NDT B31.3 tie-ins

By Dawie Date 07-09-2007 07:13

Good day. We are doing tie-in welds on existing pipelines. The fluids vary from Normal fluids to Category D fluids. My question is this - after the tie-ins are completed what is the extent of the NDT to be done on the pipeline at the tie in point. According to me 100% NDT (UT or radiographic) is necessary on the new welds made but no pressure testing is required on the old sections. One the new sections NDT is to be done according to guidelines set out in B31.3. I can't find anything regarding tie-in welds in B31.3. Regards and thanks!

By CWI555

Date 07-15-2007 07:27

B31.3 is new construction. If for instance your application is in a refinery, you may wish to look at API 570 Inspection, Repair, Alteration, and ReRating of In-service Piping Systems. 570 does specifically mention the answers for your question. For instance, The API 570 inspector is given the call to pressure test or not if deemed necessary and practical by that inspector. Without a pressure test the following applies:

Summerized from API 570
The new segments of the pipe system in question are treated as B31.3 and tested accordingly.

Tie in welds: Any final closure butt weld shall be 100 percent radiographed or UT.
MT or PT shall be performed on the root pass and the completed weld for butt welds and on the completed weld for fillet welds.

If your hot tapping there are other concerns and guides such as API Pub 2201.

I believe you are looking at the wrong code for your application.

Regards,
Gerald