HPS MA28 - U-rings

Type/Ref.: Piston seal
Pressure (bar): 40/400
Temperature (°C): –40 to + 100
< +40 in HFA, HFB, HFC
Running speed (m/s): = 0.5

HPS MA28 piston seal with asymmetrical sealing lips which are cut at an angle of less than 45°.

Standard material

Polyurethane TPU92

Area of application

reciprocating movements
extreme loads


The HPS MA28 is a single function piston seal in the form of a U-ring. Its excellent suitability for extreme loads, which is for example required for application in the working cylinders of heavy earth-moving machines, is provided by the synergy between the geometric of this seal and the special material characteristics of polyurethane. It guarantees effective sealing at low and zero pressures as well as the most difficult operational conditions which would overload.


Hydraulic oils acc. DIN 51524/51525,
lubricating oils, mineral oil based
lubricating fats, non-flammable
hydraulic fluids HFA, HFB, HFC acc.
VDMA 24317.

Operational application limits

Pressure (MPa/bar): 40/400
Temperature (°C): –40 to + 100
< +40 in HFA, HFB, HFC
Running speed (m/s): = 0.5


The HPS MA28, with a thin profile can always be installed in cut housing. Due to the high strength of polyurethane, it is necessary to use intallation tools for thick seals. To push the piston body and seal into the cylinder pipe without damaging it, a lead-in chamfer C acc. to the following table is required:

Profile width (mm) Lead-in chamfer C (mm)
4 2
5 2.5
7.5 4
10 5
12.5 6.5
15 7.5
20 10
25 10

If the housing is provided with a metallic fitting on the side opposite the pressure, the service life of the seal is lengthened. Within the operating parameters given above, depending on the pressure, a metallic wedge can be fitted between the cylinder pipe and piston acc. to the following table:

Pressure (MPa) Radial wedge G (mm)
5 0.6
10 0.5
20 0.35
30 0.3
40 0.25

The piston diameter d1 should generally be by factor 1.0 of the profile smaller than the DN diameter provided.

Please also follow the general installation instructions.


In addition, we are able to supply other dimensions required. For operating conditions other than the standard applications, other polyurethane materials are available.