Rod Seals

   

Of all the seals in a cylinder application, the rod seal is the most critical.  The importance lies in the fact that rod seal failure could result leakage of fluids to the environment, and that it will typically see the harshest service conditions.  Rod seal failure is not only a mess, but it is detrimental to proper cylinder performance and safety.  The key features of any rod seal are:

  • The rod seal acts as a dynamic seal along its inner diameter, and static along its outer diameter
  • It is directly affected by changes to the rod surface and fluid temperature fluxuations
  • Often sees the highest pressure variations or spikes in the system
Unloaded U-Cup  
U-Cups derive their name from their "U" shape. They seal on both the inside and outside diameters.  U-Cups are popular due to the small gland space required. They are usually specified in low speed, low pressure environments for both pneumatic and hydraulic cylinders. The seal is obtained by means of the flared, flexible lips coming in contact with the rod or cylinder wall. Clearance is provided at the heel for minimum friction. Seal effectiveness is increased as internal pressure increases against the inner surface of the lips. Dynamic contact surfaces should have a finish of 8 - 16 RMS.

Symmetrical Unloaded U-Cups

Urethane seal with U shape at hydraulic pressure interface for good high pressure performance.
  • Features: Pressure energized seal
  • Applications: Mobile Hydraulic; Agricultural; General Industrial
  • Materials: Urethane
  • Max Pressure: 2,000 psi
  • Temperature range: -45 °F to +265 °F
  • Max Velocity: 3.2 ft/sec
Asymmetrical Unloaded U-Cups

Urethane seal with U shape at hydraulic pressure interface for good high pressure performance.

  • Features: Pressure energized seal with back beveled lip, bump heel and film breaking capabilities
  • Applications: Mobile Hydraulic; Agricultural; General Industrial
  • Materials: Urethane or Hytrel
  • Max Pressure: 6,000 psi
  • Temperature range: -50 °F to +250 °F
  • Max Velocity: 3.2 ft/sec
Loaded U-Cup  

Loaded U-Cups derive their name from their "U" shape and the elastomeric energizer they use to provide more effective low pressure sealing.

U Cups seal on both the inside outside diameters
U Cup seals are often used for piston or rod seals due to the small gland space required
U Cups are usually specified in low speed, low pressure environments 
U Cups seal by means of the flared, flexible lip in contact with the rod or cylinder wall

Dynamic contact surfaces should have a finish of 8 - 16 RMS.
Beveled Loaded U-Cups

Urethane seal surface with low pressure energizer for better performance at low pressure and longer seal life

  • Features: Energized seal for low pressure capability with back beveled lip and film breaking capabilities
  • Applications: Mobile Hydraulic; Agricultural; General Industrial; medium duty cycle
  • Materials: Urethane or Hytrel shell with Nitrile or Viton® expander
  • Max Pressure: 6,000 psi
  • Temperature range: -50 °F to +250 °F
  • Max Velocity: 3.2 ft/sec
Deep Loaded U-Cups

Urethane seal surface with low pressure energizer. Taller than the Beveled Loaded U-Cup for increased resistance to deformation.

  • Features: Energized seal for low pressure capability with back beveled lip and film breaking capabilities  Deeper profile for improved extrusion resistance and stability
  • Applications: Mobile Hydraulic; Agricultural; General Industrial; high duty cycle
  • Materials: Urethane or Hytrel shell with Nitrile or Viton® expander
  • Max Pressure: 6,000 psi
  • Temperature range: -50 °F to +250 °F
  • Max Velocity: 3.2 ft/sec
Premium Loaded U Cup  

Premium loaded U-Cups insert a primary seal element into the base seal.  They also use the elastomeric energizer to provide even more effective low pressure sealing. This seal is an excellent choice where systems experience extremely low temperatures and leakage occurs until the system warms up.

Premium U Cups seal on both the inside and outside diameters
Premium U Cup seals are used for both piston and rod seals
Premium U Cups seal by means of two flared, flexible lips in contact with the rod or cylinder wall

Dynamic contact surfaces should have a finish of 8 - 16 RMS.
Standard Loaded U Cup

Heavy-duty rod seal for applications requiring low friction and service at extreme temperatures. Elastomeric lip for sealability combined with high modulus for extrusion resistance and toughness. In cold weather service, NBR is an excellent choice for the energized seal. This seal is available in several material combinations.

Double Lip U Cup

Heavy-duty rod seal for applications requiring low friction and service at extreme temperatures

  • Features: Elastomeric lip for sealability; excellent extrusion resistance and toughness; Low temperature materials available
  • Applications: Mobile Hydraulic; Telescopic cylinder; High duty cycle
  • Materials: Urethane or Hytrel shell with Nitrile, Viton, low temperature Nitrile top seal
  • Max Pressure: 6,000 psi
  • Temperature range: -50 °F to +250 °F
  • Max Velocity: 3.2 ft/sec
Spring Energized  

Seal for extreme conditions where conventional elastomeric seals can't be used such as corrosive media, extreme temperatures and high surface speeds

  • Features: Low compression set; secondary lip; excellent low temperature sealing; low friction; widest P/T range; custom design is available
  • Applications: Petrochemical; Extreme temperatures; Corrosive fluids; High duty cycles
  • Materials: Virgin PTFE and PTFE blends, UHMWPE; PTFE; PEEK; S/S spring
  • Max Pressure: 10,000 psi
  • Temperature range: -450 °F to +550 °F
  • Max Velocity: 3.2 ft/sec