Sampling systems handbook and approval guide

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5. Sampling systems: general requirements

5.1 Intended use

The design, composition, and construction of a sampling system and its associated equipment must suit the environment, the installation location, and the intended official use of the sampling system. The device must be able to withstand normal operation within the facility without loss of reliability or accuracy. Under normal operation, any moving parts must remain operable and any adjustments must remain reasonably constant.

5.2 Marking

The primary sampler and associated divider r pneumatic components must be permanently marked to show the manufacturer, model, and serial numbers. The rated maximum throughput capacity must also be marked on the device or be readily available based on the model number.

5.3 Repeatability

The overall dimension of the sample entry and sample cutter must be adequate for the volume and velocity of the grain being sampled, and must allow:

• All grain presented for sampling to be accepted as the collection opening passes through the grain stream
• The sample cutter to deliver the entire collected sample to the divider for reduction or to the final sample collection site

When collecting official samples:

The rate of grain flow past the sampler should not be less than 25% of the rated maximum capacity of the grain elevation/conveying system.

All sampling systems installed within an elevator must provide a similar quantity of sample when used for the same purpose. The quantity of sample delivered must be within 10% of any other sampling system when sampling the same type and quantity of grain.

5.4 Speed of traverse

Any non-programmable speed setting must be set to maximize the efficiency and effectiveness of the sampling system. The traverse speed of the sample cutter across the grain stream must be set at 0.47 - 0.51 metre per second (18 - 20 inches per second) and at an even rate of acceleration.

5.5 Power, air, and hydraulic sources

Electrical power sources for the operation of a sampler and any associated equipment must be maintained at a constant voltage to ensure the smooth and unaffected operation of the equipment.

Air or hydraulic sources for the operation of a sampler and any associated equipment must be maintained at a constant and uniform pressure to ensure the smooth and unaffected operation of the equipment. If the operation of any equipment attached to the same air or hydraulic supply affects the operation of the sampling system, a separate air or hydraulic supply will be required.

5.6 Controls

During the operation of a sampling system for official inspections, the control of the timer and resets must be under the direction of the CGC staff on site or be readily available to them. If a grain flow indicator is required to verify grain flow rates, it must be made available. Equipment controls must be marked conspicuously and be within viewing range of the CGC staff.

5.7 Enclosure and access

All sampling components must be maintained within protective enclosures. The sampling system must have strategically located access points for inspections. The locations must allow for ready and easy examination of the sampler components, including the sample cutter openings, motion activation equipment, and dust seals.

5.8 Sample collector openings

The opening of a sampler cutter must be at least 1.9 cm (¾ (0.75) inch) wide, measured horizontally to the grain stream (Figure 5.1). The opening may be reinforced with narrow support braces to provide structural support and eliminate any distortions to the opening.

A gravity or automatic sample divider must be adequately sized to reduce the quantity of sample from the primary sampler without backing up. Sample divider openings used to select the final sample must be at least 1.9 cm (¾ (0.75) inch) measured horizontally to the primary sampled grain stream.

Figure 5.1 Sampler cutter/braces

5.9 Sample return

Where the sampler system is installed downstream of a weighing system in a shipping installation or upstream of a weighing system in a receiving installation, means must be provided to return the surplus sample back to the source grain lot. Where miniature bucket elevators, screw conveyors, or drag conveyors are used to move the surplus sample, they must be adequately sized to prevent a backlog of grain in the system.

Either the return line for the sample must be to a neutral air pressure location, or automatic means must be in place to prevent any dust or lightweight material from being pressured back into the sample divider or from being vacuumed or vented out of the sample divider.

5.10 Sample delivery lines

Sample delivery lines from the sample divider to the inspection area must follow the most direct route to the inspection area with as few bends as possible (Figure 5.2). In particular:

• Delivery lines must not have a turn radius greater 90 degrees and must be laid vertically or horizontally as much as possible.
• The delivery conduit must be cut squarely and the inside edges honed to remove any roughness or burrs.
• Conduit for negative or positive pressures must be connected with an airtight coupling.
• An electrical path must be maintained over the entire delivery system with suitable grounding points to discharge any static build up. (It is recommended that sample delivery lines be of metal conduit construction, aluminum straight pipe, and stainless steel elbows.)
• The air intake on pneumatic systems must be equipped with a suitable cover to stop unwanted material from being introduced into the official sample. The cover must be removable to allow for inspection and any necessary testing.

Figure 5.2 Delivery lines for samples

5.11 Sampler delivery access

A sampler delivery system must have an access point as close to the primary sampler as possible and after any sample divider, to allow the CGC to introduce CGC drop samples.

5.12 Clearing between lots

The entire sampling system must be as self-clearing as possible to prevent sample contamination from one lot of grain to another.

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