(2)
Remove jamnuts from element fittings.
(3)
Release clamps along length of sensing element.
NOTE: Support sensing element while releasing clamps. Keep bending of element to a minimum.
(4)
Slide element fittings clear of bracket and remove.
(5)
Replace jamnuts on element fittings and install protective caps.
4. Install APU Engine Sensing Element (Fig. 401, 402, 403)
CAUTION: FIRE DETECTION MAY BE DEGRADED WITH INCORRECT UNIT INSTALLED. VERIFY THAT PART NUMBER OF NEW UNIT IS IDENTICAL TO THAT OF UNIT REMOVED.
A. Remove protective caps and jamnuts from element fittings.
B. Support element to prevent bending. Insert element fittings into bracket then clamp sensing element in position.
NOTE: Overheat sensing element M276 may be covered with a short silicone tube installed over the element to aid in prevention of false overheat annunciation. The tube is slit to fit easily over the element, and must be secured within the mounting clips, and with lacing tape. (BMS13-54, Grade D, Type III, Class 1 Finish C or equivalent) It is important to position the slit away from the bend in the element.
C. Install jamnuts.
5E2
May 01/99 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 26-15-12 Page 405
D. Remove protective caps from electrical connectors and verify that detector and airplane electrical connectors are dry, clean and free of contaminates. If contamination is found, clean connectors.
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.
E. 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.
F. On configuration II electrical connector, apply very light coat of DC-4 grease to copper sealing gasket. On configuration I electrical connector, discard old copper gasket and replace with new copper gasket (Fig. 402).
NOTE: Avoid getting grease in connector cavity or on connector pins or contacts.
G. Carefully engage contact pins into receptacles and tighten electrical connectors to a torque of 50-70 pound-inches.
H. Check bonding resistance between electrical connector and APU with bonding meter. Observe that resistance is less than 0.0025 ohm.
I. Lockwire element end fittings, jamnuts and electrical connectors together.
J. Test APU fire detection system (Ref APU Fire Detection System A/T).
5. Install APU Exhaust Sensing Element (Fig. 401, 402)
CAUTION: FIRE DETECTION MAY BE DEGRADED WITH INCORRECT UNIT INSTALLED. VERIFY THAT PART NUMBER OF NEW UNIT IS IDENTICAL TO THAT OF UNIT REMOVED.
A. Install exhaust fire sensing element as follows:
(1)
Remove protective caps and jamnuts from element fittings.
(2)
Insert element fittings into bracket on forward muffler cone, then clamp sensing element in position.
(3)
Install jamnuts.
B. Install exhaust overheat sensing element as follows:
(1)
Remove protective caps and jamnuts from element fittings.
(2)
Support element to prevent bending.
(3)
Insert element fitting into bracket on heat shield, then clamp sensing element in position.
(4)
Install jamnuts.
(5)
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.
(6)
Shake out excess liquid and dry with either dry compressed air or nitrogen at a pressure of 20-25 psig.
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