Mechanical Seal

A mechanical seal is simply a method of containing fluid within a vessel (typically pumps, mixers, etc.) where a rotating shaft passes through a stationary housing or occasionally, where the housing rotates around the shaft.

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Description

MECHANICAL SEAL

When sealing a centrifugal pump, the challenge is to allow a rotating shaft to enter the ‘wet’ area of the pump, without allowing large volumes of pressurized fluid to escape.

To address this challenge there needs to be a seal between the shaft and the pump housing that can contain the pressure of the process being pumped and withstand the friction caused by the shaft rotating.

In Summary – Why Do We Use Mechanical Seals?

  • No “visible” leak – seals do leak vapour as the fluid film on the faces reaches the atmospheric side of the seal faces.
    • This would approximate to 1/2 teaspoon a day at normal operating pressures and temperatures, if it were captured and condensed.
  • Modern cartridge seal designs do not damage the pump shaft or sleeve. 
  • Day to day maintenance is reduced as seals have inboard springs which make them self-adjusting as the faces wear. 
  • Seals have lightly loaded faces which consume less power than gland packing. 
  • Bearing contamination is reduced in normal operation as the lubricant does not become affected by seal leakage and wash out.
  • Plant equipment also suffers less from corrosion if the product is contained in the pump.
  • Vacuum can also be sealed with this technology, a problem for packing as air was drawn into the pump.
  • Less wasted product will save money, even water is an expensive commodity and less clean up of the area will be needed.