180 tonne transformer’s incredible journey

ABB supergrid transformer completes the ‘incredible journey’ to National Grid’s West London substation

Delivery of the 180 tonne 400/66 kV transformer from the factory in Sweden to the Lodge Road/St John’s Wood substation in West London was one of the most complex and demanding heavy moving tasks ever undertaken by ABB

A massive new 400/66 kV ABB supergrid transformer, weighing 180 tonnes, has recently been delivered to National Grid’s 400kV Lodge Road/St John’s Wood substation as part of National Grid’s ongoing programme to reinforce the power grid serving the London area. The delivery of the transformer, by rail, sea and road, from the factory in Ludvika, Sweden to the site in West London was so complex and challenging that it became known in ABB as ‘the incredible journey’.

Detailed planning for the delivery, carried out by ALE (Abnormal Load Engineering) the heavy transportation specialist, began more than 18 months before the transformer was due to arrive at site, as Tom Smith, ABB project manager explains: “Delivery of any large transformer within London is always a complex exercise with many factors to be considered, not least the need to seek approval and cooperation from a host of bodies such as the police, shipping agents, the Highways Agency, Local Authorities and TFL (Transport for London). However, there were a number of additional factors that made this really out of the ordinary.

“To start with, although stripped of all its accessories the transformer was still very large – measuring 8.5 x 4.5 x 4.8 metres – and even using ALE’s girder frame trailer that enabled it to be carried at a very low height above the road, the clearance at two bridges on the route was marginal, at just a few centimetres. Next there was the 250 tonne combined weight of the trailer and transformer which was clearly going to be too heavy for the existing elevated roadway on the site using normal means. This required a detailed site survey to determine the maximum safe load, followed by remedial and reinforcing works on the site, as well as the need to use a 14 axle rig to spread the load. Then there was the tight nature of the substation site, in a busy urban area, that called for the 66 metre long trailer and tractor combination to negotiate a tight dog-leg turn, crawling through the gates a few centimetres at a time with no margin for error.”

Even after solving the significant logistical and engineering problems, and carrying out a successful dry run with a fully assembled rig to prove that the planned approach would work, fate threw up another challenge – the delivery had to take place on the weekend of July 7/8. This was one of the busiest traffic weekends of the year in the Capital with the British stage of the Tour de France, the Live Earth event at Wembley and the British Grand Prix not far away at Silverstone. It was though, ‘then or never’, as major roadworks planned on the M25 would otherwise delay the delivery for months.

From rail to ship to road
The transformer began its incredible journey by rail from the ABB factory at Ludvika, Sweden to the port of Vasteras, where it was loaded on to the MV Saturn, arriving at Tilbury in early July. As an example of ABB’s attention to detail at every stage of the delivery, engineers met with the transformer at the docks to carry out accelerometer tests to monitor any potentially damaging shock loads resulting from high seas

From Tilbury, the transformer was moved by road to South Mimms service station on the M25. Then at midnight on Saturday July 7 ABB received clearance to begin the final journey into London along the route approved by the Highways Agency, who ensured that street furniture was removed temporarily where it might cause a problem, as well as clearing parked cars. Even though the route had been planned so carefully, some quick thinking was called for on the night as two recent accidents had damaged the crash barriers on a crucial elevated roundabout on the North Circular (A406). The concrete temporary bollards, combined with concerns regarding the bridge supports, prevented the convoy taking the normal approach, and it had to reverse the wrong way round the roundabout.

Transhipment
The convoy arrived at the substation gates at 3.00 am. A further three hours were then required as the trailer was manipulated with painstaking care and precision through the site to bring the transformer into position over the pre-prepared transhipment mat arrangement. Using a specially constructed Mega Lift, supported on a welded steel frame designed to spread the massive load over the existing piles in the lay-down area, the transformer was raised from its trailer, which was driven out of the way. It was then lowered on to an 8 row SPT (self propelled transport) that was used to manoeuvre it as far as possible into the transformer pen.

The next phase was to offload the transformer from the SPT and jack it down on to a PTFE skid system. This enabled the transformer to be skidded right into position, where it was aligned and jacked down on to its anti-vibration pads.

“This was probably the most complex and demanding transformer delivery exercise ever undertalen by ABB in the UK. So the successful completion of the incredible journey is highly satisfying for everyone involved” says Tom Smith. “It really is a tribute to the outstanding levels of logistical planning, coordination, teamwork, skill and determination shown by everyone involved. Not just in ABB and ALE, but also National Grid, the police and all the various authorities.



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