be proven through ECA that the joint is “fit for service” in its present condition, especially since further alteration may do more harm than good, then your customer may be inclined to accept your work as-is.

 

Also, while I agree with Herman’s suggestion to apply high-frequency peening, I would caution that this operation will not appreciably restore the static bending strength of the joint to its intended design level.  In other words, peening can be expected to have virtually no effect on its resistance to plastic collapse.  However, peening should significantly improve its fatigue performance, which actually may be more important than static strength, depending on the service conditions.

 

--Robert

 

 

From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Pieper QSI
Sent: Tuesday, February 01, 2011 4:18 AM
To: materials-welding@googlegroups.com
Subject: [MW:9641] RE: 9622] Weld Repair on PTFE lined vessel

 

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 3^rd 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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