Control valves must match the specific operational requirements of your system, i.e. fully open, fully closed, or at a precise intermediate position.
The correct position depends on your system design, process requirements, and safety considerations.
Understanding the proper positioning principles helps optimize performance and prevent system damage.
Basic Positioning Principles
Control valves regulate flow by adjusting their position in response to signals from a control system.
Normal operating positions vary widely depending on the application, with some systems requiring valves to remain partially open while others operate in an on/off capacity.
During system startup, many control valves should be in a specific position to prevent pressure surges or equipment damage.
Shutdown procedures typically require distinct valve positioning to ensure system integrity and safety.
Fail-Safe Position Requirements
Every control valve must have a defined position it will move to during power loss or system failure.
Fail-open valves automatically move to open position during failures, maintaining critical flows in cooling systems or thermal processes.
Fail-closed valves automatically move to closed position, preventing leaks or releases in chemical, fuel, or hazardous material systems.
Your risk assessment determines the appropriate fail position by identifying which state causes least harm during emergencies.
| Fail Position | Best For | Examples |
| Fail Open | Systems where flow must continue | Cooling water, Steam heating, Thermal protection |
| Fail Closed | Systems where leakage creates hazards | Fuel lines, Chemical feeds, Pressure vessels |
| Fail Last | Systems where either extreme creates problems | Balanced pressure systems, Some process controls |
Physical Installation Position
Mount control valves in the orientation specified by the manufacturer to ensure proper function and longevity.
Position most globe-style control valves with the stem vertical and actuator above the valve body.
Install butterfly, ball, and rotary valves with the shaft horizontal to minimize bearing wear and stem packing stress.
Provide proper support for actuators, particularly with larger valve sizes or extended stems.
Maintenance Positions
Lock valves in closed position when performing downstream equipment maintenance or repairs.
Position valves in open position when conducting internal valve inspection or cleaning.
Implement physical lockout devices along with tagging procedures to prevent valve repositioning during maintenance.
Document proper return-to-service positioning sequence
Position Control Technologies
Modern electric actuators like those manufactured by Aoxiang provide precise positioning across the entire valve travel range.
Position feedback sensors verify actual valve position matches control system commands.
Electric actuators with smart positioning capabilities adjust automatically to maintain setpoints despite changing process conditions.
Digital control systems track valve positions and can alert operators to valves that drift from their required positions.
Selecting the Right Position
Follow these essential steps to determine the optimal position for your control valves:
- Analyze system requirements and process conditions through detailed engineering review
- Conduct failure mode analysis to identify the safest position during power loss scenarios
- Document required positions for all operational states (startup, normal, shutdown, emergency)
- Install appropriate actuators that can reliably maintain and verify valve positions
- Implement regular testing protocols to ensure valves respond correctly to control signals
Conclusion
Proper control valve positioning directly impacts system performance, efficiency, and safety.
No universal “correct” position exists; each application demands specific positioning based on system requirements.
Aoxiang’s electric valve actuators deliver precise positioning control with advanced monitoring capabilities.
Visit aox-actuator.com to learn how our 30 years of valve automation expertise can optimize your system performance.
Reference
Control Valves Should Always be in The What Position Exactly
