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A torque limit switch, usually called a torque switch, is a protective device in many electric valve actuators. It responds to the torque the actuator is delivering to the valve. When that torque reaches a configured value, the switch signals the control system, which can stop or fault the actuator. It is a different device from the travel limit switch that marks the fully open or fully closed position, and its setting is not a universal number. The correct value depends on the valve and the actuator model, and the manufacturers’ documents decide it.
What a torque switch protects against
A valve can meet resistance it was never meant to overcome. Debris can lodge in the flow path, a stem can bind, or a seat can seize. An actuator that keeps driving into that resistance can damage the valve, the actuator gearing, or both. A torque switch gives the actuator a defined point at which it stops or faults instead of continuing to push. AUMA’s SAEx 07.2 operation manual describes torque switching as overload protection across the full travel of the valve, and it warns that a tripping torque set too high can damage the valve.
How it works in an electric actuator
In the designs described in the manuals reviewed, the torque switch is tied to a spring pack. Output torque loads the spring pack, and the spring deflects in proportion to the load. ECON’s installation and operation manual for its ELA80 actuator describes the torque spring as detecting torque variation so that damage is prevented under overload. Limitorque’s L120 manual likewise refers to releasing load from the spring pack when adjusting the setting. A simplified sequence looks like this:
- The actuator drives the valve, and output torque rises as the valve resists movement.
- The spring pack is loaded and begins to move.
- When the movement reaches the point corresponding to the configured torque, the switch contacts change state.
- The control system receives the excessive-torque signal and stops or faults the actuator, depending on how the control arrangement is wired.
The exact wiring and response are model-dependent. Bettis’s Series 2000 Aquanaught manual, dated December 2019, describes the trip point as a distinct click as the switch breaks contact, which is a useful sign to a technician that the switch has actuated. Your actuator’s documentation governs what happens after that signal.
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Torque switch versus travel limit switch
The two switches are easy to confuse because both can stop an actuator. They respond to different conditions. Siemens’s A Series Electric Actuator Installation and Maintenance Manual (Servo NXT Quick Start Guide, about 2022) treats the excessive-torque connections and the end-of-travel connections as separate signals. A travel limit switch reports that the actuator has reached a position setpoint. A torque switch reports that the load has reached a value.
| Feature | Torque switch | Travel limit switch |
|---|---|---|
| What triggers it | Output torque or load reaching a configured value | Valve position reaching an end-of-travel setpoint |
| Purpose | Overload protection for the valve and actuator | Marking the open and closed end positions |
| Typical signal | Excessive torque | End of travel reached |
| Setting basis | Valve torque specification and actuator model | Required valve travel and end positions |
| Typical adjustment | Separate open and close settings on many models (Bettis, Biffi) | Set to the valve’s end positions |
Both can be present in the same actuator. AUMA notes that torque switching still acts as overload protection over full travel, including in cases where the limit switch stops the actuator at an end position. A generic industrial limit switch, which Eaton’s limit switch guide describes as a mechanically actuated position switch, is a broader category. Do not treat a torque switch as a mechanical stop, a motor overload relay, or any other limit switch by default.
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Open and close settings
Many electric actuators provide separate torque settings for opening and closing. Emerson’s Bettis manual gives separate close and open adjustment procedures. The Biffi F02 manual, dated September 2019, describes model-specific percentage settings. Because the names, scales, and locations differ between models, a number taken from one actuator cannot be transferred to another.
Can the setting be adjusted?
Yes, but adjustment is a controlled task for qualified personnel, and most manufacturers do not expect the operator to change the setting in the field. The Limitorque L120 manual, marked March 2018, says the factory setting was based on the customer’s stated torque or thrust requirements. ECON’s manual says the torque switches are factory set and directs users to contact the actuator distributor if resetting is necessary.
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Two manufacturer statements are worth quoting directly:
- Flowserve’s Biffi F02 Electric Actuator Installation and Maintenance Instructions: “Consult the valve manufacturer torque specifications for correct limit torque configuration.”
- ECON Electric Actuator Installation, Operation Manual: “Do not reset the torque switch to a setting higher than the maximum setting stated by the manufacturer.”
Before any adjustment, the manuals reviewed call for the following conditions:
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- Simple direct coupling reduces installation and commissioning time while improving reliability by eliminating damper linkages
- Four control inputs meet the needs of most applications
- Output position feedback provides simple closed-loop control with accurate position sensing
- Electronic stall detection ensures higher reliability by deactivating the actuator motor when a stall condition is detected
- NPT threaded housing provides easy connection for electrical fittings
- Disconnect incoming power before opening the switch compartment (Limitorque L120).
- Put the actuator in manual mode and release load from the spring pack before moving the setting pointer (Limitorque L120).
- Do not exceed the maximum stop setting plate (Limitorque L120).
- Do not adjust while the actuator is under load, because this can remove torque protection (Limitorque L120).
- Use the valve manufacturer’s torque specification and the actuator manufacturer’s procedure for that exact model (Biffi F02, ECON).
- Use approved, qualified personnel for configuration and maintenance (Biffi F02).
This guide does not give a setting value or a step-by-step adjustment procedure. Those belong to the actuator manual and the valve specification.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Troubleshooting a torque trip
A torque fault is a symptom. It tells you the actuator saw more load than its setting allows, but it does not tell you why. Treat it as a reason to investigate, not as a setting problem to override.
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- 12V Mini Actuator: Mini electric linear actuator stroke: 10-200mm(0.4-8inch), Travel speed: 15mm/s(0.6inch/sec), Maximum load: 64N/14.4lbs, with reliable performance, stable running, and good environment adaptability Linear motors
- Linear Motion Actuators: The mini linear actuator compact structure, small size, light weight. Made of aluminum alloy material and equipped with high performance gear motor, built in limit switch, stop at any position, automatically stop at the top, with short circuit protection, overload protection, overvoltage protection and other functions.
- Linear Actuator: Waterproof Momentary Polarity Reverse Switch.This ON-Off-ON switch is momentary meaning it springs back to the center off position when the toggle is released; The switch will reset automatic back to off if released. Simply connect the power and two DC motor wires and the switch will reverse the direction of the motor. Add a waterproof cap to achieve IP65 waterproof level for the switch
- Easy to Install: The linear actuator will include a set of mounting brackets, makes it easy and convenient to install and connect this fast linear actuator. Positive negative 2 poles, reversing the polarity will switch the direction of movement between extension and retraction
- Application: Multi-purpose 12V Linear Actuator with switch fits automatic window, skylight and vent control, cabinet door operation, snow plow angle adjustment, snowblower chute deflector, greenhouse ventilation window, automatic chicken coop door, curtain lift, sorting diverter gate, solar tracker support, farm gate opening and 3D printer automation projects
- The actuator stops partway through travel with a torque signal. Stop and investigate the valve. Do not raise the setting to get the valve moving. Excessive tripping torque can damage the valve.
- The setting seems inconsistent with the valve’s specification. Compare the configured value with the valve manufacturer’s torque data and the actuator’s documented range before changing anything.
- The actuator has tripped repeatedly with no visible cause. Call the actuator manufacturer or an authorized distributor. A controlled inspection is safer than repeated resets.
Identifying a replacement torque switch
A replacement torque switch assembly is a physical component listed in actuator manufacturer documentation, and Siemens and Bettis both document torque-switch connections and adjustments for their products. Parts are model-specific. Find the actuator model on the nameplate and check it against the manufacturer’s documentation. The manuals reviewed are model-specific and do not establish that parts are interchangeable between models or brands.
- Record the actuator model and serial number from the nameplate.
- Confirm the open and close torque setting arrangement for that model.
- Source the part from the actuator manufacturer or an authorized industrial-controls distributor.
- Have qualified personnel install and configure it according to the manufacturer’s instructions.
Documents this guide draws on
| Document | Date as stated | What it covers |
|---|---|---|
| Siemens, A Series Electric Actuator Installation and Maintenance Manual: Servo NXT Quick Start Guide | About 2022 | Separates the excessive-torque signal from the end-of-travel signal |
| Emerson/Bettis, Operation and Maintenance Manual: Series 2000 Aquanaught | December 2019 | Close and open torque switch adjustment; manual trip-point check |
| Flowserve/Limitorque, L120 Series User Manual | Marked March 2018 | Factory setting basis, manual mode, power isolation, setting limiter |
| ECON, Installation, Operation Manual: Electric Actuator Type ELA80 | About 2025, as identified in a search result | Torque spring function; factory setting and distributor contact advice |
| Biffi F02 Electric Actuator Installation and Maintenance Instructions | September 2019 | Model-specific percentage settings; valve torque specification; qualified personnel |
| AUMA, SAEx 07.2 Operation Instructions Manual | Date not stated in the copy reviewed | Overload protection over full travel; setting appropriate to the valve |
| Eaton, Limit Switch: Guide and selection information | Date not stated in the copy reviewed | General description of mechanically actuated position switches |
Each of these documents covers particular models. Check the current revision on the manufacturer’s site before relying on any figure or procedure.
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