Prepping bins for prime time

Prepping bins for prime time

By: Dave Mowitz 07/06/2012 @ 11:10am

If you've ever failed to double-check a grain spreader mounting when tending to preharvest chores, you know what can happen. A suspension chain can come loose, and the spreader will operate in a lopsided manner not only not spreading grain but also eventually disintegrating spewing parts across the bin, which quickly became buried in grain.

To help you prepare your storage bins for harvest, here are seven duties to add to your list of must-do chores.

1. Clean empty bins. This chore is essential, but it is often overlooked. And for good reason. It's a summer job nobody wants to do. But the invitation for insect infestation from lack of cleanliness is too great to bypass this task. Beyond removing old grain, also clean and sanitize aeration ducts, augers, and other places insects could feed on dust and fine material, says Keith Jarvi of the University of Nebraska. “It is generally impossible to thoroughly clean underneath perforated drying floors,” he says. “But by removing the drying fan and using a grain vacuum, much of the accumulated debris can be removed. The bin should then be fumigated with chloropicrin to guard against future infestations under drying floors.”

Other false floor fumigants for use on empty bins include magnesium phosphide and methyl bromide. Such fumigants are dangerous. It is highly recommended that fumigation be done by a commercial pesticide applicator, says Tom Dorn, who is also with the University of Nebraska. Other residual treatments are silicon dioxide (also known as diatomaceous earth), butylcarityl plus pyrethrins, and related chemicals such as bifenthrin (Capture) and pybuthryn (Butacide, Pyrenone Crop Spray).

2. Service and then operate bin fans. “A bin of 19% moisture corn with a starting temperature of 75°F. can lose a full market grade in about five days if the aeration system shuts down, allowing the grain to heat and deteriorate,” says Dirk Maier of Kansas State University. The chore list here includes inspecting burners, fan housings, fan blades, belts, guards, bearings, and electrical controls and switches.

3. Inspect dryers and then operate them prior to use. While you're at it, be sure to calibrate your grain moisture meter in order to avoid overdrying or underdrying grain. Finish the job with a thorough cleaning, particularly of stand-alone dryers. This chore is often ignored, says Ken Hellevang of North Dakota State University. Introducing insect infestation into the bin from grain left in the dryer is one concern. But a dirty dryer is also less energy efficient and runs slower.

4. Install a monitoring system in every bin. Such systems employ moisture and temperature sensors suspended from bin roofs. A 50,000-bushel bin, for example, may have four or six cables that stretch from the ceiling to 6 inches above the floor, with about eight sensors spaced evenly along each cable.

Data from the sensors is sent to a remote terminal unit (RTU) on top of the bin. The RTU transmits readings by a wireless transmitter to a desktop computer located in the scale house or nearby office. A weather station monitors ambient air temperature and relative humidity. Installed near the bin, it transmits data to the computer for use in deciding when aeration fans are automatically turned on. The computer analyzes all data and uses preset moisture and temperature target goals for each bin.

“All our sensings are remote,” explains Randy Leka, farm manager at Grigsby Farms in Tallula, Illinois. “So I can pick it up here at the office, at home, or anywhere. We have a desktop computer at our scale house, and we feed the signals from the RTU wireless to our desktop.”

This automated system helps pay for itself in energy savings. “We run fans two or three times less and at the optimal times. Also, we bring grain out of the dryer at higher moisture to save on LP gas,” Leka adds. Another benefit is that natural air dries grain more accurately, and the farm has recorded data to calculate what's been done to the grain.

5. Check fan capacity on large bins. Tom Dorn remembers when a typical on-farm bin was 27 to 36 feet in diameter and would store grain 18 to 22 feet deep. Today, average bins are 42 to 48 feet in diameter storing grain up to 32 feet. “That's almost three times the volume of the earlier bins,” the University of Nebraska engineer says.

It is crucial, he says, that larger bins be equipped with fans capable of pushing .3 cubic feet of air per minute per bushel (.3 cfm/bu) through the bin. Those recommendations are just for aerating grain. Using a 48-foot bin for drying is a much different situation, Dorn adds.

The minimum airflow recommended for drying corn in Nebraska (check for your state's recommendations) is 1.0 cfm/bu. “A 48-foot-diameter bin with grain 30 feet deep would require three 40-hp. centrifugal fans on separate transition ducts to produce 1 cfm/bu airflow,” Dorn says.

Static pressure is affected by grain depth and airflow. At a given grain depth and airflow, the diameter of the bin does not affect the static pressure.

6. Pull auger flighting from bin unloaders to check for wear. As little as 10% to 15% wear can cut an auger's capacity by 25% and greatly accelerate grain damage.

7. Core bins immediately after harvest is done. True, this isn't a preharvest chore, but it is a chore many farmers forget to complete. This task removes the accumulation of fine material that often builds up in the center (core) of the bin during filling, explains Matt Roberts of Purdue University. “Even with state-of-the-art grain spreaders, fines can accumulate in the core,” he says. “A buildup in fines fills the air pockets between kernels and increases airflow resistance.”

The result? Grain in the core area doesn't get as much airflow. “Some studies indicate that if a bin has just 3% fine material, the airflow in that region of the grain mass would be reduced by 40%,” Robert says. “This simply means that if the core of the bin has 3% fine material, it will take longer (40% longer) to cool the core than the rest of the bin.”