The actuator’s unique design has no traveling seals, which contributes to the longevity of the seal packages. Optional cold-service seal packages enable the actuator to exceed performance standards for cold, hostile environments.
Limit switches, valve position indicators, fusible and standard lockout caps, stem protectors, and mechanical- and hydraulic-opening assemblies are also available.
During operation, hydraulic control pressure enters the cylinder above the piston. The extended stem travels downward, indicating the valve is open. The adjustable internal down-stop prevents further downward force. The gate valve is now fully open. The actuator is designed to maintain the valve (reverse-acting) in the open position with hydraulic pressure on top of the piston.
Loss of hydraulic pressure allows pressure in the valve body to move the stem and gate into the closed position.
The extended stem indicates the valve is closed. The metal-to-metal up-stop between the actuator bonnet and lower stem serves as a secondary seal if high temperatures have melted or distorted lower stem packing.
The upstream valve body pressure helps to hold the gate in the closed position. The internal spring ensures the actuator will return if there is no valve body pressure. The extended stem indicates the valve is closed. The metal-to-metal seat between the actuator bonnet and lower stem serves as a secondary seal.
- Ease of maintenance – The unit can be redressed without special tools or external pressure sources. Piston and upper stem packing is easily removable using actuator service disconnect bolts. Standardized lower stem sizes simplify spare parts requirements.
- Proven reliability – API 6A, PR2 Appendix F qualified
- Visual open/close indication – Upper stem extension indicates gate position at a glance.
- Interchangeable with all other AU models, allowing conversion from hydraulic to pneumatic actuation and vice versa