Piston and seal rings utilize fluid in high pressure environments and in those environments, the tensions of the rings is thoroughly tested. Custom piston rings and custom seal rings can withstand these testing environments. Fluid in high pressure environments will seal against moving surfaces as well as the surfaces of ring grooves. Ring tension acts as a functionary of the wall dimension. The ring has a relaxed gap. And encourages a modulus of elasticity of materials within it. Tension could be applied, if required. This is done through the use of expanders or contractors that cause the ring to exert additional pressure against mating surfaces.
The term piston or seal refer to rings that have a gap or split and are being used to prevent fluid passage. The gap or split produced improves sealing efficiency. It provides better conformability to a sealed surface. And it facilitates the installation process, as well as reducing leakage. The ring design takes into account pressure differentials, operating temperatures, the viscosity of sealed fluids, material compatibility, corrosion and linear or rotational movements, as well as the relative speed of a movement.
Rings are designed to seal and encourage expanding and contracting motions. In order to combat the propensity for leakages to occur at the gap, different gap designs have been developed. Among these designs are the step seal, the step joint and the hook joint. This latter joint is used to help the installation process where access is limited. There is also the standard butt joint. The step joint is able to provide better sealing capabilities.
Careful consideration to the selection of materials for the purpose of manufacturing these seals has to be exercised in order to deal with corrosion, temperature, thermal expansion and compatibility with related parts and components.