Only the "SafeKey" benefits the user by:

• Permitting quick, easy and safe end cap removal even when installed

• Providing maximum strength of Actuator assembly against over pressure possibility

• Protecting the technician from unsafe disassembly

• Eliminating corrosion of end cap fastening devices

Hytork^® engineers demanded the following factors when designing the "SafeKey" system :

• It must have a uniform stress distribution.

• It must not be possible to over stress the retention system during assembly.

• It must not be possible to strip any retaining threads or shear screws or bolts.

• The system must not rely on special torque limiting tools for correct and safe assembly.

• Removal of Spring Return and Double Acting end caps must be safe and simple.

• It must have a minimum of parts.

• It must be strong.

• It must not be possible to remove the end caps from a Double Acting Actuator, whilst under pressure.

• Spring Return end cap removal must be quick, to facilitate on site Spring changes that may be required for varying air supply pressures.

• The retention system must be sealed from atmospheric corrosion.

• The system of end cap retention must be easy to clean, as required in food industry applications.

Back to Top 

Compare the "SafeKey" with the potential dangers associated with conventional screws or tie rods.

Point loading on the end cap of conventional screws or tie rods causes uneven stress distribution which increases the possibility of fatigue over repeated cycles.  The SafeKey locks into the grooves when pressure is applied, either by air or Springs and cannot be removed.

In conventional designs, screws and tie rods should be assembled using torque limiting tools, but these are seldom available in the field. Over torqued, screws are overstressed and threads in alloy bodies can be stripped and the condition not be detectable. When pressure is applied to an Actuator in this condition, a dangerous failure occurs. These conventional design screws can also be removed with the Actuator under pressure resulting in a sudden and dangerous release of energy.

Back to Top

The SafeKey is totally isolated after assembly from ambient conditions for complete protection against corrosive attack. The corrosion resistant SafeKey head and 'O' Ring completely seal the SafeKey and Actuator internals from any corrosive atmosphere.

Compare the "SafeKey" with conventional screws and tie rods.

• Conventional screws are exposed to ambient conditions and can corrode, causing them to seize or weaken. Under Ioad this is not a safe condition.
• Unprotected dissimilar materials can form electrolytic cells due to the presence of ambient electrolytes. This will also cause screws to seize or weaken.
• On site, too much torque can be put on screws and can lead to stripped or weakened threads.
• Statutory requirements for pressure vessels require very stringent design codes and regular inspection and testing of such assemblies. The special torque limiting tools required for the correct assembly of end cap screws or tie rods are not usually available on site. This has led to incorrect assembly or disassembly causing on site failures.
• Controlled laboratory burst tests have shown that on similar sized cylinder bores, producing similar forces on the end caps, the SafeKey design is many times stronger than conventional screws.

All Hytork^® actuator models are regularly subjected to destructive testing on randomly selected assemblies. Cycle tests to millions of cycles and controlled pressure bursting are examples of Hytork^®'s continual product evaluation and development. In no case, after over 20 years of such testing, has any failure mode been detected that is associated with the SafeKey.

In all cases of burst tests, failure occurs at many times design pressure in components not associated with the SafeKey.

Back to Top

Back to Top