New GRP pipe liner by RELINEEUROPE proves itself in rehabilitation project for the Berlin water utility – pressure testing passed at 12 and 10 bar without pressure loss
Frisch & Faust Tiefbau GmbH used UV light-curing AlphalinerPN for the first time to rehabilitate a sewerage pressure pipe for the Berlin water utility. This GRP pipe liner developed specifically for sewerage pressure pipes was installed on 7 December with a diameter of DN 750 over 43 metres along Paul-Lincke-Ufer street. Employees of the Berlin water utility provided expert supervision for the construction site. The team used the powerful REE4000 UV curing system for the curing process.
Over the years, strong internal corrosion had affected the pressure pipe, which was constructed of grey cast iron in 1877. The pipe runs under Paul-Lincke-Ufer, along the Landwehr Canal in the Berlin neighbourhood of Kreuzburg. The rehabilitation project was necessary because it was no longer possible to ensure that the pipe could stand up to powerful pressure shocks of up to 10 bar. The Berlin water utility needed a structurally self-supporting system for this project capable of independently handling all of these loads. The Berlin company Frisch & Faust Tiefbau GmbH was able to offer an appropriate rehabilitation procedure for damage prevention at short notice in the form of the AlphalinerPN from system provider RELINEEUROPE.
“Special care is needed when rehabilitating pressure pipes and cleaning the old pipe”, as RELINEEUROPE sales engineer Firmino Barbosa explains. In the Berlin project, a smooth pipe wall had to be created after flushing, and all uneven areas removed with scrapers and milling robots. If intruding obstacles formed bulges, or “imperfections” in the rehabilitated pipe, there would no longer be any way to ensure the necessary pressure resistance.
The AlphalinerPN is a seamless GRP pipe liner with special technical properties designed for the rehabilitation of waste water pressure pipes with a sealed construction. Glass fibre-reinforced AlphalinerPN are produced continuously through a specialised winding process. Pre-impregnated fibreglass bands are wound on a cylinder in the peripheral direction in this manufacturing process. This specially developed technology creates a highly compact composite material. The winding process allows the company to use different layers to create a variety of properties. The layers with specially developed bands of cut glass fibres and fibreglass rovings form the composite thickness, and the combination creates high ring rigidity and high axial strength properties. This allows the material to handle even extreme pressure loads. To optimise the condition of the liner surface with regard to abrasion resistance and roughness, this pipe liner has a specially refined and highly transparent thermoplastic internal coating inseparably connected to the pure resin layer and the base laminate. Its seamless construction is unique in the world. The AlphalinerPN showed a barely measurable abrasion value of just 0.06 mm in Darmstadt tipping trough testing with 100,000 load alterations. In addition, a double wall on the outside of the liner protects the material and provides a reliable seal. As a structurally self-supporting pipe liner in accordance with class A of DIN EN ISO 11295, AlphalinerPN is also fully structurally load-bearing even without the old pipeline.
AlphalinerPN GRP pipe liners were designed for use in pipe systems for pressurised drainage. The product range includes diameters from DN 150 to DN 800. Special solutions up to DN 1200 are available.
The pressure liner is installed in the same manner as conventional UV light-curing pipe liners. After it is pulled into place, the liner is inflated with compressed air and the UV light chain is brought in. Frisch & Faust team leader Steffen Ertmann uses the new and powerful REE4000 UV system for the curing process. A light chain with an output of 6 x max. 3000 watts is used for diameters DN 600 to DN 1300. Only two of the three modules in the separable UV light chain were used, due to the very narrow installation shaft. This meant 4 x 3,000 watt spotlights were used. The team leader used 1,500 W of lamp output to harden the 40-metre-long pipe liner with a diameter of DN 750 and a composite wall thickness of 7.2 mm. Using the 4 x 1,500 watt power, the hardening speed was 27 metres per hour (45 cm/min). The REE4000 UV curing system allows the specialised crystal beams to be adjusted to any level; this light chain was capable of being set at beam intensities between 1,000 watts and 3,000 watts depending on diameter and wall thickness. The set UV power is permanently measured using ballast units steered by micro-controllers through a patented process. The power measured on the UV spotlights is documented in a curing protocol. The process was used to fully cure the liner in around 1.5 hours.
Pressure testing passed with 12 and 10 bar without pressure loss
In the next work step, the liner ends were fitted with specialised sleeves made of stainless steel and EPDM rubber to ensure that no vacuum could be created between the liner wall and the old pipe under dynamic loads. The pre-finished, 80 centimetre long pipe couplings were installed by Frisch & Faust employees, re-sealing the wastewater pressure line and ensuring it was ready for operation. The civil engineering company is also certified for pipeline construction, and is a DVGW permitted specialist company.
Employees at the Berlin water utility were very satisfied with the wastewater pressure pipe rehabilitation, according to sales engineer Barbosa. The test report in accordance with DVGW W 400-2 was completed by Berlin WDG Wasser- und Druckprüfgesellschaft GmbH to confirm that the pipeline section will continue being able to stand up to the loads required for many years. The pipe handled both the one hour preliminary test at 12 bar pressure and the three hour leak test at 10 bar pressure without a pressure drop. The AlphalinerPN from RELINEEUROPE is now approved for rehabilitating wastewater pressure lines by the Berlin water utility.