(MIN 2 LAYERS)
EXTERNAL PATCH - RIGID FOAM DUCT
Air Conditioning System Ducts Repair (Rigid Foam)
Figure 802 (Sheet 1)

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L25678
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747-400
MAINTENANCE MANUAL

DAMAGED AREA WITH FOAM PLUG

FIBERGLASS CLOTH AND RESIN

DUCT
MIN 2.0 INCHES (50.8 mm)

STRUCTURAL REPAIR - RIGID FOAM DUCT
REPLACEMENT DUCT SECTION
3.0 INCHES
(76.2 mm)

DUCT JOINT FIBERGLASS CLOTH FIBERGLASS CLOTH

AND RESIN JOINT AND RESIN JOINT
DUCT SECTION REPLACEMENT - RIGID FOAM DUCT
Air Conditioning System Ducts Repair (Rigid Foam)
Figure 802 (Sheet 2)

3.0 INCHES
(76.2 mm)
DUCT JOINT

L24514
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747-400 MAINTENANCE MANUAL
 D. Prepare for the Repair
 S 868-088
 (1)  
Remove the pneumatic power (AMM 36-00-00/201).

 S 868-089

 (2)  
On the bleed air control module on the pilots' overhead panel, put the pack control switches in the OFF position.

 S 018-090

 (3)  
Remove the applicable ceiling, sidewall, or floor panels to gain access to the damaged air conditioning duct joint.

 S 028-091

 (4)
If insulation is installed on the duct, remove the insulation.

 S 348-092

 (5)  
Do these steps to prepare the damaged area of the duct:

 (a)  Remove the tape and adhesive from the duct joint area.
 WARNING: DO NOT GET SOLVENTS IN YOUR MOUTH, OR IN YOUR EYES, OR ON
_______ YOUR SKIN. DO NOT BREATHE THE FUMES FROM SOLVENTS. SOLVENTS ARE HAZARDOUS MATERIALS. SOLVENTS MAY BE FLAMMABLE OR HARMFUL TO THE ENVIROMENT. REFER TO PRODUCT MATERIAL SAFETY DATA SHEETS (MSDS) AND LOCAL REQUIREMENTS FOR PROPER HANDLING PROCEDURES.
 (b)  
Use the solvent and a wiping cloth to clean the damaged area.

 (c)  
Sand the damaged area to remove any remaining adhesive and contamination.

 (d)  
Use the solvent and a wiping cloth to clean the damaged area.

 S 348-093
 (6)  
Examine the end of each air conditioning duct for damage.

 S 348-094

 (7)  
If the duct lining is damaged so that the foam core of the duct shows, then do the Duct End Repair task for the rigid foam duct.

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747-400 MAINTENANCE MANUAL
 S 348-095
 (8)  
Cut a piece of fiberglass cloth 3 inches wide and long enough to go around the duct a minimum of two times.

 S 348-096

 (9)  
Prepare the resin.

 E. Repair the Taped Joint
 S 348-097
 (1)  
Apply resin to the duct ends.

 S 348-098

 (2)  
Let the resin partially dry until it is sticky.

 S 348-099

 (3)  
Press the duct ends together by aligning the installation
 checkmarks.

 S 348-100

 (4)  
Apply a thin, smooth layer of resin to the joint area a minimum of 2 inches wider than the duct joint.

 S 348-101

 (5)  
Apply resin to one side of the cloth.

 S 348-102

 (6)  
Wind the cloth around the duct joint a minimum of two times.

 NOTE: Make sure the resin on the cloth is in contact with the duct.
　
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