Metrohm 818 IC Pump - Manual (Page 31)

4.2 Maintenance and servicing
818 IC Pump / 8.818.1023 Instructions for Use
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4.2.2 Maintenance work at the pump head
In many cases, an unstable baseline (pulsation, flow fluctuations) can
be traced to contaminated valves or faulty, leaky piston seals. For
cleaning contaminated valves and/or replacement of wear parts such
as pistons, piston seals and valves, proceed as follows:
1 Detach pump head
Unscrew connection capillary 6 from the pump head 8 with the
aid of the ¼" wrench (see Fig. 1). Then remove the pump head 8
from the pump housing by loosening the 4 hexagon screws 9
using the 6.2621.030 hexagon key. The main piston is on the left
(when viewed from front), the auxiliary piston on the right.
2 Disassemble pump head
Strip down pump head 8 in accordance with Fig. 8. Main and
auxiliary pistons are identical with the following exceptions:
• The spring 29 of the auxiliary piston (right piston) is more
powerful (longer) than that of the main piston (left piston).
• Inlet and outlet valve are not present in the secondary
cylinder.
To prevent the piston 27 suddenly jumping out of the piston cartridge
30 , the screw 26 must be undone very carefully by hand.
3 Cleaning/replacement of piston 27
Pistons contaminated by abrasive particles or deposits are
cleaned with scouring powder and rinsed free of any particles
with dist. water. Relatively badly contaminated or scratched
pistons must be replaced (spare part: 6.2824.070 Zircon piston).
4 Replacement of piston seal 34
To remove damaged piston seals 34 the special tool 38 is used.
This is screwed into the seal 34, which can then be pulled out
(see Fig. 9A).
When the special tool 38 is screwed into the piston seal 34 the latter
is completely destroyed!