HPRS MA25 - U-rings

Type/Ref.: Piston/Rod seal
Pressure (bar): 30/300
Temperature (°C): –40 to + 100
< +40 in HFa, HFB, HFC
Running speed (m/s): = 0.5

Piston and piston rod seal with symmetrical sealing lips which are cut at an angle of less than 45°.

Standard material

Polyurethane TPU92

Area of application

reciprocating movements


The HPRS MA25 is a single function piston seal in the form of a U-ring which can be used as a piston and piston rod seal due to its symmetrical sealing lips. Its seal function is very effective due to the sealing lips being provided with radial self energising which is activated by the system pressure. Due to the high wear resistance of polyurethane, this seal has a particularly long service life. For new design we recommend HRS MA30 or HPS MA28.


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): 30/300
Temperature (°C): –40 to + 100
< +40 in HFa, HFB, HFC
Running speed (m/s): = 0.5


The HPRS MA25, from an inner diameter of 25 mm and a thinner profile can always be installed in cut housing. Due to the high tensile and strength of polyurethane, it is necessary to use installation tools for thick seals. With an inner diameter of less than 25 mm, we recommend axially accessible housing. To push the piston body and seal into the cylinder pipe or over the piston rod 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 head and piston rod or 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

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.