A705-74-880 Issue K
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Edwards and the Edwards logo are trademarks of Edwards Limited.
INTRODUCTION
1.3 Gas system
The pump has a shaft-seals purge system and a gas-ballast system.
A dry compressed air supply can be connected to the shaft-seals purge inlet (Figure 1 item 31). The shaft-seals purge
pipeline then delivers the dry air purge to the shaft-seals. This dry air purge: ensures that the shaft-seals are
maintained at a positive pressure during pump operation; prevents the entry of corrosive or toxic process vapour into
the pump gearbox. It also prevents contamination of the process gases by pump oil and damage to the shaft-seals.
The gas-ballast system can deliver ambient air to the pump gas-ballast inlet to dilute process gases or to prevent
condensation of vapour. The filtered airflow is controlled by a valve (Figure 8, item 8). A flap-valve (Figure 8, item
2) prevents the escape of process gases out of the gas-ballast system into the local atmosphere.
If required dry nitrogen supplies can be connected to the pump, to deliver nitrogen gas-ballast and nitrogen shaft-
seals purge instead of air: refer to Section 3.10.
For clean applications an atmospheric shaft seal purge kit is available. This kit enables atmospheric air to be passed
via a non-return valve into the pump shaft seals, thus eliminating any air or nitrogen supply. Refer to Section 3.10.
1.4 Cooling system
The GV pump has a direct cooling system, in which cooling-water connected through the water inlet: (Figure 1 item
32) circulates around the pump-body and then passes out of the pump through the outlet (Figure 1 item 2). The inlet
to the system is fitted with a temperature control valve (refer to Figure 1, item 7) which holds the pump at an
operating temperature of 122°F (50°C) (measured at the position shown in Figure 1, item 3). If the application
requires pump operating temperatures of 112 to 194°F (50 to 90°C) an Indirect Cooling Kit accessory must be fitted.
Refer to Section 7.4.4. For higher temperature operation it is recommended that SHC630 oil be used in the pump.
A thermal snap-switch box (Figure 1 item 4) is fitted to the pump-body. This has two thermal snap-switches that are
pre set to function in warning and shut down modes:
1.4.1 Warning Switch
The output of the warning thermal snap-switch will go ‘open circuit‘ when the temperature of the pump-body is
higher than 154°F (68°C) (see Section 2.3). Use this output to provide a warning of high pump temperature.
1.4.2 Shut Down Switch
The output of the shutdown thermal snap-switch will go ‘open circuit‘ when the temperature of the pump-body is
above 167°F (75°C) (see Section 2.3). Use this output to shutdown the pump when it is too hot.
The pump-motor (Figure 1, item 16) is air-cooled by an integral cooling-fan (Figure 1, item 19).
1.5 Inter-stage pressure relief valve (PRV)
The GV410 and GV600 pumps have an inter-stage pressure relief valve (Figure 1, item 12) fitted between the third
stage and the last stage of the pump. This relief valve allows the pump to function with greater efficiency throughout
the pressure range.
At high pump inlet pressures the inter-stage pressure forces the valve open thus allowing process gases to pass
directly from the third stage into the pump-outlet, without compression in the fourth stage of the pump. At low pump
inlet pressures the inter-stage pressure is low and the valve is held closed by atmospheric pressure. Process gases
pass through all stages of the pump and are compressed in the fourth stage before they pass into the pump-outlet.
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