SUCTION AND DISCHARGE PIPING
Suction and discharge nozzle sizes of Dean pumps are selected for
proper performance of the pumping unit and are not intended to
determine the suction and discharge pipe sizes. Pipe sizes must be
determined by the user based on the system requirements.
Suction piping should have a minimum friction loss and thus should
be as short and straight as possible with a pipe diameter as large
as economically feasible for the flow rate handled.
Suction piping should never be smaller in diameter than the suction
nozzle size. When the suction piping is larger than the suction noz-
zle size an eccentric reducer is required at the suction flange and
must be installed with the taper located on the underside to elimi-
nate air or vapor pockets. The section of piping attached to the suc-
tion flange of the pump should be straight for a length of eight pipe
diameters or more.
Discharge piping may be the same size as, larger, or smaller than
the discharge nozzle as the system flow may demand.
In new installations or rebuilt systems, dirt, pipe scale, welding slag,
and general construction debris may get into the piping. It is impor-
tant to prevent this material from entering the pump and damaging
pump parts, bearings, mechanical seal faces, or lip seals. Bearings,
mechanical seals and lip seals are especially subject to damage
even by very small particles. To prevent damage, a strainer or filter
installed in the suction line is recommended. Commercially avail-
able strainers or filters as recommended by their manufacturers can
do an excellent job.
experienced.
Failure to properly align the unit will result in
vibration, short bearing life, and reduced mechanical seal life.
Pumps are not constructed to be used as pipe anchors. Both suction
and discharge piping must be supported independently of the
pumping unit and thermal expansion joints provided to guard
against expansion loads on the pump. Pipes should be anchored
between the expansion joint and the pump and as closely to the
pump as possible. Failure to provide proper piping support and
expansion joints may impose strains on the pumping unit which will
result in serious misalignment. Maximum allowable piping loads
are shown on page 7 in this manual.
No allowance for thermal expansion is made for motor driven units
in mounting the driver. Allowance for turbine mounting should be in
accordance with the turbine manufacturer’s recommendations.
Final alignment must always be checked and corrected at the
operating temperatures of the pump and driver.
Misalignment of the two shafts is of two kinds. The first of these is
angular misalignment where the axis of one shaft is at an angle
from the other. The other is offset alignment where the center of one
shaft is offset from the center of the other shaft. These effects usual-
ly occur together so that both angular and offset misalignment are
present.
Coincident alignment of the driver and pump shaft is measured at
the faces of the coupling hubs.
The pump was shipped with the coupling spacer not installed, to
allow alignment and motor rotation check. If, however, someone
has installed this spacer assembly, remove it at this time.
To one of the coupling hubs, either on the motor shaft or the pump
shaft, attach a dial indicator. Mount the indicator so that the
indicator button rides on the face of the other coupling hub near the
outside diameter of the hub. Reference the illustration “INDICATOR
SETUP TO READ ANGULAR MISALIGNMENT” below. Rotate the
shaft to which the dial indicator is clamped, allowing the indicator
button to ride on the face of the stationary hub. The indicator dial
movement will show the difference in the distance between the two
hubs. This indicates the amount of angular misalignment between
the hubs and therefore the shaft axes. Good practice suggest align-
ment to within 0.002" T.I.R. (Total Indicator Reading).
T
YPICAL
P
UMP
P
IPING
Suction line screens or strainers may usually be removed when,
after several days of use, no dirt has been collected and the system
is clean.
Remember that screens and filters in the suction line are restricting
devices which reduce the net positive suction head (NPSH) avail-
able to the pump and should be considered at the time the system
is designed.
PUMP AND DRIVER ALIGNMENT
Proper running life of a pump and driver unit depends on the accu-
racy with which the axis of the driver shaft coincides with the axis
of the pump shaft when the unit is running. Although pumps and dri-
vers are check aligned at the factory, this is only to confirm that the
unit can be aligned in the field as handling during shipment and
installation will cause the alignment to change.
The pump and dri-
ver alignment must always be checked and corrected before the
baseplate is grouted to the foundation and again before the pump
is first started.
If the baseplate mounting instructions have been
carefully followed, no difficulties in making the alignment should be
I
NDICATOR
S
ETUP TO
R
EAD
A
NGULAR
M
ISALIGNMENT
5
