12" Ball Valve Repair

[Eng_Jay]

Hi,

Newbie in the forum here !!

We have a 12" Ball Valve ( Trunion Mounted ) installed in our corrosive oil line, the OEM provided ENP coating for the ball, which lead to peeling of the coating and increased the opening torque of the Valve.
We have now decided to repair the Ball using SS316 overlay cladding ( 3mm ).
Now we are in dilemma, that what repair standard we have to follow, as no API RP ( API6DR or 621 ) states about ball repair procedure including the requirement of Post Weld Heattreatment and required surface finish of the ball.
Do anyone knows which Standard have to be followed for ball weld repair and is PWH is required for it and reccomended overlay thickness ?
Also about Ra value and machining methodology

 

[PeterIgg]

Sounds like a world of pain you are making for yourself. If 316 is the answer cannot the OEM provide a full 316 ball? It is going to be far cheaper than the route you are outlining. How are you going to get the ball spherical after welding? Ball grinding is a specialized operation that you will not find in many machining shops. You do not say what class of valve or any other detail but I would be looking at buying a new valve before undertaking this action yourself, I'm sure that you'll find a stockist with a suitable valve in less time than it'll take to weld and remachine.

 

[LittleInch]

I was thinking much the same thing. Really not sure how you can add 3mm to the existing ball and have it fit and work in the same space as before??

If the ENP is not good enough then just buy a replacement ball in 316 ready made, round and smooth.

Repairs and the standards associated are really a vendor thing. Also the fact that the standards don't mention it should tell you something, i.e. no one sees it as being something to be done, just replaced.

If you thought the sealing and torque was bad with the ENP, then wait until you try and do some local repair on the ball. This will leak 10 times as much and be harder to turn than before.

 

[johnengkol]

Agree with @LittleInch and @PeterIgg.
Another point of view may be help.
ENP can be suitable for corrosive service but, if you can mitigate the root cause of this peel off the ENP of your valve, it can be much easier to present to your management and brainstorming with your valve vendor that even with current services condition, the ENP concept is failed to protect the system. may be velocity very high or highly corrosive substance on your fluids. Just take a look to your process documentation, calculation, etc.

Then use the SS316 solid material might be the only one solution, instead of keep using plating, cladding, or weld overlay again with repetitive maintenance in short time.