Low-Friction No-Drift Bi-Directional Hydraulic Piston Seal

The design includes an integrated rubber quad ring seal in the outer filled-PTFE cap to ensure positive sealing and drift-free operation in medium- to heavy-duty service application. Designed to separate and seal two different media, e.g. fluid/gas. Commonly used in piston accumulators, mobile hydraulics and where low-friction, high-pressure drift-free sealing performance is required. Retro fits seals of similar design.

Operating Range
MaterialOperating Pressure up toMaximum Pressure up toTemperatureSurface Speed up toFluid, Media
Permachem 66433,800psi (260bar)5,000psi (350bar)-40°F to 400°F (-40°C to 210°C)6ft/s (1.8m/s)mineral oil-based fluids, fire-resistant water-based hydraulic fluids including HFA and HFB, biodegradable fluids, vegetable oils, bio-diesels, most modern hydraulic fluids and gases
Permachem 61505,000psi (350bar)6,000psi (420bar)-40°F to 400°F (-40°C to 210°C)6ft/s (1.8m/s)same as Permachem 6643
Additional standard materials available: PTFE, filled PTFE®, engineered thermoplastics, high-performance polyurethanes, NBR (Nitrile), FKM, Viton®, HNBR, EPDM, Aflas®, Hytrel®, Silicone, low- and high-temperature, FDA-compliant seal material grades and proprietary specialized Duralast™, Duraloy™, and Permachem™ materials.
Important Note: Maximum values above depend on extrusion gap, clearances, seal material, media, temperatures, pressures, surface speed, dynamic running surface finish and working environment. Seals cannot be operated at their upper ratings at the same time. Pressure ratings can be increased by reducing clearances. For pressure above specified operating pressure or for any advice, please contact engineering@ahpseals.com
Size Table (Inch)The standard range sizes listed below are the preferred sizes for new design applications. Seals are available for any bore size in 0.001inch increments, including functional range. Additionally, we offer any other seal size as required.
Bore Diameter
Groove Diameter
Piston Diameter
Groove Width
Standard RangeFunctional RangeToleranceD=B=D,BTol.+0.008/-0min.max.max.
0.625 - 1.5590.625 - 3.250"+0.003/-00.217A - 0.434A - 0.027+.000/-.0030.1650.0700.0250.008
1.560 - 3.249"1.500 - 5.500"+0.003/-00.306A - 0.612A - 0.028+.000/-.0030.2500.1000.0350.008
3.250 - 5.499"3.125 - 10.000"+0.004/-00.414A - 0.828A - 0.029+.000/-.0040.3200.3200.0350.008
5.500 - 9.974"3.500 - 9.975"+0.005/-00.483A - 0.966A - 0.030+.000/-.0050.3200.1300.0350.008
9.975 - 18.249"8.000 - 18.500"+0.005/-00.551A - 1.102A - 0.031+.000/-.0050.3750.1500.0400.008
18.250 - 27.500"12.000 - 27.500"+0.006/-0
0.689A - 1.378A - 0.034+.000/-.0060.4530.1700.0500.008
> 27.500"consult with Ahpseals engineering
* Based on using wear rings.Surface finish: bore (A) Ra 4-12µin – Static (D,L) Ra max. 32µin. See Technical Info for more specific information.

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Seal Housing Drawing