Metrohm 807 Dosing Unit - Manual (Page 41)

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4 Handling and maintenance
807 Dosing Unit
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CAUTION
Do not under any circumstances remove the black valve disc from the
cylinder base or the white distributor disc from the distributor.
4.1.2.1 Cleaning contact surfaces
CAUTION
Do not damage the valve disc under any circumstances. Even small
scratches could lead to leakage!
￭ Use a liquid cleaning agent and a soft cloth for polishing the contact
surfaces of the two discs. Abrasive cleaning powders are unsuitable
and could scratch the valve disk.
￭ Rinse the discs thoroughly with plenty of water.
￭ Dry the discs with a soft, lint-free cloth.
4.1.3 Discs adhere to one another
A film of liquid must always be present between the valve disc and the
distributor disc. If the dosing unit is used with solvent or pure water, it
could happen that this film of liquid will dry out during prolonged periods
of disuse. This could then lead to the valve disc and the distributor disc
adhering to one another so strongly that the dosing unit is no longer able
to function. It will no longer be possible to switch the stopcock position in
such cases. The control device will announce that the dosing drive is over-
loaded.
CAUTION
Do not attempt to use excessive force to separate the cylinder from the
distributor.
Separating the valve disc and distributor discs from one
another
Proceed as follows:
1 Removing the housing.
2 Remove the centering tube.