A variety of demands and loadings in numerous housings have led to the development of various designs of seals. The classification of hydraulic seals is possible, based on function and design. Hydraulic seals are also subdivided into seals, which have symmetrical or asymmetric cross-sections. Asymmetrical seals are so designed that in the installed state they contact the static surface with an initial stress over the whole axial width in order to achieve a sufficiently firm seating in the groove. Correct stressing at the moving surface only occurs therefore after fitting the seal into the assembly.

Selection of seals

In addition to the main requirement of making a good seal, a series of further demands are made by the uses of hydraulic seals:

  • operational reliability,
  • long life-time,
  • simple installation,
  • tolerance to the hydraulic medium at high and low temperatures,
  • high resistance to mechanical damage (e.g., extrusion into the gap),
  • low friction,
  • good dimensional elasticity to ensure faultless operation even with working eccentricities between the rod and the housing or the piston and the cylinder wall respectively, as well as expansion of the cylinder due to operating pressure.

The evaluation of these demands is of critical importance in the selection of seals, and in special cases so too are the operating conditions (pressure, temperature and linear velocity).

Depending on the applications and on the individual operating parameters, even higher loadings are possible. In such cases the seal should be chosen in collaboration with us, since tests to examine the operational reliability of the chosen seal are frequently indispensable.