The Hytork^® Air Fail Safe Actuator is for larger valves with higher torque requirements, requiring reliable fail safe operation utilising a unique in-built air reservoir giving fail safe action without the torque losses inherent of spring designs.  For torque requirement valves up to 28500 inch.lbs (3220 Nm.) The  AFS (Air Fail Safe) actuator is designed to provide a high fail stroke torque in a double rack and pinion actuator that cannot be achieved using springs. All the safety and performance features of double rack and pinion actuators are maintained as is the Hytork^® "XL" reliability.

Using the time proven air accumulator system, and modern design techniques, Hytork^® produces air chamber modules with all the pneumatic circuitry Safety protected within.

The HYTORK^® AFS maintains the highest seen air supply pressure within the chamber modules, to be released upon control demand. This design also prevents closure "creeping" when air supply pressures drop, which occurs with all spring return designs. Torque output is constant in the powered stroke with only a small drop off on the fail stoke. The available torques are proportional to the air supply pressure. Spring changes for various air supply pressures need not be made.

The AFS operates as a double acting actuator in both directions until there is a loss of supply pressure. When this loss occurs, the compressed air stored in the chambers powers the actuator to close the valve. This makes the AFS Series suitable for use in ON/OFF and MODULATING CONTROL situations while still providing the fail safe requirement.  The AFS is supplied already furnished with an installed, direct mount solenoid valve. The coil type is selected to suit your site requirements. This saves on site piping and ensures the assembly has been fully tested.  Click here for information on Hytork^®'s Fail Safe & Safety Spring Removal System.

Related Documentation:

• Technical Information

• Maintenance Manual

• PDF brochure for the Air Fail Safe Actuator

Actuator Features & Benefits:

• High Performance In The Fail And Powered Strokes

• High Reliability

• Compact Heavy Duty Design

• 4580AFS Actuator Torque At Various Air Pressures

• Diagrams & Charts

• Materials Of Construction
  

• Constant torque output during normal operation.
• A very low torque drop off on the fail stroke provides higher usable torque than spring designs.
  

• All components are located and protected inside the air chamber modules.
• A proven, successful track record.
  

• Similar in size to spring return designs yet three times the power output.
• Central mounting over the valve prevents pipe twisting.
• Balanced design eliminates the need for support brackets.
• No side loads to wear the valve stem packing.
• Lower actuator cost.
  

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ACTION	AIR SUPPLY PRESSURE (psi)	40	50	60	70	80	90	100
Power Strokes	Torques (inch.lbs) from air supply pressure
	to open	14204	17755	21306	24857	28408	31959	35510
	to close	14204	17755	21306	24857	28408	31959	35510
Fail Stroke	Torques (inch.lbs) when loss of supply pressure occurs
	at start of stroke	14204	17755	21306	24857	28408	31959	35510
	at end of stroke	10653	13316	15980	18643	21306	23969	26633
ACTION	AIR SUPPLY PRESSURE (bar)	3.5	4.0	4.5	5.0	5.5	6.0	6.5
Power Strokes	Torques (Nm) from air supply pressure
	to open	2043	2335	2626	2918	3210	3502	3794
	to close	2043	2335	2626	2918	3210	3502	3794
Fail Stroke	Torques (Nm) when loss of supply pressure occurs
	at start of stroke	2043	2335	2626	2918	3210	3502	3794
	at end of stroke	1532	1751	1970	2189	2408	2626	2845

Positioner Operation


Protected from corrosion - protected from mechanical abuse.

Solenoid Operation

Dimensional Drawing







ISO F16 Valve Mounting Face



 

NAMUR VDI/VDE Accessory Mounting Face

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Last Updated 11/14/08

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