Goulds Pumps 3500XD - IOM - Manual (Page 31)

3500XD IOM 8/07
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OPERATION WITHOUT A VACUUM PUMP
The Model 3500XD can be supplied both with and without a
vacuum pump. Services with design pulp consistency of 10%
or less can be supplied without a vacuum pump. When a
vacuum pump is supplied the flowing operating instructions
can be utilized.
If, for some reason, maintenance is required on the vacuum
pump and an interruption in production is not wanted, it may
be possible to change out the vacuum pump by the following
procedure.
Raise the set value of the level controller 70 to 75% and open
the dilution valves 75%. This should dilute the stock to the
point where operation without a vacuum pump can be
achieved.
Reduce the vacuum in the air removal system, watching to
make sure the level in the standpipe does not increase. If the
level increases excessively or does not stop, increase the
amount of dilution until the pump will operate without air
removal system.
Stop the vacuum pump. If the standpipe level remains at its
set valve, the vacuum pump can be removed from the system
and repaired or replaced.
MONITORING DURING OPERATION
The pump operation is monitored in the control room
with:
·
Standpipe level indication
·
Discharge control valve position
·
Pump speed, if variable speed drive
·
Upper dilution valve position
·
Lower dilution valve position
·
Amp meter or percent motor load for Model 3500XD
drive motor
·
Signal lights showing Model 3500XD running, vacuum
pump running, and air removal valve position
·
Alarms for vacuum pump not running, Model 3500
shutdown, seal water flow, and standpipe high and low
level
Monitors at the pump location include:
·
Seal water flow to the Model 3500XD, vacuum pump,
and vacuum chamber
·
Vacuum level in the air removal system
The actual value of the level control (LCI) should be within
the range of
± 5% of the set value. The normal output signal
should be as indicated in the IOM Appendix for the specific
service. If it is continuously lower than the set value, the
regulation of the level control valve may be disturbed.
If the pressure indicator (PI) in the air removal system varies
± 1 ft., the set value of the standpipe level is too low, the pulp
in the standpipe contains large amounts of air, or the level
control is not working properly.
The Model 3500XD motor load should be relatively stable,
although consistent variations would be considered normal.
Sudden changes in motor load usually indicate that more air
is entering the pump from the standpipe, which can be
corrected by increasing the standpipe level set point.
Usually the main cause for pumping problems is that the
stock in the standpipe contains large void areas, the stock is
bridging in the standpipe, the stock consistency is too high,
or because changes in consistency, pH or temperature have
caused a significant increase in the discharge piping head
loss. The above causes can be remedied by increasing the
dilution water flow.
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