737 AMM 飞机维护手册 防火 FIRE PROTECTION(43)

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B.  Remove protective cap from end fitting at one end of sensing element and loosely install in applicable flange fitting. Bend element to contour of clamps and loosely install other end fitting (Fig. 401).
C.  Install silicone rubber bushings on element so that each is centered on mounting clip and slit of each bushing faces outside of nearest bend.
D.  Install bushings in each mounting clip. Mounting clips and bushings must fit element snugly.
NOTE:  If old sensing element has been left in position reference, it should be removed at this time.
E.  Tighten jamnuts on end fittings. Torque to 50 to 60 pound-inches and lockwire jamnut to flange fitting and end fittings.
NOTE: Check that end-fitting hex is inside hex retainer on flange fitting prior to tightening.
F.  Retrace sensing element, taking up and providing slack as necessary.
NOTE:  Elements shall clear structure by a minimum of 0.50 inch except at mounting clips. As much clearance as possible is desired from units that are displaced by torque or vibrate. Double-check all bends and clearance after securing element.
G.  Remove protective caps from electrical connectors and verify detector and airplane electrical connectors are dry, clean and free of contaminates. If contamination is found, clean connector.
CAUTION:  CLEAN CONNECTORS USING METHYL ALCOHOL OR ACETONE ONLY. DO NOT USE OTHER CLEANING SOLVENTS FOR THIS PURPOSE. COMMERCIALLY AVAILABLE CONTACT CLEANERS MAY CONTAIN CHLORIDES WHICH PROMOTE CORROSION IN SEALED AREAS AND SHOULD NOT BE USED.
H.  Shake out excess liquid and dry with either dry compressed air or nitrogen at a pressure of 20-25 psig.
CAUTION:  CONNECTOR MUST BE THOROUGHLY DRY OR CORROSION MAY RESULT.
500 
26-17-11 Page 402  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  Feb 20/90 

H21781
538  Wheel Well Overheat Detection Sensing Element Installation 
Aug 01/75  Figure 401  26-17-11 
Page 403 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

I.  Apply a very light coat of DC-4 grease to copper sealing gasket.
J.  Install electrical connectors on end fitting and lockwire to flange fitting.
K.  Check electrical bond between element connector shell and primary structure per 20-22-01. Resistance should not exceed 0.005 ohm.
L.  Close applicable circuit breaker on panel P6-2.
M.  Check wheel overheat detection system (Ref 26-17-0 A/T).
500 
26-17-11 Page 404  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  May 01/03 

WHEEL WELL OVERHEAT DETECTION SENSING ELEMENT - ADJUSTMENT/TEST
1.  General
A.  Attachment of test equipment should be made by using a wire end fitting between the element end fitting and test equipment. Attach the test leads to the center contacts or the center contacts and outer shell of the wire end fittings as applicable. Use of the wire end fittings reduce the possibility of any damage to the electrical contact surface and provide a positive attach point for test equipment during test. Extreme care must be taken during the tests to keep end fittings free from dirt and other foreign substances. Replace the electrical connector or protective caps upon completion of the tests.
2.  Wheel Well Overheat Detection Sensing Element Test
A.  Sensing Element Test
(1)  General
(a)  No test of sensing loop should be done unless all units in the system are stabilized at ambient temperature. Failure of an element to meet the electrical specification noted in the following paragraphs is cause for replacement.
CAUTION:  DO NOT USE A MULTIMETER ON THE SENSOR ELEMENTS IF THE ELEMENT TEMPERATURE IS ABOVE 155°F (68°C). IF THE TEMPERATURE IS BELOW 155°F (68°C), BUT ABOVE 70°F (21°C), LIMIT METER USE TO 5-SECOND APPLICATIONS WITH NO MORE THAN 2 APPLICATIONS PER MINUTE. IF THESE REQUIREMENTS ARE NOT FOLLOWED, DAMAGE TO THE SENSOR ELEMENT MAY OCCUR.
(2)  
Equipment and Material

(a)  
Multimeter

(b)  
Deleted

(c)  
Wire End Fitting 35303-10, Fenwal, Inc., Ashland, MA.

 

(3)  
Test Sensing Element

(a)  
Disconnect wire end fittings D840 and D842 on ceiling of main wheel well.

(b)  
Test for center conductor continuity by connecting multimeter to center conductor at each end of sensing element. 1) Resistance of center conductor shall not exceed 0.2 ohm per foot of element

 

NOTE:  The wire end fittings are to be used for attachment of test equipment to the sensing elements during test procedures.
　
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