Metrohm 709 IC Pump - Manual (Page 35)

4.2 Maintenance and servicing
709 IC Pump
27
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 14 from the pump head 18 with
the aid of the ¼" wrench (see Fig. 2). Then remove the pump
head 18 from the pump housing by loosening the 4 hexagon
screws 19 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 18 in accordance with Fig. 9. Main and
auxiliary pistons are identical with the following exceptions:
• The spring 63 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 61 suddenly jumping out of the piston cartridge
64 , the screw 60 must be undone very carefully by hand.
3 Cleaning/replacement of piston 61
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 68
To remove damaged piston seals 68 the special tool 72 is used.
This is screwed into the seal 68, which can then be pulled out
(see Fig.10A).
When the special tool 72 is screwed into the piston seal 68 the latter is
completely destroyed!
If you use only aqueous eluents the 6.2741.000 piston seal can be
replaced by the 6.2741.010 PE piston seal available as an option.