5 Operation and Controls
5.1 Air removal system (general description - refer to Figure 17
and 18) 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. 17)
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 oper-
ation 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 set-
ting. 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 19 for the typical control
schematic without a vacuum pump.
5.2 Level control
(Refer to Figure 17 and 18)
For Order Specific Description - Refer to the IOM Appendix
A level must be maintained in the suction standpipe for proper pump operation and air removal. A level
transmitter (LT) must be installed to measure standpipe level and provide a signal to a level controller in
the control room.
The level measurement range is 0 - 100%. This span must be oriented properly on the standpipe and the
length of the span will be dependent on the application and the type of level transmitter used. Refer to
the IOM Appendix for the order specific information on the level span.
5 Operation and Controls
26
3500XD Installation, Operation and Maintenance Instructions
Содержание Goulds Pumps 3500XD
Страница 1: ...Installation Operation and Maintenance Instructions 3500XD ...
Страница 2: ......
