Metrohm 850 Professional IC Cation - Gradient - Manual (Page 65)

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5 Operation and maintenance
850 Professional IC Cation – HP-Gradient
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Pump head maintenance
An unstable baseline (pulsation, flow fluctuations) is in many cases the
result of contaminated valves (32-2), (32-3) 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 (17-2) and
unscrew the coupling (17-9), the pump head input capillary (17-7)
and the eluent aspiration tubing from the pump head.
3 Unscrew the pump head output capillary (17-13) from the pump
head.
4 Remove pump head from the pump housing by loosening the 4 fas-
tening screws (17-5) using the 6.2621.030 hexagon key. The main
piston is on the left (viewed from the front), and the auxiliary piston
is on the right.
Cleaning/replacing the zirconium oxide piston
Clean one piston after the other as follows:
1 Removing the piston cartridge from the pump head
Loosen the piston cartridge with a wrench and unscrew from the
pump head by hand.