SRI Ball valve problem sealing

[Thirlmere]

Hi Guys, we have an SRI ball valve in our workshop and we're having a hell of a job getting it to pass the seat test.
The seats are not spring loaded onto the ball.

How can we get the seat to move over and seal on the ball?

The seat is relatively free within its pocket, but it has an 'o' ring to creat a seal between the seat ring and pocket.

Any ideas?

Thanks

 

[gerhardl]

Please provide drawings and details of valve, seat construction and kind of leakage observed. SRI? (SUD ROBINETTERIE INDUSTRIE?).

Most small leakages for ball-valves under leakage testing stems from hairline scratches, not easily observed, in sealing surfaces on sealing rings and ball surface. In addition: O -ring might be twisted, scratced, old/unelastic or wrong dimension, and surfaces against O-ring damaged (or wrongly machined if new valve). Check for same if seat sealing rings are elastomere.

Correct procedure and pressure/fluid for the leakage test, and test according to accepted test from the facture and valve's specification?

 

[Thirlmere]

I'm afraid i don't have any drawings of the valve. The valve is soft seated and yes it is SUD ROBINETTERIE INDUSTRIE.

Brand new seat rings, brand new seats inserted into the rings by the manufacturer, brand new ball.
New seal kit all round, so new 'o' rings too.

We have carried out the body test ok, and one seat test has been fine. We just can't get it to seal going the other way.

We test according to our own specs which encompass API standards. Actually its a combination of ours and the client specs.
The seat rings are easy moving without the 'o' ring in but we don't seem to be able to get enough pressure built up to move the seat towards the ball and get a seal once the 'o; ring is in.

The valve is a 16" Class 600

Pretty new to this game so it would be great if someone could give me their version of what the correct testing technique / procedure is for such a valve.

Many thanks inadvance

 

[gerhardl]

Still the same answer: seems to be a mechanical obstruction or an unintended leakage. Wrong parts, mechanical damage or scratches, can the parts be moved at all, sticking surfaces, pressure leakage other than over seats? Damage or deformed from earlier test? Wrong greasing/fluids and rests? Twist, cleaning cloths, metal shavings, paint, cleaning agenst, welding rests ? All intended passages and borings free?

Demount, recheck and reinstall, and be sure that the factory (if you ar not directly the producer) agrees or do it themselves, so that you do not lose any product guarantee.

If you are new to the game, you should note that a number of valves typically fails by installation and first/second tests when new, mostly for reasons given above. New parts, especially when failing, is no guarantee that everything is OK with the parts, parts could be wrongly marked, machined, installed or damaged when installed and tested.

 

[Thirlmere]

I suppose technically, its possible for the pressure we apply to push past the 'o' ring between the seat ring and the pocket it sits in and out the other end of the valve.
The 'o' ring is manufacturer supplied and feels ok.

Wrong parts should be ruled out as we have new parts in both ends and a new ball. One end seals ok, one doesn't. Obviously scratched are a possibility but we can't see any after partially stripping to make an assessment.

Should this valve have a certain amount of grease pumped into it before test, or is that generally only a secondary seal option?

Thanks

 

[EnergyMix]

Why would you pass a valve that requires greasing before it seats? Seems like that would be cause to reject the valve.
You say you're using your own standards that encompass the API standards. Are you sure that the valve was designed to seat in the direction you're trying to test it in? Did the manufacturer know that would test it to this company standard?

Want to know the do's and don'ts of Eng-Tips? Read FAQ731-376.
English not your native language? Looking for some help in getting your question across to others or understanding their answers? Go to forum1529.

 

[Thirlmere]

I was merely asking the question whether it was normal to grease the valve or not. Thanks for your feedback.

We test according to our company standards. The manufacturer obvioulsy doeesn't know we'd be testing to these standards, its not a new valve, just a repair.

Thanks

 

[EnergyMix]

Thirlmere,

Maybe it's just my industry, but it's a big no-no in the nuclear world to grease a valve to get it to pass a leak test. Didn't realize it was a repair; was thinking it was a new valve you were testing as you hadn't said otherwise. That might indicate that something might not have been put back together properly.

Want to know the do's and don'ts of Eng-Tips? Read FAQ731-376.
English not your native language? Looking for some help in getting your question across to others or understanding their answers? Go to forum1529.

 

[MikeHalloran]

It's time for you, personally, to execute a disassembly and close inspection, or supervise it very very closely. What you're looking for is imperfections in the parts that were salvaged, imperfections in the new parts, and anomalies in the procedure.

You might as well replace all the seals you encounter just for fun.
Do inspect the ones you remove, looking in particular for cuts, nicks, or inclusions of foreign material.

Before doing that, you might review the history of the technician who did the repair in the first place. If it was his first repair ever, or if she's worthless on some days, or if every valve he ever touched has leaked, that may be the root of your problem.



Mike Halloran
Pembroke Pines, FL, USA

 

[Thirlmere]

OK guys, this is where we are. Valve seat ring with soft seat removed and inspected. Seems to be pretty good and no visible problem.
Used engineering blue on the soft seat and placed seat ring over ball. Once again pretty good. Fill up ring with water and one or two leaks visible.
Ring not under compression at all at this stage.

Is lapping a soft seat an option?

Thanks

 

[MikeHalloran]

When you lap soft stuff, you may have difficulty removing the abrasive when you are done. That may or may not be a problem, depending on how hard the ball is.

Which brings up a point; how hard is the seat? I haven't noticed the seat material being identified.

Are the seats symmetrical? I.e. if you can swap them end for end, and the leak follows the seal, that would suggest that the seal is a problem. If not, that suggests the seal seat may be out of round. Can you measure runout of the seat faces?





Mike Halloran
Pembroke Pines, FL, USA

 

[Thirlmere]

Hi guys, late friday we decided to lap the PTFE seats to the ball. Prior to the lapping, we placed the seat ring on top of the ball and filled the ring with water. in 5 or 6 places the water ran thru the ring and down the ball.
We lapped the soft seat to the ball and now we have no visible leakage, although its obviously under no pressure at all.

On monday we shall re-assemble and test.

Thanks again for all your help

Cheers

 

[EnergyMix]

Good luck with the reassembly.

Want to know the do's and don'ts of Eng-Tips? Read FAQ731-376.
English not your native language? Looking for some help in getting your question across to others or understanding their answers? Go to forum1529.

 

[gerhardl]

Good luck, all well?!

Happy to see it was the normal thing for the branch: when somethings does not work, something is not in order!

 

[Thirlmere]

Hi guys, just an update on the valve situation.

body / shell test passed.
Seat A passed.
Seat B currently failing.

Need to strip and lap seat to ball (again)

Cheers

 

[MikeHalloran]

Did this valve happen to get frozen while it was full of water?

Something is not right.


Mike Halloran
Pembroke Pines, FL, USA

 

[gerhardl]

What about material quality of the seatrings? Too soft materials in the seatring and some leakage maight combine to draw and misform the leaking point further. To be replaced by better (other) materials or glass fiber or carbon reinforced material?

 

[Thirlmere]

Hi, not the valve did not get frozen at all as far as i know.
Not sure what temps it might experience in the field, but its certainly never been frozen whilst its been in our possession. asked the question?

The seats were supplied brand new for this valve by the OEM, so i'd like to think they are the correct ones.

We have assembled the valve again today and carried out as many leak tests as we can whilst it was apart.
The tests involved lapping the seat to the ball, then filling the seat ring with water and using compressed air, blowing around the bottom of the seat ring in order to see if any bubbles came up thru the seat.

Initially they did, but after further lapping we had nothing.

Tomorrow morning we shall test once again.

I'm just about all out of ideas if it fails tomorrow :-(

Cheers

 

[Thirlmere]

I'm happy to report the valve has now passed hydrostatic test on all aspects.

Thanks a million for all your input.

Very much appreciated

 

[greg1950]

It sounds like it was an out of tolerance part. Had the valve been repaired before? Sometimes a valve repair facility will machine the seat pocket during the repair process and then install a custom ring to fit the new slightly deeper pocket. That creates a problem in that OEM seats will now no longer operate correctly in the altered seat pocket if installed during the next repair cycle.

Greg Johnson
Houston, Texas