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MAINTENANCE MANUAL
9) Slice a small hole in the plastic chamber and put the helium tube in the hole. 10) Work the tape flange on the injection tube so it sticks well and seals the plastic chamber.
S 486-194
(7) Set up the HeliTest Wing Kit and purge the lines with helium to remove air.
NOTE: Refer to the instructions supplied with the kit.
____
S 786-195
(8) Carefully and slowly apply about 0.2 psig helium pressure to the pressure cup or chamber.
NOTE: Start with low pressure and then slowly increase the
____ pressure. Less helium is necessary for larger leaks than for smaller leaks. Too much helium will flood the fuel tank. Inspect the chamber or pressure cup to make sure there is no leakage. If it leaks too much, rebuild the chamber because the helium can interfere with the detector.
S 796-196
(9) Apply negative ventilation, if available, around the helium chamber to draw away leaking helium to make sure it does not interfere with the detector by drifting into the tank (AMM 28-11-00/201).
NOTE: Use positive ventilation if negative pressure is not
____ available, but make sure the helium is removed from the area and does not go into the tank where the detector probe is used.
S 796-197
(10) Permit the helium to soak into the leak path for 10 to 15 minutes before you go into the tank.
NOTE: Time is necessary to push the remaining fuel out of the leak
____ path and start the flow of helium from the external leak point to the internal leak point.
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S 796-198
WARNING:_______KEEP THE DETECTOR AND THE PUMP AWAY FROM THE TANK. INJURY TO PERSONS AND DAMAGE TO EQUIPMENT CAN OCCUR.
(11)
Keep the HeliTest detector and the auxiliary pump away from the open fuel tank at all times.
S 796-199
(12)
Go into the tank with the HeliTest Visual Probe (intrinsically safe for Class I, Div I areas).
S 796-200
(13)
Slowly move the probe inside of the fuel tank.
NOTE: Patience is important.
____
S 796-201
CAUTION:_______DO NOT PUT THE PROBE INTO FUEL PUDDLES. IT CAN CAUSE DAMAGE TO THE INSTRUMENT.
(14)
If there is a puddle of fuel in the area where you expect to find the leak, use rags and compressed air to dry the area.
(a)
Build rag dams to soak up additional running fuel.
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