Flexible Full Coupling Installation  505 
28-22-141  Figure 404 (Sheet 2)  Jun 20/89 
Page 408 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

FUEL LINE AND COUPLINGS - INSPECTION/CHECK
1. General
A.  This procedure has one task, an inspection for damage in the fuel system tubing and couplings.
2.  Fuel Line and Couplings - Inspection/Check
A.  References
(1)  
28-22-141/401, Fuel Lines and Couplings

(2)  
28-22-141/801, Fuel Line and Couplings

B.  Procedure
(1)  
Visually examine all the fuel tubing to make sure it is tightly and correctly attached.

(2)  
Adjust the installation of the tubes which are not correctly attached (Ref 28-22-141/401).

(3)  
Visually examine all the fuel tubing for these types of damage and make sure the damage is permitted:

(a)  
Make an inspection for cracks.
1) No cracks are permitted.

(b)  
Make an inspection for dents (areas that are pushed into the tubing); acceptable dents (damage that is permitted) are as follows: 1) All dents must have an area that is large compared to the depth of the dent. 2) No single dent in the tubing shall decrease the diameter of the tubing by more

than 2.5%. If there are multiple dents, the total dent depth (individual depths added together) in any section five times the tube diameter long, shall be no more than 10% of the tube diameter.
3)  The dents in the tubing must be farther than one diameter of the tube from the
end of the tube. 4) The dents in the tubing must not have a depth of more than 0.025 inch. 5) If the dent is on the outer part of a bend in the tube, the dent must not have a
depth of more than 0.015 inch.
NOTE:  If any one of the above limitations is not met, the damage is not permitted and the part must be repaired or replaced.
(c)  
Do an inspection for nicks. 1) The nicks in the tubing must have a rounded bottom. 2) The nicks in the tubing must not have a depth of more than 0.004 inch. 3) You must remove all the burrs from the nick if there are some burrs.

(d)  
Do an inspection for fretting. 1) Fretting must not have a depth of more than 0.004 inch.

(e)  
Do an inspection for scoring.

1)  If you find some small scoring, you can make is smooth again, but obey these conditions: a) The scoring must not be on the outer part of a bend. b) You must not remove more than 0.004 inch of metal.

(f)  
Do an inspection for tubes with a cross section that is not fully circular (tubes with ovality). 1) Calculate the percent ovality with this formula:

503 
Aug 01/94  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  28-22-141 Page 601 

percent ovality = OD Max - OD Min X 100%
 OD Nominal

a) OD Max is the maximum outer diameter of the tube.
b) OD Min is the minimum outer diameter of the tube.
c) OD Nominal is the outer diameter of the tube at a position where the tube

is circular or almost circular. 2) The percent ovality must not be more than 10%. 3) The percent ovality must not be more than 5% for tubes with a diameter of more
than 2 inches.
(g)  Wrinkles 1) The height of a wrinkle is the distance between a straight line that touches the high point of a wrinkle and a straight line that touches the low point of a wrinkle.
2)  Wrinkles must not have a height larger than the applicable maximum wrinkle height:
Tube Diameter (inches) Maximum Wrinkle Height (inches)
less than 1  0.020 1 to 1.99 0.030 2 to 2.99 0.040 3 or more 0.050
(4)  
Repair or replace all the tubes which have damage that is not permitted  (Ref 28-22-141/801, 28-22-141/401).

(5)  
Visually examine all the couplings for external indications of these types of damage and make sure the damage is permitted:

(a)  
Do an inspection for cracks.
1) No cracks are permitted.

(b)  
Do an inspection for scratches. 1) The scratches in the couplings must not have a depth of more than 0.004 inch.

(c)  
Do an inspection for nicks. 1) The nicks in the tubing must have a rounded bottom. 2) The nicks in the tubing must not have a depth of more than 0.004 inch. 3) You must remove all the burrs around the nick.

(d)  
Do an inspection for worn areas (galling).
1) Worn areas must not have a depth of more than 0.010 inch.
2) No worn areas in the surfaces that have an O-ring seal are permitted.

(6)  
Repair or replace all the couplings which have damage that is not permitted  (Ref 28-22-141/801, 28-22-141/401).
　
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