Double offest High Performance Butterfly Valves High Pressure Closure Test Problem

[PPHHWW]

Dear Professions
My company is developing the series of Double offset High Performance Butterfly Valves High Pressure.
Now we have problems regarding the high pressure closure test.
Our product design is to API-609.
So, we follow the API 598 to conduct the pressure testings.
When we do the high pressure closure test, we set the bare stem valves on the test bench, with the seat retaining plate facing the upstream.
We close the disc with a wrench and then remove the wrench.
Then we pressurize the valve to 1.1 times of the rating pressure, it happened that the disc flipped open by the hydraulic force.
However, if we install a handle and notch plate on the same valve and run the test again.
The valve passed the test without any leakage because the disc was fixed by the handle and notch plate.

My question are:
1) Can the handle and notch plate be installed when doing the test?
2) If they can, should the valve which passed the test be regarded as qualified?
3) Although the high pressure closure testing is optional according to API 598, is it actually a mandatory test in the valve business?

Please help. Thank you.

 

[Danlap]

Dear PPHHWW,

1) Can the handle and notch plate be installed when doing the test? Yes, Seat leakage/closure test is assessing the leakage rate between Seat and Disc at 1,1 MAWP for certain test period on (deemed) close position. This is also mean that you may rely on handle and notch plate to ensure it is maintain in close position.
For soft seated butterfly valve, normally to avoid a rubber seat being bulged by the disc, before the blind flange/ testing clamp mounted towards the valve's flange(s) the disc is in partially Open position. After the clamp mounted then ones close the disc and "believe" it is close since handle / positioner pointed to Close position and remain on its position due to Notch plate. Hope you got the impression
2) If they can, should the valve which passed the test be regarded as qualified? Yes
3) Although the high pressure closure testing is optional according to API 598, is it actually a mandatory test in the valve business? I tend to believe that this is mandatory and shall be minimum requirement. Its always benefit the End user's inspection or Process Engineer of how reliable the new valve is in terms of leakage for some first period of time. Among other standard requirement of course.

Regards,
MR

All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected

 

[bcd]

It is a double-offset design, which means pressure will tend to open or close the disc. Depends upon the direction of pressure. Usually the seat, shaft bearing, and packing friction are enough to hold the valve closed for low pressure test. But high pressure test, you will need to prevent the shaft from turning. It is important to read the note at the bottom of the Table in API-598. High pressure closure test can reduce the operation life of the product. Depending upon the design, you can apply a higher load to the plastic seat and deform it more than it would see if put into a lower pressure service. The more the seat deforms, the less material that is left to wear away before the valve leaks. that is the reason for the cautionary note.

Also, point of test is a quality check. Many double offset butterfly valves have pressure energized seals. So it can be easier for the valve to pass the factory test with high pressure than it would be with low pressure. this is why low pressure is mandatory, and high is optional. The low pressure test can better evaluate the quality.

 

[PPHHWW]

Dear Danlap:

Thank you for your valuable answers.
If the valve can be tested as it equipped with a handle and notch plate, that will create another difficulties to us.
This practice might be able to be conducted during the stage of the development, however it would become impractical to do if high pressure closure test would be requested to be a normal production test. The reasons are: 1) it takes time to install and align the handle and notch plate. 2) the the notch plate might become rusted easily after hydraulic testing.
I am just wandering whether it is a normal situation to see the disc opened during the high pressure closure test when testing a bare stem valve?

Regards

 

[PPHHWW]

Dear bcd:

Thank you for your reply.
You are correct. The problem I am facing is that the test pressure helps open the disc when the pressure comes from the side of the seat retaining plate. Apparently, the overall friction are insufficient to hold the valve closed for high pressure test. We ever tried to increase the compression of the seat to increase the friction between the seat the disc. The disc did not flip open, but as a result, the operation torque increased dramatically and was too high comparing with competitors' products. However, if we tired to low our torque to be in line with other manufacturers' torque values, the situation of the disc open occurs.

Can the handle and notch plate be installed when doing the high pressure test?
I am just wandering whether it is a normal situation to see the disc opened during the high pressure closure test when testing a bare stem valve?
Are there any ways to prevent the disc opening except for increase of the seat compression?

Best regards

 

[Danlap]

hi PPHHWW,

I am fully align with bcd remarks.
Let us be clear first, what do you mean with "Double Offset High Performance High Pressure" Butterfly Valves. Are you using rubber / resilient or Metal seated? What is the size(s) and class(es) coverage of this topic? and what is the claim behind High performance e.g. cycle wise, maximum temperature, etc. and warranty over its tight shut off or what? Is your valve bi-directional or (preferably) uni-directional?

Re: I am just wandering whether it is a normal situation to see the disc opened during the high pressure closure test when testing a bare stem valve? Shall I imagine the meaning of flipped open and this is a new condition from manufacturer, then it is not common. Especially when you're claiming to be high performance and high pressure which can be miss-interpreted by most end user. Resilient seat wear over time/cycle, and ones cannot rely with notch plate forever. It may seem close from outside, but since the seat already worn-out then it is passing.

To mitigate your concern and also API 598 over prototype testing (which is lengthy and may reduce the lifetime of the subjected valve) vs production test, you can try to invite NoBo to witness the test of the prototype and sign certificate 3.2 (as minimum). And for the rest of production valve under the same design, size and class can be production tested at low pressure Closure seat. All delivery valve within xx year shall be accompanied with Certificate of Conformity (CoC) referring to 3.2. signed by NoBo. And so on
If you sub your spare parts in the first place, then the CoC should guarantee that the product deliverable manufactured under the same (good quality) sub


Regards,
MR

All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected

 

[PPHHWW]

Dear Danlap:
Thank you for your reply.
Allow me to clarify the basic specification of the "Double Offset High Performance Butterfly Valves" which we are developing.
The valves use resilient (RPTFE) seats. Sizes range from 2" to 12". The rating pressure is Class 150, equals to 285 psig.
The design of the valves conform to API-609 Category B valves. It should be Bi-directional.
Basically, it is similar to ABZ Valve Series 401&402, Jamsbury Series 815.
The practice of the high pressure closure test is according to API 598.
We understand that the high‐pressure closure test of resilient‐seated valves may degrade subsequent sealing performance in low pressure service.
However, although the high pressure closure testing is optional according to API 598, we suspect it actually a mandatory test for the production testing because I found some of competitors' brochures state so.
The problem I am facing is that the test pressure helps open the disc when the pressure comes from the side of the seat retaining plate during the High Pressure Closure Test. In order to prevent the disc opening, we tried to increase the compression of the seat to increase the friction between the seat the disc until the disc stopped opening. But as a result, the operation torque increased dramatically and was too high comparing with competitors' products. If we then tired to low our torque to be in line with other manufacturers' torque values, the situation of the disc open occurs again.

So, if it is acceptable that we install the handle and notch plate on the valve and to do the test, we can lower the torques and pass the test.
That is reason I ask for options on the forum.

Your suggestions of NoBo and certificate 3.2 are appreciated. But we would prefer to only issue certificates 3.1 without third-party witness.

Best regards