Mixed grain - Chapter 9 | Official Grain Grading Guide
Determination of commercially clean
Dockage is not assessed on mixed grain samples that meet the commercially clean specifications defined in the mixed grain export grade determinant table. All samples must be analyzed to determine if they are commercially clean prior to dockage assessment. The analysis of samples which are clearly not commercially clean may consist of a visual assessment. For example, if there is no doubt that a sample contains more than 0.1% of small seeds without hand sieving and weighing the seeds then dockage will be assessed using procedures defined under Determination of dockage. Where there is any doubt regarding whether the sample is commercially clean the sample must be analyzed using the procedures outlined in steps 1 through 5 below to confirm that the sample is not commercially clean prior to assessing a dockage.
- Using a Boerner-type divider, divide the sample to obtain a representative portion.
- Official samples shall be at least 1 kg.
- Unofficial samples shall be at least 750 grams.
- Place approximately 250 grams of the sample at a time on the No. 4.5 round-hole hand sieve.
- Move the sieves from left to right 30 times using a sifting motion. One complete motion is approximately 10 cm from the center to one side, back to the center, approximately 10 cm to the other side and back to the center.
- All material passing through the No. 4.5 round-hole sieve is weighed and the percentage calculated to determine if it meets the commercially clean specification of the grade for material removable through the No. 4.5 round hole sieve. (Column #2 in the mixed grain export grade determinant table)
- Small seeds passing through the No. 4.5 round hole sieve are weighed and the percentage calculated to determine if they meet the commercially clean specification of the grade for small seeds. (Column #1 in the mixed grain export grade determinant table)
Should the percentage concentration of either of the factors determined in steps 1 through 5 exceed the specifications set out in columns 1 or 2 of the mixed grain export grade determinant table the sample will be considered to be not commercial clean. Dockage will be assessed on samples determined to be not commercially clean by using the procedures defined under Determination of dockage.
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