A knife gate valve can be correctly selected but still experience operating problems if the actuator is incorrectly sized.
Actuator selection is therefore an important part of the complete valve specification.
What Does an Actuator Do?
An actuator provides the force required to open, close or position the valve.
Depending on the installation, this could be achieved through:
- Manual operation
- Pneumatic actuation
- Electric actuation
- Hydraulic systems
Why Is Correct Sizing Important?
An undersized actuator may struggle to operate the valve.
This can result in:
- Slow operation
- Failure to close
- Stalling
- Excessive wear
- Increased maintenance
An oversized actuator may also be undesirable because it can increase cost and potentially place unnecessary forces on valve components.
What Determines Actuator Size?
Engineers may need to consider:
- Valve size
- Pressure differential
- Seat design
- Media characteristics
- Packing friction
- Operating temperature
- Required safety factor
- Required operating speed
Pneumatic Actuators
Pneumatic actuation is common in industrial environments where compressed air is available.
The actuator must be selected according to the available air pressure and required operating force.
Automated Mining Valves
Mining plants frequently use automated isolation valves to improve process control and reduce the need for manual intervention.
For these applications, valve and actuator selection should be treated as one engineering package.
Conclusion
A valve is only as reliable as the complete system supporting its operation.
Correct actuator sizing helps ensure that the valve performs as intended throughout its operating life.