Flexible Relining of Pipes with Primus Line Pressure
September 19, 2014According to recent studies from the American Water Works Association (AWWA), as well as the Environmental Protection Agency (EPA), there is a significant need for investments in the U.S. drinking water infrastructure.
In order to guarantee the supply of high-quality drinking water to residents, AWWA estimates that investments of $526 billion are required for the replacement or renovation of deteriorated water mains in the next 25 years. The latest EPA report on U.S. water infrastructure comes to the conclusion that investments of $248 billion are required over the next 20 years. President Obama just recently signed the Water Resources Reform and Development Act (WRRDA) into law to modernize the U.S. water infrastructure.
German company Raedlinger Primus Line addresses this issue with the development of a flexible relining technology for the trenchless rehabilitation of pressure pipes. Although trenchless technologies are already well-established for gravity pipelines, little progress has been made for pressure applications. Trenchless technologies can be a viable and cost-effective alternative to traditional methods for pressure pipelines, as well. In particular, the expenses for road surfaces, soil replacement and high groundwater levels can be reduced significantly when compared to an open-trench approach. Furthermore, construction times and interference into people’s daily lives are minimized substantially. In some cases, trenchless technologies are the only economically feasible alternative.
New York Case Study
In July, the Wastewater Treatment Plant of the Hudson Valley Research Park in Hopewell Junction, N.Y., was confronted with the rehabilitation of a pressurized wastewater main. The main, which transports treated wastewater, runs from a pumping station to the final effluent pumping station. The 12-in. ductile iron pipeline has a length of 500 ft and an operating pressure of 60 psi. There are four 45-degree bends in the route of the pipeline. Since the area is difficult to access and traditional open-trench methods are expensive and time-consuming, the client opted to use trenchless technology. In that context, the client was presented with two trenchless solutions one by the local contractor Arold Construction of Kingston, N.Y., installing Primus Line and the other using sliplining.
When evaluating the proposed solutions, the Primus Line system’s main advantage was the ability to negotiate four 45 degree bends with a radius of 3 x D in one installation section. Furthermore, there was only a need to create one additional excavation pit since the pipeline was accessible via one pumping station. Due to the confined space onsite, the Primus Line system could also convince with minimum equipment requirements for the installation process. Due to the low wall thickness of the inliner with 0.236 in., there was only a minimal reduction with respect to the cross-sectional area.
The client opted to install the semi-structural Primus Line system. The self- supporting 12-in., low-pressure inliner has an outer diameter of 11.1 in. and a corresponding inner diameter of 10.6 in.. The nominal pressure design of the system is rated with 174 psi. Due to the 45 degree bends in the route of the pipeline, the maximum operating pressure must not exceed 95 psi.
First, the pipeline was taken offline, secluded from the network and opened. During the subsequent CCTV inspection, deposits and encrustations protruding into the cross-section of the pipe were discovered. In addition, the rope connection between the start and destination pit was created with the camera. The discovered encrustations needed to be removed with metal scrapers and rubber discs so that the durability of the rehabilitation is guaranteed. Since the inliner is not glued to the wall of the host pipe, a rough cleaning was sufficient.
After a second camera inspection, there weren’t any additional obstacles that could have damaged the inliner during the insertion process. Before the installation commenced, the host pipe was equipped with insertion rollers at the front and end of the pipeline so that the inliner and the rope of the pulling winch were not damaged. The 12-in. inliner was delivered pre-folded to the construction site on a transport drum with a length of 7.5 ft. Folding the inliner into U-shape, the associated pulling forces can be reduced significantly. The installation section with a length of 500 ft was installed with maximum pulling force of 1 ton. The maximum tolerable pulling force for the 12-in. low pressure inliner is 10 tons. The inliner was turned into round shape after insertion by applying compressed air of approximately 7 psi. Finally, the low pressure termination fittings that are equipped with double-sided ANSI flanges were installed on each side and mounted to a corresponding flange at the host pipe.
After installation, a leak test with a test pressure of 90 psi was performed and the renovated section was re-integrated into the pipeline network. The wastewater pipeline could be rehabilitated in less than two working days.
Andreas Gross is international account manager at Radlinger Primus Line GmbH.
What Is the Primus System?
The Primus Line system is a flexible relining solution for the rehabilitation of pressure pipes for different applications such as drinking water mains, pressurized wastewater conduits, fire mains, natural gas, crude oil and gas/oil pipelines. The system is based on a flexible inliner and specifically developed termination fittings. The relining solution can negotiate multiple bends of up to 45 degrees due to its flexible construction and installation lengths of up to 8,200 ft in a single step are feasible. The inliner is not affixed to the host pipe and an annular space remains. The system can accommodate pressures of up to 1,100 psi and is manufactured in nominal sizes ranging from 6 to 20 in. The inliner is delivered on project- specific transport drums to reduce logistic costs. The system can be used regardless of the material of the host pipe. Further, the solution is not only used for the renovation of existing pipelines. It can also be deployed to increase the pressure of existing systems by installing an inliner with a higher pressure rating. In addition, the inliner protects existing pipes against corrosion from the inside since the transported fluids only get in contact either with TPU or PE.
The first part of the system is the Primus Line inliner, which consists of three different layers. The inner layer can be selected for the specific fluid to be transported. For drinking water applications a coating, which is based on polyethylene (PE), is applied. The used PE material has been accredited until now by 15 international institutes with respect to the suitability of the products in contact with drinking water. The system is also certified according to NSF/ANSI 61. For other applications such as gasoil, natural gas pipelines or industrial wastewater pipelines, thermoplastic polyurethane (TPU) is the preferred inner coating since these fluids have different characteristics than drinking water. The middle layer consists of a seamless Kevlar fabric, which functions as a static load-bearing layer. For higher pressures a second layer of the Kevlar fabric can optionally be added. In addition, the fabric accommodates the pulling forces during the installation process. The outer layer is made of wear-resistant PE regardless of the transported fluid and protects the middle layer during the installation process.
The second part of the system is the specifically developed termination fitting for the Primus Line inliner. The termination fittings are selected based on the required pressure ratings. The manufacturer differentiates between low-pressure and high pressure termination fittings. The high-pressure fitting consists of a contoured internal core and an external sleeve. The external sleeve has a malleable steel jacket on the inside. A two-component epoxy resin is injected through a valve on the external sleeve forcing the steel sleeve and the inliner into the contours of the internal core. Thus, a durable and pull-proof connection is achieved. The low pressure fittings are available for inliners ranging from 6 to 12 in. with a nominal pressure design ranging from 406 to 174 psi. The low pressure termination fitting works similar to the high pressure fitting, however, uses a forming jacket with corresponding contours, instead of the two-component epoxy resin. The low-pressure termination fitting is installed with mechanical force to achieve a durable and pull-proof connection. Using the low-pressure system permits a quicker installation than the high pressure system since there is not any curing time for the two-component epoxy resin.