Measuring thickness at crevice area -what is the best NDT method? 1

[cducracker]

Dear team members,

Good morning to all, During our on-stream inspection at jetty facilities area, we noticed most of the area in between pipe to pipe support were corroded(crevice corrosion) with sign of metal loss. Some of these piping especially small bore had been lifted, descaled by using hand tool and measured the actual thickness by using pit gauge. But the problem is, how about the big bore piping. Is it any NDT method that we can employ to measure the actual thickness of corroded area without lifting the particular piping. Appreciate if team members can also give the best preventive action. Looking forward for the response. Thank you Regards

 

[CheMechanical]

Cracker,

If it's critical you measure the corrosion at these inaccessible spots and an internal inspection cannot be performed, I recommend you consider the following approach for each location where an examination is required:

1. Install a temporary support near original support location.

2. Cut or unbolt and remove existing support.

3. Clean and inspect pipe using pit gauge or UT (ultrasonic).

4. Repair and recoat (or replace) pitted sections.

5. Reinstall existing support (or install new support) using insulation material to prevent pipe-to-support contact. Consider installing a wear pad if appropriate.

6. Remove temporary support.

If internal inspection is available, try using a UT tool (inspection pig). Modifications may be required to the pipe to run the tool through the line.

Hope this helps.

Jerry Myers, P.E. (Chemical/Mechanical)
Senior Engineer