Torque/Thrust calculation for Dampers/gates.

The thrust required to operate the gate in this case can be reduced to two factors: overcoming the differential pressure across the gate and the friction (if any) in the shaft packing.

Thrust required to overcome differential pressure can be calculated according to the following formula: T = ΔPxAx0,3

Where ΔP is the differential pressure, A is the area of gate ant T the required thrust. (Be careful to use the same units)

The friction can be approximate (conservatively) taking 1000 Lbf per inch of shaft diameter.

The thrust to overcome friction in the shaft packing is probably minimal compared to the friction of the gate against the guides which keep it in place. It is important to know what material the guides are and to take the friction factor between the guides and gates and the area over which the gates are in contact with the guides times the total force of the pressure against the gate ie pressure times area of gates. As the gates start to open there will also be a turbulent force over the bottom of the gate which would be quite difficult to calculate - a safety factor of say 2 should be used to take this into consideration and will also account for the deterioration in material "smoothness" which will further increase friction.

I agree with you in general, but in this case, the pressure is in the order of mm H₂O, so, is quite probable that friction alone be the main factor to determine the required thrust. I've calculated some gates for water service with ΔP about 125 psi and the main factor is the packing friction.