In this year 2013 a new record was established in Lima, Peru. Polyethylene (PE) pipes with a nominal diameter/inner diameter (DN/ID) of 3,000mm were used for a deep water outfall pipeline. The PE pipes were produced using the Krah technology in Spain by PPA&Krah, Vitoria. One of the challenges in this project was to open a new site for the Krah Large Pipe Technology – The Pacific Ocean.
The Taboada wastewater treatment plant, located in Callao, is one of the biggest sewage treatment projects anywhere in the world. The aim of the project was to significantly increase the amount of treated water in the city of Lima, thus reducing ocean pollution and improving the health conditions in the area.
The daily La Republica reports that the 21 existing wastewater treatment plants are only treating 16% of the sewage generated by the population living between the cities of Lima and Callao and that the Taboada plant is expected to increase this figure to 75%. A further 25% will be added once the La Chira plant comes into operation by the end of 2014.
Main project features are:
- Project location: City of Lima, Peru
- Average treatment capacity: 14m3/s
- Maximum treatment capacity: 20m3/s
- Population served: 4 million people
A mega wastewater treatment plant normally needs a large outfall to comply with the project requirements. The dilution and hydraulic calculations were made and a pipe with an ID of 3,000mm was selected.
The outfall is located in a seismic-sensitive region and it must be corrosion free. It was decided by the end-user and main contractor Sedapal/Tedagua to consider the large diameter helical structured PE pipes according to DIN16961 fabricated using Krah technology and jointed by electro fusion technology to meet the project requirements.
The pipes and fittings were manufactured and fabricated by PPA&Krah in Spain from where they were sent to Lima in four separate shipments.
Each pipe had a length of 6m and the wall construction was not solid. It was a structured wall design, with equivalent or even superior characteristics to a solid wall pipe. A solid pipe was not available in this size and in any case, would not be suitable for these installation conditions. Due to the unique production process the pipes have no frozen stresses in the pipe wall and the profiled wall structure can be designed tailor made for the application requirements. The pipe production was done on a Krah winding machine, where the pipe wall was build up due a helically extrusion process. The layers were absolute homogenous to each other, the Krah production procedure is controlling this continuously with an integrated infrared-camera.
The helically wound pipes and fittings were welded by a patented electro-fusion welding procedure and they were ballasted on site before the launching of the sinking strings to the sea from the working ramp made onshore. All ballast blocks had no screws and bolts. By fixing them on particular points of the special made pipes, a later unwanted sliding of the blocks was impossible.
Up to 19 sinking strings were sunk and connected offshore. Each string had a length of approximately 250m, and an integrated flange was fitted on each end. The sinking method was a controlled deployment of each string which was equipped with its own floater system.
The deepest point of the installation was 22m in the Pacific Ocean. Every string was joined by integrated flanges.