Alcoa Germany depends on CT modular drives

All three massive aluminium extrusion presses at Alcoa in Hannover now depend on variable speed drives from Control Techniques, and have cut energy consumption by a huge 40%!

The cut in energy consumption saves Alcoa thousands of kilowatt hours of energy every year: in addition the Control Techniques variable speed drives have dramatically increased production time availability, increasing throughput by 10% and decreasing maintenance costs!.

The two biggest extrusion lines, both using the indirect extrusion process, accept billets of aluminium alloy at around 265mm and 412mm diameter and lengths between 400 and 1350mm, pre-heated to between 300 and 550C.

These billets are then extruded through two high pressure extruding presses at 56MN and 33MN respectively.

Both extruders are hydraulically-powered, with the oil pressure being generated by pumps controlled by Control Techniques AC drives.

The big press line was upgraded in 1998, a big project requiring the installation of 12 off 132kW Unidrives (for 12 pumps), to produce the required maximum pressure of 315Bar.

In January this year, the 33MN line was similarly upgraded with variable speed drives, this time the drives chosen were six 160kW Unidrive SPM modular drives, producing an oil pressure of 250Bar.

The operation runs around the clock, 365 days a year and so the latest installation was carried out with the line in full operation.

"In both cases, the savings are considerable," explains Herr Stefan Heine, who has responsibility for technical operations and purchasing at the Alcoa plant: "The original hydraulic plant was designed to give the required thrust with additional oil being sent through a by-pass - so effectively the pumps were running at full speed all the time.

Now Control Techniques variable speed drives integrate with the hydraulic controller using Profibus and give exactly the required power at every stage of the operation.

Not only does this save some 40% of the power, but also gives better control, giving improved quality of extrusion.

But this is just part of the story.

Because the plant (the valves, pumps, pipes and seals) is less stressed, equipment is less susceptible to breakdown and I believe that our throughout has increased by around 10% because of reduced downtime.

The oil lasts longer too - a not inconsiderable saving when you consider that the machine incorporates some 15,000 litres of oil and 6,000 litres passes through the system during each extrusion (this is then cleaned and returned)".

The savings run to thousands of Euros per year and have given Alcoa a payback of less than 18 months.

The Unidrive SPM range spans 90 kW to 1.9 MW and comprises very compact and innovative input and output modules that enable flexible power configurations to be achieved.

Multiple systems such as at Alcoa are mounted on an interconnected DC bus that allows circulation of energy between drives that are motoring and regenerating and also allows regenerated energy to be returned to the mains.

Drives can share braking duty and the whole installation requires a single AC power supply, simplifying installation.

The 38 MN extrusion press produces some 800-900 tonnes of aluminium extrusions per month, in a wide range of profiles including stars and tube down to less than10mm with wall thicknesses down to 2mm.

Single extrusions can be as long as 45metres in length and the fastest extrusion rate is 15metres per minute.

Each billet is ultrasound tested and carefully heated to a point just below its 'plastic' state, this depending on the exact composition of the alloy, so that, during the high pressure extrusion process, the pressure takes the material up to the required plastic state, but no further, in order to maintain the structural integrity of the material.

Every extrusion is stretched, cut-to-size, 'aged' in an aging furnace, then tested for hardness, tensile strength and conductivity as well as passing through three-co-ordinate measurement testing before being passed for delivery.

The Alcoa plant is now using 100% of Control Techniques drives - including conveyors, fans, pumps, pullers, cut-to-length machines, run-out tables and many more.

"We particularly like the new modular Unidrive SPM drives", comments Herr Heine: "They are extremely compact and easily fitted into our plant room.

We like the Unidrive SP range generally and routinely use SmartCards to speed up the setting of parameters when we install a new drive.

Most of the drives in our plant are connected by Profibus to the factory management system.

Over the 12 years that we have used Control Techniques drives, we have found them to be extremely stable and reliable and we get excellent service from the Drive Centre in Hennef".

Alcoa Hannover produces medium and high strength alloys primarily for the aerospace and automotive markets.

Alcoa high-strength alloys are playing a key role in the future of aircraft construction and the plant also produces safety parts for automotive brakes and chassis, and sections for engine components, using materials with high temperature stability.

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