Metrohm 844 UV/VIS Compact IC - Manual (Page 94)

Table of contents
4 Rinse column
• Place beaker beneath the column outlet.
• Set flow rate for new separating column.
• Switch on high-pressure pump and rinse column with eluent
for approx. 10 min, then switch off pump.
5 Connect column to detector block
• Screw outlet end of column 113 onto column outlet capillary
(depends on Version: 122(2.844.0010/2.844.0110), 123
(2.844.0020/2.844.0120) or 124 (2.844.0030/2.844.0130)).
4.2.4 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
replacement of wear parts such as pistons, piston seals and valves,
proceed as follows:
1 Detach pump head
• Switch off pump drive of the IC Pump.
• Disconnect aspirating tubing 82 from aspirating capillary 30
at the pump head 27/54.
• Unscrew connection capillary 24/52 from the pump head
27/54.
• Remove the pump head 27/54 by slackening the 4 securing
screws on the front of the pump head with the aid of the Allen
key 6.2621.030 from the pump housing. The main piston is
located at the left (when viewed from the front) and the
auxiliary piston is located at the right.
2 Disassemble pump head
• Strip down pump head 27/54. Main and auxiliary pistons are
identical with the following exceptions:
-
The spring 136 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 cy-
linder.
To prevent the piston 134 suddenly jumping out of the piston
cartridge 137 , the screw 133 must be undone very carefully by hand.
3 Cleaning/replacement of piston 134
• 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).