Metrohm 844 UV/VIS Compact IC User Manual

Page 97

4.2 Maintenance and servicing

844 UV/VIS Compact IC / Gebrauchsanweisung 8.844.1051

through the upper opening in the valve housing. The

individual components are rinsed with dist. water and/or

acetone, and the sapphire sphere cleaned with a paper

towel. The valve is then reassembled in accordance with

Figure 28. The components of the inlet and outlet valves are

identical, they are distinguished only by the positioning of the

ceramic holder 151 (see Figure 28).

• Valves that fail to function faultlessly after such cleaning must

be replaced.

• In the reinstallation of the inlet valve 141 or the outlet valve

142 on no account must the two outwardly identical valves be

interchanged. To determine which valve is which, note that

the liquid flows through the pump head from the bottom up.

The flow direction of the valves can be checked simply by

blowing through the clean valve. Both valves are installed with

the black face in the direction of the pump head (see Figure

28).

If by mistake an inlet valve

is installed instead of the outlet valve

, an extreme pressure buildup occurs within the working cylinder,

which is not detected by the pressure transducer and will destroy the

piston seal

6 Mounting the pump head

• Reassemble the components of the pump head 27/54 as

133 by hand. First

screw in piston cartridge 137 manually until the stop is

reached and then use a wrench to turn it through a further

30°. Firmly tighten the two valve screw holders

143 with a

wrench.

• Reattach pump head 27/54 to the pump with the help of the

4 fixing screws. Firmly tighten them with the 6.2621.030 Allen

key.

To ensure that the pump head is not positioned wrongly, the

holes at the rear for the clamping bolts have different depths,

i.e. 1 clamping bolt is longer than the rest. The deepest hole

must naturally accommodate the longest bolt. If this is not the

case, the pump will not function properly.

• Screw connection capillary 30 to pump head 27/54.
• Connect aspirating tubing 82 to aspirating capillary 30 at the

pump head 27/54.