Piston Seals

Piston Seals for hydraulic cylinders

Piston seals or piston rings ensure fluid or other media does not by-pass the piston as the system pressure pushes the piston down the cylinder during a pressure cycle.

Piston seals are dynamic seals, typically single-acting (pressure acting on one side only) and double-acting (pressure acting on both sides) seals. The choice of piston seal is determined by the way in which the cylinder operates.

Single-acting pistons

Single-acting pistons only contain pressure on one side of the piston. The seal is required to retain pressure from that direction, which then moves the piston along the cylinder.

Double-acting pistons

Double-acting pistons contain pressure on both sides of a piston without leakage. They allow maximum mechanical effort to the moving the piston along the bore of a cylinder.

For a cylinder which is exclusively single-acting, capable of sealing dynamic pressure from one side (unidirectional), it is always best to choose the type of seal designed to provide optimum sealing qualities for single-acting functions.

The best sealing capacity of a double-acting cylinder, capable of sealing dynamic pressure from both sides (bidirectional), is achieved by choosing a double-acting seal.
A piston design where two single-acting seals on the piston for a double-acting cylinder are used can easily give rise to a breakdown. The reason is that a very high pressure can be trapped between the seals.

Piston seals, both single and double-acting, can be designed for and used with integrated or separate back-up rings and guide rings.

Common types of Piston Seals

PCA piston sealPCA seal profile
A robust compact double acting seal assembly designed specifically for one piece pistons. It uses a nitrile sealing element which has proven itself in service to be extremely wear resistant and capable of working most effectively in a wide variety of medium duty applications. The seal is also suitable for two piece piston applications.

Temp. range : -30°C to +100°C (Up to +200°C on request)
Pressure : 350BAR
Speed : 0.5 m/s

Light to medium duty cylinders. Static load holding (boom lifting to hold hydraulic platforms) Compact cylinders

Mineral oils, Water soluble & Water glycol fluids

PCQ piston seal
PCQ seal profile
PCQ seals are constructed from polyurethane and NBR. The assembly of a PCQ piston seal is relatively straight forward because the material is elastic and the seal only needs a small housing. Although useful but not essential, lubricate the seat and the gasket using the same fluid as in the system or a chemically compatible lubricant.

Temp. range: -30°C to +100°C
Pressure bar: 0 to 250 BAR at 60°C
Speed: 0.5 m/s

Mineral oils

PCR piston seal

PCR seal profile
A robust compact double acting seal assembly suitable for one piece pistons. Fabric reinforcement with high mechanical strength, optimum thermal stability and lubricating properties. The small radial dimension of this type of seal, together with anti-bearing / anti-extrusion rings enable them to be assembled onto one piece pistons.

Temp. range: -30°C to +100°C (Up to +200°C on request)
Pressure: 350 BAR
Speed : 0.5 m/s

They are intended for use where housing space is at a premium and in semi severe application. Straightforward and quick to assemble.

PEE piston seal
PEE seal profile
Double acting NBR piston seal for one piece pistons, incorporating Polyester anti-extrusion rings & POM bearing rings.

Temp. range : -30°C to + 100°C (Up to +200°C on request)
Pressure : 350 BAR
Speed : 0.5 m/s


Other profiles for piston applications

Non-standard sizes for piston applications

Non-Standard Piston seals

UK Seals supply a wide range of piston seals including; PTFE seals, U Seals, fabric seals, compact seals, cup seals and V packs. We supply Compact seals/3/5 Part Piston Seals and V packs (chevron) in many sizes and profiles. Contact UK Seals for additional available profiles. Again, non-standard sizes are our strength.

Hydraulic Seals information

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