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Turning Technology Into Profit
Air classifier reduces power consumption and gives Ohio-based Piqua Materials a quality boost.

By Patrick Hernan

Piqua Materials Inc. produces a number of quality limestone products from its progressive operation in Piqua, Ohio.

A small community, Piqua is about 25 miles north of Dayton. Piqua Materials and predecessor companies have quarried limestone in the area since the Civil War era.

Once part of Armco but now privately owned, Piqua Materials mainly serves markets in Ohio and adjoining states. The firm also ships limestone products to customers in Maryland, New Jersey, Texas and other states.

Piqua Materials employs about 30 workers and prides itself on its ability to deliver standard and high calcium products that exceed customer expectations. In. line with its commitment to quality, the company recently installed an SD40 High Efficiency Air Classifier from Sturtevant Inc. of Boston.

It wasn't the first time Piqua turned to Sturtevant. The company - a family owned business that traces back its history nearly 115 years - previously provided Piqua a 16ft. Whirlwind Air Classifier to make fine product.

Although the Whirlwind and a two-compartment ball mill provided Piqua many years of reliable service, the company decided it was time to turn to new technology.

"The Whirlwind had very good mechanical reliability, but it had its efficiency limitations," says David Purk, Piqua's quality control technician. [Although] the Whirlwind was able to adjust to market demands for finer and finer limestone products, the efficiency of this older technology deteriorated at the finer settings."

Among the products the SD40 helps Piqua's make are Piqua Filler 70, which has an average particle size of 7 microns, and Piqua Filler 60, which has an average particle size of 6 microns.

Customers use these fillers in rubber, caulking, plastics, adhesives and contact cements. Piqua also markets coarser limestone products for use in a range of applications, and the company is involved in the production of road aggregate, roofing filler and agricultural products.

Ross Donovan, Piqua's plant operations manager, says the firm's customers demand quality and top-shelf service. The SD40 helps Piqua deliver.

Through the purchase of the SD40, Piqua also realized significant efficiencies and cost savings, Donovan says.

"By replacing the 16ft. Whirlwind Air Classifier and ball mill with a smaller and more efficient SD40 Air Classifier, connected horsepower was reduced by 52 percent," Donovan says.

"Average operating hours were reduced by 15 percent, and the tons per hour production rate increased 17 percent," Donovan continues. "We would consider installing another system in the future."

Piqua's Purk says the SD40's ability to save energy helps producers save money. "Electricity is a big part of production costs," Purk says. "It takes power to beat stone down to dust."

The purchasing decision

In making the decision to replace the Whirlwind and the ball mill with the SD40, Piqua considered factors such as the product's state-of-the-art design and its ability to change quickly from product to product.

Factors such as Sturtevant's reputation for mechanical reliability and its longtime industry presence also were taken into account.

Sturtevant, according to Piqua, provided a comprehensive review of Piqua's needs and conducted plant trials at the firm's Boston test facility, Joe Muscolino, Sturtevant's product manager for the SD40, says it has a number of features and benefits:

• Instead of Whizzer blades, the SD40 uses a multi-pin rejector cage. This results in better control of maximum particle size and more efficient particle classification.
• A combination of air inlet volute and baffles are used. The air inlet volute distributes airflow 360 degrees horizontally around the rejector cage; the, baffles distribute the airflow vertically in front of the rejector cage. This system minimizes turbulence and improves classifying efficiency. Airflow is generated by a fan independent of the SD40's main drive, and external settings can be adjusted quickly to accommodate multiple product finenesses.
• Cyclones are used to separate classified product, and airflow is recycled back to the SD40. This eliminates capital costs and permitting requirements that usually accompany a large dust collector. The system, meanwhile, requires only a small amount of venting for nuisancedust control.
• The SD40 uses aluminaoxide ceramic liners, rather than steel plates. This minimizes iron contamination and maintains brightness.

"We've been making air classifiers since the 1920s, with more than 3,500 installations in place," says Muscolino "The SD40 is just a further extension of our air classifying technology."

Muscolino says the SD40 features electronic components and that operations are computer programmable.

"All adjustments are made externally, which means you don't have to shut down the machine if you change from one product to another," Muscolino says. "Adjustments are endless. You can preprogram speeds to make certain products." Purk agrees. "By merely adjusting the speed of the rejector cage, you can end up with many different products," he says.

The cost-saving advantage of electronics, Muscolino says, is that no one has to stop production, get inside the machine and change the internal configuration of the air classifier.

"No maintenance crew has to disassemble the machine," Muscolino says. ""Trial-and-error time for the new products is reduced."

Donovan, who says he is "very satisfied" with the SD40, says the machine's versatility is a major feature.

"You can set it up and forget it" he says. "It can take almost anything you're geared up for without much fine-tuning and adjustment.

"For what we're doing with it," Donovan continues, "it's much more consistent than screen separation."

Purk also is a fan of the SD40's versatility. "By using this technology, if something goes wrong, such as an overload or overfeed, you can tell the machine to shut itself off," Purk says.

Before Piqua made its decision to purchase the SD40, the company provided Sturtevant with material mined at its quarry and specifications that would meet the needs of its customers.

Piqua officials then traveled to Boston to participate in plant trials at Sturtevant's test facility,
"Having the mineral processed in a pilot machine eliminates the guesswork," says Sturtevant's Muscolino. "Not only did we give them a production guarantee, we were able to predict the quantity and fineness of rejects that would have to go back to the null for regrinding."

A production-size SD20 Air Classifier using feed rates of 5 to 9 tons per hour was used to achieve accurate scaleup. Three objectives, according to Sturtevant, were met during the trial:

• The SD40 consistently maintained a fine product specification, despite fluctuations in the milled limestone's particle size distribution.
• A fine product using a high rejector speed (6 micron average, 45 micron top size) was generated. For coarse product, a low rejector speed was used to dedust undesirable fines.
• Fine-product specifications were reproduced and maintained during an extended trial with 5 tons of material.

At its Ohio, plant yard, Piqua Materials is reproducing the results of the Boston trial.

"The SD40's consistent performance does not require an operator to constantly sample products for quality," says Purk. Donovan says Piqua's customers have embraced the technology.

"We're able to give them control charts and a complete analysis," Donovan says. "Previously, some customers were demanding certification on practically every load. Now, they're accepting monthly reports."

A high-tech advantage

The "SD" in the SD-40, Muscolino says, stands for "side draft".

Muscolino says conventional air classifiers use an updraft system, a technology that is older and costs less but is considerably less efficient.

"Less expensive goes only so far" Muscolino says. Side-draft technology, which was developed over a period of five to six years, was revolutionary when it entered the market in the mid-1980s, he adds.

Piqua Materials, for one, is glad it made the investment.

Reprinted from PIT & QUARRY , December 1997
An ADVANSTAR Publication Printed in U.S.A.

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