August 01, 1999
by Stormy Wylie
Enclosed belt conveyors address safety and housekeeping issues by keeping grain dust to a minimum.
By Stormy Wylie
Not too many years ago a grain facil- ity was a dusty place, filled with people armed with brooms to keep up with the large quantities of grain and grain dust spilling out from fast-moving conveyors. But with introduction of enclosed belt conveying systems in recent years, the scene is quite different today.
“You don't have to employ an army of people anymore to sweep up grain dust,” said Bob Moser, executive vice-president of InterSystems, Inc., a manufacturer of grain handling systems based in Omaha, Nebraska, U.S.
Enclosed belt conveyors not only reduce manpower requirements in a grain elevator, but are also weatherproof, cleaner and safer than traditional “open” belt conveyors and move grain at higher capacities over longer distances than many other conveying systems, according to several grain-handling equipment manufacturers.
The majority of conveying systems used in the grain industry can be lumped into three main categories: screw conveyors, drag conveyors and belt conveyors.
Screw conveyors generally are shorter and move smaller capacities of grain. Drag conveyors, including round bottom, flat bottom or en masse, tall flight or inclines and L-path conveyors, are widely used in the industry and handle capacities up to 2,200 tonnes per hour.
Belt conveyors are a gentle and efficient way to convey product over long distances, and have relatively low installation, maintenance and operation costs. While drag conveyors can damage grain kernels by dragging them against metal, belt conveyors move with the product.
“But the ‘open' nature of belt conveyors raises safety and housekeeping issues,” Mr. Moser wrote in “Keeping horizontal conveyors running safe and strong: A practical guide to maintenance and safety” (see World Grain, July 1998). Enclosing the belt in a rectangular steel housing solves those problems, he said. The dust-tight enclosure contains spills and airborne grain dust, practically eliminating the need for housekeeping and meeting government guidelines on dust emissions.
The enclosed belt conveyor was introduced about 15 years ago, but has become widely accepted by the industry only in the past decade. Most are equipped with reclaim systems that automatically reload spilled grain back onto the belt and have been designed with external bearings as a safety feature to reduce the risk of fire or an explosion.
Several U.S.-based manufacturers of enclosed belt conveying systems recently spoke with World Grain about new developments in their product lines. InterSystems and Brock Grain and Feed, Milford, Indiana, both introduced enclosed belt conveyors to their product lines this year, while Air Conveyor Express, L.L.P., Hereford, Texas, is marketing an air-supported enclosed belt conveyor.
Hi Roller, Sioux Falls, South Dakota, a long-time manufacturer of enclosed belt conveying systems, recently unveiled a new model with a totally enclosed, movable discharge tripper.
Like all its conveyors, the new Consignor is totally enclosed, dust tight and weather tight, with no internal brackets, ledges or areas where material can build up, Hi Roller said. Spilled material is conveyed on an anti-static return belt to the patented tail section, where it is automatically reloaded onto the belt.
The Consignor was designed to replace open belt trippers, which generate a lot of dust, said Mike Spillum, Hi Roller sales manager. “The Consignor was designed with two goals in mind,” he said. “First, to be a totally enclosed and self-cleaning movable tripper with all bearings mounted externally. Second, to be completely operational from a separate control room.”
The movable tripper travels along the length of the conveyor, discharging or “consigning” grain at predetermined locations into multiple storage silos. A flexible cover allows the conveyor to pass under, providing a constant, dust-tight seal.
The Consignor moves via a variable speed electric winch, and an electronic tape measure controls positioning. A series of sensors detects metal, which uses a binary code to tell the electronics the exact bin that the Consignor is at and serves as an exact positioning device.
A slight negative pressure is maintained within the enclosure during operation, which seals the cover to the conveyor trunking and prevents dust leakage. The conveyor trunking acts as the ductwork for the aspiration system to keep the dust within the enclosure and discharge it with the conveyed product.
The system, which will convey 18,500 cubic feet of material per hour, is powered by an onboard generator and battery. The onboard computer communicates by radio waves to the hard-wired PLC mounted on the wall.
The Consignor has been in development for about five years, Mr. Spillum said. A prototype has been set up at the company's plant in Sioux Falls.
Air Conveyor Express is a new company formed recently by Grisley, Inc., Salt Lake City, Utah, and Poarch Brothers, Inc., Hereford, Texas, to market the ACX air-supported conveyor. President Ken Walser said the air-supported conveyor is ideal for handling grains and feed because it eliminates friction during operation.
“Our conveyors are based upon the philosophy that reducing the number of moving parts ensures a smooth, energy-efficient and low-maintenance conveyor,” he said.
By using air, rather than idlers, to carry the belt, the ACX conveyor also solves tracking problems common in idler and enclosed belt conveyors, Mr. Walser said. The patented V-Plenum air supported conveyor eliminates troughing rollers, reducing maintenance time and capital expenditures, he said.
The ACX conveyor uses a low-horsepower fan to support the belt. A single fan supports up to 600 feet of conveyor. The ACX conveyor also features a fully enclosed and climate-controlled belt, self-supported spans up to 40 feet, angle inclination up to 25° and eliminates the need for maintenance catwalks.
The company said Harvest States Milling has incorporated an air-supported conveyor at its flagship mill at the Port of Houston, Texas.
The Omaha-based InterSystems this year introduced a new enclosed belt conveyor, the RollerFlo, that complements all of its conveying, elevating, weighing, screening and sampling products, and positions the company as a complete bulk materials handling system provider, according to Rod Cooper, chief operating officer.
InterSystems' new enclosed belt conveyor has “broad sales potential beyond our existing line in both industrial and agricultural markets,” Mr. Cooper said.
The enclosed belt conveyor also has been in development for about five years. InterSystems is currently working on its first major installation of the system in Mexico.
It is a “feature-rich” conveying system, said Mr. Moser, the company's executive vice-president. The RollerFlo offers quick-clamped, no-tool access; self-cleaning operation with reloading tail; a high-quality spool and shaft assembly; vertical and horizontal adjustable idler shafts; stainless steel, painted or galvanized construction; and computerized belt tension, horsepower and capacity calculations.
InterSystems also is the first manufacturer to install pillow-block bearings on the intermediate rollers, Mr. Moser said. Most enclosed belt conveyors have flange bearings bolted to the housing, he said. “We mounted a pillow-block bearing outside with a seal in between so if you get a burning bearing it's away from material,” Mr. Moser said.
InterSystems' intermediate rollers also are much stronger than the industry standard, he said, and the company was the first to install intermediate shafts for tracking horizontally and vertically. The housing was designed so that the bottom liner can be replaced without removing the belt. The RollerFlo conveyor is sealed and weather-resistant.
Brock Grain and Feed, a leader in the grain storage industry, also began marketing a line of enclosed roller-belt conveyors this year as the company gears up to become a “complete systems provider,” according to Steve Ginter, product manager for the enclosed belt conveyor product line.
Mr. Ginter previously was an officer of RGF Corp., a belt conveyor manufacturer in Potosi, Wisconsin, U.S. Brock acquired RGF in 1997 and brought Mr. Ginter in as product manager. The company also hired another veteran of the belt conveyor industry, Mark Dingel-dein, as project engineer.
The two men spent their first 18 months at Brock evaluating the enclosed roller-belt conveyor designs already in the marketplace, looking for fresh ideas. “What we did was take the RGF conveyor, the Hawk, looked at its weaknesses, made design changes and introduced it back into marketplace,” Mr. Ginter said.
They came up with a galvanized enclosed roller belt conveyor that is versatile and flexible, simple yet durable, rugged yet gentle, and efficient, he said. The modular design features removable covers with a quick-release hatch so the conveyor can be maintained from just one side. Brock's enclosed belt conveyors also are self-cleaning, capable of doing full-load starts, with reloading capabilities to recapture spilled grain from the belt. The conveyors are equipped with either a stationary tripper for fixed discharge locations or a movable tripper for flat storage buildings. Capacities range from 25 to 1,500 tonnes per hour.
Removable peaked covers aid in drainage and maintenance and the conveyor can be operated with the covers removed. Expansion joints allow longer conveyors to expand and contract.
The heart of any enclosed belt conveyor is the idler pulleys, Mr. Ginter said. Brock is the first manufacturer to introduce a dynamically balanced idler pulley, he said, which minimizes harmonic vibrations while providing longer bearing life and smoother belt operation. The company has a patent pending on the design.
Brock also is the only manufacturer to use a tapered bushing, he said. All bearings are mounted externally and the belt and discharge areas are lined with a static conductive material.
“Every component was looked at to eliminate chance of a grain dust explosion,” Mr. Ginter said.
The company has already installed several units in the field, he said, including a large system for South Dakota Wheat Growers.