Overview
ISO/TR 15855:2001 is a Technical Report from ISO/TC 183 that provides a step‑by‑step, practical procedure for testing static scales used in the commercial handling of copper, lead and zinc sulfide concentrates. The report outlines simple, routine checks to assess scale performance and calibration status so operators can calculate explicit performance parameters-precision, bias and linearity-in accordance with the equations given in ISO 12745. ISO/TR 15855 is informative in nature and does not replace legal calibration requirements from National Weights and Measures authorities.
Key topics and requirements
- Purpose: Routine scale performance checks for weighbridges, hopper scales, gantry scales and platform scales commonly used for concentrate mass determinations.
- Test frequency: No single mandated interval-recommendations range from none up to multiple checks per consignment; frequency should be agreed between parties based on risk and scale reliability.
- Precision testing:
- Check and adjust zero before and after tests.
- Weighbridge procedure: perform a minimum of four duplicate determinations (data pairs) using the same vehicle to calculate precision.
- Hopper procedure: use a test mass ~5–10× the scale readability and record at least six data pairs from one weighing cycle.
- Note: precision tests do not reveal bias or linearity issues.
- Calibration (bias and linearity) testing:
- Requires certified reference weights (single heavy weight such as 1 t or 2 t, or a set of smaller certified weights).
- Single-weight method: generate at least three calibration points (e.g., zero, ~50% capacity, near-full minus test weight); deviation calculated as observed minus expected reading.
- Multi-weight method: incremental addition/removal of certified weights over the full range, recording observed vs expected readings and calculating deviations.
- Data use: Results are used to compute precision, bias and linearity as per ISO 12745.
Practical applications
- Routine in‑house verification of weighbridge and hopper scale performance at mines, concentrator plants and shipping terminals handling copper, lead and zinc concentrates.
- Pre-loading/discharge checks to reduce commercial disputes over mass determinations.
- Input for quality assurance (QA/QC), operational risk assessments and maintenance scheduling.
- Guidance for calibration laboratories and technicians performing on-site scale checks.
Who should use this
- Mine and concentrator operators
- Weighbridge and hopper scale operators
- QA/QC and metrology teams
- Calibration service providers and inspection bodies
- Commercial/contracting parties negotiating testing frequency and acceptance limits
Related standards
- ISO 12745 - Copper, lead and zinc ores and concentrates: Precision and bias of mass measurement techniques (used for the relevant equations and performance calculations)
- National Weights and Measures authorities’ technical manuals (for legal and statutory calibration requirements)
Keywords: static scales, scale calibration, weighbridges, hopper scales, precision and bias, linearity, ISO 12745, copper lead zinc sulfide concentrates, scale performance testing.