Metrohm 818 IC Pump User Manual

Page 34

4 Notes – Maintenance – Faults

818 IC Pump / 8.818.1023 Instructions for Use

5 Cleaning/Replacement of inlet valve 35

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

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

If by mistake an inlet valve

is installed instead of the outlet valve

, an extreme pressure buildup occurs within the working cylinder,

which is not detected by the pressure transducer and will destroy the

piston seal

6 Mounting the pump head

The components of the pump head 8 are reassembled as

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).