if there is high dp across the ball valve, will i have difficulties in opening the valve manually? some say yes..some say no.... 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.Floating ball valves seal by the ball physically shifting toward the downstream seat. The movement is not far, but it is a contributor to high opening torque. Trunion ball valves use springs to seal the seat against the ball both upstream and downstream, but (especially with fluids that can condense within the ball cavity) this can result in high dP across both seats and a high opening torque. Reduced port floating ball valves tend to have the highest opening torque with clean, compatible fluids. When the fluids get nasty or can swell the sealing surfaces then either kind of ball valve can have high torque.

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