It is very difficult to reach effective static sealing in the housing for non-reinforced single-acting wipers, designed to be used in closed housing grooves. This is due to the fact that wipers of this group are loosely assembled in the housings. Only the counter force of the sealing lip's contact with the rod provides the sealing force between the wiper and the cylindrical surface. At decreasing temperature, when the entire wiper seal is shrinking, the risk for leakage between its outside diameter and the housing occurs. In order to reach acceptable function, this circumstance must be compensated for in the design of the wiper seal.
Non-reinforced double-acting wiper seals of nitrile rubber or polyurethane are designed to provide satisfactory static sealing between the wiper seal and the housing.
Effective static sealing in the housing can best be reached with metal reinforced wiper seals, designed for press fit assembly.