Scraper Seals or Wipers are installed in the sealing configurations of hydraulic cylinders. They scrape dirt, foreign particles, chips or moisture from the piston rods as they retract into the system. It’s function is that of an axial seal. It creates a tight fit while still allowing a reciprocating ram rod to pass through the inner bore.
A hydraulic wiper or scraper prevents contamination of the hydraulic medium that could damage wear rings, seals and other components.
These seals keep external dirt, foreign particles, chips, moisture etc. outside.
They work as above but, especially relevant, these seals have the added function of avoiding any external leakage.