DUCTS - APPROVED REPAIRS
1. General
A. Thin wall ducts are subject to damage as a result of improper removal or installation, mishandling or abnormal operating conditions. Extremes of pressures or temperatures may in some cases, make complete replacement of components more desirable than local repair or partial replacement.
2. Duct Repair (Fig. 801)
A. Smooth dents do not require rework if they are not so deep as to restrict the airflow substantially. Smooth dents of greater depth may be removed by pulling a ball mandrell through the dented area or by the use of any applicable hydraulically or mechanically actuated expansion device. Hydrostatic pressure within the allowable pressure for the particular system used in conjunction with moderate tapping with a nonmetallic hammer around the edge of the dent from the outside is an effective method for removal of some dents.
B. Shallow scratches, gouges and corrosion having a depth not in excess of 10% of the duct wall thickness do not require rework provided the transition from base metal thickness is smooth and rounded and the bottom of the crack or gouge is also smooth and rounded.
C. Sharp scratches, gouges and corrosion can be reworked by removal of adjacent metal subject to the following restrictions:
(1)
Minimum wall thickness at the bottom of a scratch, gouge or corrosion after rework shall not be less than 90% of the minimum material gauge.
(2)
The surface roughness of the reworked area shall not exceed 40 RMS.
(3)
The slope of the reworked area shall not exceed a rise of 1 to 10.
(4)
Internal and external radii of the reworked area shall not be less than 0.12 inch.
(5)
When these defects are within 0.25 inch of a primary fusion welded joint they shall be as per par. D. below.
D. Ducts with damage which cannot be repaired within the above limits must be replaced. For repair of extensively damaged ducts, see Overhaul Manual.
3. Temporary Repair of Cracked Ducts (Fig. 801)
A. General
(1)
You can temporarily repair ducts that have a crack along the longitudinal axis.
NOTE: This repair procedure is only permitted for ducts that have a crack along the longitudinal axis. Replace ducts that have a crack along the circumference or have multiple cracks.
(2)
A duct with a longitudinal crack that is less than three inches for a flange or pullout also cannot be repaired by this procedure. It must be replaced or repaired in accordance with the Overhaul Manual.
(3)
The repair is temporary and you must replace the duct as soon as possible.
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May 01/00 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 36-19-11 Page 801
L17578
Pneumatic Duct Approved Repair 500
36-19-11 Figure 801 May 01/00
Page 802
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
B. Repair the duct with the crack
(1)
Stopdrill the crack.
(2)
Put the silicone rubber sheet on the crack and extend it three inches beyond the crack.
(3)
Put the stainless steel sheet on the rubber sheet.
(4)
Put the clamps on the duct every 1 to 1 1/2 inches and tighten the clamps.
4. Duct Flange Repair
A. Equipment
(1) Flange Reforming Tool, Adams Flange Spider
Adams - Bird, Inc.
5296 Pebbletree Way
San Jose, CA 95111
U.S.A.
B. Procedure
(1)
Get access to the duct flange that you will repair.
(2)
Use the flange reforming tool and repair the duct flange.
(3)
If you cannot repair the duct while the flange is installed, remove the duct to get access to the damaged flange (Ref 36-19-11/401).
(a) Repair the flange with the flange reforming tool.
500
May 01/00 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 36-19-11 Page 803
BALL JOINT - MAINTENANCE PRACTICES
1. General
A. The duct ball joints are located in the engine section of engines No. 1 and 2, and connect the 8th- and 13th-stage bleed manifolds to engine bleed air system and thermal anti-ice (TAI) system ducts. The ball joints consist of an inner bearing and bearing nut fixed to one of the ducts being joined, a retainer fixed to the other duct, a split or solid replaceable wear ring, and adjustment shims (Fig. 201).
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