MATERIALS | PRESSURE PIPES
Gas delivery UK-based GPS recently produced a bespoke solution as part of a £3 million (US$3.6m) project to construct a new gas mains pipeline. The line, underneath the River Foyle in Ireland, is one of the largest directional drilling gas projects ever undertaken in the country, said the company. The 660-metre pipeline uses GPS’ Excel PE100
Above and right: Molecor’s PVC-O pipe has been used to supply fresh water to Pernik in Bulgaria, after it suffered a severe drought
grade. The pipeline was needed in order to consolidate the supply of gas on the cityside of Derry – which was served by a single gas line. It offered security for the existing network, and catered for growing capacity. The project, now complete, provides gas to more than 10,000 households. The pipeline needed to be a high quality, robust solution that could withstand the rigours of horizontal directional drilling (HDD) installation. Once commissioned, it then needed to maintain its performance when at the bottom of the 50m deep river.
pressure – so a pressure drop indicates leaks. Continuously extruded webs simplify the alignment of the inner and outer pipes. An advan- tage of the continuously extruded webs is that the pipes can be separated at any point, if required. Due to the reduced component dimensions, a simple assembly is possible even in confined spaces. The connection of the individual double pipe components was carried out using simultaneous welding – which was an advantage from both an economical and processing point of view. The double containment pipe is highly flexible, so the height difference between the transition point on the mainland and the pontoons can be overcome without extra fittings.
PE 100-RC was chosen because it has a higher
resistance to slow crack growth than standard PE100. As well as resisting corrosion – from the surrounding seawater – the material also withstood wide temperature changes. After assembly, the wastewater of all floating houses is pumped towards the main line. The main line of the Poly-Flo pipe – and the connecting lines – were welded onsite. Because there is a 10m wide public area between the lake and the wastewater reservoir on the mainland, horizontal directional drilling (HDD) was used to lay the pipe.
24 PIPE & PROFILE EXTRUSION | May 2020
Relieving drought Molecor of Spain – which produces oriented PVC (PVC-O) pipes, as well as the machinery to make them – recently supplied a city in Bulgaria with pressure pipe to supply drinking water, following a severe drought. Pernik had suffered a serious drought since November 2019. A lack of rain – and the low water level in the Studena dam – threatened to leave 100,000 people without potable water. In addition, the existing water system was
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Due to the concerns of the long-term structural stability of the pipeline, a thicker pipe than is normally used for the transportation of fuel gas was needed – with 355mm SDR 7.4 Orange PE pipe specified. As a size not previously used in the gas industry, GPS says it was the only manufacturer that could manufacture and test this specific pipe. McCormack, the drilling contractor, drilled a 660mm diameter hole under the river bed in preparation for the pipe. The pipe was laid out on nearby school grounds and joined using butt fusion welding. Using school grounds put a short timeframe on the installation: it was moved into position over a weekend and pulled through the hole under the river in a continuous 10-hour operation overnight. The pipe was produced in lengths of 13.5m –
instead of the standard 12m – in order to reduce the number of deliveries needed, cut transport costs and reduce carbon emissions. It also reduced the number of butt fusion joints required, which speeded up installation.
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