Shape: KAV concave
The max. permissible operating pressure depends on the gap dimensions.
Temperature (°C): -30 to + 100
The operational application limits use are dictated by the O-ring selected. It is only the resistance of the sealing system to pressure which can be increased by the STU back-up ring.
Hydraulic oils H, HL, HLP as per DIN 51524 Part 1 – 3, mineral-oil based lubricants and greases, non-flammable hydraulic pressure fluids HFA, HFB, HFC as per VDMA 24317 to approx. + 50°C and water to max. + 80°C
The STU back-up ring is a closed ring concave in cross-section. It is produced entirely as a closed ring with no seams, by the injection-moulding process. For our STU back-up rings we use an NBR material of 90° Shore-A hardness, so as to guarantee a high level of resistance to extrusion and abrasion.
The back-up ring’s concave cross-section provides the O-ring with a larger contact surface, having the effect of allowing the O-ring almost fully to retain its circular shape under high pressures and to be less liable to deformation. This means that the shape of the O-ring is supported better and it can therefore withstand higher pressure loads. This produces a better sealing effect and increases the seal’s service life. Due to its closed design, under high pressures it is not possible for the O-ring to be damaged by a sharp edge at the open-ended joint (as is the case with open back-up rings).
The STU back-up ring is of symmetrical profile. This allows it to be used in both internal and external sealing systems.
The groove widths b1 and b2 are presented in the following table:
|S=1.35 mm||S=2.18 mm||S=3.0 mm||S=4.65 mm||S=5.99 mm|
|b1||3.5 – 3.7||4.7 – 4.9||5.8 – 6.0||8.7 – 8.9||12.0 – 12.2|
|b2||4.6 – 4.8||5.8 – 6.0||6.8 – 7.0||10.2 – 10.4||14.4 – 14.6|