(b)
Make an inspection for dents (areas that are pushed into the tubing). 1) All dents must have an area that is large compared to the
depth of the dent. 2) No single dent in the tubing is permitted to decrease the diameter of the tube by more than 2.5 percent.
3) If there are multiple dents, the total dent depth (individual depths added together) in any section five times the tube diamter long, must be no more than ten percent of the tube diameter.
4) The dents in the tubing must be farther than one diameter of the tube from the end of the tube. 5) The dents in the tubing must not have an area of more than
0.125 square inches.
6) 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 inches.
(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 it 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.
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MAINTENANCE MANUAL
(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:
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:
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