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Corn+Soybean Digest

Grain Storage On Auto-Control

Stop by the grain bin site at the Mitchell Farm near Buckingham, IA, during harvest and you'll likely not see anyone there — except inside a vehicle. Grain haulers arrive regularly with trucks and wagons at the grain pit, but they rarely exit the cab.

It takes about 30 seconds to unload grain before the drivers head back to the field. That's how fast automation works on this farm, which relies on an industrial computer or programmable logic controller (PLC), sensors, specialized software and a high-speed wireless (radio) network to monitor and control grain flow, drying, cooling and storage.

“Automation speeds the grain handling process, so there's never a bottleneck at the bin site,” says Clay Mitchell, a Harvard-educated engineer, who operates the family farm with help from his father, Wade, also an engineer, and other family members. “The combine never has to stop for the drying system.”

Never having bottlenecks at the bin is a pretty strong statement, admits Mitchell, particularly since the farm uses a class VIII combine that can harvest 5,000 bu./hour. However, it's a statement that he readily affirms, and one that can be verified by watching the farm's grain handling and storage system at work during corn harvest.

The process starts when grain haulers pull up to the grain pit and use hydraulic hoists or flow gates to automatically unload. The trucks have pneumatic-controlled end gates, which open and close with the push of a button. Drivers can look through the cab window and through screens on the box to see if it's empty and the end gate is down before pulling away.

“If you have 300 loads during harvest, you might save getting out of the truck 600 times,” says Mitchell. “This system saves on labor for at least one full-time person during harvest.”

Even though no one is physically stationed near the bins, the Mitchells still handle and monitor their grain continuously during harvest. They accomplish this with automated equipment or with laptop computers they take with them nearly everywhere they go.

“Few autonomous operations can be conducted without external input from either a human being or a connection with other machines,” says Mitchell. “We have a high-speed wireless network that covers the entire farm. Therefore, from any remote location on the farm, even mobile vehicles, we can monitor and control the bin setup through a graphical user interface (GUI) software program that Dad wrote to run on any PC.”

The farm's grain bin controls are one-of-a-kind, as a result of the GUI software, notes Mitchell. If other farmers wanted to create a similar automated grain bin system on their farm, they would also need to write a software program — or find an engineer to do it for them — that would allow them to control their PLCs from personal computers.

“The language of our controller is in industrial-control ladder logic, but we can still use it with our laptops because Dad wrote the GUI to do it,” Mitchell explains. “Our system is designed by us to overlay and control a DMC Calc-U-Dry system that uses floor augers for continuous-flow in-bin drying. We've just added more sensors and logic to further control the grain flow in and out of all the other bins.”

Despite the system's uniqueness, the Mitchells also use many readily available bin and dryer components. In addition to their Sukup burner, this includes a grain moisture sensor at the grain outlet and other off-the-shelf controls and sensors to start or stop unloading augers in the grain pit, drying bin, cooling bin and storage bins.

Having the right hardware in combination with the right software allows for automation to take place, emphasizes Mitchell. The right hardware includes items like:

  • a rotator motor in the leg distributor, so that downspouts can be selected without requiring a person physically there to pull on a cable,

  • a sensor in the pit to know when grain is present, so that a driver can unload and drive away without ever getting out of the truck,

  • sensors that will detect plugging and automatically shut down conveyors and sound an alarm,

  • dedicated conveyors from the dryer to the cooler and the cooler to storage bins, which allow grain to be immediately moved whenever it has been adequately dried or cooled,

  • floor augers in the dryer and cooler to take grain off the floor, providing a truly continuous, counter-flow system,

  • multiple thermocouples to measure grain temperature, plenum (chamber) temperature and ambient (surrounding air) temperature, which allow the Mitchells to monitor bin conditions and detect problems early.

Grain storage automation hardware and software can be helpful for saving fuel costs during the drying process in addition to generating time and labor savings, says Mitchell. The fuel cost savings result from keeping a mass of corn in the bin at just the right depth, temperature and moisture gradient, he explains.

“If the kernel is dried too fast, the heat is taken away in dry air and the moisture remains in the kernel,” he says. “If the corn is dried too slowly, the heat energy is lost and the moisture stays in the bin. However, our system matches the necessary cooling speed for minimal fuel use.”

Other farms have continuous-flow, in-bin drying systems similar to the one on the Mitchell farm. However, the Mitchell's automated cooling system is quite unique, and that, when combined with their drying system, is what allows them to save money. “By having a precisely automated, counter-flow, continuous in-bin cooling system we can remove an extra two points of moisture,” says Mitchell, “in a process where there is often no moisture removal in other systems.”

Automation also has its advantages when delivering grain to a buyer. The farm's drive-through grain unloading bin automatically refills after emptying, which is virtually instantaneous.

“Filling our trucks only takes 30 seconds,” says Mitchell, “rather than the 30 minutes that it would take to fill by auger.”

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