Getting a Lift

Hubbell Industrial Controls, Archdale, N.C., has introduced a new magnet controller after a year of field testing with SMS Mill Services. Based on the company’s experience, the controller has demonstrated that it will reduce maintenance demands while enabling maximum efficiency and control during operation, even in high duty-cycle lifting applications.

READY FOR MARKET

Hubbell will manufacture the patent-pending e-mag controller for its originators, Control Services of Westmont, Ill. Alliance, Ohio-based Winkle Industries, Hubbell’s master distributor, will market the e-mag controller for use on all makes and models of mobile cranes in recycling and steel mill material handling applications.

Control Services’ John Samila says the e-mag DC generator controller takes a new approach to controlling power fluctuations inherent in the duty cycles and demands of lifting magnet applications.“The current generation of solid state DC magnet controllers are static controlled devices that are subject to speed and load variations that may negatively impact the magnet system efficiency,” says Samila.

These systems can be outmatched by the job, absorbing voltage spikes through sudden surges and dropoffs. “Our e-mag controller withstands and eliminates inherent magnet system problems by controlling the source, which is the generator,” Samila says.

The e-mag controls the flow coming out of the generator before it becomes an issue. In essence, the e-mag is designed to prevent failures by protecting the magnet system and controlling the generator output for optimum efficiency.

Samila says the e-mag controller is designed with a closed-loop circuit that responds to the generator’s demand for power and matches the output to the demand. The e-mag controller de-energizes the generator output when the magnet is not in use, preventing failures that can result from a power spike when the crane operator releases the load.

The e-mag design is intended for high-demand operations and is available for generator in the 5-kilowatt to 50-kilowatt range.

THE MOTHER OF INVENTION

As one of America’s largest producers of magnet controllers, Hubbell says it is familiar with magnet systems and the problems that inherently arise. Steve Loeck, Hubbell vice president of sales, reports that the need for a new solution became clear when a customer was attempting to commission a magnet system for a drop-ball application. “This was an incredibly rigorous application,” he recalls. “The drop-ball application required a near 100 percent duty cycle. The customer was attempting to operate the generator at the required1800 rpms and 230 volts, but the on/off cycling of the application requirements caused erratic rpm spikes in the generator that effectively raised the voltage of the generator above 300 volts or more,” he says. “The existing open loop magnet controller was not up to handling the spikes and the variations in generator rpms during the loading and unloading process.”

He continues, “With the e-mag, the generator loading and unloading voltage spikes are effectively removed and are no longer an issue. The e-mag controls the generator output and, as a result, when power is not required, the generator is no longer producing voltage. Therefore the generator is not affected by spikes and has a much more efficient cooling cycle.”

Often, traditional controllers also rely on the crane’s compensation valve to shield them from the impact of sudden surges and drops in hydraulic pressures. However, with the e-mag fluids can flow freely, even in cranes that aren’t equipped with a compensation valve, according to Hubbell.

By controlling the power to the generator output, the e-mag controller also allows greater flexibility in matching the magnet to the material it is handling, Hubbel says. The e-mag is designed to enable voltage control within the speed requirements of the generator. Power can be increased to the maximum for short periods without damaging the magnet, according to the company, and operators have equal control over the magnet’s drawdown time. For heavily saturated loads, such as steel slabs, the release time can be increased to as much as 14 seconds, Hubbel says.

With this added control, operators could configure their magnet system to pick up more material in less time and release it more efficiently. Combined with a high-duty-cycle magnet, the result could be more cycles, which can lead to more material being moved in every working shift.

PUT TO THE TEST

Units were installed on four Liebherr 954 material handlers at SMS Mill Services in Indiana in December 2008. SMS owner Rick Gertler reports that all four cranes are in operation around the clock and equipped with 72-inch and 78-inch magnets powered by 25-kilowatt or 30-kilwatt generators.

Gertler says he is pleased with the results. “We have had zero downtime with these units. By that I mean that, over the past 15 months, we have had no service or repairs to the controller, no servicing for the magnets, no problems with the generators.” Gertler continues, “As one of our long-time maintenance hands said, ‘I’ve never found a maintenance-free system like this.’” He adds, “I’m pretty sure we’re stretching the life of our generators, too.”

The four cranes handle a varied mix of material: steel slabs, billets, bushelings, bales and slag. Gertler reports that, with the e-mag controller, the magnets are moving their loads faster and more efficiently.

Each magnet is fitted with a scale to ensure the accuracy of the material going into the customer’s melt mix. Gertler says the cranes have no trouble lifting their loads, with no bogging down on the pick, and no material falling off through the carry. “With the old controllers,” he says, “we would just run out of generator. Now we can run right up to the material and pick the load easily.”

Gertler is convinced enough that he plans to include the e-mag controllers in future upgrades to the rest of his crane fleet in Burnham, Ill. “It’s simpler. In this work, simpler is what you need.”

EASY INSTALLATION, LOWER COST OPERATION

Joe Schatz, president of Winkle Industries, says he expects to see e-mag controllers taking a prominent place in his future business with mobile crane customers.

“Those four units at SMS Mill Services were installed in 16 hours total—just 4 hours each. Installing a conventional controller easily takes a 9-hour day each, with two technicians on the job,” Schatz says. “The whole system is surprisingly simple.”

He continues, “The e-mag makes setup and troubleshooting dead easy, too. Everything is easily accessible. If there’s an issue, you’ll know right where to look. And in the long run, with no spiking or overheating, our magnets are going to stay in service much longer, too. Heat is the worst enemy of magnet coils and generators. Customers will really get the most service life and most productivity out of all the equipment in their magnet systems with the use of the e-mag. It’s a very cool concept, in more ways than one.”

Schatz says he believes that, by improving the control of the system’s power profile, e-mag controllers will allow cranes to use smaller generators to power their magnets. “You’re able to run up the voltage for short periods to get extra power out of the generator when you need it. But then the generator gets a chance to cool off through the release cycle, whereas other controllers don’t give you this flexibility.”