MOTORS & DRIVES


because the hydraulic motor is directly connected to the churn shaft. It’s a hundred times better.”


A hidden process issue brought to light In fact, switching to a direct drive solution revealed an issue that Futamura had not previously been aware of. After the first Hägglunds drive was installed, the churn began stalling when the vacuum was applied.


“We didn’t see this with the electromechanical systems, because the gearboxes hid the problem,” says Asbridge. “But cross-checking the motor load showed that this had been happening all the time. With the hydraulics, because there’s no gearbox in between, the spike change is significantly bigger.”


Once the issue was apparent, it was easily resolved through the flexibility of the control system. The drive now automatically stops, ramps down, restarts and ramps up, which usually provides the torque to overcome the problem. Operator intervention is only required after a third stall.


to the size of the drive. “It’s a massive change,” he says. “Compared to the electromechanical solution, the Hägglunds option is around a 60% saving on space.”


Yet Asbridge is even more impressed by the noise level. “The Hägglunds motors are so silent!” he exclaims. “Two of the churns are in their own room, and when we first replaced those drives we weren’t even sure if the churns were running. It’s phenomenal how quiet they are. The noisiest thing in there now is the ventilation.”


Most importantly, Asbridge notes, the solution is a good match for the process. “The way the Hägglunds system operates is perfect for what we required,” he says.


Gentler and faster churn handling Among the improvements with the Hägglunds drives is the stepless adjustable speed. Although Futamura runs its churns at fixed speeds, the variable speed is used to ramp the drive up or down, rather than starting and stopping the churn abruptly.


“Effectively, this is like a big paddle mixer inside a vessel,” Green explains. “Being able to start and slowly increase the rotation increases longevity of the paddle, the shafts, the coupling –


20 everything.”


“Ramping is kinder to the churn itself,” Asbridge agrees, “and there are parts of the cycle where we don’t have to stop now. Previously we had to stop the motor, wait, allow the changeover of the gearbox, then restart. Now we don’t have to stop the electric motor at all. We just ramp the pump down to zero, change the speed and then ramp it back up again. So it’s reduced the time for speed changes a lot, and any time we can save is very useful.”


Certainty means greater safety Safety has also improved with the Hägglunds solution, especially at the point when alkalized crumb is added to the churn. To prevent the creation of other hazardous areas down the line, operators need to know that enough crumb has been added.


“Previously we checked the level by monitoring the load on the electric motor, but the losses from the gearbox and couplings meant the difference was just a few amps and difficult to see,” Asbridge says. “Now we monitor the hydraulic pressure, and there’s a distinct change – around 35 bar of pressure for an empty churn, and around 100 bar when it’s full. You see that change


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“The drive has improved our understanding of what’s actually taking place in the process,” says Green.


Clearly part of Futurama’s future As Futamura nears the implementation of all ten Hägglunds drive systems, the two engineers are very pleased – not only with the results but also with the process.


“The collaboration with the Hägglunds team is very good,” says Green. “The person who comes on site to do the installation and commissioning is the same one who handles the ongoing maintenance, so we have a close relationship already.”


If anything, the two would like to see even more Hägglunds systems on site. “There are other places where we’ve got legacy electromechanical systems and old gearboxes,” says Asbridge. “From my point of view, I’d like to install Hägglunds drives anywhere we can think of!”


“I have to concur with Shaun,” says Green. “There are a lot of applications where Hägglunds solutions could help us.”


Liselotte.Strandberg@boschrexroth.se www.boschrexroth.se


Enquiry No. 20


INDUSTRIAL PROCESS REVIEW


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