Wiper seals are also known as Scraper seals. They tend to be used in conjunction with other sealing elements. Wiper seals create a tight fit whilst still allowing a reciprocating ram rod to pass through the inner bore of the seal.
Despite it’s important function, the wiper seal is possibly the most undervalued seal type in the pneumatic cylinders. Wiper seals are used to eliminate contaminants such as moisture, dirt, and dust. Contamination can cause significant damage to the rod, cylinder wall, seals, and other components. This is one of the primary causes of premature seal and component failure in a fluid power system.
Some Wipers or Scrapers have a secondary lip used to capture any oil that may have bypassed the main seal. The secondary lip may also remove any bonded contaminate from the rod surface. These types of wipers are often called ‘double-edged wipers’.
The common compound for wipers is polyurethane. Metallic scrapers may be used for sub zero temperature applications, and particularly arduous applications where foreign materials can deposit on the rod.