Riffle Sample Divider

What is the Riffle Sample Divider?

A riffle sample divider splits a coal sample into two equal halves by pouring it through alternating chutes into opposite receivers. It is the standard gravity-fed tool for reducing sample mass while keeping the split representative.

Overview

The divider is a set of an even number of parallel chutes, typically eight to twenty, that discharge alternately to the left and right. Sample is poured evenly across the full width of the chute bank, either manually with a scoop or from a vibrating feeder, and each side collects half the material. Representativeness depends on the chute width being at least two and a half to three times the top particle size and on feeding the whole bank uniformly, so coarse samples need wide chutes and dividers are supplied in several sizes. Stainless steel construction limits contamination and cleaning is straightforward, since the chutes can be brushed or washed. The tool is robust, needs no power and is the usual choice for dividing coal from a few millimetres down to about 10 mm, while fine pulverized coal is better handled by a rotary divider.

How does it work?

Coal is heterogeneous, so sample preparation must cut particle size and sample mass without changing composition. Size reduction proceeds in stages: a jaw or roll crusher takes lump coal down to a few millimetres, a hammer mill or crusher reduces it to about one millimetre, and a vibratory ring mill or disc pulverizer grinds a laboratory portion below 200 µm, or to 75 µm for ash and elemental work. Between stages the sample must be mixed and divided, because mass reduction must be proportional: a riffle divider splits a stream into two equal halves through alternate chutes, and a rotary divider collects a controlled stream in rotating vessels to give identical fractions. Moisture control is critical, so equipment is enclosed, pass-through times are short and contact surfaces are chosen to avoid adding iron or other contamination that would bias ash and elemental results.

What are the key features?

• Even number of alternate chutes for a two-way split
• Chute width sized to the top particle size
• Uniform manual or vibratory feeding across the bank
• Stainless steel body for low contamination
• Two receiving pans supplied as a pair
• Several frame sizes for different top sizes

What are the technical specifications?

A typical riffle sample divider configuration offers number of chutes of 8–20, even number, chute width of 2.5–3 times top size, applicable top size of 1–25 mm depending on model, sample capacity per split of 5–200 kg, material of Stainless steel 304 and frame dimensions of 200–800 mm wide. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Riffle Sample Divider is used in dividing crushed coal samples in the field, reducing sample mass before pulverizing, coke and mineral sample splitting and inspection laboratories and mine sample rooms. Across the wider Coal Sample Preparation class, laboratories also deploy it for coal mine and preparation plant sample chains, power station coal quality laboratories and commercial inspection sample preparation.

Which standards and certifications apply?

Relevant standards and methods include ASTM D2013, ASTM D2234, ISO 1988, ISO 13909-1, ISO 18283, GB/T 474, GB/T 475 and IEC 61010-1. Certification candidates for this model are CE and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Prepare samples in a controlled room where moisture loss is limited, and work quickly through each stage, weighing after every division so that mass balance can be checked. Clean equipment between samples with brushes and, where necessary, by running a small amount of the next sample through, to avoid cross-contamination. Record the top size, mass and equipment settings for each stage so the reduction history can be audited. Keep grinding sets within wear limits, since worn plates change product size and can raise ash through iron pick-up. Guard feed openings, provide dust extraction rated for coal dust and use motors and switches suitable for a dusty environment. Reference materials and duplicate samples should be put through the same chain as routine samples to verify that no bias is introduced.

How do I select the right Riffle Sample Divider?

Select the riffle divider size from the top particle size of the material you divide, not from the sample mass. Specify chute count, chute width, material and pan sizes, and plan to check the split by weighing both halves periodically.

How does it compare with other Coal Sample Preparation variants?

Plan the whole chain before buying individual machines. Match the top size of incoming material to crusher feed openings and the required final fineness to the pulverizer, and keep reduction ratios moderate by using several stages rather than one large step. Check throughput against the number of samples per shift, and check that the product size table of the sampling standard is respected, since the minimum sample mass depends on top size. Choose contact materials with contamination in mind: manganese steel wears well but adds iron, while tungsten carbide or ceramic grinding sets cost more and keep ash and trace element results cleaner. Look for enclosed, dust-tight designs with extraction connections, quick-release bowls or plates for cleaning, and drives rated for continuous duty. For dividing, riffle dividers suit gravity flows and rotary dividers give the best precision on fine coal.