Metrohm 700 Dosino - Manual (Page 19)

2.3 Dismantling the dosing units
700 Dosino, Instructions for Use
13
It is not normally necessary to dismantle the dosing unit when
changing the reagent. Owing to the minimal exchange volume of
only a few microliters and the
'EMPTY' and 'PREP' functions,
which each control instrument possesses for the Dosino, the rea-
gent in a dosing unit can be comfortably exchanged without much
loss of reagent; please refer to chapter 3.2.
Check the piston and cylinder of a dosing unit regularly (i. e. twice
per year), see chapter 3.3. If alkaline, corrosive or concentrated
reagents are used then a shorter interval should apply as the
glass cylinder could be attacked by aggressive alkalis or crystals
may be formed. We also recommend that dosing units with ETFE
cylinders are used for alkaline reagents.
• You should empty the cylinder before opening a dosing unit by
using the
'EMPTY' function of the control instrument.
2.3.1 Opening the housing
The internal construction of a dosing unit with an ETFE cylinder is
different from that of a dosing unit with a glass cylinder. Disman-
tling a dosing unit with a glass cylinder is described below. Points
which have to be taken into account when dismantling a dosing
unit with an ETFE cylinder are mentioned on page 16.
• First remove the dosing drive; see chapter 2.2.4.
• Remove all tubing and the drying tube from the dosing unit. In
order to remove the drying tube press the rotating axis of the
tube firmly and turn it counterclockwise until the screw nipple is
loose.
If the dosing unit is mounted on a reagent bottle screw it off and
remove the filling tube.
• Place the dosing unit on a flat surface so that
the marking showing the volume is facing to-
wards you.