Equalize Pressure for 18" Ball Valve
Equalize Pressure for 18" Ball Valve
(OP)
We have found one 18” Metaltite ball valve (full-bore, fail-close), from KTM, cannot be operated (cannot command to open), even though the equalize valve was already opened and the differential pressure across the valve was already 0 bard. Please be noted that there was no fault in actuator system.
Normally, this valve is always left open, while its operating condition (gas pressure) is around 70 barg. However, when we tried to reduce some gas pressure, we found that this valve can be opened.
After checking and comparing with other valve with the same size and type (also same actuator type), we found that some valves have tubing connection from the valve’s drain port to one side of differential pressure transmitter (low-pressure side).
Then, here come the questions:
- What is the function of this connection? Is it a balance line?
- Is this connection a must for this failed-to-open valve? If yes, why do we find some valves that can be operated without this connection? Do the operation conditions (pressure) concern?
- Are there any papers/articles/document regarding this application? If yes, please kindly advice.
Normally, this valve is always left open, while its operating condition (gas pressure) is around 70 barg. However, when we tried to reduce some gas pressure, we found that this valve can be opened.
After checking and comparing with other valve with the same size and type (also same actuator type), we found that some valves have tubing connection from the valve’s drain port to one side of differential pressure transmitter (low-pressure side).
Then, here come the questions:
- What is the function of this connection? Is it a balance line?
- Is this connection a must for this failed-to-open valve? If yes, why do we find some valves that can be operated without this connection? Do the operation conditions (pressure) concern?
- Are there any papers/articles/document regarding this application? If yes, please kindly advice.





RE: Equalize Pressure for 18" Ball Valve
BigInch
-born in the trenches.
http://virtualpipeline.spaces.msn.com
RE: Equalize Pressure for 18" Ball Valve
I suspect that the main valve could be siezed do to non use. If this is a pneumatically acutated valve (it must be actuated to be fail closed), consider applying higher air pressure using an air cylinder. Be very careful regarding the maximum pressure rating for the actuator if you go this direction.
RE: Equalize Pressure for 18" Ball Valve
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RE: Equalize Pressure for 18" Ball Valve
Max pressure in the actuator, some big-strong guys, >pushing< on a big cheater bar. ( Use appropriate care: Don't let anybody get in front of it 'cause once the valve starts to move it will likely go fast and it could cause an ouchie.)
RE: Equalize Pressure for 18" Ball Valve
For comments on increasing air pressure at the actuator, we have tried rising the pressure to 6 bar (25% increase from normally 4.8 bar), unfortunately, this could not help.
For comments on valve siezed, it might be possible. However, why the valve was siezed? Only from its non-operate? And why reducing some pressure in the line can make the valve re-operable?
Moreover, when thinking of the other valves (same size, same type), that have a connection from the valve's drain port to discharge side of differential pressure transmitter, I still wonder for the purpose of this connection. Also for equalization? Why using drain port? And why connect to one side of differential pressure transmitter instead of equalized valve?
Do anyone have any idea?
RE: Equalize Pressure for 18" Ball Valve
Reducing pressure in the line will take some force off the contacting parts and thereby reduce any friction between the components.
I use valve drain connections for drains. If I need a dP, I make separate connections upstream and downstream of the valve.
BigInch
-born in the trenches.
http://virtualpipeline.spaces.msn.com
RE: Equalize Pressure for 18" Ball Valve
RE: Equalize Pressure for 18" Ball Valve
Best Regards,
Scalleke