Metrohm 872 Extension Module Sample Prep - Manual (Page 26)

3.8 Switching valve ￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭
18 ￭￭￭￭￭￭￭￭ 872 Extension Modul – Sample Prep
Setting the flow rate
The contact pressure lever of the tubing cartridge must be adjusted in
order to regulate the flow rate. Proceed as follows:
1 Setting the contact pressure
￭ Fully loosen the contact pressure lever (8-5), i.e. press it all the
way down.
￭ Switch on the peristaltic pump.
￭ Raise the contact pressure lever one step at a time until liquid
flows.
￭ When liquid starts flowing, raise the contact pressure lever by an
additional 2 ratchet increments.
The contact pressure is now set optimally.
The delivery rate depends not only on the correct contact pressure
but also on the interior diameter of the pump tubing and the rota-
tional speed of the drive.
Note
Pump tubing is consumable material. The service life of the pump tub-
ing depends on the contact pressure amongst other factors.
3.8 Switching valve
3.8.1 Mode of operation of the switching valve
During sample preparation, the switching valve functions as a switch
between two different flows.
Connectors
The switching valve has (just like the injection valve) six connectors, which
can be connected with one another as required.