NDE for External Attachments 1

[EAJG]

1 - For an average refinery or production carbon steel pressure vessel, regarding the clips for platforms and ladders, clips for pipe supports, rings for insulation, davits and other external attachments welds , What is the most extended practice weld examination method: MT (magnetic), UT (ultrasonic) or PT (penetrant)?
(DO NOT consider lifting and tailing lugs).

2 - In what extension or how much should these attachment welds be examined: at least all (100%)?, half (50%)?, one in five (20%)?, one in ten (10%)?

I'd appreciate your valuable comments and answers.

 

[JoeTank]

For API storage tanks... clips, brackets, nozzles, etc. would normally be examined by MT or PT

Joe Tank

 

[vesselfab]

if it's p-1 material with no special service or high loads....none

 

[MJCronin]

EA....


What exactly do you mean by "the most extended practice weld examination method" ?

-MJC

 

[zerosum]

As an owner's representative in the chemical process industries (not refinery service as your post stipulates), I would agree with vesselfab.

 

[GRoberts]

In lieu of "none", VT would be the minimum in my opinion.

 

[zerosum]

GRoberts,

VT with retained documentation in the vessel/tank folio?

Good thread to get a cross section of opinions/practices.

 

[HightyHo]

Are you talking about a new vessel or an existing vessel? With new vessels we require VT as a minimum on ALL welds and documenting in the file your inspection results. Process equipment that has been in service is a different story. Thoughts on different load stresses and process upsets should all play a big part in determination of NDE. If you are talking about an existing vessel I would contact a qualified API 510 Inspector for suggestions. Here are a few suggestions on NDE:

VT – Great inspection but sometimes will miss small cracks especially at the toe of the weld. If the unit is painted then imperfections (porosity) in the weld will sometimes become more visible. Cracking can be seen as the propagation occurs with the paint cracking also.

MT – Great inspection, best if the Wet Fluorescent method is used. This is the most sensitive and you can find subsurface imperfections if used properly. The downfall is the electricity required along with low lighting. Most shops use the Dry method for inspection because the low light requirement is not an issue. This method is the least sensitive and is very operator dependent unless large defects are present.

PT – This inspection is used mainly as a supplement to VT. The inspection will only tell you surface flaws. This method is very messy and time consuming.

UT – This method is typically only used on Full Penetration butt welds. I have never personally used this method for inspection on fillet welds (Clips, Insulation Rings, ect…).

Please remember each method compliments the other and the above mentioned methods are just the basics with NDE. There are so many other methods out there that could possibly help you accomplish what is good engineering practice.