Overview
ISO 7622-1:2013 - "Steel cord conveyor belts - Longitudinal traction test - Part 1: Measurement of elongation" specifies a laboratory method to determine the elongation of steel cords taken from the carcass of conveyor belts. The standard defines how to measure elongation at forces equal to 10% and 60% of the specified tensile strength. It applies exclusively to conveyor belts with a steel carcass and is intended primarily for destructive testing (e.g., in litigation or when no manufacturer certificate is available).
Key Topics and Requirements
- Test principle: Measure cord elongation with an extensometer while applying tension up to 60% of specified tensile strength via a dynamometric tensile testing machine.
- Specimens: Four cords extracted from the belt (minimum 400 mm sample), prepared as two S-twist and two Z-twist specimens; rubber coating stripped where clamped.
- Apparatus:
- Dynamometer with adjustable force, jaw separation rate 25 mm/min ± 5 mm/min, and jaw separation capability of at least 250 mm.
- Holding device preventing slip (e.g., two fixed grooved pulleys ≥50 mm diameter or 10× cord diameter).
- Extensometer accurate to at least 0.01%; measurement interval 100–300 mm.
- Procedure:
- Tests carried out at least 5 days after manufacture.
- Standard test atmosphere: 23 °C ± 2 °C and 50% ± 5% RH (ISO 18573, Atmosphere B) unless otherwise stated.
- Apply initial tractive force equal to 50 × linear density of the cord to define zero; record elongation at 10% and 60% of specified tensile strength.
- Results & reporting:
- Express elongation as a percentage of initial length.
- Report the arithmetic mean of the four measurements, rounded to 0.1%.
- Test report must reference ISO 7622-1 and note any optional or exceptional conditions.
Applications and Users
ISO 7622-1 is used for:
- Quality control and verification of steel cord conveyor belts.
- Forensic testing and litigation where belt performance is disputed.
- Independent testing laboratories, belt manufacturers, procurement/specification teams, and end-users in mining, bulk handling, and heavy industry.
- Situations where manufacturer certificates are unavailable or need confirmation.
Related Standards
- ISO 7622-2 - Measurement of tensile strength (companion standard).
- ISO 18573 - Conveyor belts - Test atmospheres and conditioning periods (referenced for conditioning and climate control).
Keywords: ISO 7622-1, steel cord conveyor belts, longitudinal traction test, measurement of elongation, extensometer, tensile strength, conveyor belt testing, steel carcass.
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