Conveyor Science Investigation. Cause of Excessive Vibration Found - Mystery Solved!

ZMI, LLC and the Gearbox Gurus have solved the riddle of excessive vibration on critical conveyor drives at a major grain export terminal in Southern Louisiana.

This particular drive is in service on a conveyor load out system.

Continental Engineering was hired to design and supply the drives for two conveyors that load grain from the terminal to the ship. CE initially wanted to supply two 500 HP drives in a dual pulley set up with VFDs and the customer insisted on a 550 HP dual drive, single pulley configuration with fluid couplings that utilizes a staggered start. The customer’s preference created challenges and some unusual operational dynamics.

The main issue is excessive vibration with the dual drive configuration. The Gearbox Gurus were enlisted to study the system and find the root causes of the vibration.

The Gearbox Gurus took detailed vibration measurements at critical points on each drive, the tower platform and structure as well as temperature readings, current flow and other important operational data. The vibration causes really came to light when Pepper Maintenance was hired to film the drives in operation.

The first video is of BC 113 Upriver, showing one side of the drive in use. On both videos, the frame on the left is in real time and the frame on the right is time lapse. You can see the base bounce, flex and twist; almost like the tail wagging the dog. The video of BC 113 Downriver focuses on the motor of the opposite side.

BC 113 Upriver Drive Video

BC 113 Downriver Drive Video

After compiling the data and consulting with the suppliers of the drive components, the Gearbox Gurus focused in on two areas; the drivebase platform, and the drivebase design and materials.

Our recommendations are to fill the drivebase platforms with concrete to fully engage the inner support channels, stiffen the baseplate on the drives with in-line lateral channels, eliminate the staggered start on a loaded belt and use VFDs in the event of current/power fluctuations.

We’re interested in your feedback. Has anyone else witnessed similar issues in other applications? It’s already cost the customer one 550 HP motor; it was pulled and rebuilt after six months of service.

There’s another 800 HP drive showing similar excessive vibration issues at this facility. The motor catastrophically failed and was replaced after four months of operation. We’ll be vetting that one in our next round.