Internal Painting Before Hydrotesting.

[TheMehanic08]

Hello Guyz,

Currently we are fabricating a pressure vessel details as below.

ID = 850 mm
TL to TL = 8500
Design Pressure = 18.0 bar
Design Temperature = 90 deg C
Material = SA 516 Gr 70
No lethal No Sour No H2 service.

The Vessel has dish ends on both its ends and 2 hand-holes. No Manhole; Our proposal of a Manhole to ensure proper painting was rejected by the client.

The above vessel is internal coated, however since it doesn't have a manhole we had proposed the vessel to be internally coated before being hydrotest.
Kindly advise if this is advisable?

Alternatively we plan to put forward the following to the client.

1) Fabricate the entire vessel with a larger length say 100 mm.
2) Test the vessel (to ensure the shell long seams are checked for).
3) Cut open the weld of one dish end at the side with extra length.
4) Paint the vessel internally. Pre paint the cut dish from inside (except for the weld edge preparation region).
5) Reweld the pre painted dish.
6) Retest the vessel.
7) Final touch-up internally the circ seam through the handhole to the best as possible.

The Client was notified about the internal painting not being upto the mark and is accepting the same.

Kindly Advise guys.

 

[TD2K]

I think the client is asking for problems.

Fabricating, hydroesting, then cutting off one end, coat, touch-up and then rehydro? Sounds like a recipe for a mess. You don't say what size the handholes are but I would question how good of a coating touch-up you can do which depends on how it has to be applied.

You don't say what their objection to a manway is and I assume they also wouldn't consider a flanged end but someone on the client's side is not being practical/realistic in my opinion.

 

[SnTMan]

TheMehanic08, painting / coating prior to hydro is permitted under some circumstances, see UG-99(k), if you under ASME Sec VIII, Div 1.

Like TD2K, I dont't care much for your scheme; much prefer to complete the vessel including coating, then hydro and be done with it.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[chicopee]

What if the hydro test fails and welding repairs have to be done, what would happen to the coating at the area of repair within the vessel?

 

[SnTMan]

Definitely better if it could be coated after hydro, but it doesn't seem in the cards. Hopefully the leak test of UG-99(k) would prevent this.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand