Axelson Actuator – Pneumatic Diaphragm Actuator
The AUD pneumatic actuator is designed for simplicity, ease of maintenance and adaptability. Its modular design and few components help improve field performance.
This actuator is designed to close upon loss of control pressure (fail-safe). The actuator’s nylon-reinforced diaphragm has a large piston area allowing for a low control pressure.
The maximum control pressure is 150 psi. Due to it’s fail safe design, the actuator is ideally suited for wellhead, flowline, header, pipeline system, and casing relief blowdown valve applications.
Actuators are available for API gate valve sizes from 1-13/16 in. through 12 in. and larger upon request.
Benefits
- Less maintenance – Rolling diaphragm design eliminates moving o-ring seals and leads to longer seal life.
- Proven reliability – API 6A, PR2 Appendix F qualified packing
- Lightweight – Easy to install and maintain. Can be redressed without special tools or external pressure sources.
- Quick disconnect – Actuator can be removed from the valve without the use of special tools or an external pressure source.
- Large diaphragm area – Permits use of a low pressure air or gas control system. A relief valve on the cylinder acts to protect against damage to the diaphragm in case of excessive pressure increases.
- Visual open – close indication – Upper stem extension indicates gate position at a glance.
Actuator Design and Principle of Operation
Pneumatic control pressure enters the cylinder. The extended stem travels downward indicating the valve is open. The adjustable downstop prevents further downward movement. The gate valve is now fully open. The actuator is designed to maintain the valve (reverse-acting) in the open position with pneumatic pressure on top of the diaphragm.
Loss of pneumatic pressure allows pressure in the valve body and spring force to move the stem and gate into the closed position. 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. Upstream valve body pressure helps to hold the gate in the closed position. The spring allows the gate to close with less than 100 psi in the valve body.
A surface safety valve is a full-opening, pressure-actuated, normally closed gate valve.
When control pressure is released, the valve is designed to close even when subjected to high flow line pressure.
It closes completely and rapidly as the control pressure is released. Flowline fluid does not enter the operator mechanism, nor exhaust to the atmosphere when the valve operates.
The surface safety valve assembly consists of a hydraulic or pneumatic actuator which operates a reverse-acting gate valve. The actuator design makes it an integral part of the valve assembly by adapting directly to the valve bonnet.
Pressure applied above the piston pushes the piston, stem, and gate down. This downward movement opens the gate in reverse-acting gate valves.
Pressure in the valve body is sealed at the lower stem and prevented from entering the actuator assembly. The area below the piston is vented to the atmosphere.
When control pressure above the piston is exhausted by the operation of the pilot system, the valve closes. Valve body pressure works across the area of the lower stem to force it out of the valve body, drawing the gate into the closed position.
With no pressure (less than 100 psi) in the valve body, the spring returns the valve to the closed position.
A visual indication the valve is in the open position is when the stem is protruding approximately 1/4 inches above the cylinder. If the stem is protruding visually 1/4 inch more than the stroke of the valve, this is an indication the valve is closed.
STANDARD WELLHEAD ACTUATORS
Pneumatic
AUP – Pneumatic Piston Actuator
AUD – Fail Safe Pneumatic Diaphragm Actuator
Axelson MHA – Pneumatic Actuator suited for higher pressures
Axelson MHA-1A – Pneumatic Actuator – pressures are 10K or less
Axelson AM-1A – Pneumatic Actuator with built-in manual override
Hydraulic
ACTUATOR ACCESSORIES
- Limit Switch (see information below)
- Valve Position Indicator
- Lockout Caps – Fusible and Standard
- Transparent Stem Protectors
- Mechanical Opening Assembly
- Hydraulic Opening Assembly
Axelson Limit Switch or Proximity Switch for Actuator Applications
AUD AND AUP ACTUATOR APPLICATIONS
Actuator Accessories
Limit Switch
Valve Position Indicator
Lockout Caps – Fusible Lockout Caps and Standard Lockout Caps – Fusible Lock Open Caps Axelson
Transparent Stem Protectors
Mechanical Opening Assembly
Hydraulic Opening Assembly
