Electrical Upgrade Rejuvenates Ash Grove Ship Unloader

For forty years, a Siwertell rail-mounted ST 440-C screw-type ship unloader has secured environment-friendly cement handling operations for Ash Grove’s Duluth, Minn., operation.

“Ash Grove’s port equipment has a high utilization rate and because of booked slot times through all locks crossing the Great Lakes, the operator has to meet very precise port arrival and departure schedules,” said Mats Jönsson, key account manager, Bruks Siwertell. “As a result, all maintenance work must be planned and organized well in advance, minimizing downtime and disruption to scheduling.”

To keep up with current cement demands in the port, the unloader needed to be in peak condition, and that meant a new electrical motor control center (MCC) housing. “The old electrical relay system and many of the system’s parts were no longer manufactured. Following an inspection and owner discussions, we suggested a new electrical housing that met today’s standards,” Jönsson said.

Photo:Bruks Siwertell

The upgrade work was carried out in 2022, and also included a human machine interface (HMI) with touchscreen. This offers improved visual information, giving operator’s better control and an enhanced overview of unloading operations and performance.

Complementing these upgrades, to improve control over the unloader’s movements, modern variable frequency drives (VFDs) were fitted. In addition, the inlet feeder gear and electric motor were updated from direct current operation to alternating current with VFD-control. Other work included new travel drive units, which also feature VFDs.

In total, the project took three weeks to complete and was carried out in three phases, as Ash Grove needed the unloader to continue working. “This project showcases how we are able to work with operators to not only bring machines back into peak performance, but also schedule work to a timetable that best suits them,” concluded Jönsson. “We hope that our customers feel that we are on hand to help not just from delivery but decades down the line.”

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