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发表于 2009-7-23 21:53:32
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来自： 中国四川成都
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This continuous monitoring system is designed to detect, by means of detection loops, any ambient overheat. This is to protect the structures and components near the hot air ducts in the fuselage, pylons and wings, against possible leaks or bursts.
The aircraft leak detection system is divided into LH and RH zones by the crossfeed valve in the crossfeed duct at STA1537 (FR35). Each leak detection system operates independently.
Both wing/fuselage leak detection systems are made up of twin loops (A and B) of overheat sensing elements. This eliminates the possibility of incorrect warnings, due to an AND logic.
The overheat sensing elements are installed in each wing along the forward face of the front spar. Clamps and rubber grommets attach the overheat sensing elements at regular intervals along the whole length.
In the fuselage, the elements are installed at STA1537 (FR35) and close to the crossover bleed-air duct. They continue (LH side elements only) up to the APU check valve on the pressurized fuselage between STA2189 and STA2243.
A single loop system is installed along the bleed air duct between the APU check valve and the APU bleed valve.
In each of the pylons, there is a single loop. Each loop is located near the pylon ventilation duct.
The overheat sensing elements have a solid nickel center conductor set in a ceramic insulation of porous aluminum oxide. An inconel tube contains these components and is sealed at both ends. Eutectic salt fills the space between the tubing, the ceramic insulation and the center conductor. This mixture is compounded to give a signal at alarm temperature. For the wing and fuselage, the alarm temperature is 124 plus or minus 7 deg.C. The pylon alarm temperature quantity is 204 plus or minus 12 deg.C.
The impedance between the conductor and the outer tubing decreases suddenly when the alarm temperature is reached. At this temperature, the center conductor grounds and gives an alarm signal.
The overheat sensing elements continuously monitor the surrounding areas for overheat conditions. They are connected in series and detect overheat conditions at any point along the length of the elements. When only a few inches of the elements are heated to the pre-determined temperature, an alarm is caused. When this occurs, the bleed air supply is shut off automatically.
If one loop is inoperative (loop A or B), the remaining loop takes over. If hot air escapes from the bleed air duct and heats an element of the operative loop, a signal is given.
The signal causes:
- the amber FAULT light on the AIR COND overhead panel to come on,
- the activation of the ECAM system.
When the ECAM system is activated:
- the MASTER CAUT lights on the panels 131VU and 130VU come on amber
- a single chime sounds
- the message on the upper ECAM display unit comes on
- the BLEED page on the lower ECAM display unit comes on.
The FAULT light stays on as long as the overheat condition exists. The valves associated with the loop close automatically. If the overheat condition is eliminated, the circuit must be reset to open the valves.
The different FAULT warnings on the AIR COND overhead panel 30VU are:
- the FAULT legend on the ENG 1 BLEED pushbutton switch which comes on if there is an overheat condition in the LH zone (LH pylon, LH wing and LH MID fuselage),
- the FAULT legend on the ENG 2 BLEED pushbutton switch which comes on if there is an overheat condition in the RH zone (RH pylon, RH wing and RH MID fuselage),
- the FAULT legend on the APU BLEED pushbutton switch which comes on if there is an overheat condition in the MID and AFT fuselage (APU duct).
At the same time as the FAULT legend on the ENG 1 BLEED pushbutton switch comes on, the following valves close automatically:
- the LH pressure regulating valve,
- the LH wing anti-icing (if the wing anti-icing system is operative) valve,
- the APU bleed valve (the APU pushbutton switch is in the ON position),
- the crossbleed valve (the selector is in the AUTO position).
When the FAULT legend on the ENG 2 BLEED pushbutton switch comes on, the following valves close automatically:
- the RH pressure regulating valve
- the RH wing anti-icing valve (if the wing anti-icing system is operative)
- the crossbleed valve (the selector is in the AUTO position).
When the FAULT legend on the APU BLEED pushbutton switch comes on, the APU bleed valve closes automatically (the APU pushbutton switch is in the ON position). Engine start sequence prevents that the APU bleed valve and the crossbleed valve (the selector is in the AUTO position) close.
A functional test can only be carried out on the ground by automatic control activation. It checks the outputs or status of each leak detection loop in-turn. The maintenance test permits the maintenance crew to check a specific function of the system. Additionally, the maintenance test finds a failed Line Replaceable Unit (LRU).<div class=\"tal s3\">
scal320 于 2009-07-23 21:54 又补充说</div>摘自AMM希望对你有帮助 |
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