Tests have been carried through to study the ability of different types of wiper seals to stop or to minimize the amount of contamination particles to pass the wiper seal into a cylinder. The tested wiper seals were type PA of polyurethane (1) and SKF type GA of nitrile rubber (4), a metal reinforced single-acting wiper seal from Japan (3) and a non-reinforced double-acting wiper seal from the USA (2). The figures in brackets refer to the diagram 1.
A maximum of 10 000 particles of the size 10 to 20 µm were allowed to have passed the wiper seal into a certain amount of oil after 500 000 stroke cycles with a stroke length of 2 × 50 mm (one way) and a frequency of 60 cycles/min. The rod diameter was 50 mm. The SKF type PA was the only wiper seal that passed the test.
Please contact SKF for complementary information on this test or comparative tests with double-acting and single-acting wiper seals.