Water & Wastewater Treatment Magazine
Issue link: https://fhpublishing.uberflip.com/i/515382
www.wwtonline.co.uk | WWT | JUNE 2015 | 23 Project focus A s the first Severn Bridge approaches its 50th anniversary, the millions of drivers that cross it each year will be blissfully unaware of just how crucial the pumping operation is some 70m Pumps and pumping systems All change for vital Severn tunnel pumping system Project focus ● Automated pumping system protects power cable beneath Severn Bridge ● Four rotary lobe pumps replace two existing screw pumps ● Maintenance in place (MIP) facility allows for reduced maintenance time ingress from underground springs. Systems are firmly in place to prevent homes and industry from any power shortages, but the knock-on effect from a total pump failure would cost around £1M to £1.25M per day. Mention the Severn Bridge to most people and they'll usually refer to the mighty construction that hosts part of the M4, but just to be clear, we're talking here about its perhaps less glamorous neighbour, hailed as the dawn of a new economic era for South Wales when opened 30 years earlier by the Queen. This is the first Severn Bridge, slightly further up the river, which now carries part of the M48 motorway. Deep down in the tunnel with the National Grid cable, it's a strangely warm, damp, noisy environment where the lights have to stay on and corrosion sets to work amid the somewhat eerie stalactites. Following a refurbishment of the tunnel a decade ago when the pumping out of the spring water was reduced from two points to just one - at Aust on the English side of the Severn - National Grid has been busy working towards the best possible solution for automated control of the tunnel's pumping system. This recently culminated in an upgrade which saw two screw pumps replaced by four rotary lobe pumps, and a major improvement in the way the system is maintained, as Substation Engineer, Steve Parker, explains. "We've gone from what could be described as 'panic breakdown maintenance' – to a controlled, managed quarterly program", says Parker. "This has come on the back of switching from two screw pumps to four rotary lobe pumps made by Börger. Although this upgrade has involved a capital cost, we're already well on our way to getting that back by the huge amount of time and labour we save on servicing. "For the screw pumps, we'd need a minimum of three personnel just to go down into the tunnel to carry out an inspection that could take at least two and half hours. To bring one of the pumps out for repair or maintenance required winches, which then became an extremely time-consuming health and safety event, lasting up to two and half days. "Including the cost of two full-time fitters, we'd have to jack the screw pump apart in order to cut the main rotor in half, which overall, was a The 2.2 mile tunnel requires pumping to protect it from water ingress below the land in the tunnel that connects a vital National Grid cable from England to Wales. Valued at £80M, the 2.2 mile tunnel is protected by pumps that remove one million litres per day of water