Focus on upgrade and retrofit of hydraulic systems

Following the demands of their customers to work with increased cable lengths, Blue Offshore, a rental company for specialized cable laying equipment, decided to upgrade the capacity of its existing equipment. Bosch Rexroth from Boxtel was approached, to increase the pulling force of the hydraulic cable tensioner and to upgrade and modernize the complete hydraulic installation.

"This was a challenging and evenly exciting job," says Remco Buskens, Sales Engineer Specialized Services at Bosch Rexroth. "The complete installation of Blue Offshore is based on hydraulic drive and control technology, and was thoroughly checked, serviced, modernized and upgraded. The subsea cables are stored in huge basket carousels for offshore installation, driven by hydraulic motors. Also the two rubber tensioner tracks that accurately guide the cables, are adjusted relatively to each other by means of hydraulic cylinders. To store an increased amount of cable, the height of the basket carousel had to be increased. The ‘cable guidance device’ in between the basket carousel and the tensioner is tilted by a hydraulic cylinder, as the angle of the cable changes when the amount of cable on the storage wheel in- or decreases. Powered by a dedicated 37kW hydraulic power unit, this complete installation can be defined as a stand-alone unit.

Efficient service operations

“One way of getting such jobs done is to fully replace all old components with new ones” says Buskens about the extensive service project. “But it is far more cost efficient for our customer, to clean and repair as many hydraulic components as possible. Only those parts that had to be replaced were replaced, others have been brought back in their original state by our service engineers. To do so, we worked closely together with both our experienced team in Zwijndrecht and the technical engineers from Blue Offshore, with whom for example the revised manifolds have been thoroughly discussed.”

Increased pulling force

The increased cable length that is stored in the basket carousel will add up to an astounding 80 kilometers. To handle the bigger forces resulting from this increased size and weight of the basket carousel, the tensioner equipment was modernized and provided with a double set of revised hydraulic cylinders and new Hägglunds hydraulic motors, which are able to generate high torques at low rotations. “By applying these powerful motors from the Rexroth portfolio and replacing all hydraulic piping and hoses, we were able to increase the pulling force of the tensioner from 5 up to 10 tons!” Remco Buskens added. “As these ships mostly operate in demanding marine environments, reliability of the equipment is a very important issue. The hydraulic HPU that powers the compact Hägglunds motors of the tensioner, includes a highly reliable control and monitoring system, providing Blue Offshore with solid insights about the condition of the hydraulic equipment.”

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