K-BOS Bushing Oil Seal

Kaydon Ring & Seal has perfected the classic bushing oil seal assembly. Long the mainstay for shaft sealing of centrifugal compressors, the bushing oil seal is simple in its design and easy to maintain. Oil is supplied between two clearance bushings at a pressure slightly greater than process gas pressure and prevents process gas from escape.

Historically, oil leakage to process (sour oil) was controlled with tight clearances that made the seals more susceptible to incidental contact with the shaft and permanent increases in clearances and leakage rates.

The Kaydon bushing oil seal (K-BOS) allows for tightly controlled leakage rates while maintaining a larger nominal clearance to the shaft. This is achieved by way of engineered pumping geometry in the bore of the process seal ring, which works with shaft rotation to generate a relative offset to seal oil pressure. This geometry is designed to provide optimal performance at normal operating speeds, while a short constant clearance section of the ring controls leakage rates during shutdown.

Gold-plated K-BOS for Corrosive Applications

Kaydon gold-plated bushing oil seals are ideal for hydrogen recycle and wet gas compressor applications where high concentrations of H2S or chlorides may form after rotor wash and attack traditional Babbitted bushings. Kaydon retrofits of gold-plated K-BOS seals have increased compressor run times from less than one year to 7+ years between seal overhauls.

Features and Benefits

  • Non-contacting seal
  • Unlimited axial movement
  • Low sour-oil leakage controlled by engineered seal geometry and more generous clearances
  • Pre-tested cartridge for shorter installation times (hours vs. days for component seal designs), and demonstrated performance
  • Can be designed to fit existing seal oil system pressures and flows
  • Standard Babbitt-lined seal rings
  • Optional gold-plated process ring is resistant to chemical corrosion and erosion
  • Triple bushing configurations available for high-pressure services
  • Capable of operating directly on shaft


  • Natural gas processing plants
    • Lift gas, sales gas, raw gas, residue gas compressor shaft seals
  • LNG boil-off and refrigeration compressor shaft seals
  • Refinery
    • Hydrogen recycle, platformer, reformer, hydrotreater, wet gas, coker, alkylation, isomerization, crude unit.
  • Petrochemical
    • Ethylene, propylene, polypropylene, charge gas, propane refrigeration, iso-butane, ethylene oxidepolyethylene, carbon monoxide, methanol, synthesis gas, acetylene, feed gas

Why Kaydon Ring & Seal?

Kaydon is the only supplier of bushing oil seals able to stand behind its products performance with decades of experience and factory performance testing. Kaydon is able to provide a drop-in solution for reduced sour oil leakage and improved reliability. In some cases sour oil leakage can be reduced by an order of magnitude or more allowing payback to be achieved in as short as a few months. Customers who are accustomed to taking days to replace component seal designs are always amazed at how quickly and easily Kaydon cartridge seal designs are installed.

Kaydon has the broadest range of compressor seal types available in the industry. Our goal is to supply you with the best solution for your circumstances, whether it is repair, upgrade or replacement of your existing seal.