Piston seal, double-acting

Double-acting piston seals of the types KD 02 (without notches) and KD 03 (with notches) are ideally suited for use in hydraulic systems and promise stick-slip-free running as well as good dry-running properties. The media used in these applications range from mineral oil-based hydraulic liquids, environment-friendly bio-oils and water to flame-resistant hydraulic liquids and air.

While the PTFE profile ring provides dynamic sealing against the cylinder surface, the elastic O-ring ensures there is a uniform contact pressure of the PTFE profile ring onto the cylinder surface and at the same time a static sealing between profile ring and groove base.

Even at low pressures, the piston seal shows a good sealing effect due to the inherent preload of the PTFE profile ring and the contact force of the preloaded O-ring. At higher system pressures, the medium pressurizes the O-ring causing it to press the PTFE seal with enhanced force against the cylinder surface.

With different material combinations, the piston seal can be used reliably across the whole pressure, speed and temperature range.


To ensure that the preload on the seal is maintained under sudden changes in pressure and in direction of motion, it can be provided with two radial notches on both sides (Type KD 03).

Application media

  • Mineral oil-based hydraulic liquids
  • Water
  • Air
  • Environment-friendly bio-oils
  • Flame-resistant hydraulic liquids
  • Other media, depending on the O-ring material

Application range

Pressure: up to 40 Mpa (400 bar)
Speed: approx. up to 15 m/s
Temperature: -30 °C to +200 °C (depending on the O-ring material)


Roughness depthRaRt
Running surface≤ 0,3 µm≤ 3,0 µm
Groove base≤ 1,6 µm≤ 16,0 µm
Groove flank≤ 1,6 µm≤ 16,0 µm


Heavy designCylinder ø D
Standard design
light designGroove base ø dGroove width+0,2Radius R10 Mpa max.Gap size S 20 Mpa max.40 Mpa max.O-Ring line ø
8,0 – 14,915,0 – 39,9ød – 4,92,20,40,30,20,151,78
15,0 – 39,940,0 – 79,9ød – 7,53,20,60,40,250,152,62
15,0 – 39,940,0 – 79,980,0 – 132,9ød – 11,04,21,00,40,250,23,53
40,0 – 79,980,0 – 132,9133,0 – 329,9ød – 15,56,31,30,50,30,25,33
80,0 – 132,9133,0 – 329,9330,0 – 669,0ød – 21,08,11,80,60,350,257,0
133,0 – 329,9330,0 – 669,9670,0 – 900,0ød – 24,58,11,80,60,350,257,0
330,0 – 669,9670,0 – 900,0ød – 28,09,52,50,70,50,38,4

PTFE profile ring material

PTFE + bronze

The standard for hydraulic applications, good gliding behavior, particularly pressure and abrasion resistant, cannot be used in aqueous solutions or acids

PTFE + Glas-MoS2

Particularly good resistance to wear and abrasion, application is possible even with poor lubricating pressure fluids, in water and in water-oil emulsions

PTFE + carbon

Exceptionally resistant to abrasion and extrusion, can be used in water-hydraulics

O-ring material

Nitrile rubber NBR: Temperature range − 30 °C to + 120 °C
Fluororubber FPM: Temperature range − 25 °C to + 200 °C

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