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.