Overview
ISO 8656-1:1988 - "Refractory products - Sampling of raw materials and unshaped products - Part 1: Sampling scheme" specifies standardized methods and conditions for taking representative samples of raw refractory materials and prepared unshaped refractory products. It defines sampling principles (increments, bulk sample, laboratory/test samples), rules for sample protection and preparation, and how to choose sampling intensity to achieve a required sampling precision. The part is intended to provide a reproducible sampling scheme for quality control and specification verification; it excludes very large static quantities or cargoes from which reliable samples cannot be taken.
Key topics and technical requirements
- Sampling terminology and roles: Definitions for lot, consignment, increment, bulk sample, laboratory sample, test sample, and coefficient of variation.
- Sampling procedure fundamentals:
- Preferential sampling from material in movement (loading/unloading); use periodic systematic sampling with a random start.
- Increments must be taken at regular mass or time intervals and aggregated to a bulk sample.
- Samples must be protected against changes and prepared so as not to alter the tested properties.
- Keep a reserve (split) increment for dispute resolution when needed.
- Increment mass and number of increments:
- Minimum increment mass is related to the material’s maximum grain size (see Table 1 in the standard).
- The required number of increments depends on the lot mass and the property’s variation class (Table 2) and aims to achieve a specified relative precision.
- Variation classes and statistics:
- Coefficient of variation v = (standard deviation / mean) × 100%.
- Variation classes: small (v
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