What's the Story on Piston Cups?
Piston cups are used on piston heads, plungers or rams in pneumatic or hydraulic applications. They are commonly used because of their superior service life, universal acceptance, and ultimately their economic cost.
Homogeneous piston cups are typically used in low pressure applications (under 150 psi) for service in pneumatic, hydraulic fluids and water. Fabric reinforced piston cups prevent extrusion in medium pressure installations (up to 1000 psi) or where diametrical clearances are greater.
Piston cups come in duck/rubber, urethane, leather, homogenous buna, molythane, and fabric reinforced rubbers. The most commonly used are duck/rubber. Homogenous piston cups are generally used in low pressure service applications due to the flexibility and responsiveness of the sealing lip. Homogenous piston cups are usually Nitrile, but are also available in other homogeneous materials such as EPR, fluorelastomer and silicone. A piston cup seals on the outer lip and is held in place by a follower plate. Temperature ranges are determined by the compound used.
Many piston cups come with no center hole. The hole size may vary with each application, so the customer can drill the appropriate size hole, rather than try to make a wrong size hole work on their application.