6 maintenance work at the pump head – Metrohm 790 Personal IC User Manual
Page 167
5 Notes – Maintenance – Faults
790 Personal IC
158
5.2.6
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 at the
high-pressure pump. For cleaning contaminated valves and/or re-
placement of wear parts such as pistons, piston seals and valves, pro-
ceed as follows:
1 Detach pump head
• Disconnect aspirating tubing from aspirating capillary 32
32
32
32 at
the pump head 34
34
34
34 (see Fig. 3 and Fig. 4).
• Unscrew connection capillary 35
35
35
35 from the pump head 34
34
34
34.
• Remove pump head 34
34
34
34 by loosening the 4 hexagon screws
33
33
33
33 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 34
34
34
34 in accordance with Fig. 17. Main
and auxiliary pistons are identical with the following excep-
tions:
− The spring 87
87
87
87 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 cylin-
der.
To prevent the piston
85
85
85
85
suddenly jumping out of the piston cartridge
87
87
87
87
, the screw
84
84
84
84
must be undone very carefully by hand.
3 Cleaning/replacement of piston
85
85
85
85
• 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
92
92
92
92
• To remove damaged piston seals 92
92
92
92 the special tool 96
96
96
96 is
used. This is screwed into the seal 92
92
92
92, which can then be
pulled out (see Fig. 18A).
When the special tool
96
96
96
96
is screwed into the piston seal
92
92
92
92
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.