Replacing The Check Valve Cartridge - LC Packings SWITCHOS II User Manual

c) Remove the spring guides, the springs and the support washers (items 4, 5,
7; FIGURE 6-5).
d) You can remove/replace the piston seals (backflushing seals) now. Use an
appropriate tool (e.g. a small screwdriver) to remove the seals (item 8;
FIGURE 6-5).
e) Loosen the spacing bolts (item 6; FIGURE 6-5). Remove the two spacing
bolts and then remove the pressure plate (item 9; FIGURE 6-5).
f) You can remove/replace the piston seals (high pressure seals) now. Use an
appropriate tool (e.g. a small screwdriver) to remove the seals (item 11;
FIGURE 6-5).
Note: The seals should only be replaced when the pump leaks. The useful
lifetime depends on the mobile phase to be pumped and the back pressure of the
system. The typical lifetime of the seals is in the order of 2500 h. It is
recommended that both seals be replaced if one is defective.
g) To remove the titanium inlays, remove the four bushings, the check valves
and the PEEK adapters (items 13, 14, 15; FIGURE 6-5).
h) Carefully insert new seals. The spring side should be placed as indicated in
FIGURE 6-5.
To re-assemble the pump head:
a) Insert the titanium inlays, the two check valve cartridges (item 13; FIGURE
6-5) and the two PEEK adapters (item 14; FIGURE 6-5). As you replace the
check valves, make certain that they are inserted in the right position.
Caution: Make certain that the orientation mark of the check valve cartridges is
CAUTION
placed so that the mark is on the bottom. Installing the check valve cartridges in
the wrong direction may lead to a damage of a cartridge or the pump head.
b) Alternating from one to the next tighten the upper and the lower bushing half
a turn at a time by hand.
c) Replace the pressure plate with the 2 o-rings (items 9, 10; FIGURE 6-5) and
the two spacing bolts (items 9, 10; FIGURE 6-5). Alternating from one to the
next tighten the two bolts by hand.
d) Tighten the two bolts, and then tighten the 4 bushings. Make certain that all
screws are securely tightened.

6.3.5 Replacing the Check Valve Cartridge

The inert pump head is equipped with two check valves (item 13; FIGURE 6-5),
one on the inlet side of the main piston (lower right) and on the outlet of the
main piston (upper right) while two PEEK adapters are used on the auxiliary
piston (lower and upper left side).
User's Manual Switchos II
Maintenance and Troubleshooting
D850R3
6-7