Overview
EN ISO 9856:2016 (ISO 9856:2016) specifies a laboratory method for determining elastic and permanent elongation of conveyor belts and for calculating the belt elastic modulus. The procedure is intended for full‑thickness, longitudinal test pieces of conventional conveyor belts (not applicable to light conveyor belts covered by ISO 21183‑1). It defines sampling, specimen preparation, conditioning, test apparatus and a cyclic tensile test protocol that produces force‑elongation records for evaluation.
Key Topics and Requirements
- Scope: Measurement of permanent elongation (permanent stretch), elastic elongation (elastic stretch) and calculation of elastic modulus for conveyor belts.
- Test principle: A rectangular test piece is subjected to a sinusoidally varying tensile force between defined upper and lower reference forces for 200 cycles; elastic and permanent elongations are read from the force‑elongation graph.
- Specimen dimensions and preparation: Three longitudinal specimens (50 mm × ≥300 mm free length) are cut from full belt thickness; covers are trimmed to leave 0.5–1 mm cover thickness.
- Apparatus: Dynamic tensile testing machine with force measurement calibrated per ISO 7500‑1 (machine class 3 or better), extensometer (≥100 mm, 0.1 mm accuracy) and a recorder for force‑elongation graphs.
- Loading parameters: Initial preload (0.5% of nominal tensile strength × specimen width), sinusoidal loading at about 0.1 Hz between upper (10% of nominal tensile strength) and lower (2% of nominal tensile strength) reference forces.
- Results and calculations: Permanent elongation (%) and elastic elongation (%) calculated relative to reference length; elastic modulus expressed as ΔF divided by fractional elastic elongation (N/mm width). Arithmetic mean of three specimens is reported.
- Conditioning and sampling: Specimens conditioned per ISO 18573; samples selected according to ISO 282.
Applications and Users
- Who uses it: Conveyor belt manufacturers, independent testing laboratories, quality control teams, procurement/specification engineers, plant operators and consultants.
- Practical value:
- Verifies belt dimensional stability after mechanical conditioning.
- Supports supplier‑customer agreements on expected permanent stretch and elastic behavior.
- Informs belt selection and installation tensioning to control tracking and load handling.
- Used in conjunction with standards such as ISO 3870 and ISO 5293 for system design and performance assessment.
Related Standards
Keywords: EN ISO 9856:2016, conveyor belts, elastic elongation, permanent elongation, elastic modulus, tensile testing, extensometer, belt testing, ISO standard.
