INNER EXHAUST DUCT - REPAIRS
____________________________

 1.  General
_______
 A.  This procedure contains the tasks to repair the inner exhaust duct. The aft end of the inner exhaust duct can crack and pieces can break off. Areas that were damaged can be repaired by welding.
 B.  You must remove the accoustic liner and the inner exhaust duct before you do the repair procedure. The inner exhaust duct is in the outer exhaust duct. The accoustic liner is in the inner exhaust duct. The acoustic liner must be removed before you remove the inner exhaust duct.
 C.  You can get access to the inner exhaust duct from the aft end of the exhaust section through the exhaust duct.
 D.  Cracks in the inner exhaust duct can be repaired by welding. All of the welds used in this procedure are butt welds.
 TASK 49-81-02-308-001
 2.  Inner Exhaust Duct Repair (Fig. 801)
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 A.  Standard Tools and Equipment
 (1)  
Arc Welder

 B.  
Consumable Materials

 (1)  
F00039 Inconel 625 filler material.

 C.  
References

 (1)  
49-81-02/401, Inner Exhaust Duct

 (2)  
IPC 49-81-51 Fig. 1

 D.  
Access

 (1)  
Location Zone 317 APU Compartment-Outer Tail Section Through Exhaust Duct, LH

 318  APU Compartment-Outer Tail Section Through Exhaust Duct, RH

 (2)  
Access Panel
 317AL APU Access Door
 318AR APU Access Door

 E.  
Procedure

 (1)  
Remove the accoustic liner (Ref 49-81-03/201).

 (2)  
Remove the inner exhaust duct (Ref 49-81-02/401).

 S 318-003

 (3)  
Repair the crack:

 (a)  
If the crack ends less than 1 inch (25.4 mm) from any seam weld baffle, doubler, or sheet, do these steps: 1) Drill a hole in the material where the crack ends. 2) Weld the crack.

 S 018-008
 S 018-002
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747-400
MAINTENANCE MANUAL

LEAF SPRING SEALOUTER SECTION BROKEN OUT

APU Inner Exhaust Duct Damage (Typical)
Figure 801

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 (b) (c)  Do not repair any crack that ends less than 1 inch (25.4 mm) from the seam weld baffel, doubler, or sheet.Areas of the material that have broken off can be repaired as follows: 1) Splice in a new section of Inconel 625 by butt welding.
 (4)  S 358-004File any weld beads to a height of 0-0.005 inch (0-0.127 mm), and a 125-microinch finish by hand grinding.
 NOTE:____ Welded beads need to be removed only to provide for clearance when installing acoustic liner and inner exhaust duct. If the welded bead is in an area where clearance is not a problem, grinding the bead down is not required.
 (5)  S 238-005Dye penetrant inspect the weld for cracks.
 (6)  S 428-007Install the accoustic linner (Ref 49-81-03/201).
 (7)  S 418-006Install the inner exhaust duct (Ref 49-81-02/401).

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747-400 MAINTENANCE MANUAL
 ACOUSTIC LINER - MAINTENANCE PRACTICES
　
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