Page 194 - Know and Understand Centrifugal Pumps

Pump Shaft Packing

The lantern ring

The lantern ring performs three basic functions:
1. To supply new lubricant to the packing rings, which is normally lost
in operation.
2. To supply ‘back pressure’, which aids in impeding the entrance of
abrasive and corrosive material into the stuffing box. Abrasives and
corrosives will damage the shaft or sleeve, and disintegrate the
packing.
3. To cool the packing and shaft and dissipate the heat generated
between these members, which will increase the normal service life
of the packing and pump.
Oil, water, grease, or any liquid or substance compatible with the fluid
are forced under pressure into the packing through the lantern ring by
means of a connection on the stuffing box wall to provide these three
functions.
Recommended instructions for packing a pump are:
1. On installing Teflon packings, place and seat each ring ringer tight.
Do not use wrenches or pliers.
2. Bring the gland up to the packing rings and adjust the gland nuts by
hand. (No tools yet.)
a. Open the flush line to the packing.
b. Start the pump.
3. Permit the pump and packing to leak generously for about 15
minutes to allow the packings to absorb the pumped fluid, swell,
seat and adjust to the stuffing box wall and the shaft.
4. If excessive leakage continues, tighten the gland nuts y6th of a turn
with a wrench. Don’t permit the temperature to rise in the packing.
5. Continue adjusting the gland nuts y6th of a turn every 15 minutes
until the leakage is controlled to about 1 drop per second per inch
of shaft diameter.

PRECAUTION
Too many gland adjustments will cause the packing to crystallize and
burn, which will shorten the packings’ useful life and damage the shap
or pump sleeve.

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