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With the aid of the ”backing pump“ relay box (6) the DCU power supply (2a) can be conver-<br />
ted to a pumping station controller that can switch on both turbopump (1a) and backing pump<br />
simultaneously.<br />
Either a fan (4), or water cooling (3) for high gas loads, can be attached to cool the pumps.<br />
An electric vent valve (8) vents the turbopumps if the RPM declines below a given speed. In<br />
the event of a brief power failure, the vent valve will remain closed to maintain the vacuum.<br />
The pumping station will then re-start immediately when mains voltage is restored. <strong>How</strong>ever<br />
this necessitates a backing pump with a safety valve that will close automatically in the<br />
event of a power failure.<br />
For UHV applications, a heater (9) can be connected to the pump that switches on automatically<br />
after a preselected RPM is attained, and switches off when RPM decreases.<br />
Electromagnetic sealing gas valves (7b) with matching throughputs, as well as sealing gas<br />
throttles (7a) for pumps of various sizes, are available for corrosive gas pumps.<br />
Page 71<br />
<strong>Vacuum</strong><br />
<strong>Technology</strong>
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