Overview
EN ISO 7971-1:2009 - "Cereals - Determination of bulk density, called mass per hectolitre - Part 1: Reference method" (CEN adoption of ISO 7971-1:2009) specifies the reference laboratory method to measure the bulk density (mass per hectolitre) of cereals as grain. The standard defines the principle, calibrated apparatus, measurement procedure and performance requirements used to obtain traceable, repeatable bulk density results expressed in kilograms per hectolitre (kg/hl).
Key topics and technical requirements
- Definition: Bulk density (mass per hectolitre) = mass of cereal divided by the volume it occupies after pouring under defined conditions; reported in kg/hl (grain as received).
- Principle: Controlled pouring from a hopper into a 20 L measuring container, followed by weighing the contained grain.
- Apparatus: detailed components and geometry are specified - pre-filling container (nominal 24 L), filling hopper with tapered tube and distributor, 20 L measuring container, guiding collar, levelling straightedge, collecting box and chassis with verticality adjustment. Some mandatory dimensional and clearance tolerances are given for reliable results.
- Weighing requirements: Non-automatic balance compensated for empty container; maximum balance error ≤ ±0.01% of load (10–20 kgf) or weights’ errors ≤ ±0.02%.
- Calibration and adjustment: Calibration by comparison with a national/international standard instrument. Procedure requires six paired measurements (apparatus under test vs reference) using a wheat sample (recommended mass per hectolitre ≥ 80 kg/hl), specific conditioning (spread thinly in test room for ~10 h, relative humidity ≤ 60 %). Maximum permissible accuracy error ±10 g; adjust by changing distributor height if exceeded.
- Procedure controls: Straightedge motion, hopper/distributor setting, and coaxial vertical alignment are critical to ensure reproducible packing and volume.
Applications and users
EN ISO 7971-1:2009 is used where high-accuracy, traceable measurements of cereal bulk density are required:
- Grain testing laboratories and national reference labs
- Grain traders and commodity exchange quality control
- Cereal processors, millers and feed producers for inventory and process control
- Equipment manufacturers (metering/handling systems) for calibration and validation
- Research institutions studying cereal physical properties
Practical benefits include consistent grading, improved contract specification enforcement, and traceable calibration of routine instruments.
Related standards
- ISO 7971-2:2009 - method of traceability for measuring instruments
- ISO 7971-3:2009 - routine methods for bulk density
- ISO 24333 - recommended sampling for cereals (sampling not part of this method)
- OIML R 15 - referenced apparatus requirements
Using EN ISO 7971-1:2009 ensures internationally harmonized, reproducible bulk density (mass per hectolitre) measurements for cereals and supports reliable quality assessment across the grain supply chain.
