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Walking on water


There aren't that many construction sites at sea but those there are need kit - and operators - that can brave some pretty appaling weather conditions. Emma Forrest talks to Seacore supervisor Tony Halliday about walking the high seas

OF ALL the items of plant available in the world, there cannot be that many that can walk on water. But to a geotechnical marine engineer, being able to stride out into the waves has something of an advantage.

This is where Cornwall-based Seacore's 150-tonne, eight-legged offshore platform, the Seawalker, comes in.

Supervisor Tony Halliday has been using the machine from its earliest development. The result of a £500,000 investment, sea trials on the Seawalker began in August 2000. One of the two people originally trained to operate the platform, Tony used the machine to work on the construction of a lifeboat platform off the coast at Cornwall's Sennan Cove in 2002.

'Most of my experience of the platform has been picked up on the job.

When we were testing Seawalker I was in the right place at the right time as they needed someone to co-ordinate sea trials, ' he says, modestly. 'I had experience of mining and management of rigs. Now, although I am not the only person who has used it, I have spent the most time on it.'

With the ability to operate in depths of up to 30 m and based on a rig originally developed in 1994, the Seawalker is equipped with four jacking legs attached to a sliding frame that can be raised and lowered at fixed points. Two other moveable pairs of jacking legs are to be found either side of the platform.

Once in position, the four main legs are jacked to the seabed to lift the platform clear of the water. The two sliding frames are then jacked forward and the legs dropped to support the platform, after which the main legs are retracted from the sea bottom and the entire platform jacked forward through the side frames.

Mr Halliday, whose background is in geology, has been with the firm since 1983 and now largely supervises Seacore's drilling activities on anything from site investigations to pile installation. He says the platform operates 'surprisingly smoothly'.

At 1.4 m a step, the machine can cover 40 metres an hour. By contrast, the first prototype managed only 25 m an hour.

'The platform proved itself at Sennen, ' says Mr Halliday. 'It can get into areas that other pieces of kit can't and it can work in quite heavy surf. You just have to make sure that you are not lifting the legs too far while walking it.

'I'm still learning on it and there is a lot to be learned from the maintenance programme - the walking system needs a lot of attention.'

Seawalker is now in South Africa for sea mining trials, where it has been on site for a year.

'Its potential is huge. It is such an innovative machine that it needs a client brave enough to take the step to use it.

But every time someone new hears about it, they think of new application. I feel very proud to have been involved with this machine. If another job cropped up I would love to go with it, ' says Tony.


Weight: 150 tonnes

Speed: 40 m/hr

Deck area: 12 m x 12 m

Do you drive a machine we should know about? Email Emma Forrest at: emma. forrest@construct.