How a 24.5 MW Compressor Motor Guarantees Production in the Petrochemical Industry

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TURCK GmbH

EDL Anlagenbau Gesellschaft mbH

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Siemens AG

Special Requirements

Direct starting is unusual for such a large motor. It takes a large amount of energy from the electrical grid and the voltage drop is higher than that normally permitted; in fact, permission is required from Vattenfall before it can be started.

“We also have to inform neighboring industries before we start,” says Samu Salo.

The motor’s external features were also specially adapted. “Normally, the motor is manufactured and the foundations are built afterwards. As we already had the foundations, the motor was manufactured accordingly,” explains Jörgen Wrennfors, Sales Manager for process automation at Siemens.

The motor was dimensioned according to the surface it would be mounted on. Borealis sent drawings to Berlin, and a customized solution was produced jointly, which involved the motor being embedded in the concrete foundations. As the motor is longer than its predecessor, the terminal box was also adapted and made almost a meter longer.

Technically Advanced

The titanium coolers that cool the motor using salt water are redundant. This means that back-flushing can be carried out with the plant in full operation. In terms of vibration, the motor has been adapted to the API standard (American Petroleum Institute) and has an explosion-proof design. It is pressurized so that no gas can enter the inside of the motor. A 15 percent increase in capacity has been built into the motor.

“There aren’t many companies in the world that can manufacture such a large and technically advanced motor,” says Samu Salo.

“Few people understand how complex it is. Lowering the short-circuit output to start the motor goes against all principles. You have to think outside the box,” says Tobias Andersson, who performed many grid voltage calculations and had lots of discussions with grid experts in order to draw up the right specifications for Siemens in Berlin.

“There are certain network preconditions, which means that you have to calculate what will happen when starting and stopping. The starting current imposes a load on the grid so that the voltage dips, and this in turn causes a drop in torque which is proportional to the square of the voltage drop. Sometimes, there will be a lower short-circuit output, sometimes higher. In addition to electrical issues, the mechanical situation must also be carefully taken into account,” states Tobias Andersson.

“Siemens has the know-how and experience that is needed. We have done this in order to guarantee availability. It is all about increasing productivity and guaranteeing production. We’re very pleased with the motor that Siemens has designed and built for us,” explains Samu Salo.

* The author works with Siemens AG Industry Sector, Industry Automation Division in Upplands, Väsby/Sweden

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