Agilent Technologies 9191610, User Manual

Page: 82 / 98

5 Technical Information
Heater Replacement
82/98 VacIon Plus 300 pumps User Manual / 87-900-103-01 (H)
Heater Replacement
To replace the heater element proceed as follows:
1
Disconnect the pump from the high voltage;
2
Disconnect the heater element from the main supply;
3
Disconnect the heater plates from the pump case;
4
Disconnect the heater connection box from the upper side of the
pump;
5
Install the new heater elements as described in the paragraph
“HEATER INSTALLATION”.
Bakeout Operation
When a VacIon pump does not reach the desired base pressure, and
there are no leaks, it is necessary to bake the system. This is done by
heating the pump and all the components in the system, and is
generally required to achieve base pressure less than 10
-8 mbar.
1
Heat the pump body and the system with a bakeout oven unit or
heating strips to temperatures between 150 °C and 220 °C
(220 °C is the maximum allowable for most bakeable high voltage
cables). This temperature is high enough to degas the pump
surfaces of water vapor without damaging the magnet and high
voltage connector. Note that the system components must be
compatible with the bakeout temperature. The heating must be
approximately even on all surfaces or evaporated water will
condence on the colder surfaces resulting in an incomplete bake
and preventing achievement of UHV vacuum pressure.
2
Leave the pump control unit on and monitor the pressure.
Agilent recommends that current during bake not exceed 50 mA;
if this value is exceeded, turn the bakeout off and then on again
when low pressure is restored.
To control the heaters and to monitor the high pressure limit
during bakeout, an automatically controlled relay may be used.
3
Bake the VacIon Plus pump for at least 24 hours. Longer bakeout
periods are recommended when the pump has been used with
heavy gas loads or when UHV pressure, 10
-9 mbar or less is
desired.