Piston Seals
Piston seals, also known as piston packings, are mounted on a piston head which moves through the bore of a hydraulic or pneumatic cylinder tube. The inner diameter of the seal is fitted in a static housing/ groove within the piston head. Piston seals can either be single acting seals (designed for pressure from one side only), or double acting seals (designed for pressure from both sides) and are usually used in a sealing system with bearings, which are either incorporated into the seal or separately in additional housings. Sometimes single acting seals are mounted back-to-back on a piston head in separate grooves to provide a double acting arrangement. The correct combination of seals, bearings, housing and piston tolerances, and surface finishes for the application will reduce leakage across the seal, improve the systems energy efficiencies, as well as prolong seal service life reducing maintenance costs. Standards relating to piston seal housings are:ISO 5597 (single acting piston seals)ISO 6547 (double acting seals with integral bearings)ISO7425-1 (elastomer energised plastic faced double acting seals) Hydraulic seals are available in a large number of designs or cross-sectional profiles. Single acting symmetrical seals. These can be used for either rod or piston applications. They can be U-rings (or U-cups) or positive squeeze seals. The most common material is polyurethane, the positive squeeze seals often being energised by a nitrile (NBR) O-ring Double acting piston seals. These could use thermoplastic elastomer or filled PTFE faces, energised by a nitrile (NBR) O-ring, in a composite or co-axial arrangement. For higher pressures a T-shaped NBR energiser is often used in combination with a plastic face and hard engineering plastic anti-extrusion rings are fitted. Double acting piston seal with integral bearings. These generally have nitrile (NBR) sealing elements, thermoplastic elastomer support rings and acetal (POM) bearings. Vee packs. These are generally symmetrical and can be used for rod or piston applications. These are typically constructed from fabric reinforced elastomers such as nitrile (NBR). For double acting applications the vee-pack sets are mounted back-to-back separate grooves.
Piston seals, also known as piston packings, are mounted on a piston head which moves through the bore of a hydraulic or pneumatic cylinder tube. The inner diameter of the seal is fitted in a static housing/ groove within the piston head. Piston seals can either be single acting seals (designed for pressure from one side only), or double acting seals (designed for pressure from both sides) and are usually used in a sealing system with bearings, which are either incorporated into the seal or separately in additional housings. Sometimes single acting seals are mounted back-to-back on a piston head in separate grooves to provide a double acting arrangement.
The correct combination of seals, bearings, housing and piston tolerances, and surface finishes for the application will reduce leakage across the seal, improve the systems energy efficiencies, as well as prolong seal service life reducing maintenance costs.
Standards relating to piston seal housings are:ISO 5597 (single acting piston seals)ISO 6547 (double acting seals with integral bearings)ISO7425-1 (elastomer energised plastic faced double acting seals)
Hydraulic seals are available in a large number of designs or cross-sectional profiles.
Single acting symmetrical seals. These can be used for either rod or piston applications. They can be U-rings (or U-cups) or positive squeeze seals. The most common material is polyurethane, the positive squeeze seals often being energised by a nitrile (NBR) O-ring
Double acting piston seals. These could use thermoplastic elastomer or filled PTFE faces, energised by a nitrile (NBR) O-ring, in a composite or co-axial arrangement. For higher pressures a T-shaped NBR energiser is often used in combination with a plastic face and hard engineering plastic anti-extrusion rings are fitted.
Double acting piston seal with integral bearings. These generally have nitrile (NBR) sealing elements, thermoplastic elastomer support rings and acetal (POM) bearings.
Vee packs. These are generally symmetrical and can be used for rod or piston applications. These are typically constructed from fabric reinforced elastomers such as nitrile (NBR). For double acting applications the vee-pack sets are mounted back-to-back separate grooves.
