Guide to Taking a Representative Sample

4.1 Overview

Grain may be manually sampled when conveyed in trucks and railcars. The double sleeve trier is used to sample grain stored in these conveyances. Follow all safety precautions when sampling from these conveyances. Draw samples from these conveyances in prescribed probing patterns and reach the maximum depth of the conveyance.

Sampling with a double sleeve trier that does not reach the maximum depth of the conveyance and/or not following the recommended probing pattern increases sampling extraction error and the risk of collecting a sample that does not accurately represent the lot.

Recommended equipment and methods used for manual sampling of static grain are described in this section.

4.2 Double sleeve trier

The double sleeve trier is typically constructed of brass or aluminium, and is available in varying lengths. It consists of 2 tubes, one inside the other. It can be used to sample static lots that are contained in sacks (bags) or totes, or lots that are in bulk provided the trier has sufficient length to reach to the bottom of the conveyance being sampled. The aperture must be a minimum of 19 mm (0.75“) in width.

Types of double sleeve triers

Compartmented

Compartmented double sleeve triers have an inner tube that is divided into compartments. The outer tube has slots that match the compartment openings of the inner tube. When the tubes are aligned, grain flows into the compartments. The sample can only be discharged into a long trough or drop sheet. However, this type can make the sampling process cumbersome.

Open-throat

Open-throat double sleeve triers have an inner tube that is open, as is the probe handle. This feature allows the sample to be poured from the probe directly into the sample container. However, open-throat probes tend to draw more of the sample from the top portion of the grain in the lot compared to the compartmented probe. Therefore, the composition of a sample obtained with an open-throat probe may differ slightly from that of a sample drawn with a compartmented probe. A design to address this issue features apertures that open in sequence, starting at the bottom, when turned to open. This design addresses the influence of grain pressure that allows more grain to flow into the top of the probe when sampling vertically.

4.3 Method for using double sleeve trier vertically

1. Insert the closed trier through the top of the conveyance at a slight angle until it reaches the bottom of the conveyance.
2. Turn the inner sleeve until the inner and outer openings align and agitate the trier slightly to allow the openings to fill.
3. Gently close the trier to the point of resistance, and withdraw it from the grain.
4. Collect the sample in a clean container. For compartmented probes, use a large drop cloth or a clean container (trough) that is the same length as the trier to collect the sample.

4.4 Probing patterns