Aspects of butt-welding with PE large pipes

Sea discharge line of a thermo-electric power plant

FENIX Power Peru constructed a thermo-electric power plant 64 km south of Lima. The planned output amounts to 520 megawatts (MW). Seeking to provide 10 per cent of the national energy requirements, the project carries an especially high significance for Peruvian economic growth. Three turbines are available for operation, two for natural gas and one steam-powered turbine. Operation started in March 2013. Approximately $776 million is set to be invested in the construction.

A total of four pipelines were installed – two to transport sea water into the unit and two returning it into the sea. Each pipe is approximately 500 m in length with an overall incline of 13.5 m. A total of 1,120 m of piping was installed and was made of PE 100 with a diameter of 1,800 mm, and 680 m with a diameter of 1,400 mm. The project also makes use of polyethylene (PE) structured wall pipes, welded with an integrated heating coil.

The butt-welds were performed with a stationary assembled butt-welding machine for pipes with a diameter of up to 2,000 mm using the WIDOS 20000 welding machine. The machine is fitted with a hydraulic crane to enable better handling. The welding parameters were established in accordance with the German DVS guidelines 2207-1.

The first construction phase saw the manufacture of pipe runs approximately 100 m in length. Working on a provisional track system with trolley, similar to that used in the mining industry, these pipe runs were transported to a jetty on the coast.

The second construction phase will see the 100 m pipe runs welded together on the jetty and pulled into the sea. Several hundred metres in length, the pipeline is floated on the water’s surface. After the last welding work has been performed, the pipe is flooded and sunk to the sea floor with concrete weights. The pipes are laid underground on the beach and the jetty will be dismantled after completion of the work. Thus the beach should be returned to its original state. The rail system and the jetty are only provisional construction units and will be dismantled upon completion of the work.

Cooling water pipeline for a thermo-electric power plant

Thermal Power Corporation India is constructing a 1,320 MW power plant on India’s southern coast. The project began in December 2011.

A cooling water pipeline with a total length of approximately 2,500 m is to be installed, of which approximately 1,300 m runs from the power plant to the coast and approximately 1,200 m from the coast into the sea.

The PE100 pipes have a diameter of 1,600 mm and are welded using the WIDOS 16000 welding machine. Using roller stands, the welding is performed stationary, yet the welding machine will be deployed in a partially mobile fashion; i.e. moved by a pipe length after every weld. The welding parameters were established in accordance with the German DVS guidelines 2207-1.

Latest project: Pre-fabrication of PE pipe runs

This represents the most recent large-scale project, with which WIDOS has again demonstrated that large dimensions often require entirely new solutions. A butt-welding machine was constructed especially for the project. This machine enables the welding of pipes and pipeline components with a diameter of up to 2,500 mm.

All the important welding functions are steered using a joystick remote control. Wheels are mounted on the base frame for the transport of the welding machine.

The heating element, hanging from a guide rail is moved horizontally to ensure the shortest conversion times during the welding of such large dimensions. The machine frame has a levelling stamp as a bearing to prevent the machine from tipping whilst shifting its weight due to the dynamic of the movement. This also serves to align the machine, as it is usual to move the machine towards the pipe.

The classic butt-welding machine planer was replaced by a plane finger, which is significantly smaller and lighter. With the plane finger, the pipe end is not planed, rather pared from within. Depending on the revolutions, the cut-off knife moves some way outwards until the end of the pipe wall has been reached.

The machine is equipped with a stub-end holder with radially adjustable clamping jaws.

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