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SafeKey End Cap Retention
System |
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The Hytork® "SafeKey" (Fig. 1) is a
unique patented method of securing the actuator end caps to the actuator
body, which overcomes the dangers and problems associated with bolts and
tie rods.
The SafeKey
is
a flexible 316 stainless steel key that fits into a key way. The
key way is formed when the body and the end cap are in their
correctly assembled position as the machined grooves in both
parts line up. Once assembled, any pressure caused by air or springs, locks the SafeKey in position, preventing it from being removed.
Only by removing these pressures (a safe condition), can the actuator be
disassembled. |
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Sectional Diagram
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The load is distributed
evenly around the whole circumference of the end cap, preventing
distortion and point loading stresses.
This SafeKey
system also prevents the possibility of
overstressing bolt hole threads during assembly.
Click here to see how the
SafeKey
system works.
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Benefits |
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Only the
"SafeKey" benefits the user by:
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Permitting quick, easy and safe
end cap removal
even when installed
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Providing maximum strength of Actuator assembly
against over pressure possibility
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Protecting the technician from unsafe
disassembly
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Eliminating corrosion of
end cap fastening
devices |
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Design Features |
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Hytork® engineers demanded the following factors when designing the "SafeKey" system
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It must have a uniform stress
distribution.
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It must not be possible to over stress the
retention system during assembly.
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It must not be possible to strip any retaining
threads or shear screws or bolts.
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The system must not rely on special torque
limiting tools for correct and safe assembly.
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Removal of Spring Return and Double Acting
end caps must be safe and simple.
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It must have a minimum of
parts.
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It must be strong.
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It must not be possible to remove the
end caps
from a Double Acting Actuator, whilst under pressure.
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Spring Return end
cap removal must be quick, to
facilitate on site Spring changes that may be required for varying air
supply pressures.
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The retention system must be sealed from
atmospheric corrosion.
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The system of end
cap retention must be easy to
clean, as required in food industry
applications.
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Safety Features |
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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.
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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.
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Corrosion Protection |
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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.
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Extensive Destruction Testing |
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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.
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Ease And
Speed
Of Assembly And Disassembly Reduces Maintenance Costs |
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- No special spring compression rigs are
required.
- On site disassembly is both quick and safe.
- A typical Hytork® actuator can be completely
disassembled and reassembled again in less than a quarter of the time
taken for actuators with end caps retained by screws.
- Hytork®'s
Safety Spring Removal System
makes disassembly and assembly both quick and safe. No
dangerous conditions for the operator or
technician.
- Compare this with
conventional screw and tie rods.
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Unique Hytork®
Features |
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- Impossible to overstress during assembly.
- Sealed from atmospheric corrosion.
- Made from 316 stainless steel.
- Many times stronger than conventional screws.
- Design makes Actuator cleaning easy.
- "Safety Spring
Removal System" makes on site maintenance
quick, simple and safe.
- A single item, reducing the possible loss of
vital parts that could lead to a dangerous release of energy.
- Does not require specific tools for disassembly or
assembly.
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