Valve Worm Gearbox Sizing Calculator
Enter your valve's operating torque to find the required worm gearbox ratio, output torque and handwheel turns — so you can match a gear operator to the valve.
From the valve data sheet (break-to-open / seating torque).
≈ rim pull (N) × handwheel radius (m). 360 N on a 0.4 m wheel ≈ 72 N·m.
Recommended gearbox
FAQ
How do you size a worm gearbox for a valve?
Take the valve's operating (break-to-open) torque from its data sheet, multiply by a safety factor (typically 1.25-1.5) to get the required output torque, then divide by the available input torque times the gearbox efficiency to get the minimum gear ratio. Select the next standard ratio at or above that value so the gearbox output torque exceeds the valve torque.
What is the efficiency of a worm gear valve operator?
Self-locking worm gear operators are typically 30-50% efficient (about 0.40 is a common design value). The low efficiency is what makes them self-locking, holding the valve position without back-driving.
How many handwheel turns are needed to operate a quarter-turn valve through a gearbox?
For a quarter-turn (90°) valve, the number of input handwheel turns equals the gear ratio divided by four (turns = ratio / 4). A higher ratio means more turns but less effort per turn.
Why use a worm gearbox on a valve?
A worm gearbox multiplies a small handwheel input into the high torque needed to operate large or high-pressure valves with reasonable effort, gives precise positioning, and is self-locking so the valve stays put.