Mechanical Seals vs. Packing Rings
Sealing a pump casing around the shaft periphery to prevent the pumped liquid
from leaking into atmosphere is a major concern. Effective sealing can be
accomplished by providing the pump with mechanical seal or packing rings.
That part of the pump casing that contains the mechanical seal or packing rings is
called the stuffing box (or seal chamber). Horizontal end-suction pumps and
vertical pumps have only one stuffing box, whereas horizontal between-bearing
pumps are provided with two stuffing boxes on both sides of the pump casing.
Advantages of using mechanical seals
Disadvantages of using mechanical seals
Advantages of packing rings
Disadvantages of packing rings
Sealing a pump casing around the shaft periphery to prevent the pumped liquid
from leaking into atmosphere is a major concern. Effective sealing can be
accomplished by providing the pump with mechanical seal or packing rings.
That part of the pump casing that contains the mechanical seal or packing rings is
called the stuffing box (or seal chamber). Horizontal end-suction pumps and
vertical pumps have only one stuffing box, whereas horizontal between-bearing
pumps are provided with two stuffing boxes on both sides of the pump casing.
Advantages of using mechanical seals
- lower frictional drag than traditional packing means improved pump
efficiency - a mechanical seal will not wear out a shaft, or sleeve, as fast as packing
rings - near zero leakage is possible with mechanical seal; packing requires
some leakage (usually visible) for proper lubrication - properly applied mechanical seals require less periodic maintenance than
packing - specially designed mechanical seals can be applied to higher pressures
and speeds than traditional packing.
Disadvantages of using mechanical seals
- less tolerant to shaft deflection and misalignment
- less tolerant to dirty or contaminated liquid; will require cyclone separator
to clean the liquid - require expensive seal piping to flush and quench
- mechanical seals are more expensive than packing rings
Advantages of packing rings
- lower upfront cost
- very simple selection, installation, maintenance, and trouble-shooting
Disadvantages of packing rings
- require small amount of leakage for lubrication and cooling - therefore
packing rings are unsuitable for use in liquids that are toxic, flammable, or
otherwise hazardous or polluting - usually require a stack of several packing rings for effective sealing; need
longer stuffing box, which in turn results in higher shaft deflection - easily wear out resulting in more frequent replacement of packing rings
CENTRIFUGAL-PUMP.ORG
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Related topics
Mechanical seals vs. packing rings
Double or tandem mechanical seals
Mechanical seal flush piping plans
Mechanical seals vs. packing rings
Double or tandem mechanical seals
Mechanical seal flush piping plans
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