Why Use Mechanical Seals ?
1. Lower Mechanical Losses
- Mechanical seals cause lesser mechanical losses compared to packed glands and thus makes the pump more efficient.
- Mechanical losses due to frictional drag of the shaft sleeve running against packing account for the largest of the mechanical losses generally incurred in a centrifugal pump.
2. Lesser Sleeve Wear
- For mechanical seal fitted pumps handling clean, non-corrosive liquids, shaft protecting sleeve can be eliminated. Even where shaft sleeves are used, they are not subject to wear for mechanical seal fitted pumps.
- In case of packed gland pumps the sleeve under the packing is subjected to wear especially when the pump liquid contains abrasive particles or when the packing sit fixed very tightly on the sleeve.
- Sleeve damage is costly not only because of the cost of sleeve but also due to the time involved in replacing the worn sleeve with a new one.
3. Seals high pressure as well as low pressure
- Increased pressure puts a limit on serviceability of the packed stuffing boxes.
- Mechanical seals are able to seal higher pressures & can be used with higher speed pumps than packing.
- Gland packing can seal effectively only up to pressure of 125 PSI (8.6 bar).
4. Seals high temperature liquids
- Mechanical seals are always used when it becomes difficult to pack with conventional packing because of temperature of the liquid or its nature.
- Nornmal packing can not withstand temparature above 350°f (176°c)
5. Compensating for wear
Unlike packing, seal doesn't have to be adjusted for wear
6. Bearing Life
- Prevents premature bearing failure
- Packing leakage is a major cause of bearing failure.
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