We have a local gravel pit and asphalt operation near our Springfield OH repair shop. Over the years, we have built a solid relationship with this customer, doing field service, motor and mechanical repairs.
This project started in September of 2016 when Dave Whited and Karl Hoppe met with the corporate engineer and local management about ways to improve power factor. Initially, we looked at PF correction capacitors and then into AC drives as a way to improve power efficiency.
The slurry system consists of three pumps – a fresh water pump, a sand pump, and a waste pump. All part of the cleaning system for the gravel they produce. The aggregate comes over on a conveyor to the cleaning tower and goes on a screen. Water is then sprayed to clean the silt and dirt from the gravel. The product then goes to the sand tank and becomes a water and sand slurry mix. The product then goes to the classifier to grade the aggregate size and it then gets conveyed into different piles. The water goes to the waste pump that returns it to the waste water pond. Who knew gravel production was this complex?
Previously, the sand and waste pumps ran full speed. The fresh water pump had a gate valve to limit the flow but the motor ran full speed. The motors are rated at 60, 75, and 200 HP. The customer’s corporate engineer was looking for a way to improve their power factor from .77 to a .9 target. Since the power company was fining them for their low power factor, they offered a rebate to cover half the cost of the three AC drives needed for the slurry system pumps.
Dave Whited continued to discuss power factor improvement options with the corporate engineer and local management. The decision was finally made to use VFD’s to improve power factor and reduce power usage, due to pump affinity laws. A 10% reduction in speed results in a 23% reduction in energy usage. Horner Industrial drives engineer, Tom Wagner, was then called in to inspect the project and bless it.
The project consisted of supplying 3 new ABB ACS 550 drives, Cool Blue chokes for line harmonics, line reactors, long lead filters, ultrasonic transducers to monitor tank levels, and a Horner APG touch screen controller. Chuck Ridgeway assisted with the controller and recommended an integrator to assist us with this project. Dave Whited and I made a trip to the integrator’s headquarters to witness test the program with the drives connected and operational.
Springfield field service performed the equipment installation during this past winter shutdown and commissioned the drives. A rep from the integrator came in and commissioned the controls and performed a test run and set calibration levels for the transducers. From the control tower, the operators can stop/ start, control speeds, monitor tank levels, and water pressure at the cleaning tower – all through the Horner touch screen controller.
In a follow-up with the plant manager over the final billing, he stated that he was very pleased with the project outcome. He said that he was impressed that everyone on-site was very professional. Based on this system’s payback over time, the customer may consider similar projects at some of their other plant sites.
This project is an example of what can happen when sales, engineering, and field service pools their talent to fill a customer need.