Upgraded controller gets mill rolling faster

A bespoke control solution for Graham Perry Steels has delivered an increase in production of rolled steel from 24 to 91m/min on a Schmitz cold rolling mill.

Wyko has supplied a complete control solution to Graham Perry Steels, delivering an increase in production of rolled steel from 24 to 91m/min on a Schmitz cold rolling mill.

Two control cabinets were designed and assembled by Wyko to replace outdated DC control systems.

One is employed to control an 110kW motor driving the main work rolls of the press and the other governs the winding on system.

Wyko also supplied an 80kW motor off the shelf for the winding-on process that produces 5t reels of rolled steel ready for distribution.

The original system at Graham Perry Steels' Wolverhampton site was based on two functioning, but obsolete, resistor based DC drives that were becoming time consuming and expensive to maintain.

The first was used to drive an 110kW motor powering the main rolling mill through a right angle reducer gearbox and a two-way splitter box.

A second DC drive controlled a 80kW motor used for the winding-on assembly that recoils the rolled steel coming out of the mill into 5t 72in-diameter reels, ready for dispatching.

This second motor was failing and needed to be replaced along with the drives so a request had been submitted to the nearby Tipton branch of Wyko to quote for the supply of new units.

Initial analysis had shown the control system as a whole was operating at less than 50% capacity, making complete replacement the optimum solution when maintenance time and projected increases in output were considered.

As a result, Roger Evans and Victor Harris, both Wyko drives and motors specialists were called on by the branch to design a completely new control system.

Two 185kW regenerative, digital PLX DC drives from Sprint Electric were fitted into two new control panels and a new 80kW Leroy-Somer DC motor specified.

Harris explains: "The complete system was designed, delivered, installed and commissioned within the Christmas shutdown week".

"This was no mean feat considering that the drives specification required close work with Sprint Electric, motor selection by us and Leroy-Somer, tacho generator upgrades by the Wyko servo team, custom panels to be designed and built, with final commissioning to be done by our staff here at Wyko Aintree".

Daniel Averty, Wyko Senior Drives Engineer, checked final control wiring and commissioned the drives within half a day allowing the machine to go back into production a full 2 days ahead of schedule.

The final cost of the upgrade was under GBP 30,000 and has increased the control and power to the cold rolling mill to such a degree that is has made it possible to increase the steel throughput from 24m/min to a rate of 91m/min.

The result is a 500% increase in production.

After some scheduled service work has been completed on the main splitter gearbox, the Schmitz mill is expected to run safely up to 305m/min.

This is an impressive increase when you consider the rolling mill can exert a 1Mt of pressure to reduce 8mm thick high carbon steel to 2mm thick strip.

The resultant steel strip is used for applications in a broad range of industries from automotive to white goods.

Overall speed control has been kept simple for ease of use, a manual speed change offers ten preset speed levels and the power ramp-up and synchronisation is done automatically.

The new 80kW Leroy-Somer motor fitted to the on-wind recoiling system is driven in torque mode at 5% above the speed mode of the main mill, offering simpler, more economic and reliable operation than the old fluid coupling based limiter.

Wyko also designed the cabinets as two identical main panels, with a central panel being used for attaching the main power cables into the system to facilitate initial installation by the Graham Perry electrical engineers and power distribution to the DC drive panels.

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