Hydraulic Machines: Pumps - Wastewater Operators - page 126

Coupling —Device to join the pump shaft to the motor shaft. If the
pump and motor are constructed on a common shaft, the assembly
is referred to as a close-coupled arrangement .
extended shaft —For a pump constructed on one shaft that must be
connected to the motor by a coupling.
frame —The housing that supports the pump bearing assemblies. In
an end-suction pump, it may also be the support for the pump cas-
ing and the rotating element.
Impeller —The rotating element in the pump that actually transfers
the energy from the drive unit to the liquid. Depending on the pump
application, the impeller may be open, semi-open, or closed. It may
also be single or double suction.
Impeller eye —The center of the impeller, the area that is subject to
lower pressures due to the rapid movement of the liquid to the outer
edge of the casing.
Priming —Filling the casing and impeller with liquid. If this area is
not completely full of liquid, the centrifugal pump will not pump
efficiently.
Seals —Devices used to stop the leakage of air into the inside of the
casing around the shaft.
• gland —Also known as the packing gland , it is a metal assembly
that is designed to apply even pressure to the packing to com-
press it tightly around the shaft.
• lantern ring —Also known as the seal cage , it is positioned
between the rings of packing in the stuffing box to allow the
introduction of a lubricant (water, oil, or grease) onto the surface
of the shaft to reduce the friction between the packing and the
rotating shaft.
• mechanical seal —A device consisting of a stationary element,
a rotating element, and a spring to supply force to hold the two
elements together. Mechanical seals may be either single or
double units.
• Packing —Material that is placed around the pump shaft to seal
the shaft opening in the casing and prevent air leakage into the
casing.
• Stuffing box —The assembly located around the shaft at the rear
of the casing. It holds the packing and lantern ring.
Shaft —The rigid steel rod that transmits the energy from the motor to
the pump impeller. Shafts may be either vertical or horizontal.
Shaft sleeve —A piece of metal tubing placed over the shaft to protect
the shaft as it passes through the packing or seal area. In some cases,
the sleeve may also help to position the impeller on the shaft.
Shroud —The metal plate that is used to either support the impel-
ler vanes (open or semi-open impeller) or enclose the vanes of the
impeller (closed impeller).