GB 00871 - Edition 03 - January 2007
3/3
A 20
Alcatel Vacuum Technology France - Drytel 1025 User’s Manual
Description
Automatic air ballast
operating principle
Principle diagram
Powering up the solenoid valve opens it and introduces a calibrated
quantity of air via a nozzle parallel to the pumped gas.
The sintered metal PORAL disks protect the nozzle from dust or foreign
bodies carried by the gas or from the atmosphere.
The air inlet filter protects against dust or foreign bodies from the
atmosphere.
In case of accident or if the pump stops, a valve closes this inlet and
keeps the pump anti-suck back.
For more efficiency, it is possible to use a dry neutral gas as a purge
gas.
See sheet B 30 Connecting the automatic air ballast (option)
See sheet C 40 Using the automatic air ballast (option)
When condensable gases are pumped, depending on the nature of
the pumped gases, pressure and temperature conditions, they may
condense in the dead volumes of the primary pump.
When the pumping unit is at low pressure, the primary pump is at
the limit vacuum. The gases no longer pass through, its check valves
no longer open and the condensates remain inside.
These condensates mix with dust and create a destructive abrasive
for the pump diaphragm.
The introduction of gas at the last stage of the pump has various
effects:
ythe dilution of the pumped gas and the reduction of the partial
vapor pressure of the residual gas in the pump.
yit increases the compression of the pump and heats it, reducing the
risk of condensation by increasing of the temperature of the
internal pump.
yit reduces in the last stage the partial pressure if the pumped
gas and it stops its condensation when the gas reaches the
atmospheric pressure.
yin case of pumping at low pressure, when there is no flow, it gives
the possibility to open the valves and evacuate the residual gases.
