Metrohm 761 SD Compact IC - Manual (Page 101)

6.2 Maintenance and servicing
761 SD Compact IC / Instructions for Use 8. 761.1043
93
1 Detach the pump head
• Disconnect the "tubing connection to the eluent MPak" 23
(with PEEK coupling 55) from the aspirating capillary on the
pump head 24 and detach it.
• Unscrew the connection capillary 25 from the pump head 24.
• Remove the pump head 24 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 auxil-
iary piston is located at the right.
2 Dismantle the pump head
• Strip down the pump head 24 in accordance with Figure 15
into its components. The main piston and auxiliary piston are
identical, apart from the following exceptions:
− The spring 71 of the auxiliary piston (right-hand piston) is
more powerful (longer) than that of the main piston (left-
hand piston).
− The inlet and outlet valve are not present in the secondary
cylinder.
In order to prevent the piston 69 suddenly jumping out of the piston
cartridge 72 , the screw 68 must be undone very carefully by hand.
3 Clean/replace the pistons 69
• Pistons contaminated by abrasive particles or deposits are
cleaned with scouring powder and rinsed free of any particles
with distilled water.
• More heavily contaminated or scratched pistons must be re-
placed (spare part: zirconium piston 6.2824.070).
4 Replace piston seal 76
• Use the special tool 80 to remove damaged piston seals 76.
The tool must be screwed into the seal 76 which can then be
pulled out (see Figure 16A).
When the special tool 80 is screwed into the piston seal 76 , the latter
is destroyed completely!