PolyPaks are multi-purpose seals that are precision molded, multi-purpose sealing devices combining an O-Ring type O-Spring with a conventional lip Seal. PolyPaks provide excellent seal from hard vacuum to more than 60,000 Psi. The PolyPaks won’t leak under low pressure like many conventional U-packing seals and maintain lip loading on the ID and OD interface during temperature extremes.
PolyPak Seals offer these advantages:
• High conformability • Excellent sealability • Extrusion resistance • High stability
• Long service life • Easy retrofit • Wide choice of profiles • Wide choice of materialsPolyPak seals are available in three styles:
• Standard PolyPak (SPP Profile) • Deep PolyPak (DPP Profile) • Type B PolyPak (BPP Profile)Rod Sealing with PolyPak Seals
As a general rule, rod seals are more critical in nature than their companion piston seals. With increasing OEM requirements for “dry rod” capability, both to conserve system fluid and avoid leakage, the design and selection of the rod seal can be more challenging than its piston counterpart. Parker recommends the use of the Type B PolyPak (BPP Profile) for rod seal applications due to its design features, including:
• Excellent film-breaking capability of the beveled lip design
• The higher level of lip loading provided by the Type B offers maximum sealability
• The long body of the design provides maximum stabilityPiston Sealing with PolyPak Seals
Piston seals can be classified in two categories: single-acting and double-acting. The single acting seal is only required to seal in a single direction as system pressure is seen on only one end of the piston (return of the piston in a single-acting system is accomplished either by gravity or spring loading). The double-acting cylinder requires that the piston be sealed in both directions of stroke as system fluid is applied to one side or the other to achieve movement. Please see the individual PolyPak profile pages for explanation and differentiation on selecting the PolyPak profiles for piston applications.