I would like to calculate the closing/opening time of a Gate valve using an hydraulic actuator. What are the input parameters required and what is the formula for this calculation?

On the emergency closing side you will often require very fast closing, perhaps in two steps, first one step to about 80% very fast, and rest slow to avoid water hammer. In other cases (large valves, long pipelines, high pressure) you will have to go, or wish to go, extreemly slow (three minutes to up to more than twice or triple the time) to avoid water hammer and pressure peaks higher than necessary for a perhaps 'lighter constructed' pipeline (cost reasons).

You have to start somewhere, and normally you will start with a given oil pressure from a 'normal' aggregate, select a cylinder diameter area (less the rod area on one side) to give a high enough force (P times A) to be sure to have sufficient force for all situations, especially sticking force when opening the valve after a long closed periode.

You know the stroke length (diameter of valve plus something small), and hence the volume.

The smallest restrictions (pipeline and/or solenoid valve real diameter or cv, and inlet/outlet openings integrated in the cylinder) for your 'normal' selected components are also known.

This will enable you to (somewhat approximate) calculate the closing time, or the actuator/piston supplier will be able to inform you, given the oil pressure. The reservoir have to be sufficient large to avoid significant pressure drop on input side under operation of the piston.

Too fast? (This is usually the case) : throttle down on input or output line, with hand operated throttle valves.

To slow? Increase pressure, and/or linesize, and/or reservoir, and/or aggregate capacity or solenoid cv. Change cylinder inlet/outlet borings?

For large rupture protection valves in high-pressure watermains or for hydroelectric turbine inlet valves with emergency shut-down,  oil-hydraulic opening and fallweight closing with two step throtteling of the return oil is a common solution. Two reasons: not depending on electricity or other external force other than gravity, and fast and controlled closing.

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