Overview
ISO 6153:1989 - Chromium ores - Increment sampling specifies standardized methods for taking representative samples of chromium ores at points of dispatch and receipt to determine chemical composition and moisture content. Applicable to both manual and mechanical sampling of natural or processed chromium ores, the standard defines sampling plans, equipment, and procedures (including a hammer-and-shovel method in Annex A) to reduce bias and achieve required precision.
Key topics and requirements
- Purpose and scope
- Sampling to produce increments, gross samples, sub-samples and test samples suitable for chemical and moisture analysis.
- Applies to loading/unloading from conveyors, wagons, containers, ships and stockpiles.
- Sampling methods
- Increment (periodic systematic) sampling, stratified sampling and two-stage sampling for wagons/containers.
- Manual (shovels, probes, sampling frames) and mechanical (rotary-arc, bucket, cutter-chute) samplers with defined design and operational requirements.
- Equipment and minimum dimensions
- Tools specified (increment shovels, probes) with dimensional guidance; mechanical samplers must have effective openings at least three times the nominal top size for coarse ores and meet filling/cutter-speed criteria.
- Mass and number of increments
- Minimum increment mass depends on the nominal top size of the ore (see Table 1 in the standard).
- The standard provides formulae and tables to calculate the number of increments required based on consignment mass, desired precision and estimated quality variation.
- Quality variation and precision
- Classification into large or small quality variation; sampling precision and overall precision concepts are defined (with reference to ISO 8542 for precision checks).
- Procedures to ensure near-uniform increment mass (coefficient of variation
