WET News

MAY 2016 WET NEWS 11 MAY 2016 WET NEWS 11 providing the biggest economical advantages, is the elimination of the concrete collars required for the installation and sinking of the pipes. Buoyancy When installing pipes under water, consideration must be given to the pipe buoyancy, due to the lower density of PE com- pared to water (~5 %). To solve this in the past, concrete collars were usually placed around the pipe every few metres, but while this ballasted the pipe it caused many other problems. With Weholite, these collars were eliminated, because the ballasting function is achieved by the material that has been previously pumped into the hollow profile. This new way of undertaking the execution of outfalls and intakes has several points in its favour. For example, there are no collars to interfere with the installation process, and there is no risk of damaging the pipe through possible sliding of the collars during the sinking stage. By using the grouting system, Weholite submersion is much easier to control and ultimately safer. Additionally, with no concrete collars, a smaller trench is needed, so dredging and excavation is minimised and the shear stress normally caused by point load every 6m along the pipe is eliminated. The Weholite profile filling is homogeneous and spreads the load without any concentration, achieving an even distribution along the pipe. Once the pipe strings were ready, they were filled internally with marine balloons and towed individually up-river by CMP via tugboat to be prepared for submersion. Here the services of specialist divers were used – as opposed to expensive submarines – to bolt up the innovatively designed quick-connect flanges that joined each pipe string. The flanges were designed by Asset / Uponor in conjunction with CMP to allow for easy connection under water. Similar flanges have been used extensively by Uponor PS in major marine projects all around the world, including the Petron Bataan Refinery in the Philippines and a euro200M data centre in Hamina, Finland. Weholite pipes for the project were prefabricated in South Wales and transported to the London site with the flanges already in place, saving significant time. The project also included the installation of more than 11,000m2 of steel sheet piling to facilitate the dredging of the Thames river bed so the pipes could be laid free from obstruction. Finally, to keep carbon footprint to a minimum, much of the 28,000m3 of material dredged was reused to backfill the pipes, once installed, vastly reducing the quantity of material that needed to be taken off site. n Dr Vasilios Samaras is technical director of Asset International www.z-tech.co.uk 01223 653500 engineers@z-tech.co.uk Complete one-stop in-house solutions from dig to data: • Flowmeters • PRV's & Needle Valves • Burst Detection • Pumping Sets & Stations • Pressure & Level Monitoring Complete one-stop in-house Problem Solvers 24/7 EMERGENCY RESPONSE SERVICE concrete steel clean water civils waste water FULL REFURBISHMENT SERVICES FOR RESERVOIR & WATER TOWERS, CLEAN & SEWAGE TREATMENT WORKS, STEEL/CONCRETE TANKS & VESSELS, SPILLWAYS & AQUEDUCTS, BRIDGES, PIPEWORK, PIPE BRIDGES & OTHER ASSETS. FULL CIVIL ENGINEERING CAPABILITY INC NEW BUILD PROJECTS. PLEASE CONTACT US FOR OUR FULL SCOPE OF SERVICES. TECHKNOW • Weholite HDPE pipes were used for the twin culverts • A giant 7m x 11m x 5m Weholite Modular box to house two 3,000mm spool sections • The pipes' hollow profiles were filled using a vacuum pump connected to a grout lorry NEED TO KNOW 1 Timings were meticulously planned to synchronise with the ebb and flow of the tide 2 The pipes and modular boxes were manufactured and prefabricated at Asset's factory to save time 3 The pipe strings were filled internally with marine balloons 4 Much of the 28,000m3 of material dredged was reused to backfill THE VERDICT "This unique and complex project required ground breaking solutions. The finished result is an impressive example of high end engineering at its very best." Emmanuel Costes, construction manager, MVB Each pipe string was towed up-river using a tugboat Consideration had to be given to pipe buoyancy Pipes had to be submerged under an existing jetty structure

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