Metrohm 872 Extension Module IC Pump - Manual (Page 49)

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6 Operation and maintenance
872 Extension Module IC Pump
￭￭￭￭￭￭￭￭ 41
Salt crystals between the piston and seal cause abrasion particles which
can find their way into the eluent. These lead to contaminated valves, a
rise in pressure and in extreme cases scratched pistons. It is therefore
essential to ensure that no precipitates can occur (see Chapter 6.3.2.3,
page 40).
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 turning on
the pump.
6.4.2 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 (31-2), (31-3) 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 Turn off high pressure pump and wait until pressure is released.
2 Loosen the pressure screw on the inlet valve holder (20-2) and
unscrew the coupling (20-9), the pump head input capillary (20-7)
and the eluent aspiration tubing from the pump head.
3 Unscrew the pump head output capillary (20-13) from the pump
head.
4 Remove pump head from the pump housing by loosening the 4 fas-
tening screws (20-5) using the 6.2621.030 hexagon key. The main