Metrohm 881 Compact IC pro – Cation - Manual (Page 62)

5.5 High pressure pump
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881 Compact IC pro – Cation
Caution
In order to spare the pump seals, the pump should not be operated dry.
Therefore ensure that the eluent supply is correctly connected and that
there is enough eluent in the eluent bottle each time before switching
on the pump.
5.5.2 Maintenance
Caution
Maintenance work on the high pressure pump may not be carried out
unless the instrument is switched off.
Pump head maintenance
An unstable baseline (pulsation, flow fluctuations) is in many cases the
result of contaminated valves (29-2), (29-3) or defective, leaking piston
seals on the high pressure pump. Proceed as follows for cleaning contami-
nated valves and/or replacing worn parts such as pistons, piston seal and
valves:
This maintenance work should be carried out at least once a year.
Removing the pump head
1 Switch off high pressure pump and wait until pressure is released.
2 Loosen the pressure screw on the inlet valve holder (14-6) and
unscrew the pump head input capillary (14-7), the coupling (14-9),
and the eluent aspiration tubing from the pump head.
In the process, eluent will spill. Hold the eluent aspiration tubing up
high and allow the eluent to flow back into the eluent bottle.
3 Unscrew the pump head outlet capillary (14-13) from the pump
head.
4 Remove pump head from the pump housing by loosening the 4 fas-
tening screws (14-5) using the hexagon key (6.2621.030). The main
piston is on the left (viewed from the front), and the auxiliary piston
is on the right.