At 137 metres tall and 2872 metres long, the Queen Elizabeth II toll bridge in Dartford is the second biggest cable-stayed road bridge in Britain – behind the Severn Crossing. It provides a vital link between the Northern and Southern sections of the M25 across the River Thames and if it were to shut a large part of London and the UK economy would quite literally come to a standstill.
As with any large structure or building the bridge needs regular cleaning and maintenance – sometimes even a full overhaul of its operating systems. This was indeed the case when the bridge’s existing aviation lighting reached its end of life and needed bringing into line with new Civil Aviation legislation.
Here Comes Delta
Industrial lighting solutions specialist, the Oldham-based Delta Group, is a world leader in developing and installing bespoke aircraft warning light systems. Its subsidiary company Delta Obstruction Lighting (DOL) was invited to tender by the QEII’s controlling authority in August 2008 and was awarded the contract in September 2008 to design, manufacture and install a system that went above and beyond Civil Aviation requirements.
DOL Managing Director, Tariq Mukhtar said: “We were delighted to be awarded the QEII job because it was a mark of how far we’ve come and of what we are capable of. From design to installation there have been many challenges but at each stage our talented workforce has adapted well, providing a product and a service that is second to none.”
DOL’s brief was to design, manufacture and install a lighting system that was compatible with the bridge’s remote-controlled SCADA (Supervisory Control and Data Acquisition) framework with six lights at each fixing point lasting at least 100,000 hours. DOL assigned itself the designing and manufacturing phases with sister company Delta International Steeplejacks (DSJ) commissioned for the installation.
Working on the QEII Bridge
Far from being the highest structure Delta has worked on, the QEII Bridge has certainly been one of its most challenging with one of the world’s busiest shipping lanes running under it, Britain’s busiest motorway running over it and one of Europe’s busiest flightpaths passing directly above it.
From the signing of the contract right through to the job being signed off, challenges were a plenty. Delta departments including design, manufacturing, logistics and installation were all effectively called into action at various stages in the process, demonstrating the company’s unrivalled ability to adapt to a project’s changing needs.
DOL’s initial scouting mission illustrated this perfectly. The original brief was to provide a single duty light at each fixing point but DOL’s design team’s proposal to incorporate both duty and standby at each fixing point was eagerly accepted by the bridge’s contractors.
Their initial plan was to fix two LED lights side-by-side but on viewing the fixing points they discovered one light would block out the glare from the other. They also realised that red lights carry major significance to shipping so, in order to prevent a potential disaster, it was imperative that no glare could be seen by ships passing underneath the bridge.
At first they considered sitting the duty light on top of the standby but that would have taken 10 weeks to develop and they only had two. Their ingenious solution was to design a single light where both LED lights sat within one casing unit. The shipping issue was overcome by reflecting the light so the red glare was directed to the side and upwards.
Once finalised, the design was submitted for production and thanks to the state of the art manufacturing facilities at Delta’s Wrigley street factory in Oldham – the Dual WL2500 (duty and standby) Medium Intensity Aviation Obstruction Light was born.
“At our factory we have the ability to adapt to design changes extremely quickly, an area in which our competitors struggle. We managed to turn the WL2500 around very quickly and are very proud of the finished product. To my knowledge, this product has not been developed before anywhere in the world, it’s an industry first.” said Tariq.
With the product designed and manufactured and logistics in place, a DSJ team headed down to London in late December to implement the job’s final phase. Deadlines were tight. The initial installation – one light at mid level on each of the four towers and two further lights sat atop of the Southwest and Northeast towers – was scheduled for five working days.
With 180,000 cars passing over the bridge daily, access was a serious consideration. Each pillar had a lift and guarded platforms on mid and upper levels so once inside the tower working was relatively safe but in order to enter the tower each morning the inside lane of the A282 had to be closed and that was a decision not taken lightly by the bridge’s contractors.
As the previous system was failing and outdated, it was absolutely necessary to gain access to the pillars, so authorisation was given to close the inside lane on one of the carriageways for 10 minutes each morning and again in the evening when the team needed to disembark. Each time, temporary speed limits were introduced and a roadblock of 6 highway trucks ushered vehicles into the central lanes to protect Delta’s engineers.
Once inside the tower the team took the lift to either the mid or upper levels and began work. They used the electrical feed from the bridge’s previous system to power the WL2500s. They connected the light, earthed it and attached it with bracket and pole fixings. At the end of each day they radioed the bridge authorities and headed down to ground level to disembark.
Fortunately, despite a powerful North Sea wind and the biting cold, the job progressed well and by the end of the five days all lights were installed to an extremely high standard and the system had passed the IET (Institute of Engineering and Technology) BS 7671 17th edition – a British standard.
“Our lads have installed systems on BT towers in the Outer Hebrides and many other tall structures around the world so they are well used to unfavourable conditions. In December, the main issue was time. We aimed to be off the bridge before nightfall each day but the short days put extra pressure on us,” said Tariq.
A Job Well Done
The team have since been called back twice to overcome snags relating to interfacing with the previous system. The system has now passed a function test and testing to ensure that it has fully interfaced with the bridge’s control tower and has been signed off by the client.
“Its very important we continue to take on huge structures like the QEII bridge and do a first class job. It is the ultimate shop window for us as it demonstrates to millions that our products are of excellent build quality and our workforce is highly skilled at fitting them,” added Tariq.