Metrohm 790 Personal IC - Manual (Page 169)

5 Notes – Maintenance – Faults
790 Personal IC
160
• To install a new piston seal 92 92 92 92 the special tool 97 97 97 97 is used.
• First the new seal is inserted firmly in the recess of tool 97 97 97 97 by
hand (see Fig. 18B). The seal spring must be located on the
outside.
• The tool 97 97 97 97 together with the seal is then inserted in the
pump head 34 34 34 34 and the seal pressed into the pump head re-
cess with the aid of tool 96 96 96 96 (see Fig. 18C).
The seal surface in the pump head 34 34 34 34 must not be damaged (avoid
contact with tool)!
5 Cleaning/replacement of inlet valve 93 93 93 93 and outlet
valve 94 94 94 94
• Contaminated or blocked valves are cleaned by rinsing with
dist. water, RBS solution or acetone. The rinsing effect can be
reinforced by brief treatment in an ultrasonic bath (max. 20 s;
if longer the sapphire sphere of the valve can be damaged).
• If this does not have the desired effect, the valves can be
disassembled as shown in Fig. 19. The valve components are
pushed out with the aid of a syringe needle inserted through
the upper opening in the valve housing 98 98 98 98. The individual
components are rinsed with dist. water and/or acetone, and
the sapphire sphere cleaned with a paper towel. The valve is
then reassembled in accordance with Fig. 19. The compo-
nents of the inlet and outlet valves are identical, they are dis-
tinguished only by the positioning of the sapphire sleeve 101 101 101 101
and the ceramic holder 103 103 103 103 (see Fig. 19).
• Valves that fail to function faultlessly after such cleaning must
be replaced.
• In the reinstallation of the inlet valve 93 93 93 93 or the outlet valve 94 94 94 94
on no account must the two outwardly identical valves be in-
terchanged. To determine which valve is which, note that the
liquid flows through the pump head from the bottom up. The
flow direction of the valves can be checked simply by blowing
through the clean valve. Both valves are installed with the
black face in the direction of the pump head (see Fig. 19).
If by mistake an inlet valve 93 93 93 93 is installed instead of the outlet valve
94 94 94 94 , an extreme pressure buildup occurs within the working cylinder,
which is not detected by the pressure transducer and will destroy the
piston seal 92 92 92 92 !