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A
747-400 MAINTENANCE MANUAL
 S 117-001
 WARNING: DO NOT GET SOLVENTS IN YOUR MOUTH, OR 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 ENVIRONMENT. REFER TO PRODUCT MATERIAL SAFETY DATA SHEETS (MSDS) AND LOCAL REQUIREMENTS FOR PROPER HANDLING PROCEDURES.
 (2)  If there is grease on the duct, use solvent, Series 92 (AMM
 20-30-92) to clean it.

 D. Clean the Bare Titanium Ducts
 S 287-002
 (1)  
Examine the titanium duct for hydraulic fluid contamination or other damage (AMM 05-51-12/201 or 36-11-01/601).

 S 027-006

 (2)  
Remove and replace the ducts that are damaged or have unacceptable deterioration (AMM 36-11-01/401).

 S 117-007

 (3)  
If the duct had contamination on it, use a scraper and acetone to remove the contamination.

 E. Clean the Gold Coated Titanium Ducts
 S 117-009
 (1)  Use a lint free clean cloth with isotropyl alcohol to clean the gold-coated titanium duct.
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747-400 MAINTENANCE MANUAL
 PNEUMATIC DUCT - APPROVED REPAIRS
_________________________________
 1.  General_______
 A.  You can repair thin wall ducts that are damaged.
 B.  It may be necessary to replace the ducts as an alternative to duct repair.
 C.  Refer to the Overhaul Manual if you need to weld or do other repairs not included in this procedure.
 D.  This procedure also contains the task to repair the duct while the duct is installed on the airplane.
 TASK 36-11-01-208-017
 2.  Examine The Duct for Damage___________________________
 A.  Examine the duct to see if it is necessary to repair it.
 S 208-019
 (1)  
The damage is permitted if:

 (a)  
There are smooth dents that do not decrease the airflow.

 (b)  
There are thin scratches or corrosions that have a depth that is less than 10% of the duct wall thickness.

 (c)  
The two edges of each scratch are smooth and rounded.

 (d)  
The bottom of each scratch is smooth and rounded.

 S 308-025
 (2)  Repair or replace the duct if there is more damage.
 TASK 36-11-01-308-020
 3.  Repair the Dent in the Duct___________________________
 A.  Repair a smooth dent with one of these procedures:
 S 358-026
 (1)  
Pull a ball mandrel through the dented area of the duct.

 S 358-027

 (2)  
Use an expansion device in the duct.

 S 358-028

 (3)  
Increase the pressure in the duct (do not exceed the maximum permitted pressure limits of the system) and hit around the edges of the dent lightly with a mallet that is non metallic.

 TASK 36-11-01-308-018
 4.  Repair the Scratch in the Duct (Fig. 801)______________________________
 A.  To repair a scratch in the duct, remove metal that is adjacent to the scratch with the conditions that follow:
 S 228-021
 (1)  The minimum wall thickness at the bottom of the scratch after it is repaired must not be less than 90% of the minimum duct wall thickness.
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747-400
MAINTENANCE MANUAL

0.12 INCH
PRIMARY
RAD MINIMUM

90% MATERIAL GAGE MINIMUM
DUCT REWORK (EXAMPLE)

SILICONE RUBBER SHEET

MAXIMUM CRACK LENGTH DUCT REPAIR (EXAMPLE)
MUST NOT BE MORE THAN THE DUCT DIAMETER.
Pneumatic Duct Approved Repairs Figure 801
　
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