sealing system

Simple Explanation of Seals

There are numerous sealing products, technologies, and techniques to keep oil in and contaminants out of the hydraulic system, each providing unique benefits. Further, in some harsh applications, the features of individual seals do not fulfill the demanding requirements for the equipment and a sealing system is required.

Here are the basics of seal designs:


  • Provide aggressive wiping force to prevent mud, water, dirt and other contamination
  • Allow lubricating oil film to return to system on inward stroke
  • Protect main sealing elements, thus increasing life of seals
  • Are often made from Polyurethane, which offers high abrasion resistance
  • Are often used as a linkage pin grease seal

Rod seals:

  • Contain system fluid from escaping to atmosphere
  • Must provide sealing function at low and high pressure
  • Require excellent extrusion and wear resistance
  • Should provide good pump-back capability for lubricating oil film
  • Often must withstand up to 6000 psi

Buffer seals:

  • Must withstand high pressure exposure
  • Protect the rod seal against pressure spikes
  • Pressure relieving capability prevents pressure build-up between seals
  • Increase rod seal life
  • Allow for wider extrusion gaps
  • Require high wear resistance

Wear bands:

  • Prevent contact between metal parts in the cylinder
  • Center rod and piston from housing elements
  • Increase seal life




Craig Cook

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