Ball valve high passing rate problem

[kassem86]

Peace upon you[highlight #204A87][/highlight]

Good day

we have leakage problems in ball valves size 24 - 20- 16 inch i tried to inject the recommended sealant from the manufacturer but still i make a leak test and the same problem exist and i inject flashing chemicals also.

so i need a recommended type of sealant or a new technique to solve this problem.

the working field: natural gas transmission pipeline 70-40 bar 10-30 C

 

[LittleInch]

Sounds to me like either your ball is heavily scratched / corroded or your seat material is damaged.

Your only real option is to remove the valve from service and send to workshop / valve supplier for repair and maintenence.

Valve sealant is only a last resort to obtain bubble tightness if absolutely required and should not be seen as a general use sealant or to make a leaking valve non leaking

Usually you find that these valves have been opened against high differential pressure or have been used for throttling, both of which will lead to a level of damage which cannot be repaired externally by use of sealants.

How old are these valves?
What is their use and have they been subject to opening under pressure?
Are the valves being used in the correct direction or are they bi-directional?
Have you vented the inner chamber down to see which seat is leaking?
Are the seats single or double piston effect?
What type of seats are they?

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[kassem86]

Dear LittleInch


thanks a lot for your reply

the valves are 15 years old

isolate sections in gas pipeline ( on / off)

bi-directional

double piston effect

metal seats

but those valves damaged after hydraulic tests of the pipeline.they are always opened as they supply a pressure reduction metering station non stop operation high flow rates 420 cubic meter/hour?

I want to know if there is any other types of sealant that can deal with highly scratched ball valves

 

[LittleInch]

Not that I know of or would trust.

Your only option is to remove them and replace or repair the balls and seats. Metal seats are great, but don't seal tight after a few operations / years of operations, especially if you open them under high differential pressure.

If they are double piston you could always try venting the body down and seeing if the leakage rate past the upper seal is less than your venting rate.... I still wouldn't want to do any work D/s of these valves though.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way