High dp across ball valve
High dp across ball valve
(OP)
if there is high dp across the ball valve, will i have difficulties in opening the valve manually? some say yes..some say no....
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High dp across ball valve
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RE: High dp across ball valve
..and all are right. This will depend on necessary opening torque, starting movement of the ball. The opening torque is the largest torque, torque will be smaller when the ball is moving.
Opening torque may vary as much as 1:10 (and more), all else being eqaul on construction and size and pressure for the ball valve, but type of fluid, drying caracteristics, stickiness, abrasive flud rest on ball, compability of fluid to sealing, time closead (deforming of seals over time) etc, etc varying, and giving variation to required opening torque.
If you have clean, compatible fluids, valve constructed for the purpose and operational data within construction limits, gearing adapted to highest torque possible, it should be no problems with hand operation.
What is large dp? What is size? Even with larger sizes (one meter and above,) and fairly large pressures (64 bars), or 160 bars up to 300mm, there is no problem with hand operation with stem gearboxes for double eccentric ball valves constructed for water/clean fluids.
Check that the construction you want to use are suitable for your operational requirements!
RE: High dp across ball valve
David
RE: High dp across ball valve
Don't mislead the guy by stating that all 'Trunnion' ball valves have springs as you did in thread408-134074: Trunion Mounted ball Valve. Take a 'Jamesbury' 10" 6000 series, these purely use polmer seating technology and a very unique design to load the seat onto the ball despite being trunnion ball valves.
Also I personally would have said a full bore valve rather than reduced would/is harder to turn as the seat is larger and the ball bigger, which taking load over area means that the pressure on the ball is greater!
Get the right sized gearbox and you won't have any difficulty what so ever.
B
RE: High dp across ball valve
I suppose I should have said "pre-loaded seats" instead of spring-loaded seats. But you know what? Who (outside of possibly Jamesbury trying to differentiate themselves or trying to save the cost of a spring) really cares. The point is that floating ball valves seal by shifting the seat and the seal in trunion valves is started by indegral equipment.
You are right that full port valves have the potential for more starting torque because of the larger area that the dP is acting on--it has just been my experience that I have had more torque problems with reduced port valves, I don't know why, that is just what I've observed.
David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
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RE: High dp across ball valve
Valves are harder to open when there is more differential pressure across them.