Metrohm 818 IC Pump - Manual (Page 34)

4 Notes – Maintenance – Faults
818 IC Pump / 8.818.1023 Instructions for Use
28
5 Cleaning/Replacement of inlet valve 35 a nd outlet
valve 36
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. 10. Therefore the valves are
inserted into the holder of 6.2617.020 special tool and the
components of the valve are pushed out with the aid of the push
rod (also included in 6.2617.020 special tool) inserted through
the upper opening in the valve housing 40. 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. 10. The components of the
inlet and outlet valves are identical, they are distinguished only
by the positioning of the sapphire sleeve 43 and the ceramic
holder 45 (see Fig. 10).
Valves that fail to function faultlessly after such cleaning must be
replaced.
In the reinstallation of the inlet valve 35 or the outlet valve 36 on
no account must the two outwardly identical valves be
interchanged. 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. 8).
If by mistake an inlet valve 35 is installed instead of the outlet valve
36 , an extreme pressure buildup occurs within the working cylinder,
which is not detected by the pressure transducer and will destroy the
piston seal 34 !
6 Mounting the pump head
The components of the pump head 8 are reassembled as
shown in Fig. 8. the screw 26 and the piston cartridge 30 may
be tightened only by hand. On the other hand, the two valve
screw holders 37 are tightened with a wrench. The pump head is
then remounted on the pump (see section 2.2).