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 ( h ) N o i s e . A crackling noise may indicate excessive suction lift. A
rumbling noise is usually caused by irregular discharge conditions, as when a
pump operates at low capacity or beyond its discharge rating.
(i) Water Hammer. Water hammer results from a sudden change in velocity
o f a liquid column. Avoid water hammer by starting the pump with its
discharge valve closed, then slowly open the valve after the pump starts.
When stopping, close the discharge valve slowly before stopping the pump. In
some installations, pumps stop and start suddenly. If water hammer conditions
seem dangerous, a slow-opening and slow-closing check valve should be
i n s t a l l e d . This permits a gradual increase of flow when starting and a
gradual decrease when stopping.
Proceed as follows when taking a pump out of service.
3.4 System Shutdown.
( a ) Close the discharge valve before stopping the drive. This permits
gradual reduction of the load on the driving unit, and protects the pump
casing from possible damage caused by water hammer, especially in
h i g h - p r e s s u r e operation. I t also protects the check valve from possible water
hammer action.
(b) Stop the driving unit.
( c ) Close valves supplying water to seal cages (lantern rings), if so
fitted.
( d ) Close suction valve.
(e) Drain the pump to prevent damage, if the pump is to be out of
s e r v i c e for an appreciable period of time and there is a possibility of
freezing weather.
4
OPERATION OF CONDENSATE RETURN UNITS. Observe the following procedures
f o r the operation of condensate return units.
4 . 1 Startup Inspection. When starting a new unit or after a general
o v e r h a u l , check for the following conditions.
( a ) M a k e s u r e a l l i n s t a l l a t i o n , r e p a i r , and cleanup work is completed.
(b) Test installation for leaks.
S e e that all pipe connections are
tight.
(c) See that pump and motor are lubricated with an approved lubricant.
(d) Turn pump shaft by hand to make sure it rotates freely.
( e ) See that adequate electrical supply of correct frequency and voltage
i s available.
( f ) See that switches, starters, and protective devices are adequate and
are correctly installed.
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