Piston U-Ring Set P31

Single-acting Piston U-Ring P31 for standardised housings according to ISO5597 has asymmetrical profile and shortened outer lip, High extrusion resistance thanks to integrated back-up ring and pressure-relieving grooves

Piston U-Ring P31 can be installed in “back-to-back” position in double-acting piston design with pressure on both sides.

Heavy duty Earth moving equipment
Standard hydraulic cylinders.
Truck tail lift
Stabilizer cylinders
Agriculture equipment
Construction machinery

Standard material
Material set code SU512
U-cup Material Polyurethane 94 ShA
Back-up ring Acetal resine (POM)


The U5002 material has high mechanical properties, high wear, high abrasion and media resistance

Pressure, Speed
Working pressure, P 40 Mpa
Running speed, v 0,5 m/s
Medium; Working Temperature
Material set code SU512
Hydraulic oils HL, HLP -30 … +110 °C
HFA, HFB fluids +5 … +60 oC
HFC fluids -30 … +40 °C
Water +5 … +50 oC
Mineral greases -30 … +110 °C
Max. permissible gap dimension, emax
Max operating pressure S=7,5mm S>7,5mm
16 Mpa 0,80 1,00
26 Mpa 0,70 0,90
32 Mpa 0,50 0,65
40 Mpa 0,40 0,55
Surface quality*
Surface roughness Ra Rmax
Sliding surfaces 0.05.. 0,3 μm ≤ 2,5 μm
Groove base ≤ 1,6 μm ≤ 6,3 μm
Groove flanks ≤ 3,0 μm ≤ 15 μm

*Contact area Mr = 50% to 90% at cutting depth c=Rz/2 and reference line Cref=0%