Painting before hydrotest 1

[starrproe]

We have a column, 2m ID x 10.6 m T/T length.
Design pressure is 35.6 kg/cm^2.

We are planning to paint the column prior to final hydrotest in order to save a few days in schedule and deliver it in time.
Is it technically acceptable?

 

[vesselfab]

there have been several studies about the ability of paint to actually plug and seal off small pin holes and other defects.

I know of no users/engineers that would allow it.

 

[roca]

ASME VIII Div 1, UG-99 allows painting before hydro except for items in lethal service (well it does in the version I have).

However it does point out that paint could mask leaks which would otherwise be visible.

No client I have ever worked with has accepted external or internal painting or coating prior to hydrotest.

You need to discuss this with your client.

 

[gr2vessels]

starrproe,
The hydrotest is for checking the joints strength;- if it is feasible to you to mask the welds before painting, the rest can be painted without restriction. Also, if you had lots and lots of tests done on those welds, the hydrotest is only a formality. If the skin of the paint is holding your column together, you should look for another job perhaps.
Cheers,
gr2vessels

 

[miked7]

Hi Starrproe,
You have got this the wrong way around. What is stopping you painting? Is there any part of spec or standard that says do not paint prior hydrotest. If there is then you need to put in a concession. If there is not then you are free to paint before hydrtotest.

 

[davefitz]

As I recall, there are some paints which are brittle after drying, and performing a hydrotetst may lead paint cracking at stress raisers. This implies a paint "holiday" will be formed, and that section will not be protected.

 

[SaCaZu]

But is It neccesary to apply painting before an hydrotest? or is it a procedure to gain time due to few leakages that could happen according to reliable results of RT?

Thanks.

 

[GregLamberson]

starrproe

I'll echo roca, davefitz, and vesselfab - I have not worked for or with an Owner company that would allow paiting before a hydrotest.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[justinwest]

Our AI asked us not to paint and joints before he can witness the hydrotest.
He said we could paint the shell prior, but we saw no point in painting part, only to come back and paint the rest later.
Ultimately, it would be up to your customer, but I would check with your AI to make sure he is happy with the arrangement as well.

 

[Tomtation]

It is permissble to paint before hydrotest but ensure that the external inspection has been done and signed-off by your A.I. otherwise he could make you remove the paint to do his external inspection.

 

[bvi]

If you are a project manager focussed on schedule, or a contractor you will want to paint.

If you are focussed on the final leak tightness of the system, you will not. There is an article by Jon Batey that shows how you could burst vessels with holes drilled in them, that were subsequently painted but before leak testing, that would burst under internal pressure before leaking through the drilled holes that were painted over.

 

[AravindSujay]

Painting before hydrotest witness should not be done.

 

[CodeRef]

I would go even farther and prefer that sandblasting or vessel cleaning (prior to coating) be performed before the hydrotest.

 

[JStephen]

For paint/lining integrity, you generally wouldn't want to sandblast before a hydrotest (unless you blasted again afterwards).

 

[vesselfab]

i would never blast before hydro-test unless the purchaser was willing to pay for the blast (it's no good for painting or coating after test) and all handling to get it outside the shop to blast and extra labor incurred to hydrotest outside of the shop area or handling to move it back inside.

 

[GregLamberson]

Vesselfab/JStephen

Agree 100%, blasting before hydrotest is pointless - as stated, it'll have to get done again.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[PVinspector]

Justinwest,

Did your AI supply a Code reference supporting the no painting rule, or is asking you to tailor your process to his/her personal likes or preferences. AIs are charged with following, enforcing, and verifying the Code rules, not deciding what is sound engineering. If it is not prohibited, it is allowed.

 

[JoeTank]

PVInspector,
While I agree with your basic statement about AI duties, they do sometimes impose upon manuafcturers their own quirky opinions. It's not supposed to be that way, but it does happen. That said, if I were the AI I would not allow painting before hydro either as it could mask a leak. It's not specifically addressed by the Code, but it's a Code-related issue and worthy of action by the AI.

I would also agree that the Code does not cover all instances, but I'm not so sure that I could go as far as agreeing that "If it is not prohibited, it is allowed".

Joe Tank

 

[jamesl]

There is a code interpretation on this issue. The inquiry was about 2 mil or less paint before hydrotest. The answer is yes.

 

[gr2vessels]

Gents,
This topic was well debated, but without a consensus is unfinished. It seems that the coating issue on the vessel, before hydrotest, is raising a leak detection obstruction issue. It is a reflex engineering to have the welds totally open for inspection, particularly during the final, last chance to detect a possible failure. That is in despite of blind fate in the PQR which in many cases is a substitute for good 100% inspection and tests. Better still, we have 100% confidence in the certificates for materials, welding procedure, PWHT, 100% tests and inspections. But no skin of paint on my weld, please, it could cover a tiny leak which went undetected, even after radiography tests, UT's, etc...
Indeed, the blast cleaning would remove that little pore covering, to allow the spring of the leak...However, you have to paint in about 2 hours after the blast cleaning, so you better hurry with the hydrotest, then quickly transport it to the paint shop...unless you paint it before hydrotest..
Gents, there is the Australian Pressure Vessel Code, the AS1210, which specifically prohibites the painting before the hydrotest, to prevent the masking of a potential leak (Clause 5.10.2.5). But again, that was issued in 1997, written probably in '95, '96.
This is a weird word, one is contradicting the other, we should have a common, unified code, valid in China, Australia and Italy also..
Until then, I'll try to be an engineer and use my skils rather than emotions.
cheers,
gr2vessels