Benchset are the actual pressure ranges for travel of the actuator with no friction. These are the actual maximum and minimum pressures that move the actuator from end to end of its range of operation. This is typically performed on the actuator before it is mounted onto the valve.
Stroking is the pressure range for the operation with friction. Stroking takes into account the added pressure required to overcome friction forces when the actuator is connected to the valve assembly.
When stroking a valve, two sets of pressure ranges are produced. There is one pressure range that actuates the valve from fully open to fully closed. The other range is generated from actuating the valve from fully closed to fully open.
The operational stroking range adds pressure and flow effects.
With any type of friction, the problems arise where the pressure to drive the device in one direction will be different to that required to drive it in the other direction. To move the valve in the positive direction, then the force has to exceed the benchset pressure by the amount of the friction. To drive the actuator in the opposite direction, the force has to go below the benchset pressure by the amount of the friction. This is the hysteresis and applies when friction is present.
The amount of friction determines the amount of variation from the benchset pressure range.
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