TL;DR: “Electrically operated valve” can mean a solenoid valve, a motorized valve, or a pneumatic valve controlled by an electrical solenoid. Selection depends on required function (on/off vs control), available power, cycle rate, fail position, and chemical compatibility of wetted parts.
Teams often run into problems with electrically operated valves because the term is overloaded. If you specify “electric valve” without clarifying actuation method and failure behavior, you get the wrong response time, the wrong duty cycle, or the wrong fail position during power loss. This guide gives a clean way to specify these valves for process and chemical systems.
What counts as an electrically operated valve?
- Solenoid valves: coil moves a plunger to open/close flow (direct-acting or pilot-operated).
- Motorized valves: an electric motor drives a valve (ball/butterfly) via gearing.
- Pneumatic valves with solenoid pilot: air actuator does the work; electricity controls the pilot/positioner.
Actuator types: quick selection rules
- Solenoid: best for small-to-medium on/off, fast response, simple control; watch coil heat and pressure requirements (pilot types).
- Motorized: good for larger quarter-turn valves, slower response, moderate cycle rates; verify torque and duty cycle.
- Pneumatic: best for high cycle, larger sizes, and defined fail-safe behavior; requires clean instrument air.
Wiring basics (what you must specify)
- Power: AC/DC voltage and allowable tolerance.
- Control: simple on/off, PWM, or analog (for positioners).
- Feedback: end switches, position feedback, local indicators.
- Hazard environment: enclosure rating and any required approvals.
Fail modes (power loss behavior)
- Fail closed: stops flow on power loss (common for chemical isolation).
- Fail open: maintains flow on power loss (used where continuous flow is safety-critical).
- Fail last: stays in last position (common in motorized unless spring-return is used).
Common failure modes (and how to prevent them)
- Wrong actuation method: solenoid specified where torque-driven quarter-turn is needed.
- Duty-cycle overheating: coil or motor not rated for cycle rate/ambient temperature.
- Pilot pressure mismatch: pilot solenoids require minimum ΔP to actuate.
- Material mismatch: seats/O-rings/diaphragms incompatible with chemical and temperature.
Related: Solenoid Valve: Direct-Acting vs Pilot.
Related engineering resources
Frequently Asked Questions
No. It can be a solenoid valve, a motorized valve, or a pneumatic valve controlled by an electrical solenoid. Specify the actuation method and required performance.
Fail position on power loss (fail open, fail closed, or fail last) plus whether the valve must be spring-return or can remain in last position.
Pilot-operated designs often require a minimum differential pressure to actuate. If ΔP is too low during startup or low-flow conditions, the valve may not open or close reliably.
