Xylem 8100 Series Centrifugal Pumps AC2515 REV.C - Manual (Page 17)

FIGURE 13 – SUCTION PIPING
ARRANGMENTS
Discharge Piping
CHECK VALVE
If the discharge piping is short, the pipe
diameter can be the same as the discharge
opening. If the piping is long, the pipe
diameter should be one or two sizes larger
than the discharge opening. On long
horizontal runs, it is desirable to maintain an
even a grade as possible. Avoid high spots,
such as loops, which will collect air and
throttle the system or lead to erratic pumping. GATE VALVE
SUCTION PIPE INSTALLED
WITH A GRADUAL RISE TO PUMP
INCREASER
LEVEL
CENTER LINE
OF PIPE
CORRECT
AIR POCKET
INCORRECT A slow closing check valve and an isolating
gate valve should be installed in the
discharge line. The check valve (triple duty
valve), placed between pump and gate valve,
protects the pump from excessive back
pressure, and prevents liquid from running
back through the pump in case of power
failure. The gate valve is used in priming and
starting, and when shutting the pump down.
AIR POCKET
INCORRECT
AIR POCKET
Pressure Gauges
Properly sized pressure gauges should be
installed in both the suction and discharge
nozzles in the gauge taps provided. The
gauges will enable the operator to easily
observe the operation of the pump, and also
determine if the pump is operating in
conformance with the performance curve. If
cavitation, vapor binding, or other unstable
operation should occur, widely fluctuating
discharge pressure will be noted.
INCORRECT
GRADUAL RISE
TO PUMP
NO AIR
POCKETS
CORRECT
GRADUAL RISE
TO PUMP
NO AIR
POCKETS
STUFFING BOX LUBRICATION
ECCENTRIC
REDUCER
Contaminants in the pumped liquid must not enter
the stuffing box. These contaminants may cause
severe abrasion or corrosion of the shaft, or shaft
sleeve, and rapid packing or mechanical seal
deterioration; they can even plug the stuffing box
flushing and lubrication system. The stuffing box
must be supplied at all times with a source of
clean, clear liquid to flush and lubricate the
packing or seal. It is important to establish the
optimum flushing pressure that will keep
contaminants from the stuffing box cavity. If this
pressure is too low, fluid being pumped may enter
the stuffing box. If the pressure is too high,
excessive packing or seal wear may result; and
extreme heat may develop in the shaft causing
higher bearing temperatures. The most desirable
condition, therefore, is to use a seal water
pressure 15-20 psig above the maximum stuffing
box pressure.
CORRECT
DISTANCE PLUS
ECCENTRIC REDUCER
STRAIGNTENS FLOW
CORRECT
PATH OF WATER
INCORRECT
If the pump system pressure conditions vary
during the day, packing adjustment becomes
17