Limit Switch
An electrical device mounted on a valve to signal when the valve has reached its fully open or fully closed position. Sends feedback to the DCS or SCADA. Required for ESD valves and all valves in automated safety loops.
Related Terms
Related Products
Frequently Asked Questions
What is a Limit Switch?
An electrical device mounted on a valve to signal when the valve has reached its fully open or fully closed position. Sends feedback to the DCS or SCADA. Required for ESD valves and all valves in automated safety loops.
How is a Limit Switch sized for a valve?
Actuator sizing requires the valve's breakaway torque (BTO), running torque (RTO), and end-to-close torque (ETO) at the maximum differential pressure and operating temperature. The actuator output torque at minimum supply pressure must exceed the valve BTO by a safety factor (typically 1.25x minimum). For pneumatic actuators, the supply pressure range, fail-safe direction (spring return FC or FO), and speed requirements must also be specified.
When is a Limit Switch required versus manual operation?
Automation is required when: (1) the valve is in a remote or hazardous location, (2) rapid opening/closing is needed for emergency shutdown (ESD), (3) the valve must respond to a control signal (4–20 mA, HART, or fieldbus), (4) the operating torque is too high for manual operation, or (5) the valve is part of a Safety Instrumented System (SIS) requiring SIL certification. Contact Vajra Industrial Solutions for fully automated valve packages including actuator, limit switch, solenoid, and positioner.
Need a Quote?
API 6D certified valves. Ships to 357+ cities worldwide. 24h response.
Request QuoteContact EngineerAll Categories
Technical Support
Have a Technical Question?
Our valve engineers can help specify the right valve for your application. Full project documentation available: MTCs, test reports, dimensional inspection, and third-party inspection coordination.