How To Accurately Calculate Torque On Your Valve Actuators

If you’re using ball-joint swivel valves to regulate flow in your hydraulic or pneumatic applications, you’ll need to understand how mechanical torque enables operation and precision control.

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Applied torque allows engineers and operators to open and close the unit and set the throughflow rate. Variable torque actuators allow different power setups to run on the same hardware. Here’s how it works.

What Are Valve Actuators?

Valve actuators are secondary valves (i.e. attached to a primary valve) that open or close the primary valve on receiving a fixed signal (e.g. an electrical pulse, kinetic push, manual lever release).

Rotational valve actuators provide operators with excellent variable control. When an external axle rotates a chambered, semi-open ball to the right, a precise, safe level of throughflow and pressure is generated. The release angle (typically within 0-90° or a 25% turn) specifies the level of power transferred.

Quick-release rotational setups are also handy for creating emergency hydraulic and pneumatic overflows and shutoffs. Force-triggered point-to-point rotational actuators are extremely quick to respond to signals.

How Is Torque Applied?

When enough vector force (measured in J) applies in one direction (i.e. clockwise or counter-clockwise) to a central pivot, torque causes a circular motion (represented as N.m). The valve then opens or closes. Different degrees of applied force will transform into correspondingly strong torque.

Types Of Valve Actuator Torque

  1. Breaking Torque – The fundamental Tb value of push needed to move the valve’s ball joint from base position to ‘open’ against flow and pressure. You’ll need an actuator release mechanism that can specify this minimum.
  2. Running (Dynamic) Torque – The Td level of torque applied on each turn against the joint’s friction (resistance) while the axle is in motion. N will determine the angle (relative to 0°) the actuator’s pivot settles on – useful for variable designs.
  3. Closing Torque – The inverse of breaking, where Tb is the minimum retrograde force needed to reset the ball valve to ‘closed’. Closing Tb may be substantially different from Breaking Tb due to the valve’s active flow.

How Do I Calculate Valve Actuator Torque?

When specifying rotational valve actuators, it’s crucial to calculate your application’s torque settings correctly using accurate guide values. Underpowering or overpowering a simple clockwise-counter-clockwise movement risks damaging or stalling the valve.

You can use the formulae below to determine how much raw force you’ll need for each turn and counterturn. You can then measure any shortlisted actuators and prototype designs against your approximate benchmark.

Calculate Breakaway Torque with Tb = A (ΔP) + B. The same equation applies to Closing Torque.

(A represents initial force, determined by the type and strength of the actuator pivot.

B represents friction and mass resistance against initial torque.

ΔP represents pressure drop and air (or fluid) resistance against internal temperatures.)

Calculate Running (Dynamic) Torque in motion with Td = C (ΔP).

(C represents the constant force applied to move the pivot. All other values are as above.)

Adding a c.25% excess force buffer on top of your final figure may prove wise. Actuator pivots can jam up with time, use, and wear, creating additional friction.

Consult the product manual if you’re unsure of your A, ΔP, and B values. In custom-built or specialist systems, practical testing may better determine ‘actual’ actuator torque and performance.

Valve Actuators And Precision Torque Tuning From Hydrastar

If you’re looking for valve actuators or want to design your own, get in touch with Hydrastar. We’ve been supplying custom designs, stock components, and expert consultancy since 1979. Speak with one of our experienced design engineers to learn more about our services.


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