Case Studies & Field Reports

Vibratory sifting improves brownie throughput

October 1, 2011
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Brownie baker upgrades its homebrew screener to keep up with increasing orders.

Particles larger than 0.25- x 0.25-in. square discharge through an upper spout, on-size particles move through lower spout. Source: Kason.

Greyston Bakery has an unusual history for a commercial bakery. It was founded in 1982 as the for-profit arm of the Greyston Foundation, which uses the bakery’s earnings to fund community development initiatives. Greyston Bakery has been baking brownies for blending with ice cream since 1988. Since then, it has grown into one of the industry’s top suppliers, producing more than 20,000 lbs. of ice cream mix-ins daily.

“Our 23,000 sq.-ft. facility is in an urban location where storage is at a premium, so we keep only minimal inventories. Every step of the production process needs to keep up the pace. We ship them as fast as we cook them,” adds Vincent Lombardo, plant engineer.

After mixing, baking, cooling and sizing brownies, pieces intended for single-serve cups move to the vibratory screener, where chunks larger than 0.25 in. x 0.25 in. are removed. Greyston’s first vibratory screener was a tray-in-a-tray box model driven by two rotary air vibrators built in-house by Lombardo. It was unable to keep up with the flow of production.

“It was not robust enough to handle 20 hours per day of production,” Lombardo says. “We considered going with either a rotary or a vibratory screener. We eventually decided on the circular vibratory screener because of its low maintenance requirements, screen longevity, capacity and price.”

Lombardo specified a 24-in. diameter Vibroscreen circular vibratory screener from Kason Corporation. The gravity-fed, food-grade unit is driven by a single, low-horsepower, 230-volt three-phase, imbalanced-weight gyratory motor mounted in an enclosed cage directly beneath the screening chamber. Due to height limitations, the Vibroscreen screener is limited to one screen deck, yet it meets throughput requirements while offering reserve capacity.

When the brownies enter the screener, multi-plane inertial vibration of the nylon screen causes the 0.25-in. square pieces to fall through its apertures. Larger chunks are transported across the screen surface along controlled pathways into the discharge spout, which ejects them onto a conveyor that takes them for regrinding.

“We opted for only one screen, since we’re more concerned with removing oversized pieces than removing any fines that were not removed by the tumbler,” says Lombardo. “If we needed to, we could drop the 0.25-in. square pieces onto a 10 mesh screen and remove any fines that fell through.”  Instead, the 0.25-in. square pieces drop onto a pan and exit past a vertical metal detector. If the detector senses any slivers of metal in the brownies, the batch is discharged automatically through a cylinder-activated chute and discarded.

While blinding is not an issue, the screener requires daily cleaning. “We run production for 20 hours, then shut down for four hours to clean the whole system,” says Lombardo. “The motor and connector box are watertight, so we can rinse down the interior and exterior with a hose, apply a foaming cleanser and then rinse it down again,” he explains. 

For more information:

Henry Alamzad, Kason Corporation, 973-467-8140 or

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