Cap seals offer a low friction seal for use in dynamic reciprocating applications.
A plastic cap provides a seal against the dynamic sealing face, an O-ring is used to energize the plastic cap and operates in a static environment. The O-ring uses the system pressure to increase the sealing force acting on the cap. The cap also prevents extrusion of the O-ring energizer when used in high pressure applications.
The plastic cap is typically made from a low friction material, such as PTFE. Under low pressure conditions, liquid media can provide lubrication as it migrates between the dynamic sealing faces through a capillary effect. Cap seals are often referred to as wet seals as they allow a small amount of fluid to pass across the seal.
Cap seals can be offered in two different designs, a heavy duty cap or a low profile cap:
Heavy duty cap
- Provides a thicker cross section of sealing cap for use with high pressure, up to 40 MPa
- Requires a non-standard groove for fitment
- Thicker section allows for greater wear, due to higher sealing forces induced
Low profile cap
- Generally for light to medium duty
- Can be retro fitted into standard O-ring grooves
- Provides good wear resistance and low friction, due to lower sealing forces induced