One of the largest expansion projects in the flour milling industry this year has been at General Mills Inc. in Great Falls, MT. Utilizing new equipment supplied by Buhler Inc., Minneapolis, MN (612-545-1401), the company doubled the capacity of its white flour/durum semolina swing mill to 7,000 cwts. per day and added a new 3,000-cwt.-per-day durum mill, which will supply semolina to a new Pasta Montanapasta plant adjacent to the General Mills property.

With the need to boost cfm output to power all the new equipment, the company decided to use the opportunity to replace virtually all of the blowers powering the pneumatic systems in the grain elevator and the mill. And General Mills chose to standardize with 40 blowers, all supplied by Blower Engineering, Lewiston, NY (800-388- 1339).

“We had a real hodge-podge of blowers around the plant, MDs, Duroflows, Sutorbilts” says Milling Superintendent Ed Klein. “We’d been having a lot of problems with some of them, and there was a lot of downtime.” He notes that by standardizing on a few models supplied by a single manufacturer, the company could streamline its maintenance procedures and hold parts inventory to a minimum. Klein and Plant Manager Jeff Shapiro first tried out a recommended blower after meeting with Blower Engineering representatives at the 1994 Association of Operative Millers Trade Show in Calgary, AB. They tried one blower on a railcar loadout system, then two others elsewhere in the plant, and liked the performance.

Among the features Klein particularly likes:

• A tight oil seal design for long life with relatively low maintenance.
• Reliance on a baffle-type muffler system rather than insulation for relatively quiet operation.

Working closely with Blower Engineering President Tom Byrnes Sr., General Mills had the following blower models installed this year at Great Falls:

• Four Model RB 30 blowers, ranging in operation from 1,750 to 3,241 rpm and in output from 90 to 200 cfm. Uses - enrichment, fluidizing blower, flour feed-in, screenings.
• Fifteen Model RB 60 blowers, ranging in operation from 1,573 to 2,811 rpm and in output from 200 to 467 cfm. Uses - wheat conveying in portions of the cleaning house; flour conveying to bulk bins, the rebolter, and elsewhere through the mill; screenings; bran and shorts mill lift; semolina conveying; providing air for the C-mill and cleaning house.
• Eight Model RB 80 blowers, ranging in operation from 1,460 to 2,380 rpm and in output from 450 to 860 cfm. Uses - separator to surge bin, storage bin to surge bin, general flour conveying, storage to metal detector, moisture control to bin, and flow- through bin to storage bin.
• Twelve Model RB 90 blowers, ranging in operation from 1,801 to 2,067 rpm and in output from 860 to 946 cfm. Uses - storage to cleaning house, general wheat conveying, general flour conveying, wheat tempering system, conveying finished semolina to the Pasta Montana plant.
• One Model RB 100 blower, operating at 1,977 rpm and generating 1,242 cfm, for moving flour from bulk storage to the packing line.

Perhaps the biggest challenge in the General Mills blower project was the limited space available, two rooms in the mill basement. The larger of the two rooms was only 222 inches wide x 268 inches long, and neither room was large enough to admit a forklift. In some cases, 2,000- lb.-plus blowers had to be lifted by a ceiling-mounted hoist to within six inches of the ceiling. To make sure blowers were lifted along their center of gravity, Byrnes designed a lifting lug consisting of a ½-inch-thick steel plate with three holes two inches apart. The lug was suspended directly beneath the hoist, and the hoist chain could be passed through whichever hole allowed the blower to be lifted closest to its center of gravity.

Another space-saving suggestion from General Mills — triple-stacked blowers on a frame designed by Byrnes with considerable input from General Mills engineers. Byrnes says he recommended a 5-inch-by-5- inch steel tubing for the frame. The extra-heavy-duty construction contributes to reduced vibration and quiet operation.

In addition to the blowers, each of the blower rooms is equipped with a large fan to bring in cooling air.

Klein says the blower system has performed well so far and has required minimal maintenance. “All you need to do is change the oil and make sure the filters are clean he says. “Ideally, you should do that once a month.”

Zdrojewski, editor

Reprinted from October/November/December 1997 MILLING JOURNAL