Figure 13-14.--Stuffhg box on a centrifugal pump.
In some pumps, the shaft sleeve is pressed onto the
casing wearing rings, impeller wearing rings, shaft, and
shaft sleeves in particular.
shaft with a hydraulic press, and you must machine off
the old sleeve in a lathe before you can install a new
The operation of a centrifugal pump wears away
one. On centrifugal pumps, the shaft sleeve is a snug
both the area of the shaft that goes through the packing
slip-on fit, butted up against a shoulder on the shaft and
gland or mechanical seal and the casing-impeller
held securely in place with a nut. The centrifugal pump
sealing areas. They must be renewed from time to time
sleeve-shaft-shoulder joint is usually made up with a
to maintain the efficiency of the pump.
hard fiber washer. It prevents liquid from leaking
through the joint and out of the pump between the sleeve
The shaft, casing, and impeller in a centrifugal
pump are designed so they can be renewed without
replacing them. The shafts have tightly fitted renewable
The impeller wearing ring is usually lightly press-
sleeves, while the casing and impeller have renewable
fitted to the hub of the impeller and keyed in with
surfaces called casing wearing rings and impeller
headless screws (also called Dutch keyed). To remove
wearing rings. You can see the arrangement clearly in
the worn ring, withdraw the headless screws or drill
them out and then machine the ring off in a lathe.
When it is necessary to renew these parts, the rotor
The amount of diametrical running clearance
assembly, consisting of the pump shaft, the impeller and
between the casing rings and the impeller rings affects
its wearing ring, and the casing rings, is usually brought
the efficiency of a centrifugal pump. Too much
into the shop. The following paragraphs explain the
clearance will let too much liquid leak back from the
method you should use to replace these parts.
discharge side to the suction side of the pump. Not
enough clearance will cause the pump to "freeze."
The repair parts generally are available from the
Before you install a new wearing ring on the impeller,
ship's allowance, but you may need to manufacture
measure the outside diameter of the impeller wearing
them. Before you proceed with these repairs, consult the
ring, and the inside diameter of the casing ring. (See
manufacturer's technical manual and the applicable
blueprints to get the correct information on vital
clearances and other data.
lit and clearance data you have on hand, ask your