The AirAuger from AirLanco is a novel system employing high volume airflow from the bin floor to “lift” and help grain unload. It serves double-duty as a heavy-duty aeration system.
High volume fans force outside air into concrete troughs created in floors that are sloped toward an unload sump. The troughs have a steel grating cover with small holes so pressurized air flows freely upwards, but grain doesn’t drop in. The performance of the system depends on the volume of air blown in, and that in turn is determined by the crop inside the bin.
Radically slanted concrete dividing ridges force grain in the bin down toward the troughs. Air pressure within the troughs lifts the grain and channels it toward the unload point. All moving parts and electrical components are located outside the bin. That fact, along with the total cleanout, means there is no need for workers to ever enter the bin.
Although the AirLanco head office is in Winnipeg, the AirAuger plant is in Nebraska. Josh Kaster is an engineer on AirLanco systems, including the AirAuger project. He says AirAuger is nothing like a GrainVac or a conventional aeration system.
“We do use aeration-style fans to aerate the tank, but more significantly we use the fans to move grain out of the tank. The fans are spec’d out to do much more than just aeration,” says Kaster, going on to explain how fans move grain.
“The system operates at 16 inches static pressure in the floor troughs. That much pressure will fluidize the grain and cause it to lift. The grain actually floats. The concrete dividing ridges are sloped toward the exit sump. Fluidized grain flows toward the sumps or discharge area at your unload point.
“We install multiple fans in a large bin. We can unload 10,000 bushels per hour per fan. Depending on the specific system and the number of discharge sumps, we can unload up to 40,000 bushels per hour from a bin. That’s with no augurs or conveyors in the bin floor. Just air pushing grain toward the sump.”
Kaster says the design and fan specs for each system depends on the cubic feet per minute (CFM) per run. Length of run is the key factor determining how much CFM will be needed to properly unload. He says engineers have worked out this information so it’s ready at their fingertips.
Engineers slope the bin floor and concrete ridges so they exceed the angle of repose of all common grains. Angle of repose is important in the design of systems for particulate materials. Smooth-rounded grains need a low angle of repose to flow when unloading. Very fine, sticky materials or particles with sharp edges lock together more, so they need a higher angle of repose.
There are three basic patterns for laying out the ridges and troughs. The centre-draw-off pattern channels all grain to a central sump. The side-draw-off pattern channels all grain to a sump at the side of the bin. The centre-multiple-gates pattern allows for more sumps to be used.
“Typically, we install most of these systems in concrete silos, because that’s what farmers buy down here. But we can do galvanized bins also. Once we know the diameter and the eve height of any bin or silo, then we know the length of runs and horsepower needed for each fan and the CFM requirements for each run.
“In a corrugated steel bin, we have to install the concrete troughs and ridges in the bottom to create the slopes and angles. And you require an extra stem wall inside the bin to control the air. Also, you could install a system in an existing steel bin, but it would be a lot of trouble. You’d have to lift the bin to build the stem wall for the bin walls to set on, and so you could get all the concrete ridges and troughs in there.”
Kaster says he doesn’t recommend storing wet grain in AirAuger bins or silos. This is what he calls a working tank system. He expects it to be loaded and unloaded a minimum of four times per year.
With grain bin accidents on the rise, safety has become a bigger factor driving the sale of AirAuger systems. All electrical and mechanical components are located outside the bin. Workers are not exposed to hazards, such as fumigants, toxic dust or rotating augers. It easily empties product that normally bridges or gets hung up inside storage bins, so there’s no need for anyone to get inside with a shovel or grain vac.