The gearboxes driving game-changing subsea technology

Now in its final stages of testing and ready for launch onto the market this year, Macgregor’s fibre-rope subsea crane is set to deliver some of the most significant advances the offshore load handling market has seen in years. A retrofit modular system, developed by Macgregor and utilising fibre-rope tensioning technology perfected by Parkburn Precision Handling Systems, the patented capstan winch at the heart of the system is powered by Brevini^® Motion Systems gearboxes from Dana Inc.

Parkburn capstan winch powered by Brevini^® Motion Systems

Key benefits of fibre:

The advantages of fibre over steel wire in deep water are well-known. In brief: weighing almost nothing in the water means that, regardless of the length of rope paid out, nothing is added to the load experienced by the crane, meaning that a 150 SWL fibre-rope crane can lift loads at depths of 3,000 m that would require a 250 SWL wire-rope crane. 4,000 metres of 88 mm fibre rope weighs approximately 20 tonnes, compared to over 200 tonnes for the equivalent length of steel rope, also impacting on the speed of deployment and recovery.

However, replacing steel with fibre rope is not without its problems, particularly when using a conventional drum winch where lower spooling tension is normally achieved by the operation of two drums in parallel. Parkburn set about addressing the issues – the tension of soft fibre rope, disruption to an even wind and the frictional heat created as the rope tensions and relaxes – leading to the development of their patented deep water capstan traction device, driven by Brevini^® Motion Systems gearboxes.

The winch development:

Parkburn’s capstan winch consists of two drums, each with 16 interlocking fingers merged together, with precise offsets in both the vertical and horizontal plane, around the rotational centre line to form a cylinder that creates an elliptical, hellical rope path: the fibre rope transfers between the drums at top and bottom, dead centre, never leaving the winch. Merged into one unit, each winch drum has its own independent, dedicated motor and gearbox on their respective drive flanges and synchronised with a centre power shaft which runs through the core of the winch.

Gearbox specification:

Dana SAC UK were commissioned by Parkburn to specify the gearboxes integral to the successful development of the capstan winch technology and the team supplied units from Dana’s Brevini^® Motions Systems range, offering the features and advantages critical to the successful operation of the new system. Dana specified slewing drive type gearboxes with integrated output shaft and pinion, allowing for installation of the gearboxes directly into the gear wheel / slew, without the need for extra bearings. Eccentric output support with multiple oil level / drain ports allows for fine-tuning of the meshing between pinion and gear wheel / slew bearing by ±2mm by rotating in its mountings, while still always having a port located at or near horizontal for checking oil level, and a port at the bottom of the gearbox for draining the oil during maintenance. Backstop-equipped brakes allow the brakes to be driven through during the hoist without release. This reduces mechanical losses in the system and, in turn, reduces temperature rise – a key benefit, mindful of the temperature issues associated with fibre rope. When the crane comes to a stop, the brake is already engaged so there is no drop in load, thus improving safety.

Martin Terjesen, head of technical sales at Dana SAC UK comments,
“When Parkburn commissioned Dana for this project, we were delighted as it clearly had the potential to be a groundbreaking development for the offshore industry. As a sector where Dana (and, formerly, Brevini) have vast experience and expertise, it has proved very satisfying to be involved. We look forward to seeing the impact of this technology, and to further developing our relationship with Parkburn.”

The FibreTrac 1500 crane will be certified under DNVGL-ST-E407, a new standard for Deepwater Deployment and Recovery Systems.