O-Ring-Loaded Symmetrical U-Cup with Scraper Lip Design

Uni-directional, single-acting with scraper seal lips designed to move contamination away from the sealing lips. For use as either rod or piston seal in light- to medium-duty hydraulic applications where low-pressure startup may be present. K18 will retrofit any square, deep or B polypak type seal or seal of similar design. To avoid potential seal failure, do not use energizer-loaded seals for back-to-back bi-directional piston sealing applications.

Operating Range
MaterialOperating Pressure up toMaximum Pressure up toTemperatureSurface Speed up toFluid, Media Compatability
Duralast 42033,800psi (260bar)5,000psi (350bar)-22°F to 260°F (-30°C to 125°C)1.6ft/s (0.5m/s)mineral oil-based fluids, fire-resistant water-based hydraulic fluids including HFA and HFB, sea water, biodegradable fluids, vegetable oils, bio-diesels, and most modern hydraulic fluids
Duralast 44035,000psi (350bar)8,000psi (520bar)-22°F to 260°F (-30°C to 125°C)1.6ft/s (0.5m/s)same as Duralast 4203
Duralast 81662,300psi (160bar)3,800psi (260bar)-4°F to 392°F (-20°C to 200°C)3.2ft/s (1.0m/s)fire-resistant fluids, phosphate esters, mineral oils, greases, and most inorganic acids and chemicals, gasoline and gasoline/alcohol blends, hard vacuum
Duralast 51012,300psi (160bar)3,800psi (260bar)-22°F to 212°F (-30°C to 100°C)1.6ft/s (0.5m/s)mineral-oil based hydraulic fluids, silicone greases, petroleum-based oils, water and alcohols
Duralast 61462,300psi (160bar)3,800psi (260bar)-30°F to 302°F (-35°C to 150°C)2.0ft/s (0.7m/s)excellent heat and oil resistance, including exposure to such oil additives as detergents, anti-oxidants and anti-wear agents
Additional standard materials available: High-performance polyurethanes, NBR (Nitrile), FKM, Viton®, HNBR, EPDM, Aflas®, Hytrel®, Silicone, low- and high-temperature, FDA-compliant seal material grades, PTFE, filled PTFE®, engineered thermoplastics 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, please contact engineering@ahpseals.com
Size Table (Inch)Standard range sizes listed below are preferred sizes for new design applications. Seals are available for any shaft diameter size in 0.001 inch increments, including functional range and optional groove width. Additionally we offer any other seal size as required.
Groove Width
L Groove Width
Optional Standards
Standard RangeFunctional RangeD=
A, BPD, BGBP=BG=Tol.+0.010/-0Tol.+0.010/-0min.max.max.
0.250 - 0.999"0.500 - 2.500"0.125A + 0.250+0/-.002+0.002/-0D - 0.024A + 0.0260.2050.138/0.2750.0550.0150.006
1.000 - 1.999"0.500 - 5.000"0.188A + 0.375+0/-.002+0.002/-0D - 0.024A + 0.0260.3430.205/0.275/0.4130.0800.0200.006
2.000 - 3.999"0.750 - 10.000"0.250A + 0.500+0/-.003+0.003/-0D - 0.027A + 0.0270.4130.275/0.343/0.5500.0800.0200.008
4.000 - 6.249"1.000 - 12.000"0.313A + 0.625+0/-.003+0.003/-0D - 0.029A + 0.0290.5500.343/0.413/0.6880.0850.0250.008
6.250 - 9.999"1.000 - 40.000"0.375A + 0.750+0/-.004+0.004/-0D - 0.030A + 0.0300.6880.413/0.550/0.8250.0900.0300.008
10.000 - 15.999"2.000 - 70.000"0.500A + 1.000+0/-.005+0.005/-0D - 0.031A + 0.0310.8250.550/0.688/1.1000.1200.0300.008
16.000 - 24.999"2.500 - 70.000"0.625A + 1.250+0/-.006+0.006/-0D - 0.032A + 0.0321.1000.688/0.825/1.3750.1400.0300.008
25.000 - 35.999"5.000 - 70.000"0.750A + 1.500+0/-.007+0.007/-0D - 0.033A + 0.0341.3750.825/1.100/1.6500.1700.0400.008
36.000 - 72.000"6.000 - 70.000"1.000A + 2.000+0/-.008+0.008/-0D - 0.034A + 0.0361.6501.1000.2300.060
> 70.000"consult with Ahpseals engineering
* Based on using wear rings. Surface finish: dynamic Ra 4-12µin – Static Ra max. 32µin. See Technical Info for more specific information.

Seal Size Selector – Request a Quote

  • Enter shaft, rod or bore diameter
  • If recommended size is not feasible, please enter your preferred dimensions
  • If recommended size is not feasible, please enter your preferred dimensions
Back to Products page
Seal Housing Drawing