Powder rifflers and splitters divide or reduce a larger sample into smaller representative samples while maintaining the particle size distribution of the original sample. A powder sampler splitter reducing or splitting a sample in half or into two samples would have a division ratio of 1:2 or a 50% fraction. Splitters dividing a sample into ten samples would have a division ratio of 1:10 or a 10% fraction. In order to produce a sample small enough for chemical assay, particle size or shape analysis or other powder tests, multiple passes through through the powder riffler may be required.

Powders and granular solids have a tendency to segregate or separate out during handling. A powder sample in a container will likely have a higher fraction of fine particles on the bottom of the sample because vibrations and gravity will causes these fine particles to settle and drop through the interstitial spaces or voids between the larger particles. A powder sample poured out into a cone on a table will tend to have a higher than representative amount of fine particles on the top of the cone. Powders with wide particle size distributions are more prone to separation and settling effects. Particle separation can be aggravated by material density differences such as elemental blends of metal powders or high specific gravity mineral fillers blended with resin powders. Particle shape (spherical, elongated, angular, flake and irregular) can influence sample segregation as well.

Types of Powder Rifflers and Powder Splitters

A wide variety of powder splitters, powder reducers or powder rifflers are available.

• Laboratory or manual powder sample splitters or dividers are benchtop or floor mounted units used for dividing a sample already extracted from a production line or received from a supplier.
• Production or inline solids splitters or dividers are mounted within the solids or powder production line and divide the solids stream for representative sampling purposes. The inline units may take a cut of the split stream or have feature to enable extraction of a representative sample. Solids or powder dividers can also be divided into stationary and rotary types.

Chute riffers and boerner dividers are types of stationary splitters.

• Jones or chute rifflers consist of a series of vertical slots that split the sample into several streams or smaller representative samples. Some chute rifflers have multiple tiers or levels for additional splits.
• A Boerner divider or stationary cone splitter has a fixed conical shape where the powder falls onto a cone and then into chutes.

In rotary cone dividers, a powder sample is dropped onto a spinning cone, which splits the sample into several channels or containers located around the periphery of the device.

 Several rotary or spinning solids dividers are available.

• Rotary or spinning rifflers mechanically distribute the powder into several collectors or sample vessels by a dispensing or feeding powder above a ring of rotating riffles or collectors.
• Gamet or rotary disc dividers use a spinning disc below a hopper to centrifugally mix and divide a powder sample into two smaller samples.
• Sieving riffle splitters can deagglomerate a sticky or clumped powder sample and exclude larger contaminants or coarse particles from the sample for analysis.
• In rotating tube dividers, a stream of a powder sample flows out from a tube rotating around a cone shaped chamber with an opening, which captures a portion of the power stream on each revolution.

Many other types of powder sample or powder stream splitters are available such as the Vezin splitter, the cascade riffler, the mini-riffler, the microsplitter, the cargo divider, the California divider and the newer ANDIS™ divider.

Most powder splitters can handle dry powders. Some powder dividers will split slurry or wet solid samples. Certain splitters like the Boerner divider will divide delicate seeds and fruits without damaging the food product.

Image credits:

Quantachrome Instruments | Fritsch