Overview
EN ISO 7971-3:2019 - "Cereals - Determination of bulk density, called mass per hectolitre - Part 3: Routine method" specifies a practical, repeatable procedure for measuring the bulk density (mass per hectolitre / hectolitre mass) of cereals as grain. It covers routine use of manual or automatic mass per hectolitre measuring instruments (mechanical, electric or electronic) and sets out how results should be recorded and reported for quality control and trade.
Key topics and technical requirements
- Scope and principle: Defines mass per hectolitre as the mass of cereal occupying a known volume under specified filling/flow conditions; result expressed in kg/hl.
- Instruments: Differentiates hand-operated and automatic measuring instruments. Instruments must be verified for performance and traceability in accordance with ISO 7971-2:2019.
- Analytical balance: The standard requires an analytical balance with appropriate readability depending on container volume (examples given in the standard: weighing to nearest 1 g for a 1 L container or 0.1 g for smaller containers).
- Measurement procedure:
- Prepare samples by removing large impurities and equilibrating temperature.
- Perform measurements in duplicate (two determinations); when repeatability criteria are not met, increase to four measurements and use the mean.
- Use separate test portions when sample size allows (repeating on the same portion may change packing).
- Ensure equipment is level, avoid jolting during filling, and follow manufacturer instructions for each device.
- Expression of results: Take the arithmetic mean of determinations when repeatability conditions are satisfied and express result to the nearest 0.1 kg/hl.
- Precision and uncertainty: The standard includes precision data from interlaboratory trials and guidance on repeatability, reproducibility and uncertainty evaluation.
- Annexes: Informative annexes describe example hand instruments (e.g., KERN and NILEMA litre) and interlaboratory test results; a formula for NILEMA litre results (wheat & barley) was introduced in the 2019 revision.
Applications and users
This routine method is directly applicable to:
- Grain laboratories and quality control teams in milling, feed and seed industries
- Grain traders and inspectors performing commodity grading and acceptance testing
- Storage and logistics operators monitoring bulk density for silo/transport planning
- Manufacturers of hectolitre mass measuring instruments and calibrations services
- Regulatory bodies and standardization organizations ensuring consistent test methods
Practical uses include commodity valuation, lot grading, calibrating automatic analyzers, and verifying equipment traceability.
Related standards
- ISO 7971-2:2019 - Method of traceability for measuring instruments (referenced for instrument verification)
- Other parts of the ISO 7971 series (list available on ISO website) and national adoptions (EN ISO 7971-3:2019) apply where CEN members have implemented the standard.