IS 8920:1978 is the Indian Standard (BIS) for methods for sampling burnt clay tiles. This standard lays down the procedure for sampling burnt clay tiles to ascertain their conformity to a given specification. It covers terminology, the scale of sampling for visual and physical characteristics, the method of selecting samples, and the criteria for conformity.
Methods for sampling burnt clay tiles
| Parameter | IS Value | International | Source |
|---|---|---|---|
| Lot Definition | Tiles of the same class, type, and size from a single source of manufacture, submitted for inspection at one time. | A basic unit of brick or tile from a single source, of the same size, color, and texture, offered for inspection at one time. | ASTM C67-22 |
| Sample Size (Dimensional Checks for a mid-size lot) | 32 tiles for a lot of 2001 to 10000 tiles. | 10 tiles for determination of dimensional characteristics, irrespective of lot size. | BS EN 1304:2013 |
| Sample Size (Strength Test) | 12 tiles for flexural strength test. | 5 specimens for flexural strength test. | ASTM C67-22 |
| Acceptance Criteria (Visual/Dimensional) | Based on number of defective tiles (e.g., for sample of 32, accept if defectives ≤ 2). | Based on statistical evaluation (mean and range) of measured values against declared values (e.g., D1, D2 tolerance categories). | BS EN 1304:2013 |
| Re-sampling Provision | Mandatory if the number of defectives is in an intermediate range (e.g., between 3 and 5 for a sample of 32). | Generally not specified for lot acceptance. Failure of initial sample is final. | ASTM C67-22 |
| Method of Random Selection | Select at random. If from a stack, divide into 8 notional sub-groups and draw equal numbers from each. | Take units at random from various parts of the whole lot or shipment. | ASTM C67-22 |