Xylem 8200 Series Base Mounted Centrifugal Fire Pumps AC2675 REV.C - Manual (Page 15)

15
FIGURE 8 – SUCTION INSTALLATIONS
(PIPING SUPPORTS NOT SHOWN)
Suction piping should be short in length, as
direct as possible, and never smaller in
diameter than the pump suction opening. A
minimum of ten (10) pipe diameters between
any elbow or tee and the pump should be
allowed. If a long suction pipe is required, it
should be one or two sizes larger than the
suction opening, depending on its length.
CAUTION:
SUCTION PIPE INSTALLED WITH A
GRADUAL RISE TO PUMP CHECK VALVE
GATE VALVE
INCREASER
LEVEL
CORRECT CENTER LINE
OF PIPE
AIR POCKET
An elbow should not be used directly
before the suction of a double suction pump if its
plane is parallel to the pump shaft. This can cause
an excessive axial load or NPSH problems in the
pump due to an uneven flow distribution. If there is
no other choice, the elbow should have
straightening vanes to help evenly distribute the
flow. Failure to follow these instructions could
result in injury or property damage.
INCORRECT
AIR POCKET
INCORRECT
Eccentric reducers should be limited to one
pipe size reduction each to avoid excessive
turbulence and noise. They should be of the
conical type. Contour reducers are not
recommended.
AIR POCKET
INCORRECT
When operating on a suction lift, the suction
pipe should slope upward to the pump
nozzle. A horizontal suction line must have a
gradual rise to the pump. Any high point in
the pipe can become filled with air and
prevent proper operation of the pump. When
reducing the piping to the suction opening
diameter, use an eccentric reducer with the
eccentric side down to avoid air pockets.
GRADUAL RISE
TO PUMP
NO AIR
POCKETS
CORRECT
GRADUAL RISE
TO PUMP NO AIR
POCKETS
NOTE: When operating on suction lift never
use a concentric reducer in a horizontal
suction line, as it tends to form an air pocket
in the top of the re-ducer and the pipe.
ECCENTRIC
REDUCER
CORRECT
To facilitate cleaning pump liquid passage
without dismantling pump, a short section of
pipe (Dutchman or spool piece) so designed
that it can be readily dropped out of the line
can be installed adjacent to the suction
flange. With this arrangement, any matter
clogging the impeller is accessible by
removing the nozzle (or pipe section). DISTANCE PLUS
ECCENTRIC REDUCER
STRAIGNTENS FLOW
CORRECT
Valves in Suction Piping
When installing valves in the suction piping,
observe the following precautions:
PATH OF WATER
a. If the pump is operating under static
suction lift conditions, a foot valve may be
installed in the suction line to avoid the
necessity of priming each time the pump
is started. This valve should be of the
flapper type, rather than the multiple
INCORRECT