PAL-AT Installation Manual
63
Figure 9-3
PHLR Sensor Package
9.4.1 Cleaning Sensor Elements Procedure
The replacement sensor package consists of 10 disks: seven screen disks and three sensor disks as
shown in figure 9-3. The replacement package includes all removable parts: probe cap, sensor elements,
and actuator. Replacement sensor elements can also be purchased separately.
The following procedure is a general guideline to follow to clean the probe and sensor elements after
exposure to hydrocarbon liquids.
Caution: It is the user’s responsibility to determine safety precautions and the suitability of
exposing personnel to the hydrocarbon liquid on the probes and various cleaning solvents
suggested.
The sensor disks swell after exposure to fuels and solvents. The swelling forces the actuator to move and
operate a low-force sealed switch. Volatile hydrocarbon liquids, such as gasoline, will eventually evaporate
resulting in the sensor disks returning to their original size. This allows the switch to return to the normal
position. A faster resetting process is to disassemble the probe to speed the evaporation of the liquid.
Other liquids, such as diesel fuel and jet fuel that do not evaporate, must be flushed with a solvent to
remove the contamination. Disassemble and clean the probe as follows:
1. Remove excess hydrocarbon contamination from the exterior of the probe.
2. Hold the switch in a vertical position with the cap downward and unscrew the cap. Do this over a table
so the small parts are not lost if they are dropped. Be very careful not to lose the sensor disks.
They are very similar to contact lenses in size and texture.
3. Place the actuator, screens, cap, and sensor disks into a small container of solvent. Coleman Camp
Fuel, which is naphtha, works well and evaporates very quickly. Other solvents that evaporate quickly
and completely are also suitable.
4. Soak the components for a minute or two and then remove them.
5. Let the solvent evaporate until the disks return to the original diameter and fit into the cap easily. If
the sensor disks do not slip easily into the circular holder in the cap, repeat the cleaning process. The
disks should be about 0.5” [12 mm] diameter when dry.
(1) ACTUATOR
(1) CAP
(4-7) SCREEN DISKS
(3) SENSOR DISKS
PROBE HOUSING
PROBE
LEADS
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