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Painting before hydrotest

Painting before hydrotest

Painting before hydrotest

(OP)
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?

RE: Painting before hydrotest

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.

RE: Painting before hydrotest

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.

RE: Painting before hydrotest

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

RE: Painting before hydrotest

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.

RE: Painting before hydrotest

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.

RE: Painting before hydrotest

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.

RE: Painting before hydrotest

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: www.oil-gas-consulting.com

RE: Painting before hydrotest

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.

RE: Painting before hydrotest

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.

RE: Painting before hydrotest

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.

RE: Painting before hydrotest

Painting before hydrotest witness should not be done.

RE: Painting before hydrotest

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

RE: Painting before hydrotest

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

RE: Painting before hydrotest

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.

RE: Painting before hydrotest

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: www.oil-gas-consulting.com

RE: Painting before hydrotest

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.

RE: Painting before hydrotest

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

RE: Painting before hydrotest

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

RE: Painting before hydrotest

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

RE: Painting before hydrotest

gr2vessels
The amount of testing done on the welds is not the same for each and every vessel.
If the client is happy to paint first before hydro then its his decision – he’s paying remember.
If the codes are so outdated then why do all the major oil / chemical companies still insist on hydro first then paint?
Have you ever convinced a client to paint first using your engineering skills?

RE: Painting before hydrotest

I am one of the "Clients"..
I do mind if any fabricator in Australia would contradict the AS1210, Clause 5.10.2.5 and sure it will mind the witnessing inspector also. A specific interdiction in the AS1210 is not the Client's option, paying or not. I don't mind to discuss options with the ASME, PD fabricators and involve the AI in discussions... Some fabricators would voluntarily increase their NDE's at no extra cost to the Client, if the painting before hydro would benefit them. However, one has to weigh-up the benefit of extra NDE, to eliminate the surprise of undetected weld pore (highly unlikely anyway with the WPS/PQR and NDE's)
It's quite a frequent occurence these days to allow the fabricator to paint before hydrotest, if this will shorten the delivery by 3 weeks, for eg. Any damage to the paint is obviously at his cost. Yes, I'm using my engineering skils, together with the fabricator's skils, to maximise the hydrotest purpose and minimise the damages risk.
cheers,
gr2vessels

RE: Painting before hydrotest

By client do you mean the end user or the engineering contractor acting on behalf of the client?

RE: Painting before hydrotest

No matter how well-proven the WPS may be defects will occur. There is a high probability of a difference in quality between a procedural weld test and a production weld in shop or field - nothing will persuade me otherwise. Small pinholes are notoriously easy to miss by RT/UT and/or MT/PT, if they were not then corrosion monitiring would be much simplified.

I would suggest that the tradition holds  - hydrotest before paint.

Nigel Armstrong
Karachaganak Petroleum
Kazakhstan

RE: Painting before hydrotest

So:  no concern about the effects of painting prep, including blasting, on the wall thickness of the materials involved?  Never seen a blaster remove a bit too much material then?!  Or damage an improperly masked flange face?

It's the owner's call.

BTW, in the case of an internally lined vessel I'd want the hydrotest done FIRST, along with any other NDE required to ensure that I was able to deposit a holiday-free coating- and then a coating inspection done afterward.  The last thing you'd want to do is to put an expensive internal coating on something which is scrap!

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