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Types of Plies
Ply categories The main types of ply are as follows:
Nappes Sommet de Protection (NSP) (breaker strip) = elastic cables.
Nappe Sommet de Travail (NST) (bracing plies) = fretted or unfretted
cables.
Nappe Carcasse (NC) (casing ply) = fretted, unfretted cables.
Cable Visual characteristics for each type of cable:
elastic
fretted
unfretted
Damaged cable A cable is damaged when it shows at least one of the following features:
Metallic cable Textile cable
Separated from the surrounding
rubber
Oxidized in depth
Unfretted
Worn
Broken
Separated from the surrounding
rubber
Frayed
Worn
Broken
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Verification of casings
Crown The crown represents the external part between points (B): joint of the tread with
the sidewalls.
The crown includes the tread area and the shoulder area.
Sidewall The sidewall is the external part between the tread / sidewall joint (B) and the
guide rib (A).
Bead The bead is the part between the guide rib (A) and the bead point rubber (F).
FE zone
The FE zone is the part between the bead point rubber (F) and a point (E)
inside.
This FE distance is 75 mm for 10.00R20 and 295/80R22.5.
Interior The interior is the internal part between points (E).
Cables injuries can NOT be repaired
in FE area
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Verification of casings (continued)
Remarks on inspection
Inspection is both visual and with hands / fingers.
Inspection of each zone entails a complete rotation of the casing.
Correct examination of the interior requires spreading the beads and adequate
lighting of the zone to be verified.
All damage must be carefully identified.
Take care against projected shadows (work at a station with good lighting).
It is important to draw up a "monitoring" document for the casings shown.
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Cleanliness of "interior / exterior" casings
Obstacles to optimum inspection
Any casing coming in for retreading may show a level of dirt incompatible with
the acceptable limit for verification.
If the amount of dirt is excessive, faults in detection may occur.
The innerliner may show locally adhesive materials or not, which might prevent
the detection of a crown perforation or GI damage.
Beads covered with assembly grease or rim calamine and sidewalls full of dirt
do not ensure conditions for an optimum inspection.
Any detection is made impossible.
The pollution is too concentrated to enable quality verification.
Obligation
The casings must be dry before inspection.
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Cleanliness of "interior / exterior" casings (continued)
Examples of dirt Examples of dirt not acceptable without washing:
Dry crust Dust layer
Assembly lubricant Grease runs
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Inspection of sidewall and shoulder
Examination of shoulder
Verify if there are deep cuts or cracks.
Search for signs of previous retreading(s)
Examination of
sidewall area Reading the markings (engravings) enables identification of the casing.
Decoding of the DOT code indicates the place and date of manufacture
of the tyre.
Verify the condition of the rubber (cuts, scratches, cracking, alteration by
hydrocarbons).
Verify the condition of visible cable.
Search for indications of previous retreading(s)
Technical specifications:
The casings are rejected in the following cases:
DOT older than 8 years.
Markings of size, load and/or speed index illegible.
Heavy buffing on the sidewall.
Rubber cracks with a depth greater than 1 mm.
Rubber damaged by hydrocarbons
Cracked rubber.
Surface irregularities detected by touch or using incident light (deformations
unrelated to presence of a patch).
Rubber / cable separation following damage causing infiltration of inflation
air.
Break in the casing ply in sidewall: LxW = 90 x 20 mm or 120x10 mm (L
taken in the cable direction).
Maximum 5 patches (total of 2 existing and 3 to be done) AND Maximum 2
patches per sidewall.
Examples of defectiveness
The photos below illustrate the cases of defectiveness identified above.
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Inspection of sidewall and shoulder (continued)
Buffing Examples of buffing:
pronounced sidewalls
sidewalls with cables visible
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Inspection of sidewall and shoulder (continued)
Rubber Examples of rubber:
Damaged (hydrocarbons)
Cracked (ageing)
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Inspection of sidewall and shoulder (continued)
Sidewall damage
Size measurement
Out-of- tolerance damage
L
L*l=90*20
L*l=120*10
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Inspection of sidewall and shoulder (continued)
Wear well Example of wear well (cracked at bottom or peripheral):
Perform a skiving operation to check the condition of the NC.
In presence of "oxydation DECHET", there is a risk of "Rupture NC circulair"
(CASING PLY circular rupture).
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Inspection of a bead
Examination to be carried out
Guide rib area Detect deformations by touch or using incident light (bumps and dents).
Verify if there are deep circular cracks.
Bead area Search for deformations (surface, profile).
Verify the condition of the rubber (separation, bakelization) and the presence of
visible cable.
Technical specifications:
The casings are rejected in the following cases:
Deformations (by touch or using incident light).
Circular cracks with a depth greater than 2 mm.
Visible cable.
Deterioration caused by a wheel in poor condition.
Rubber tearing or cracking reaching the cables.
Deformation of the bead point rubber greater then the limits specified (case
of flat seat and drop centre).
Twisted bead.
Tearing of bead point rubber greater than 80 mm, or more than 3 tears per
side, or two tears distant by less than 75 mm.
Examples of defectiveness
The photos below illustrate the cases of defectiveness identified above.
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Inspection of a bead (continued)
Examples of defectiveness (contd)
Irregularities (bumps)
Irregularities (dents)
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Inspection of a bead (continued)
Examples of defectiveness (contd)
Deep circular cracks
Visible cable
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Inspection of a bead (continued)
Examples of defectiveness (contd)
Deterioration (wheel in poor
condition)
Cracks reaching
cables
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Inspection of a bead (continued)
Examples of defectiveness (contd)
Flat seat deformations
Good Deformed Overturned
Excessively deformed or overturned beads (B>5mm) must be refused.
Drop centre deformations
The diagram below shows the limits beyond which the casing is rejected for
retreading
Beads not overturned
Beads overturned max. acceptable
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Inspection of a bead (continued)
Examples of defectiveness (contd)
Twisted bead
Tubeless bead point rubber tearing
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Inspection of internal area
Examination of internal area
Examination of internal area (sidewall and crown):
Check condition of innerliner (perforations, cracks, mottling).
Check condition of casing ply (folding, perforation).
Verify the condition of existing repairs.
Detection method Visual observation and direct lighting.
Tactile In the Crown / Shoulder joint using back and forth movements of the hand.
Search for deformations (separation between casing ply and crown), then validate
the separation using incident light.
Tuning fork method Is performed on a station free of disturbing noise.
Search area Crown / Shoulder joint (under end NST1).
Methods Using short and consecutive strikes, with a pick hammer, hit the interior of the
casing in the search area, every 3 to 5 cm approximately and on the whole of the
circumference of the casing.
If areas of separation are present, a change in tone will be heard when passing
through the area.
Technical specifications:
The casings are rejected in the following cases:
The innerliner is coated with an anti-puncture product or a balancing product
(excluding balance patch).
Maximum 5 patches (total of 2 existing and 3 to be done) AND Maximum 2
patches per sidewall.
A repair using patch in poor condition.
Deterioration of the innerliner: mottling, "plucking", cracks.
Deformation, folds, cable deviations.
Separation between casing ply and crown.
Calendering of oblique or radial cracking or small cracks.
Opening of the innerliner joint.
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Inspection of internal area (continued)
Examples of defectiveness
The photos below illustrate cases of defectiveness identified above.
Anti-puncture product
Repair in poor condition
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Inspection of internal area (continued)
Examples of defectiveness (contd)
Mottling Wipe off systematically, using the following: bare or gloved hand,
cloth, paper.
Any other resource is PROHIBITED
Only the mottling still visible after wiping will be addressed.
"Mottling then plucking"
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Inspection of internal area (continued)
Examples of defectiveness (contd)
Cracks at base of membrane ribs
Cracks
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Inspection of internal area (continued)
(contd)
Radial cracks
Opening of the innerliner joint
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Inspection of internal area (continued)
Examples of defectiveness (contd)
Fold in the casing ply
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Inspection of crown
Examination of
crown area Check the condition of the tread (abnormal wear, cuts, separations).
Check the condition of the crown (perforations, visible cable, oxidation).
Important: Remove any metallic or other visible object, foreign to the casing,
remaining in the damage to the crown (pin, screw, bolt…).
Technical specifications:
The casings are rejected in the following cases:
Deterioration of the crown with diameter greater than 25 mm (diameter
measured on the casing ply).
More than 1/3 of breaker strip visible or damaged, following excessive re-
grooving or excessive wear.
Crown scarred with many cuts.
Examples of defectiveness
The photos below illustrate cases of defectiveness identified above.
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Inspection of crown (continued)
Examples of defectiveness (contd)
Deterioration of crown
(interior view)
Deterioration of crown greater than 30 mm (seen from interior)
Deterioration of crown
with oxidation
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Inspection of crown (continued)
Examples of defectiveness (contd)
Excessive wear
Abnormal wear with deterioration
of ply
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Inspection of crown (continued)
Examples of defectiveness (contd)
Scarred crown
Excessively deep re-grooving