Hale Q Series Muscle - Manual (Page 28)

 Introduction
28 MUSCLE (Midship) Pumps Installation, Operation, and Maintenance Manual
p/n: 029-0020-63-0
The vanes guide water from the inlet to the discharge and reduce the turbulence of
the spinning water.
Figure 2-8: Impeller Operation
As water discharges from the impeller, it enters the volute (pump body). The volute
increases in size from the cutwater to its full capacity at the volute throat.
This gradual increase maintains a constant average velocity through the volute. Fig-
ure 2-8: “Impeller Operation,” traces a drop of water from the intake of the impeller to
the discharge outlet.
Clearance Rings
Clearance rings prevent pressurized water that is leaving the pump volute from return-
ing to the intake of the impeller. Clearance rings at the impeller intake also prevent
leakage, accomplished by limiting the radial clearance between the spinning impeller and
the stationary clearance ring. Also see Figure 2-7: “Typical Midship Two-Stage Cen-
trifugal Pump” on page 27.
Typically, a new clearance ring has a radial clearance of about 0.005” (0.127 mm) or a
0.008” (0.203 mm) diameter. However, due to foreign material found in the water,
this clearance increases over time as the pump is operated. Clearance rings are
designed for replacement when wear limits exceed NFPA satisfactory performance.
2.4 PUMP SEALS
Two types of seals are used - a packing seal or a mechanical seal.