Overview
ISO 21178:2020 - "Light conveyor belts - Determination of electrical resistances" specifies standardized test methods for measuring the electrical behavior of light conveyor belts. The standard defines procedures to determine surface resistance, volume resistance (perpendicular to the belt plane), and longitudinal and transverse volume resistance (parallel to the belt plane). It also provides methods to evaluate surface resistivity and volume resistivity, and references conditioning procedures (ISO 18573).
Key Topics and Technical Requirements
- Measured properties: electrical surface resistance, electrical surface resistivity, electrical volume resistance (perpendicular and parallel directions), and electrical volume resistivity.
- Test methods: two principal approaches for surface resistance (Method A - omni‑directional; Method B - directional longitudinal/transverse) and specified procedures for volume resistance and resistivity measurements.
- Apparatus: defined electrode arrangements (coaxial cylindrical electrodes including a circular and an annular electrode), electrode materials (brass or stainless steel), and electrical supply requirements (direct‑current source adjustable up to 500 V with current limited to not greater than 10 mA).
- Test pieces and preparation: requirement for new, uncontaminated test specimens (not tested sooner than five days after manufacture), specific dimensions and conditioning/cleaning steps, and use of insulating supports.
- Reporting: prescribed expression of results and test report contents to ensure repeatability and traceability.
- Normative references: links to related standards such as ISO 21183‑1 (belt classification/requirements) and ISO 18573 (test atmospheres and conditioning).
Applications and Who Uses This Standard
ISO 21178:2020 is used where electrical properties of conveyor belts affect safety, product handling, or electrostatic control. Typical users:
- Conveyor belt manufacturers - to certify belt electrical characteristics and for R&D of antistatic or conductive belts.
- Materials and product testing laboratories - to perform accredited resistance and resistivity testing.
- System integrators and OEMs - to select belts that meet electrostatic discharge (ESD) or process requirements.
- Quality assurance and procurement teams - to specify acceptance criteria in contracts and technical datasheets.
- Regulatory and safety engineers - to assess risks where electrostatic buildup can affect flammable or sensitive environments.
Related Standards
- ISO 21183‑1 - classification and requirements for light conveyor belts (referenced for belt types and context).
- ISO 18573 - test atmospheres and conditioning periods (normative reference in ISO 21178).
- Developed by ISO/TC 41 (Conveyor belts) in cooperation with CEN/TC 188.
Keywords: ISO 21178:2020, light conveyor belts, electrical resistance testing, surface resistivity, volume resistivity, conveyor belt testing, electrostatic.