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Parker Back-Ups

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Parker ParbakŪ 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.


  • 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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