Mechanical Seals in Centrifugal Pumps. The mechanical seal acts as a check valve and a slider bearing. The obvious function is that of a check valve to prevent liquid under pressure from leaking out of the pump, or from drawing air into the pump when under vacuum conditions.

Function of a Resilient Metal Seal
Function of a Resilient Metal Seal

The sealing performance of resilient Metal Seals is based on a the relative high specific contact load at the sealing line generated by the compression of the seal to a certain groove depth and a certain resiliency or spring back of the elastic metal seal.

Typically resilient metal seals are compressed 20%. As an example a 3,18 mm FH (free height) seal is compressed to approximately 2,5 mm.
  • Point B illustrates the maximum groove depth. At this point the seating load already passed 90% of its maximum.
  • Point C illustrates the minimum groove depth, or the point where the seating load reaches its maximum. Reducing the groove depth even more and thus increasing the compression ratio can lead to seal failure.
  • Point D At this point the seals’ resilience overcomes the remaining (decompression) load, this resilience is called springback.
  • Point E Springback of the seal at 20% of the maximum load (Lmax) is the useful springback.
  • Point F Springback of the seal at zero load is total springback = elastic recovery of the seal.