Goulds Pumps 3500XD - IOM - Manual (Page 25)

OPERATION AND CONTROLS
AIR REMOVAL SYSTEM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
LEVEL CONTROL - TYPICAL . . . . . . . . . . . . . . . . . . . . . . . . . . 22
DILUTION SYSTEM - TYPICAL. . . . . . . . . . . . . . . . . . . . . . . . . . 24
SEAL / VACUUM FLUSH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
PUMPING WATER OR LOW CONSISTENCY STOCK. . . . . . . . . . . . . 26
START-UP PROCEDURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
SHUTDOWN PROCEDURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
OPERATION WITHOUT VACUUM PUMP. . . . . . . . . . . . . . . . . . . . 27
MONITORING DURING OPERATION . . . . . . . . . . . . . . . . . . . . . . 27
TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
AIR REMOVAL SYSTEM
(General Description - Refer to Figure 16A and 16B)
For Order Specific Description - Refer to the IOM Appendix
For most Model 3500XD installations, the air removal
system consists of an on/off control valve (ARV), a
vacuum relief valve (VR), a compound pressure gauge (PI),
a vacuum pump and piping from the Model 3500XD to the
vacuum pump. (Fig. 16A)
The vacuum pump pumps the air from the Model 3500XD,
via the degas piping. The vacuum pump is a Nash Model
AHF75 liquid ring pump operating at 1750, 1450, or 1150
RPM. The vacuum pump requires about 2-3 GPM service
liquid flow (operating and maintenance instructions for the
Nash vacuum pump are included in the Appendix).
Vacuum pump control is on/auto/off through a switch in
the control room.
In the on mode, the vacuum pump is running. In the auto
mode, the vacuum pump starts when the model 3500XD is
started, and stops when the Model 3500XD is shutdown.
If the vacuum pump stops during operation, an alarm must
warn the operator.
The air removal valve (ARV) prevents stock from entering
the air removal piping when the Model 3500XD is not
running, or the stock consistency is low.
The air removal valve is equipped with a pneumatic
actuator and solenoid valve, with the choice of operation
auto/on/off through a switch in the control room. In the on
mode, the ARV is 100% open, in the off mode, the ARV is
closed. In the auto mode, the ARV will be open when the
level control valve (LCV) is open and closed when the
LCV is closed.
The vacuum relief valve (VR) is used to control the
pressure in the air removal system at a constant setting.
The pressure in the air removal piping is indicated on the
compound gauge (PI).
Before start up, the pressure in the degas system should be
set at -5 inches Hg (mercury) vacuum gauge. This
operation is carried out by starting the vacuum pump with
the ARV closed, and adjusting the VR until a reading of 5
in Hg vacuum shows on the compound gauge (PI).
During operation, if fiber is being drawn into the air
removal system, the vacuum level should be reduced by
opening the VR valve. If discharge pressure or pump
operation is erratic, the vacuum level should be increased
by closing the VR valve.
For design pulp consistencies of 10% or less, it is possible
to operate without a vacuum pump with the Model
3500XD design. In this case a degas valve would be
present to allow isolation of the system and the degas
nozzle would be piped to drain or an air separator. Refer to
Figure 16B for the typical control schematic without a
vacuum pump.
3500XD IOM 8/07
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