Parker
Parbak® Contoured Continuous Back-up Rings
The Parker Parbak is a supplement to a pressure
seal such as an O-ring. It is not a seal in itself.
The primary reason for the use of a back-up
ring is to reduce the clearance gap on the low pressure side
of an O-ring or similar type seal. An O-ring and Parbak combination
will withstand much higher pressures than an O-ring alone.
Parker Seal's Parbak back-up rings are outstanding
for several reasons. To begin with, Parbaks are molded of
a hard rubber compound in one continuous circle, yet they
can be stretched easily into place. Because they are not split
or spiraled, Parbaks do not cause the localized wear on O-rings
characteristic of back-up rings of that type of construction.
Parbaks have proved to last longer with greater
reliability than all other types of back-up rings tested.
They are lower in cost than competitive products.
Parbaks extend the operating pressure range
of O-rings or other types of seals. Some additional benefit
such as increased lubrication of the O-ring may also be obtained
because the Parbak will trap small amounts of lubricant between
itself and the O-ring.
The use of Parbaks permits a far greater metal-to-metal
clearance between moving parts. This helps overcome difficulties
encountered with wide or out-of-tolerance bores and shafts.
The elastic nature of the O'ring seal and the
clearance reducing capability of the Parbak offers an important
cost reduction opportunity. In many applications, machining
tolerances can be increased at a considerable dollar savings.
Advantages:
- Easy to assemble
- Cost reduction item
- Shaped for better performance
- Low in price
- Increased O-ring life
- Improved lubrication
- Resist higher pressures
- Uniform materials and sizes
- Total Diametral Clearance
- Parbak Gland Design
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