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Granada’s partnership with Siemens: a new foundation davit that meets the offshore challenge.

Challenging conditions exist for servicing offshore wind turbines
Challenging conditions exist for servicing offshore wind turbines

With a complete focus on safety, reliability and efficiency, and the result of over two years’ development and partnership with Siemens, Granada Material Handling offers world-leading technology for the offshore wind turbine sector.

There are few applications as demanding as offshore work, and wind turbine servicing is a rapidly growing area with its own unique set of challenges. Lifting heavy equipment from a boat to a stationary platform is tricky, to say the least. One rogue wave and everything being lifted could crash through the boat deck, endangering lives at sea.

As a leading specialist in offshore lift equipment, Granada continually reviews options and developments for the wind turbine sector. Finding Siemens to be the perfect partner for its demanding sea operations serving the growing number of offshore wind turbines around the UK coast, Granada decided on a redesign from the ground up, to provide customers with a tailor-made solution.

The resulting Granada foundation davit sits on a wind turbine platform, part-way up at the base of the blade tips, on the access platform which is permanently in place. The crucial factor is that the unit, when lifting loads varying from maintenance kits to tool bags, must align itself to the position of the boat, which is semi-moored to the turbine base, and must not allow the load being lifted to lower back into the moving boat deck at any point in the unloading process – especially if the boat breaks free from its moorings for any reason.

This is a tremendous challenge for any lifting and handling equipment, and requires an extremely fast accelerator on the hoist. Siemens reviewed the complete drive train for this transition piece davit along with their Solutions Partner Iconsys, to provide the ideal solution for Granada. The resulting hoist can handle up to 1 tonne of load and features an IE2 Siemens Simogear 4kW geared motor with output speed of 19.8 rpm and gear ratio of 73,640:1.

Additional challenges included the fact that the unit is permanently in place, at the mercy of corrosive sea water 24 hours a day, so many exposed components had to be specially manufactured and protected. Special stainless steel shafts, stub shafts, encoder torque arm and pressure breathers were specified, along with additional protection and enclosures for components such as the IP66 brake environment, the motor’s non-output side, gear shafts and all seals. The unique hinge design of all Granada foundation davits – which have a patent pending – means that all parts can be maintained from deck level, avoiding the need for operators to work at height.

Control system’s challenging environment

Iconsys designed and built the control system for the davit, using the Siemens Sinamics G120, PM240 Power Module with built-in brake chopper and CU250S-2 PN control unit with integrated safety and ProfiNet communications.

The design of the control system for the project was split into two elements: the main drive panel, housed within the structure of the turbine tower, and an IP66 warning board fitted to the side of the davit crane and located outside the tower in a harsh marine environment. The warning board includes an emergency stop button, siren, three-lamp LED tower and plug connector for a removable operator pendant. The pendant was designed with a 12-metre flexible cable, to be removed and stored when not in use.

Space in an offshore turbine tower is always tight so the main drive panel had to be very compact. For the crane control, in-built digital and analogue IO on the control unit meant a separate PLC was not required. This controller is the latest generation of hardware for the Sinamics G120 and now includes an encoder input feature which was critical to the over-speed safety requirements of the system. A Siemens Sirius safety relay was also incorporated for the safe brake relay. All Siemens components were designed to work together to optimise performance, maximise safety and reliability, and minimise maintenance requirements.

Ensuring that all drive train components are perfectly matched to the application and loading requirements, Siemens integrated drive systems (IDS) ensure reliability and efficiency throughout the product lifecycle, plus planned maintenance and significant long-term savings.

For the Granada foundation davit, extra safety features were built in by Iconsys. During the lowering process regenerative power is generated by the load. This excess energy is dissipated into a specially designed marine resistor. The resistor element is to marine standard and housed in a purpose-built marine-grade stainless cover with mesh surround to prevent direct contact with wet clothing or operators‘ hands. Another key feature of the system was a separate supply to accommodate anti-condensation protection on the motor and a motor limit switch utilising a second isolated 110v AC supply.

On time delivery with the highest quality control was critical, and Granada selected Iconsys partly for the ISO 9001 quality management systems it adhered to for the design and manufacturing processes, in house testing and shop-floor facilities. Third party technical verification underwriting the performance of this third generation foundation davit gives Granada, and their customers, a significant advantage.

Minimising risk at all levels

Working with Granada for over two years, Siemens account manager Nathan Adams commented: “With such a challenging environment, Granada Material Handling needed the reassurance of a fully integrated system that works perfectly under all conditions. With the Siemens integrated drive system and high level of quality assured products and systems we were able to provide this.”

Inherent in Granada’s philosophy is competitive pricing, based on simple maintenance regimes and robust, long-life solutions that are safe and operator-friendly. Mark Sidwell, Granada’s Sales Director, confirmed this and added: ”Key to our decision-making was the ready availability of world-leading drives from Congleton and geared motors from Leeds. We also liked the integration and quality assured aspects of this world-leading technology, which has helped us grow our business exponentially.”

The Granada foundation davit in operation on an offshore wind turbine
The Granada foundation davit in operation on an offshore wind turbine
The Iconsys designed control system for the new Granada davit crane
The Iconsys designed control system for the new Granada davit crane