Valve Gearboxes
Our valve gearboxes can be operated both manually or motor driven, featuring WRAS approved coatings, robust iron construction and configuration options to ensure they are ideally suited to your needs.
What is a valve gearbox?
A valve gearbox is a device that consists of a series of interlinked (or meshed) gears that provide force amplification, also known as a mechanical advantage, that enables the gearbox to produce an output torque (the force needed to rotate around an axis, such as a valve stem/shaft) multiple times greater than the input torque.
Valve gearboxes reduce the input torque required to operate large/high-pressure valves and allow for more precise obturator positioning (an obturator is a moving component inside the valve that obstructs/controls the flow of liquid, e.g. a gate or plug).
This force multiplication is expressed as a ratio:
rotations of a driver (input) gear : rotations of a driven (output) gear
E.g. if a handwheel-driven gearbox has a 4:1 ratio, turning the handwheel four times will result in one full rotation of the output gear (which moves the valve obturator). With the gearbox, each turn of the handwheel only requires a fourth of the effort needed to turn the handwheel manually in one full rotation.
The input torque needed to operate a gearbox can be transmitted by rotating a manual handwheel or by a powered actuator.
What's the difference between multi-turn and quarter-turn valve gearboxes?
Multi-turn gearboxes allow for endless rotation of the drive gear, which results in corresponding turns of the output gear depending on the gear ratio (such as the 4:1 example above). Multi-turn gearboxes are best suited to valves that require the stem/shaft to rotate multiple times for full obturator travel, such as wedge gate, knife gate, penstock, pinch and globe valves.
Quarter-turn gearboxes, or worm gearboxes, require multiple rotations of the drive gear, but the output gear is restricted to 90° of rotation by adjustable mechanical end stops that prevent over-travel. Worm gearboxes are typically used with ball, butterfly and plug valves where the obturator only has to travel 90° to fully isolate or allow flow.
For applications where the input and output shaft are aligned, spur gearboxes have straight teeth mounted on parallel shafts that provide high precision for multi-turn valves.
Bevel gearboxes are best for applications where the input shaft is at 90° angle to the valve stem, common in confined space installations.
Multi-turn gearboxes are available with spur and bevel gears, while worm gearboxes generally only feature bevel gears.
Spur gearboxes are designed for applications where the input and output shaft are aligned, with straight teeth mounted on parallel shafts for high-precision obturator positioning.
Bevel gearboxes are best for applications where the input shaft is at 90° angle to the valve stem, common in confined space installations.
Valve Gearbox FAQs
Valve Gearbox Case Studies
Reduction Spur Gearbox for Out-of-Hours Emergency
When a UK water provider came to T-T Flow in urgent need of a gearbox, our experts were able to specify and ship a gearbox suitable for a DN1200 gate valve within a few hours of receiving the order.
The authorities’ original actuation supplier was unresponsive and the equipment was needed fast due to a fractured pipe at a waste treatment facility causing major environmental damage.
