Pressure testing of lined butterfly valves 3

[Actionman123]

If you buy a lined butterfly valve according to API 609 cat A, the valve shall be tested according to API 598.
API 598 say that pressure testing shall be done before painting.
But this makes no sense for a lined valve with the liner as sealing surface against the flanges of the pipes.
If you get a leak through the liner, the leak will travel between the liner and the valve body to atmosphere. The leak will not travel through the valve body.
Why do we then have to do the pressure testing before painting of the valve body?

 

[Intotherain]

In my opinion, API598 test is for the valve itself to make sure its quality. Refer to the connection leak, it is outside the valves. In that case(connection leakage)it had nothing to do the valve quality, but may be the assembling problems.

Larry with regards

 

[Actionman123]

Thanks for your reply Intotherain.

The main question is still:
Why do we have to pressuretest a lined valve without paint?

AKA milanflyer@

http://www.valvezone.com

 

[gerhardl]

Although beeing European and not familiar with the mentioned rules, please allow me to try to comment anyway.

All tests/rules for valves, all over the world, have mainly four general purposes:

1. To ensure that measurements, materials and general metal (material) construction of pressure bearing parts (main construction) are OK.

2. To ensure that the finished valve body/pressure bearing parts (with open valve) can withstand a given pressure (given test pressure by given standards).

3. To ensure that the finished valve can operate properly and seal as described over the seat sealing according to given specifications.

None of theese three points exclude the other, and you will often find that the one overlaps to some extent the other.

4. In addition you will have a fourth set of diversified additional rules and tests, as for instance: singel special material tests, painting tests, corrosion tests, emission tests, extended function and operating tests, fire tests, etc. etc.

The end user, or the market (and the valve producers you compete against) will largely give what minimum tests and rules you have to include in your normal production standard to have a high-quality competing product.

If you deviate from the test description given by an authority, you will not have a proper test recognized or qualified by QA-control. If there is doubt on how to understand the test text the issuing company is the only one authorized to answer you.

In some (seldom) cases the description is 'old' in the context that production or construction (by new materials or methodes not available when the original text was described) ought to lead to a correction of the text, but this is not (yet) done. This does not change anything on your side.

Summary: you need to follow the described procedures, even if it gives 'no sense', but nothing will hinder you to put in additional tests to prove to the market that you have a high-quality product.

PS. In some cases a non-painted metal construction that is pressure tested can reveal leakages and materiel faults not occuring when painted.

Anyway, a completed and finished (painted) valve, not pressure and function tested, both for house and seat leakage will be a step lower in quality and preference scale than one from a factory testing all valves for this.

If still in doubt ask your customer directly what tests to use or suggest what you find best.

Good luck!

 

[Actionman123]

Thank you for your valuable input gerhardl.

AKA milanflyer@

http://www.valvezone.com

 

[russoint]

This is for valve manufacturers. They are to test before painting to assure the quality of the casting as the body will then be painted inside and out. To ensure that they do not cover up the interior seal of the body with epoxies so that if there are imperfections in the casting they can find it before finishing the valve. This is for manufacturers and is part of the process of fabrication.


Chance Russo

http://www.russointernational.com

 

[Actionman123]

Thank you russoint for your input.

I have investigated a little bit further.
The valves are made of WCB-material according to ASTM A 216.
This material shall be tested according to ASTM A 703.
In ASTM A703 chapter 11.1, they specify a hydrostatic test of the casting.
I assume this will lead to a hydrostatic pressuretest of a standalone body casting, without internals.

Am I correct to assume this?

AKA milanflyer@

http://www.valvezone.com