Water & Wastewater Treatment Magazine
Issue link: https://fhpublishing.uberflip.com/i/515382
Project focus: pumps and pumping systems costly and sacrificial exercise that I considered no longer manageable. Removal of one of the two screw pumps also le us vulnerable with a single point of failure. We needed a much smaller, more reliable, more cost-effective and easier to maintain pump regime, which is where Börger came in". The installation of four stainless steel Börger pumps, which was carried out by Almax Technologies, has reduced inspection time to just 40 minutes. For servicing, the Maintenance-In-Place (MIP) feature of the factory-tested pumps means that all four can be stripped down, oil changed, rotors checked, in a day (or less), right back to the gearbox seals. Fitted with "Optimum rotors", the 18.5kW Börger units pump out 40m 3 per hour at 70m head (7.5 BAR vertical discharge), and have a suction li of -5.5m. Only two pumps are in action at any one time, operating alternately on a 20 minute shi system so as to preserve their lifetime. In the event of a flood, then all four pumps would automatically leap into action – and compared to leaving just one screw pump in place, removal of a Börger unit would still leave three working if needed. So- start inverters get the variable-drive pumps up and running so as not to shock the pipework. "In fact, it's been the existing pipework that has presented us with more problems", continued Steve Parker. "We're now changing over from plastic to stainless steel to reduce vibration". Installation of the pumps took over a month, and the system underwent intensive Witnessed Performance Testing prior to acceptance. National Grid is also introducing a new control and monitoring system, which Parker says he held back on until the performance and maintenance of the pumps could be firmly established. Flow meters currently check on the pumps' typical 63m 3 per hour of water, but the new smart system will help improve efficiency on site even further, because a complete history will be available at an operator's fingertips, with graphics to study trends and much more – accessible via a smart phone if required. Parker concluded: "Compared to the saga of servicing our screw pumps, all we need to get at the Börger pumps are basic tools, which can be taken down into the tunnel with ease in a small holdall. The simplicity of the Maintenance-In- Place feature is a real benefit - four Eye-bolts on the front of each pump – and the pumps themselves are rock solid, despite being in such a harsh, almost oil-rig type environment. They have taken massive hammerings – but been totally resilient and beautifully reliable." By Chris French Two screw pumps were replaced by four rotary lobe pumps • Perspectives David Brown, Managing Director, Borger UK: "This is one of the most demanding installations we've ever undertaken. Reliability and back-up is absolutely crucial to this site. The Maintenance-In- Place feature provides particular benefits here, where space is at such a premium". Steve Parker, Substation Engineer, National Grid: "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". ● Reliable pumping system needed to protect underground cabling owned by National Grid ● Any pump failure would result in power cuts costing at least £1M per day ● Quarterly, planned maintenance programme preferred to ensure performance • Drivers The first Severn Bridge is nearly 50 years old, with essential cabling underneath 24 | June 2015 | WWT | www.wwtonline.co.uk