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Rubber compounder PTE finds peace of mind in Hägglunds direct drives

Bosch Rexroth AB, Linda Wallin
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With a capacity of 100,000 metric tons per year PTE is among Germany’s largest rubber compounders. For many years, the company has relied on Hägglunds direct drive systems which have become a valued part of its compounding operations.

Staying ahead through technology

Though its main operations are in Wittenberg, Germany, PTE is a global player in the rubber industry. The company serves customers not only in Europe, but also in North America, South America, India and Asia. These turn to PTE for 2500 active recipes, used in everything from high-performance tires to white goods.

“We try to keep pace with state-of-the-art equipment,” says Dr. Wolfgang Keil, Managing Director of PTE. “It’s part of giving good service in this industry, where products are tailored to a certain customer’s production. Each rubber customer has specific needs, which means we look for flexibility.”

In compounding, that flexibility is achieved through mixers and roll mills – and often through their drive systems. For the latter, PTE has frequently turned to Bosch Rexroth, supplier of Hägglunds hydraulic direct drives.

Favorable first impressions

When Dr. Keil joined PTE fourteen years ago, Hägglunds direct drives were already well established at the company. Though his previous experience had been mainly with electromechanical drive systems, Dr. Keil was quickly impressed by the direct drives’ unique advantages.

“Hydraulic drives save space because you can place the pumps anywhere and simply connect the hoses,” says Dr. Keil. “Since the pumps are isolated in their own cabinets, there are also clear advantages in terms of noise reduction.” He further notes the hydraulic motors, which mount directly on the driven shaft without an additional drive train.

But for Dr. Keil, the main advantage is obvious. “Of course safety is the most important,” he says.

Unmatched degrees of safety

Safety is the key reason why PTE has Hägglunds direct drives on every one of its roll mills: two mills each in eight mixing lines, for a total of 32 drives. “We have open roll mills,” says Dr. Keil, “and the Hägglunds drives offer us the best safety feature we can get.”

The feature he refers to is Bosch Rexroth’s quick-stop function, which opens the gap between the rolls and brings them to a full stop in down to 3° of rotation, depending on machine. “If we press the button, the rollers stop immediately,” Dr. Keil explains. “You can’t stop an electromechanical drive that fast. If something were to happen and an operator’s hand or arm were caught by the material – I don’t like to think what would happen.”

Optimizing one shaft at a time

Of course, safety is not the only advantage Dr. Keil sees in using Hägglunds direct drives on roll mills. “We use them not only for safety, but also because it’s easy to adjust the speed and friction,” he says. “Each mill roll can be driven independently.”

In fact, PTE has also experimented with this advantage on the internal mixer in line five. This mixer is of the tangential Banbury type, whereas PTE’s other mixers are intermeshing.

“After our experience with roll mills, we installed two Hägglunds direct drives on the tangential mixer, where they’ve been operating for five or six years,” Dr. Keil says. “We can drive both of the rotors independently, which offers something very new, especially on a Banbury mixer.”

Undisturbed production

With the drives on the Banbury mixer, PTE has a total of 34 Hägglunds direct drive systems at its Wittenberg facility. And according to Dr. Keil, everything is running smoothly. “We now have several generations of Hägglunds systems in operation,” he says, “and all of them do what they should.”

One reason, in his opinion, is the ruggedness of the drive motors themselves. “These are closed drives, so if you have a dusty environment like ours, it doesn’t matter,” Dr. Keil explains. “Fillers, carbon black, moisture, fumes – you don’t have to provide additional encapsulation against these things. It’s perfect.”

That leaves only routine maintenance, which Dr. Keil finds to be less than with electromechanical drive systems. “Our environment is not exactly gentle, but the drives stay in service under all types of conditions,” he says.

Confidence in the future

As PTE looks ahead to an increasingly global market, Dr. Keil foresees further cooperation with Bosch Rexroth, a global drive and control company. “Bosch Rexroth is a fine name and a big company,” he says. “We always work very well together, with open discussions and a good relationship.“For new projects we’re likely to choose Bosch Rexroth and the Hägglunds products again,” says Dr. Keil. “We’re so very used to them at PTE. There’s no question of it.”

Complete Hägglunds drive solution for roll mills
Complete Hägglunds drive solution for roll mills

Safety for rubber Roll Mills

Speed is the key to efficiency, but also to safety. Nothing in the rubber industry makes this clearer than a roll mill, where hands and arms are at constant risk. When a roll mill emergency occurs, every degree counts. The Quick-Stop function of our Hägglunds direct drive systems stops the rollers in down to 3° of rotation, depending on machine. This is faster than any other solution on the market - and much faster than the 57° required by current standards applicable to rubber industry safety . The difference is significant on an 84" roll mill. By today's European standard, the rollers have 340mm in which to stop. But with our Quick-Stop function, they travel down to less than 50mm.

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