Wiper seals (also known as wiper scraper seals) are axial seals that form a tight fit whilst still allowing the reciprocating piston to pass through the inner bore of the seal. They are usually installed in hydraulic and pneumatic cylinders to allow dirt, scrap, or moisture to be flushed from the piston rod and pistons as they run through the system. Doing so prevents pollution that could damage the piston rings, piston seals and other components within the system. Even if they are in good condition, wipers should always be replaced when other seals are replaced.
They are usually used for: