Hydraulic Sealing Products

Twinset - for rods, glands & pistons

Twinset is our pressure-responsive packing set that boasts a record of success stretching back over 50 years. Although we recommend our more advanced designs for many traditional Twinset applications, this product remains a firm favourite with many operators of older hydraulic plant.

The packing set comprises an endless U-ring firmly supported by a header ring. The lips of the U-ring are slightly flared to provide an interference fit for initial sealing. When system pressure is applied, the sealing force is increased significantly by reaction within the tongue-shaped cavity of the U-ring.

Under slight axial compression, the header ring also spreads the U-ring lips slightly to improve low pressure sealing efficiency.

Special features

  • Very well proven on reciprocating plant worldwide.
  • Readily available in traditional inch and metric sizes for older plant.
  • Suitable for adjustable and non-adjustable axial length housings.

Typical applications
Twinset was developed for vertically reciprocating hydraulic shafts and rams. Current applications include the main rams of upstroking/gravity return presses and downstroking/prefilling type presses. It is also successful on press drawback rams, hydraulic piston heads, jacks and hoists, and hydraulic valves.

Note: This packing set should not be used under abrasive conditions or for heavy-duty applications (eg, forging or extrusion presses), or on rams subjected to shock loads or side loads. In such cases, please ask our Technical Support Team to recommend a suitable product.

Operating capabilities

  • Maximum operating pressure: 34MPa (4931psi).
  • Maximum temperature (standard materials): 100°C (212°F).
  • Maximum surface speed: 0.5m/s (98.4fpm).

Materials of construction
Standard materials: cotton fabric proofed with a blend of synthetic rubbers.

Header ring
Standard materials: nylon or similarly hard composite.

Spring-loaded header ring
Header rings of 6.5mm section and above can be supplied with multiple coil springs for the automatic compensation of wear when used in non-adjustable housings.

Media capability
Standard materials are suitable for use with most mineral-based hydraulic fluids, lubricating oils and greases at temperatures up to 100°C (212°F). They are also resistant to water and air.

The standards materials prove satisfactory for use with a number of fire-resistant fluids, including many of the phosphate ester type. Although swell will occur, most users find that this does not impair plant performance. Where fire-resistant fluids are used, it is essential to advise our Technical Support Team of the type and designation.

How supplied
Endless rings only, up to 1675mm (66 inch) OD, with sections from 5mm (0.19 inch) upwards. Please state whether housings are adjustable or non-adjustable. For sizes above 1675mm (66 inch) OD, please consult our Technical Support Team. Fitting instructions are supplied with every set.