Due to increasing safety requirements and stricter environmental regulations, the use of electric drive technology in the offshore sector is being discussed more and more.
Its higher precision and better dynamics and efficiency are convincing more and more users on the high seas. In cooperation with the industrial gear and gear motor suppliers
Bonfiglioli, offshore boom lattice boom cranes, have been put into operation by crane manufacturer Palfinger Marine with an innovative electric drive concept.
For steel lattice boom cranes with a reach of up to 57 m and a safe working load of 60 t, it was necessary to develop compact electric drives for the main winch and the tree winch. The steel lattice structure of the crane jib has specified the installation space strictly because, for safety reasons, nothing can protrude beyond the lattice structure.
At the same time, the size of the crane also dictated the rope thicknesses and lengths, and the dimensions of the drum. After calculating the necessary torques and motor power, it became clear that a simple electric drive could not meet the requirements within the available space. The design task was therefore to distribute the power over several engines, transferring the total torque to the winch drum.
Due to the tight space requirement, which requires a specific layout and is based on calculations within the given conditions, the drive of the cable winch, which operates the hook, has been based on four electric motors of size IEC 280, each weighing approximately 1.2 t split. The boom winch has two IEC 315 motors, each weighing 1.7 t. This took care of the entry side, but there was another design task – the effective placement and connection of the engines with the winch system.
Not only the transmission of the drive power should be considered, but also the size and the weight of the motors themselves. At about 2 m in length and at the said high weight for each engine, the special asynchronous motors are an important factor. In the load distribution of the drive, which is controlled electronically, and mechanical elements must be securely arranged.
The mechanical solution of Bonfiglioli consists of two components on both sides of the drum, a motor flange and an angle system that flows into the actual winch system. For the boom winch, the angle gear is designed so that it has a fail-safe brake for the emergency situations against the engine side. This has a significant impact on safety as the crane boom stays in place and does not sag even when the power is interrupted.
A bevel gear arrangement efficiently transfers the engine input torque to the planetary gear of the winch located in the winch drum. The winch itself is located at the crane tower and experiences only the rotational movements of the tower. When lubricating the angular gear, there should be no anomalies. An overriding control system ensures the synchronous operation of the drives on both sides of the winch.
The large winch drum with a width of approx. 2 m is mounted near the tower in the boom of the crane. The four winch drives are also located on both sides of the winch drum with two drives facing each other directly on each side. These motors are also mounted to a bevel gearbox with a motor flange. This transmits the power of the two motors, which are connected at right angles to the integrated in the winch drum planetary gear.
The specially designed drive components were implemented by engineers from Bonfiglioli, who have decades of experience in drive technology. In close cooperation with machine manufacturers, he develops and designs machine-specific solutions in a short time. After a wide range of tests tailored to the specific needs of the application, the product goes into series production and ensures reliable supply to customers.
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