Inservice PV inspection. 2

[tc7]

I have an ASME stamped vessel as part of a high pressure (upto 3000 psi) air system. The flask is about 10 yrs old and has not been inspected since the original installation, except for a system hydro and we send the saftey valves out every 3 years for calibration. I am reading the NBIC code (I only have a 1995 copy) requirements for inservice inspection and RB-3233 lists a variety of NDE methods, everything from visual to penetrant to mag, etc., etc. I am the facility manager where the air system is used and so I guess I am considered the "owner". What is the guidance on the method chosen for an inservice inspection and is it common to inspect internal and external surfaces? By the way, this flask has no manway or inspection ports, so an internal inspection can only be done with a bore scope.
Thanks,
Tom

 

[metengr]

tc7;
We have various objects including air receiver tanks. The external inspection is performed every 3 years, concurrent with the operating certificate renewal. Our Jurisdiction mandates operating certificate renewals for unfired pressure vessels every 3 years. This is the time for performing the external/internal inspections.

Based on your post, I would recommend a borescope inspection of the vessel interior surface coupled with an external inspection of the vessel walls and selective ultrasonic thickness testing (UT) at the time you overhaul your safety relief valves. The visual can be performed using a fiber-optic device (borescope). Selective UT provides information as to consistency in wall thickness based on any internal inspection results or signs of distress from the external inspection. If you spot internal corrosion as a result of moisture, the UT will provide information as to the extent of corrosion damage.

 

[tc7]

Thanks Met,
Do I have to strip the paint off of the vessel for UT?
Also, it seems that there is a light coating of rust on the inside, which I don't know how to remove except for a chemical wash. What would your suggestion be for this situation?
Thanks again,
Tom

 

[metengr]

tc7;
If you do not see any evidence of local corrosion pitting attack from the internal visual inspection - leave the oxide layer alone. Locally strip the paint on the exterior surface of the vessel at a few locations (one 4" x 4" area at the top, similar area near the middle and similar area at the bottom) and perform spot UT. You will need to remove the paint to obtain a proper thickness reading. Don't forget to re-paint the surfaces after the UT is completed.

 

[eyec]

one other thing. you would be wise to MT all seam & circumferential welds along with any socket/attachment welds around the safeties.

i agree leave the oxide alone unless you see something glaring from the borescope inspection.

there are some UT meters that can read thru coatings but unless you have been trained on dual trace meters contract someone to do it for you.

 

[tc7]

Thanks for good advice, and will do on MT the welds.
-T