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Case Study

Creating a complex rotational test rig for a new tidal turbine – in less than three months!

Tidal Generation Ltd approached Armada with an urgent challenge. They had built a prototype of a new 500kW tidal turbine which was ready for deployment to a test site in Orkney. However, delays in the construction of the subsea foundations meant that they had a four-month window of opportunity during which they wanted to carry out some valuable land-based rotational testing.

The maximum speed of rotation required would be 20 rpm. This would demand an input power requirement of 380 kW from the hydraulic power unit.

Tidal Generation had already made inquiries with their existing contacts but had been told that building a test rig of this kind would not be possible within the time available, that the lead time for building the hydraulic equipment required was around 16 weeks, and that the hydraulic power units needed were not readily available either. Tidal’s engineers were aware of Armada’s expertise in this field and made contact in the hope that we might be able to crack this daunting problem.

The Armada team immediately got in touch with their contacts at Bosch Rexroth Ltd. They were able to source a Hagglunds CB560 radial piston motor from America and two Rexroth A4V closed circuit pumps to drive it. Armada used their strong relationship with the company to persuade them to commit to delivery within six weeks. Within two weeks of taking the call from Tidal, Armada had prepared proposals for three alternative solutions to their problem, each with detailed budget costs, and all achievable within the extremely tight timeframe.

At the beginning of April, Tidal selected their preferred option and placed an order for the rig, which needed to be delivered to Orkney by 6th June. This meant that Armada had only eight weeks to complete the detailed design, build the hydraulic power unit and the flange adaptor to connect the Hagglunds motor to the turbine rotor, house all this equipment and its control systems in a 20 foot shipping container, and carry out all the necessary factory testing prior to delivery.

The rig was completed and tested by 30th May, delivered to Orkney on 2nd June and set up on site by the Armada team. On 5th June, the rig was rotated under hydraulic power for the first time – right on schedule!

Armada Engineering’s Managing Director, Joff Collins, says:

“This was a great example of how we used our international contacts and our specialist expertise to deliver a solution to a problem which other suppliers believed was impossible to achieve with the required timeframe.

“Despite the fact that we had to move at an incredible pace, we ensured that every part of the system was planned and designed with extreme care and attention to detail. For instance, the control system had to be capable of varying the flow and pressure steplessly from 0% to 100%. We achieved this by the use of electro-hydraulic proportional control of the pump swash plates and of their pressure compensators.

“To make operation easier for the Tidal team, a remote control panel was provided which was installed in the site control room. We also built in the facility for the hydraulic pump unit to be controlled by an outside computer system. Our engineers assembled all of the test rig equipment on site.

“Tidal Generation were delighted with the solution that we provided and how it performed. As a result of Armada meeting their challenging deadline, Tidal’s engineers were able to carry out a full two-month test programme. This meant that they could resolve a wide range of initial technical problems. This resulted in vital cost savings for their team while also ensuring that they achieved the optimum performance and maximised the return on their investment in this new turbine.”

Following this rigorous testing programme, the new turbine was successfully deployed. Within its first 18 months of operation, it had delivered over 200MWh into the grid.