e. Now draw a line connecting the two.
f. Date the calibration chart so as not to
confuse it with the previous chart.
NOTE
On the back of the chart it is a good practice
to put the serial number of the Wratten filters
used and on the front it is required to have the
machine serial number.
FREE WATER DETECTOR
(AEL MK I AND AEL MK II)
The free water detector (fig. 3-8) was developed to
measure accurately the amount of free water in fuels.
This detector is used with the Contaminated Fuel De-
tector in the normal fuel inspection and surveillance
programs; the test should be executed as soon as possi-
ble following the sampling.
The free water detector consists of an ultraviolet
light source, a set of standards indicating 0, 5, 10, and
20 ppm, and water detector pads.
A test sample of fuel is passed through a chemically
treated filter pad in the filter holder of the Mk III
detector. The chemical on the pad is sensitive to any free
water in the fuel. If water is in the fuel, the pad produces
a visible fluorescent pattern when it is placed under an
ultraviolet light.
Instructions for using the AEL free water detector
are as follows:
1. Mark the polyethylene bottle 3 1/4 inches from
the bottom. When the bottle is filled to this mark, a
500-ml sample will be obtained.
2. Fill the polyethylene sample bottle to the 500-
ml mark with fuel to be tested.
3. Open a free water detector envelope and place
the detector pad, orange side up, on the contaminated
fuel detector base. Attach the bottle receiver to the filter
base and plug in the ground wire jack.
CAUTION
Handle the detector pad with forceps only.
Do not touch the pad with your fingers or it
becomes contaminated before you even start
the test.
4. Check to see that the contaminated fuel detec-
tor fuel flask is empty and the drain cock closed.
5. Shake the bottle containing the 500-ml fuel
sample vigorously for approximately 30 seconds.
6. Immediately after shaking, turn the vacuum
pump on, unscrew the bottle cap, place the bottle re-
ceiver firmly over the end of the bottle, and insert the
filter over the end of the bottle. Then insert the filter
base into the contaminated fuel detector. This step
should be done in as short a time as possible to keep any
free water in suspension.
7. After the 500-ml sample has passed through
the detector pad, turn off the vacuum pump IMMEDI-
ATELY, and remove the bottle and bottle receiver.
NOTE
DO NOT continue to draw air through the
detector pad. If the moisture in the air is drawn
through the pad, you get an incorrect reading.
8. Remove the pad from the filter base with for-
ceps and place it (orange side up) in the free water
detector slide depression.
9. Light the ultraviolet bulb in the free water
detector by holding the light switch in the ON position,
and insert the slide containing the test pad.
10. Look through the view port of the box and
compare the brightness of the test pad with that of the
set of standards to determine the amount of free water.
Free water content is indicated in ppm by the numbers
located directly above the standards.
11. If the result is over 20 ppm, take a new sample
of one-half the standard sample and double the answer.
NOTE
The standards card in the free water detec-
tor must be replaced after 6 months of use
according to PMS.
The standards in the box when received should
be marked with the date on which the detector is first
put into use. The reason for replacing the standards
every 6 months is that the fluorescent inks in the
pads deteriorate after prolonged exposure to ultra-
violet light.
To replace the ultraviolet bulb, turn the used bulb
one-quarter turn and lift it out of the fluorescent lamp
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