Hach 911 User Manual page 67

7.8.5.1 Replacing the Hydrophobic Filter
1 Filter, smooth side down
®
A single Teflon hydrophobic filter (Cat. No. 3390) is installed in the top of the canister to
prevent liquid from entering the vent tube.
For best performance and to avoid grease buildup on the filter during submergence or
surcharge conditions, hang the canister vertically so that the end facing the sensor points
downward.
1. Disconnect the tubing from the top of the desiccant canister.
2. Unscrew the hex-head tubing nipple from the top of the canister and discard the old
filter.
3. Discard any remnants of Teflon tape from the nipple's threads. Reapply two turns of
Teflon tape (Cat. No. 10851-45) to the threads, pulling the tape into the threads until it
conforms to the shape of the threads.
4. Place a new filter over the hole. Make sure that the smooth side of the filter faces the
inside of the canister.
5. Place the threaded nipple on top of the filter.
6. With a slight pressure, press the filter into the hole with the nipple threads and begin
threading the nipple into the hole. The filter deflects upward and feed completely into
the thread until it disappears. The filter must rotate with the nipple as it is threaded into
the cap. If it does not, it is torn. Start over with a new filter.
7. Inspect the installation. A small, dim light spot should be visible in the upper cap when
held up to the light. A bright spot indicates a torn filter. Start over with a new filter.
1
Figure 39 Replacing the Hydrophobic Filter
2 Hex-head tubing nipple
2
3 Finished assembly
Maintenance
3
65