The limiting values for the gap at the non-pressurized side of the seal are determinated by the pressure loading, by the type of the seal and by the material of the seal.
When calculating the gap widths, the given play at the guide (fitting tolerance) and the elastic stretching of the cylinder bore under pressure must be considered. Otherwise the permissible gap width will be exceeded with offset installation of the rod or piston.
If the permissible gap widths are exceeded, then extrusion wear (see figure) occurs at the back of the seal and this destroys the seal after a short period of time.
