The state-of-the-art elevator moves 4,500 tons per hour, the fastest rate globally, and ZGC continues to upgrade and innovate operations to improve efficiency. One of the key pieces of machinery that ZGC depends on is called a Continuous Barge Unloader (CBU). It can unload a full Mississippi barge or approximately 60,000 bushels of grain in a single hour. In other words, it’s a massive machine.
The CBU is essentially a chain of buckets, each roughly equal to one ton of grain capacity. The buckets drag through the barge and collect grain, which is then transferred to a gathering conveyor. The gathering conveyor sends the grain to a series of belt conveyors that route it to scaling systems or storage.
ZGC ran into a problem when one of their two CBUs was installed. It had a vibration issue, and over the past few years, this issue had been destroying the machine foundations. For a machine that is the width of two Mississippi barges, this was a significant challenge. The problem was in the design, but ZGC needed a way to fix it.
First, Ross McEllhiney, the Director of Operations at ZGC, recruited a vibration specialist to analyze what was causing the vibration. The vibration specialist determined that the CBU operated at a resonant frequency close to the machine’s natural frequency. Understanding the natural frequency of a machine is essential as it can help engineers design machines that are less prone to vibration and resonance.
If a machine’s natural frequency is too close to an external force, it can experience resonance, causing destructive vibrations and even machine failure. When a piece of machinery the size of a CBU vibrates, it can vibrate right off the dock. ZGC needed a solution — the right one.
McEllhiney had enjoyed 20+ years of collaboration with Jasen Sappenfield, co-founder of Finite Engineering, and he knew that Jasen’s team could weigh in on this unusual problem with expert advice. “That’s where Finite really shines. They are knowledgeable people and have a deep understanding of engineering, so they find creative solutions,” said McEllhiney.
Our team performed an analysis of the proposed solution from the vibration specialist, which included 3-D modeling and motion studies. The goal was to reduce the force applied to the machine near the resonant frequency.
“It’s not something people generally do much of, because people typically do not design machines that operate near their natural frequencies. The analysis of the motion of a piece of machinery near its resonant frequency is a difficult subject,” said McEllhiney. “And when it goes bad, it goes very badly. The average engineer doesn’t work on this very often, so that’s why we went to Finite. We knew they would listen.”
Ultimately, the team at Finite Engineering determined that the vibration specialist’s recommendation would not be effective. Although that result may initially sound like bad news, it was a win for ZGC. The proposed solution for the vibration problem on the CBU would have cost $3 million.
“Finite didn’t solve the vibration problem, but they saved us money by telling us the recommendation was wrong,” said McEllhiney. “It was money well spent.”
