Advantage of O-Ring & Theory of Shaft Fretting
 


ADVANTAGE OF AN O-RING SEAL COMPARED TO OTHER ELASTOMER SHAPES
 

 
  • O-Ring can flex and roll
 
  • With the installation of back up rings, O-rings become the standard for all high pressure mechanical sealing.
 
  • Less shaft Fretting : O-ring can fret a shaft, but takes longer than other designs.
 
  • Misalignment : O-ring can compensate for gland misalignment better than any other configuration.
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THEORY OF SHAFT FRETTING
 

 
  • Shaft fretting can be recognized as a grooving or wearing of the shaft sleeve in the vicinity of the seal elastomer.
 
  • In the most seals, vibration, shaft end play, and/or misalignment of the seal faces cause the dynamic shaft secondary sealing devices to slide back & forth over the shaft revolution. This wearing motion causes grooves to worn into the shaft or sleeve. As this area is exposed to the service fluid, any metal, including stainless steel will oxidize. The movement of the secondary sealing device over this area wears off the protective oxide coating and exposes more bare metal to the fluid. The repeated action continually removes metal in the fretted area.
 
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