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15. SHAFT SEALING
STANDARD COMPRESSION PACKING
One type of shaft sealing used in these pumps is formed ring packing with or without a lantern ring. When using a
packed box pump, use formed packing rings. DO NOT use a one piece spiral wrap of packing. Packing rings are
available in a wide selection of materials for various applications and temperatures. Previous experience with the
pumped fluid is the best guide in selecting the proper packing ring material for your particular application.
Some backplates are furnished with tapped holes on the stuffing box to provide access to the lantern ring or
packing set for either flushing or grease lubrication. An external flush or lubrication of the packing may be
necessary for proper operation and to help prolong the life of the packing and shaft.
A flush is recommended when the fluid to be pumped is abrasive or the pump operates with negative inlet
pressure (suction lift). Clean water is often used to flush the packing. On applications where clean water is not
available or where it is incompatible with the fluid being pumped, other clean, nonhazardous liquids may be used
for flushing the packing. The flush should be supplied to the stuffing box at a rate of ¼ to ½ gallons per hour (1 to
2 liters per hour). The pressure of the flushing liquid should exceed the sum of the inlet pressure and half of the
differential pressure by 10 to 15 psi [70 to 100 kPa].
If the packing is to be grease lubricated, a good grade of bearing grease should generally be used. Should
bearing grease be unacceptable or incompatible with the fluid being pumped, another paste type lubricant may be
used. Lubrication of the packing must be performed with the pump stopped. Before daily start-up, if applicable, is
a good time.
To lubricate the packing, stop the pump. Carefully clean the stuffing box pipe plugs of any contaminants. After
removing the pipe plugs from the stuffing box, install a lubrication fitting into one of the tapped holes. Lubricant
now may be injected into the stuffing box through the lube fitting. Inject clean, fresh unused lubricant until it is
seen coming out of the other tapped hole. Clean up any excess lubricant and remove the lube fitting. Replace the
pipe plugs. This procedure should be performed daily, prior to start-up if the pump is purchased with provisions for
grease lubrication. In certain applications, more frequent lubrication of the packing may be necessary. Experience
will provide a guide as to how frequently the packing should be lubricated. Applying lubricant often will extend the
life of the packing and shaft.
CARE OF PACKING
Packing hooks are commercially available to help in removing packing rings from the stuffing box. It is generally
not recommended to reuse old packing rings. When installing packing, use formed packing rings.
DO NOT use a one piece spiral wrap of packing. Before installing packing, carefully clean the stuffing box and
shaft.
Packing rings should be installed one ring at a time, with the joints of adjacent rings staggered approximately
180 . Each ring should be seated firmly before the next ring is installed. DO NOT forget to install the lantern ring, if
applicable. Three rings of packing, followed by the lantern ring, should allow the lantern ring to be approximately
aligned with the flush/lube holes in the stuffing box.
The packing gland nuts should first be evenly tightened with a wrench to seat the packing firmly in the stuffing box
and against the shaft. DO NOT over-tighten the packing. The gland nuts should then be backed off until finger-
tight. Connect the flush or lubricate the packing if either method is used. After the pump is started, note the
amount of leakage from the stuffing box. If the packing leakage exceeds ten drops per minute, stop the pump and
adjust the gland nuts. The gland nuts should be adjusted evenly in 1/6 to 1/3 turn (1 to 2 flats on the nut)
increments. Start the pump and allow it to operate for several minutes. Again, visually examine the stuffing box for
excessive leakage. Repeat the above procedure until the stuffing box leakage is between five to ten drops per
minute.
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