Talleres F. Larrinaga

PRODUCTS: Quarter-turn Gear Operators for valves

Quarter turn gear operators torque output (Kg.m)


1 Kgm = 9,8070 Nm      1 Nm = 0,73756 lbf.ft     1 Nm = 8,8507 lbf.ins

General Description

90” type operators are self-locking worm gears with a 90-degree turn and adjustable stops at ±5 degrees at each end.

Due to its mode of operation, a worm gearbox enables high step-down ratios.

They can only be used in those valves that require turning torque without thrust.

Are provided in either manual or motorizable versions.

The input shaft where the handwheel is coupled is supplied with a key in accordance with our range of handwheels. This is provided with a position indicator.

The worm shaft made of carburized steel is hardened, the toothing is grinded. The worm gear consists of a high-quality bronze alloy, the toothing is milled.

Housing made of grey cast iron.

Low-backlash construction < 6 angular minutes possible.


These operators are fitted on valves that require 90-degree turns for their operation, such as ball valves, butterfly valves, plug valves, etc.

These are designed for use outdoors in accordance with standard IP 67.

Are designed weatherproof in accordance with standard IP67.

All our actuators are coated acc. to UNE–EN ISO 12944-6 with a total thickness of 230µ that allow them stand under marine C5 atmosphere.

The range of temperature for continuous operation is from -20 to +120 ºC.

All external castings are Cast Iron, providing high strength and impact resistance.

These operators are supplied with a flat mounting base according to the ISO-5211 standard.

All flanges always have threaded mounting holes.

The quadrant is supplied solid. At the customer`s request, quadrants can be supplied with a bore and keyway machined in accordance with the diameter of the valve spindle.

The position of this keyway must be indicated.
Option, on request for square shaft.

For the standard one, aluminum bronze is used according to ASTM B148 C95800. On demand, Ni-Resist is used according to ASTM A439 type D2 in compliance with the API standard 600.

The driving nut is solid. Should the customer wish, it can also be threaded, with a groove for the key, etc.
The gearboxes can be used in all installation positions. The technically most favourable and thus recommended installation position is when the worm shaft is horizontal and located at the bottom.
As standard, the worm gearboxes are delivered with right-handed worm shafts. In the special design, delivery with left-handed gear teeth is also possible. Please enquire this.
The actuators are lubricated with permanent grease.

The achievable efficiency depends on rotational speed, torque, installation position, sealing, and lubricant type.

Operating torque is applied by pulling on the Handwheel Rim. That’s called, Rim Pull

The amount of applied torque depends on the Rim Pull and the Handwheel size

The standard API RIM pull effort for manual applications is 360 N (80 pounds-force), but most applications are sized to 400 N RIM pull effort

Applied torque = Rim Pull x Half the Handwheel diameter.

Worm gearboxes are statically self-locking if starting from standstill with driving worm gear is impossible.

The self-locking depends on the pitch of the toothing. The angle is 2.5° to 5°.

Please enquire these.

Vibrations may override / deactivate the self-locking. Therefore, a self-locking toothing cannot always take the place of a brake or an antireversing device

Worm gearboxes are dynamically self-locking if, with rotating gearbox mechanism, continued operation is impossible due to torque action on the worm gear (output side) of the gearbox. The overrun occurring after switching-off depends on the rotating masses on the drive side.

Dynamic self-locking is only possible with very large gear ratios in the range of low driving speeds. Please enquire these

If driven parts have high mass inertia moments no self-locking must occur during the run-down process. Extremely high load peaks may occur in case of sudden blocking of the gearbox.

In such cases, a gearbox with multistart worm should be used whenever possible.

Also, if a braking motor or a separate brake is used on the drive side, the braking torque must not be too high, and it must be mitigated by using an additional flywheel mass on the drive side.

Our gearboxes can be outfitted with a number of accessories. Please contact us for more detailed information.

Once the actuator has been mounted on the valve, the latter should not be raised by means of the actuator.

In order to store the actuators, proceed as follows:

  • Store in clean dry place.
  • Protect the mechanized areas from shocks and rust.
  • Turn the input spindle several times every four month during storage.