The recommended test method applies to hydraulic actuators that are components of commercial and military aircraft control systems. This recommended practice establishes guidelines for comparison testing and reporting the effectiveness of rod scrapers only against dry dust and ingression of ISO standardized test dust into the fluid and should not be construed as a qualification process for rod scrapers since the macro contaminants which are not being tested here can affect scraper performance. To fully evaluate rod scraper effectiveness, the subject actuator design and its full operating environment needs to be evaluated.
The function of a reciprocating rod scraper is to keep contaminants away from seals and the hydraulic fluid. If the seals are exposed to contaminants, their life will be shortened. If the fluid is contaminated, other components of the hydraulic system such as pumps, servo valves and valves may also wear prematurely and may cause malfunction of hydraulic system.