ISO 703:2017

Overview

ISO 703:2017 establishes a standardized test method to determine the transverse flexibility (troughability) of conveyor belts, expressed as the ratio F/L. The method measures the maximum vertical deflection of a transverse belt section under its own weight and is intended to help assess whether a belt's troughing characteristics are suitable for the intended application. The method is not suitable for light conveyor belts covered by ISO 21183‑1.

Key Topics

• Scope and purpose: Determines transverse flexibility (troughability) as a ratio F/L to inform belt selection and quality control.
• Symbols and measures: Key symbols are F (vertical deflection corrected for belt thickness), L (flat length = full belt width), and d (belt thickness).
• Test piece: A rectangular section with longitudinal length (in belt direction) of (150 ± 2) mm, overall width L and thickness d as the overall belt thickness.
• Conditioning: Test pieces must be conditioned in accordance with ISO 18573 using atmosphere A, B or C and tested immediately after conditioning.
• Apparatus essentials: Two rigid horizontal bars, two clamps with suspension lugs, four equal-length steel suspension wires and means to measure deflection to the nearest millimetre.
• Procedure highlights:
  • Fit the test piece carrying face uppermost into swivelling clamps.
  • Allow the piece to fall under its own weight into the troughed position while suspending forces remain vertical.
  • After 5 minutes measure the vertical deflection F and add 0.5·d to obtain the corrected F value.
• Result expression: Report the ratio F/L.

Applications

This test method is practical for:

• Belt selection: Determining suitable belts for troughed conveyor designs to avoid lateral travel and instability.
• Quality control: Routine verification of transverse flexibility during production and incoming inspection.
• Design assessment: Supporting engineering decisions for idler and troughing arrangements where transverse stiffness affects belt tracking and loading behavior.

Practical keywords: conveyor belt, troughability, transverse flexibility, F/L ratio, test method, conditioning, quality control.

Related Standards

• ISO 21183-1 - Light conveyor belts (method not suitable for these belts).
• ISO 18573 - Conveyor belts: test atmospheres and conditioning periods.
• ISO 583 / ISO 7590 - Methods for measuring belt thickness and cover thickness referenced for thickness measurement.

Test Report Essentials

Per ISO 703 the test report shall include:

• Reference to ISO 703
• Identification of the conveyor belt tested
• Test length L and thickness d
• Conditioning atmosphere used (A, B or C)
• Value of F/L and date of test

This structured, repeatable method helps manufacturers, inspectors and design engineers evaluate troughing performance and maintain consistent belt quality.