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6.2.2 Cleaning FRG-700
Cleaning the measuring
chamber and the polarity
insert
Cleaning or replacing the
anode
Cleaning the Pirani element
Inverted Magnetron Pirani Gauge FRG-700 FRG-702
The parts can now be cleaned or replaced individually.
Unfasten the hexagon head screw (3) on the magnet unit (4) and remove
the magnet unit.
The magnetic force and the tendency to tilt make it difficult to
separate the magnet unit and the measuring chamber (7).
Remove the circlip (5) and the polarity insert (6) from the measuring
chamber
Remove the three hexagon socket screws (8) incl. lock washers (8a) on the
back of the measuring chamber.
Carefully remove the following parts in this order (without exerting stress on
the Pirani element (13)): pressure piece (9), complete anode (10), FPM seal
(11) incl. support ring (12), Pirani element (13) incl. FPM seal (13a).
Using a polishing cloth rub the inside walls of the measuring chamber and
the polarity insert to a bright finish.
The sealing surfaces must only be worked concentrically.
Rinse the measuring chamber and the polarity insert with cleaning alcohol.
Allow both to dry.
Remove the used ignition aid (10a) with tweezers.
Using a polishing cloth rub the anode pin to a bright finish.
Do not bend the anode. Do not carry out mechanical work on the
ceramic part.
Rinse the anode with cleaning alcohol.
Allow the anode to dry.
Insert a new ignition aid (10a) into the mounting tool.
Carefully press the anode (clean or new)
centered and parallel to the tool axis into
the ignition aid and insert it to a depth of
approx. 15 mm. The final positioning is
established after the anode is installed.
21
Anode
Ignition aid
Mounting tool
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