Grain Storage: Bin Measurement

Since starting the Grain Guy Fifty blog, I've shared several articles on grain storage. My first was "Grain Storage Planning: The Essential Guide to Bin Utilization," followed by articles on the history of grain storage, types of storage, using grain bags, and a three-part series on aeration. In this two-part series, I’ll delve into grain bin measurement and grain quality management utilizing technology.

The practice of storing grain and measuring quantities goes back to ancient civilizations. Early humans likely inspected their skin bags to gauge how much grain they had to ensure survival. The oldest known instances of measuring stored grains date back to 9,500 BC, using visual observations or simple measuring devices like sticks or ropes. As grain bin designs evolved, increasing in height and diameter, traditional measuring systems became less accurate. I recall my early days of measuring steel bins by standing on the ground, throwing a rock against the metal, and counting the rings. As bins grew taller and my pitching arm weaker , that method quickly became impractical.

The history of grain bin measurement is closely tied to the development of agriculture and trade. The need to store and measure grain prompted the creation of various units and systems, evolving from localized practices to standardized international measures. Early civilizations developed distinct systems of weights and measures. The Greeks, for instance, employed units like the cotyle and kyathos for measuring grain and other commodities. The growth of trade and manufacturing led to more standardized systems, with fundamental units defined by precise metrology methods. The UK and the US developed their own systems of weights and measures, including the bushel for grain. Modern grain bins are often measured in bushels, with capacity calculated using formulas based on the bin's dimensions and the grain's density (Iowa State University Extension and Outreach).

Before we get too much more  into bin measurement let’s review why we measure grain bins. Inventory management is a primary reason, knowing how much grain is on hand and then calculating the value of it is required for prudent financial management and cash flow. If you are a licensed warehouse you are required by regulation to conduct routine grain inventories. Knowing if you have enough grain in a bin to load a truck or train or if you have enough room to dump another truck or rail car is necessary for efficient operations. Having this information allows for data driven decisions.

So how do we approach bin measurement today? I Suppose there may be a few places out there with a guy with a strong  arm is still throwing rock against the bin wall but most of us have progress to some level of measurement tools or technology to conduct these measurements more accurately.

One common method is sending someone up a ladder to drop a tape measure down to the grain surface. However, this method has challenges, such as the location of the access hole for measurement may vary—either at the top of the bin wall or the peak of the roof—and the grain surface will not be level. These factors can significantly affect measurement accuracy.

There are mathematical models that allow you to take into consideration cones or inverted cones with known angle of repose for a specific commodity  but they still rely heavily on human objectivity in the measuring process. Other factors influence the outcome such as the design and location of the bin discharge , grain moisture & quality, and weather. ( I question on a  zero-degree day with a twenty-mile hour if ample time and care is being provided by the employee doing  the measurement.)  Also remember you cannot stick your head in that bin to get a visualization without a grain bin entry permit. According to OSHA if you break the plane, you are in the bin.

Now, looking at technology, what options do we have? The closest alternative to the manual tape method is a smart bob, which can be remotely lowered, read, and raised. There are also level sensors using contact or pressure, which can be used in place of climbing the bin, though these have the same disadvantage when it comes to measuring uneven grain surfaces.

Technology has evolved to non-contact measurement devices such as Lasers, Ultrasonics or Radar. Lasers are accurate but negatively impacted by suspended dust. Ultrasonics uses sound waves to take measurements and can be effected by internal bin environmental conditions .  Radar level meters operate by emitting electromagnetic waves (microwaves) towards the surface of the grain. The waves reflect off the grain's surface and return to the sensor. The time it takes for the waves to travel to and from the surface is used to calculate the distance, and thus the grain level. 

Radar level sensors generally offer superior accuracy and reliability compared to laser and ultrasonic sensors, especially in challenging environments. Radar technology is less susceptible to environmental factors like dust, temperature, and moisture, which can distort ultrasonic readings. Historically, radar units were not cost competitive compared to other non-contact technologies, but that price gap has narrowed considerably. Depending on the bin diameter, typically  multiple units will need to be deployed.

 Thank you for taking the time to read this post! Whether you’re a farmer, a grain elevator operator, or simply interested in agricultural technology, there’s a wealth of innovation to discover. Stay tuned for more insights and discussions on enhancing grain storage practices and ensuring optimum grain quality. Your feedback fuels this blog, so don’t hesitate to share your thoughts or personal experiences. Together, we can cultivate a better understanding of modern grain storage solutions.

Best wishes, 

Grain Guy Fifty

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