Fail-Open (FO)
An actuated valve that opens automatically on loss of instrument air or power. Used where the safe failure mode is to maintain flow: e.g., cooling water supply to heat exchangers, quench water to fired coils.
What is Fail-Open (FO)?
An actuated valve that opens automatically on loss of instrument air or power. Used where the safe failure mode is to maintain flow: e.g., cooling water supply to heat exchangers, quench water to fired coils.
Vajra Industrial Solutions is an engineering-driven industrial valve manufacturer and supplier. Concepts such as fail-open (fo) inform how we select, manufacture, and document valves for industrial service.
Related Terms
Related Products
Frequently Asked Questions
What is a Fail-Open (FO)?
An actuated valve that opens automatically on loss of instrument air or power. Used where the safe failure mode is to maintain flow: e.g., cooling water supply to heat exchangers, quench water to fired coils.
How is a Fail-Open (FO) 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 Fail-Open (FO) 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
Related Troubleshooting
All troubleshooting guides →Have a Technical Question?
Our valve engineers can help specify the right valve for your application. Full documentation available: MTCs, test reports, dimensional inspection, and TPI coordination.