Friday, January 30, 2009

Rosyth prepares for Royal Navy supercarriers

Rosyth prepares for Royal Navy supercarriers
An Equipment and Logistics news article
30 January, 2009

The Royal Navy's two new aircraft carriers will be assembled at Rosyth on Scotland's east coast in the next decade. Work is already well underway to make sure the dockyard is ready. Report by Steve Moore.

If you see huge sections of warship on barges inching their way up the UK coast in a few years' time, chances are they are on their way to Rosyth. Work is underway to prepare the Firth of Forth yard's No 1 dock - originally built in 1916 - to accommodate the two massive 65,000 tonne aicraft carriers to be in service in the next decade.

The yard contains the largest non-tidal basin for ship repair in the UK and Babcock Marine is working to increase the capacity of the dock, as well as widening the entrance to allow entry of the parts and departure of the 280-metre long, 56-metre high carriers. A £15m 120-metre span crane - nicknamed Goliath - is also being installed to straddle the dock.

Up to 150 staff from BAM Nuttall are doing the engineering in a £35m contract with Babcock on behalf of the Aircraft Carrier Alliance, which also includes BVT Surface Fleet, Thales UK, BAE Systems and MOD's Defence Equipment and Support (DE&S) as both participant and client. There are workers from around 50 other sub-contractors also working on site.

Work on No 1 dock began last March and is set to be completed by summer 2010:

"The project is in full swing and on schedule," said Sean Donaldson, Babcock's carrier project director at Rosyth. "The first parts of the first carrier will arrive in the summer of 2011, so we are not going to be short of things to do in the next few years."

Staff at Rosyth have been preparing for the work for at least two years:

"The work presents some challenges because it is related to old structures and, as the majority is below ground and in a marine environment, the project has significant risks," said Mr Donaldson. "We have spent two years on site investigations and de-risking activity to get to this stage. But working with the MOD we knew that investing the money up front would save us much in the long term."

The first carrier should be in dock for between 18 and 24 months. Assembly of the second will begin soon afterwards. It is a complex logistical process:

"It is a joint team doing the integration, led by BVT, to make sure all the pieces of the puzzle do fit together," said Mr Donaldson. "It is a very challenging timeline but it is in all our interests to make sure everyone comes together. We are all incentivised to work together to complete the project.

"We were refitting nuclear submarines at Rosyth until 2001 and they were massively complex projects. We have also refitted each of the current aircraft carriers. But we are certainly not complacent. We have had a team in place, three years ahead, to make sure we can complete this task."

"The Goliath crane will rest on two uprights either side of the dock and will be a towering icon of engineering endeavour and industrial capability."
Director Capital Ships, Tony Graham

The dock is long enough to accommodate each vessel but its cross- section is unsuitable for modern warship building, the ship's hull being flat-bottomed rather than the traditional V-shape. Huge granite steps, known as altars, that stick out from the side of the dock are being cut back to the width of the top tier. The dock floor will be nine metres wider when they have been removed.

Work is now underway to widen the main entrance to the Rosyth basin from the Firth of Forth. The 38-metre-wide entrance features a sliding gate to hold the tidal water back but is soon to be increased to 42 metres. A 25-metre-deep wall will be installed behind the existing entrance wall to allow excavation work, with the void filled with concrete. This will allow the existing entrance wall to be demolished before the final face of the new entrance is installed. Goliath is due to arrive in August 2010 with handover soon after.

Built by Shanghai Zhenhua Port Machinery, the 68-metre gantry crane to straddle the dock will be able to lift up to 1,000 tonnes from three hooks, two suspended from an upper trolley and one from a central, lower trolley which will have a capacity of 500 tonnes.

The individual capacity of each of the three hooks provides valuable flexibility in lifting awkward loads and will allow units or blocks to be turned over. Nearly 90 reinforced concrete bored piles are being socketed three metres into the underlying rock on the eastern side of the dock as foundations for the crane, with further piles driven up to seven metres into rock on the western side.

The crane will arrive partially erected through the newly-widened dockyard entrance and will be 'skidded' from ship to shore onto the crane rails. DE&S visitors to the dockyard to see the progress Babcock are making have included the Director Capital Ships, Tony Graham, who saw the works in the autumn:

"This is an exciting time for the CVF [future carrier] project as, around the UK, we make final preparations for cutting of steel on the ships in early 2009," he said. "For stability, the Goliath crane will rest on two uprights either side of the dock and will be a towering icon of engineering endeavour and industrial capability.

"In this sense, it parallels an ever-ready and world-class carrier strike capability, resting as it does on the two iconic ships - HMS Queen Elizabeth and HMS Prince of Wales - lifting the Royal Navy into a new modern age."

Dam marks big milestone

A major milestone has already passed at Rosyth's No 1 dock with the completion of a cofferdam, a huge enclosure of steel and rock-fill extending 14 metres from the basin floor to dockside level. The cofferdam creates a dry working environment where the civil contractor can work.

Five circular steel 18.5-metre-diameter cells have been built to sit on the bed of the main basin and then filled in with thousands of tonnes of imported rock. It is the biggest cofferdam of this type built for many years:

"Modifying a dock in a marine environment like this is not easy," said Babcock civil engineer Mike Murray. "The design and installation of the temporary works needed to hold back the water during the construction period can be very challenging.

"The No 1 dock cofferdam alone weighs more than 50,000 tonnes and has to resist around 8,000 tonnes of thrust imposed by the retained water in the basin. It has to be buildable and sealable. Sealing is the craft bit and the difficulty is making the seal at the basin bed.

"We are on time. The No 1 dock cofferdam was constructed in six weeks and is working well," he added.

When work on No 1 dock has finished the cofferdam will be removed and installed at the basin entrance along with another bespoke structure on the river-side to allow the entrance to be widened.

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