CompositesWorld
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AUGUST 2015 54 CompositesWorld INSIDE MANUFACTURING To produce an IFL for a recent nominal 152.5 mm (6-inch) outside diameter pipe, the system pulled from a battery of more than 250 spools of dry Kevlar aramid cords to weave a high-strength, single-ply, 2.0-mm-thick cylindrical structure. DuPont defnes a Kevlar cord as a single string of Kevlar, which is composed of a number of threads, which, in turn, comprise a number of flaments. While the fnished core cylinder moved downward as it was woven, the highly corrosion-resistant inner and outer thermo- plastic layers were extruded onto it (Step 2, p. 52). Te inner barrier layer — the initial line of internal corrosion defense — was frst extruded onto the inside surface of the Kevlar core. For this layer, which is directly exposed to the corrosive service medium, APS chose Solef PVDF, a polyvinylidene fuoride resin from Solvay Specialty Polymers (Alpharetta, GA, US). Tis semi-crystalline fuoropolymer provides stability in harsh thermal and chemical environments and has an established record of high-performance service in ofshore hydrocarbon applications. Te IFL's outer layer, which contacts the inner surface of the host pipe, was then extruded onto the exterior of the core. Te outer layer is an abrasion-resistant thermoplastic polyurethane (TPU) from BASF Polyurethanes (Waterloo, Germany). After inner and outer extrusion layers were applied, the liner was allowed to cool under controlled conditions until the extruded thermoplastic layers crystallized and solidifed against the core. When the crystallization phase was complete, no secondary manufacturing operations were necessary. During the entire process, the vertical cylinder of core and its interior/ exterior ther- moplastic layers continued to move downward, held under tension to assure a smooth and consistent operation as the liner was continu- ously produced and then cooled. In this way, the liner "actually removes itself from the weaving system and related internal and external extrusion processes," Walters explains. Te cooled crys- talized liner was then automatically reeled directly onto a trans- portation drum in a fat confguration and prepared for shipment to the customer's location (Step 3). Shipping reels are specifcally designed to accommodate up to 5 km of liner and can be packed into standard 20-ft- or 40-ft-long shipping containers. Successful, cost-efective installations Te frst installations, in 2013 and 2014, went into internally corroded pipelines that had been marked for imminent closure. Te inaugural IFL, in the summer of 2013, was installed by APS in a 203-mm (8-inch) diameter, 1.5-km-long crude oil pipeline oper- ating at 10 bar, between two ofshore platforms in PETRONAS's Samarang oil feld in the South China Sea, located ofshore from Sabah, East Malaysia. Te liner was shipped to the project yard in Labuan, where it was put through a folding-and-banding process: Te fat liner was pulled from the shipping reel and passed through a series of machines that fold it lengthwise into a U-shape, then use fexible PVC flm-based tape to hold the liner's folded shape in position. Tis process reduced the liner's diameter and, thus, reduced the pulling forces required to pull it through the host pipe. Te folded/taped liner was then reeled onto a dedicated installation drum (Step 4, p. 53). Te drum and other installation equipment and personnel were transported to the ofshore site and a guidance framework was set up to defne the liner pulling path. Te host pipeline was cleared of its fow media and thoroughly cleaned, measured and assessed for its exact condition. Next, the riser pipe — the vertical pipeline that connects the platform-based processing equipment above the water line to the horizontal pipeline network and related equipment on the seabed — was modifed to accommodate instal- lation of the liner end connector units after liner installation. A winching cable was pulled into position in two steps: First, a specially designed pig was blown from the main winching platform to the liner installation drum platform. (A pig is a device commonly used for cleaning and maintenance of pipelines; it can be blown through a pipe by raising the air pressure behind it, which pushes the pig forward). Te pig carried a small, lightweight cable through the pipeline. A secondary winch on the installation platform was then attached to the small cable, which, in turn, wss used to pull a larger, main winching cable through to the installa- tion drum for connection to the liner towing head. When the existing pipeline was thoroughly cleared and cleaned, the winching cable was in position and other liner installa- tion preparations were complete, the liner was positioned (Step 5) and pulled through the host pipe (Step 6). Pulling force was closely monitored and controlled during the installation process. Tis pulling operation is normally performed at an approximate pulling speed of about 10 m/min, Walters notes. A liner can be pulled through a 1.5 km pipe in about 2.5 hours. After it was in place, the liner was cut to length, and then infated, using low air pressure (Step 7). As it infated, the banding tapes broke and the liner expanded to ft tightly against the host pipe's inside surface. End-termination connectors were then installed and the pipe was hydro-tested for 24 hours at a pressure set at approximately 1.5 times the normal pipeline operating pressure, or ~15 bar (1.5 times the 10-bar pipeline pressure). When the hydro test was deemed successful, the pipeline system was recommissioned for service. Another IFL installation, in a 152.5-mm (6-inch) diameter, high- pressure (60 bar) gas pipeline, took place at the same time and in Read this article online | short.compositesworld.com/SubseaPipe Read more online about "Cured-in-place pipe: Trenchless trends" | short.compositesworld.com/JJbE84UH PETRONAS Carigali says the IFL has saved as much as 50% of the capital cost of a replacement pipeline.