Xylem GOULDS AC8743, Инструкция по эксплуатации

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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 will become
filled with air and thus prevent proper operation on
the pump. When reducing the piping to the suction
opening diameter, use an eccentric reducer with
the eccentric side down to avoid air pockets.
NOTE: When operating on suction lift, never use a
straight taper reducer in a horizontal suction line,
as it tends to form an air pocket in the top of the
reducer and the pipe.
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.
Valves in Suction Piping
When installing valves in the suction piping,
observe the following precautions:
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
spring type, sized to avoid excessive
friction in the suction line. (Under all other
conditions, a check valve, if used, should
be installed in the discharge line. See the
section entitled Valves in Discharge
Piping.
b. When foot valves are used, or where there
are other possibilities of “water hammer,”
close the discharge valve slowly before
shutting down the pump.
c. Where two or more pumps are connected
to the same suction line, install gate
valves so that any pump can be isolated
from the line. Gate valves should be
installed on the suction side of all pumps
with a positive suction pressure for
maintenance purposes. Install gate valves
with stems horizontal to avoid air pockets.
Globe valves should not be used,
particularly where NPSH is critical.
d. The pump must never be throttled by the
use of a valve on the suction side of the
pump. Suction valves should be used only
to isolate the pump for maintenance
purposes, and should always be installed
in positions to avoid air pockets.
e. A pump drain valve should be installed in
the suction piping between the isolation
valve and the pump.
Discharge Piping
If the discharge piping is short, the pipe
diameter can be the same as the discharge
opening. If the piping is long, pipe diameter
should be one or two sizes larger than the
discharge opening. On long horizontal runs, it
is desirable to maintain as even a grade as
possible. Avoid high spots, such as loops,
which will collect air and throttle the system or
lead to erratic pumping.
Valves in Discharge Piping
A triple duty valve should be installed in the
discharge. The triple duty valve placed on the
pump protects the pump from excessive back
pressure, and prevents liquid from running
back through the pump in case of power
failure.
Pressure Gauges
Properly sized pressure gauges should be
installed in both the suction and discharge
nozzles in the gauge taps, provided on
request. 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.
Pump Insulation
On chilled water applications most pumps are
insulated. As part of this practice, the pump
bearing housings should not be insulated since
this would tend to trap heat inside the housing.
This could lead to increased bearing temperatures
and premature bearing failures.