Tc 67/sc 4 n date: 2005-03-9 iso/wd XXXXXX ISO tc 67/sc 4/wg 6 Secretariat: Design of dynamic risers for offshore production systems Élément introductif — Élément central — Élément complémentaire Warning
Installation, retrieval and reinstallation of flexible risers
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- Transportation and Handling
- Installation Considerations
- Disconnection and retrieval
- Reinstallation
- Hydrostatic Testing
Installation, retrieval and reinstallation of flexible risersThe following is from Installation, Retrieval, and Reinstallation of Flexible Risers of Section 3.8, API-2RD-1998 First Ed.: Preparations and required support equipmentIn addition to the considerations in 3.7.1, the considerations discussed below apply to flexible risers. Compatibility of the riser with installation equipment, including winches, pipe tensioners and overboarding chutes, should be checked to ensure that the riser under installation tension is not damaged by crushing, bending or kinking. If the flexible pipe is installed dry, the installation equipment should be able to hold the riser should it be accidentally flooded. Installation procedures and equipment should account for the installation of riser appurtenances such as anodes at intermediate couplings, bending stiffeners, bending restricters, buoyancy modules and end connectors. The installation procedures and equipment that is used should be able to install the risers and then check that the risers are within the installation tolerances. The equipment arrangements on the installation vessel should consider weight, function and the presence of all ancillary support equipment. Additional reloadings of the installation vessel may be required, due to space or stability limitations. Installation procedures should allow for pigging and hydrostatic testing of the riser after installation.
Transportation and HandlingFlexible pipe can be stored in either reels or carrousels. Reels with a horizontal axis are commonly used for storage of long lengths of flexible pipes. Reels, used in conjunction with a winch, can be used to maintain the riser tension during installation and recovery. The following should be considered when handling flexible pipe with reels:
the drum radius should meet or exceed the minimum bending radius for storage of the flexible pipe; if used for installation, the reel dimensions, structural design, construction and seafastening should account for installation and transportation loads, and the reel should be compatible with the winch system; the reel design should ensure that all surfaces in contact with the flexible pipe be compatible with the outer jacket of the flexible pipe. The reel should protect the end fittings and other pipe accessories that may damage the outer layer of the adjacent layer of pipe; the flexible risers should be prerigged with any slings, hold back wire rope, and “Chinese fingers” that will be required to install the riser. Because of the inherent torque-balanced characteristics of flexible pipes, a fixed basket should not be used for storing or deploying flexible risers. However, rotating baskets or carrousels can be used. Since carrousels are not normally capable of supporting significant pipe tension during installation, a pipe tensioning system is normally used in conjunction with a carrousel. The design requirements for carrousels are similar to those for reels. The flexible riser should be stored under conditions that are not detrimental to its performance: maximum and minimum storage temperature should be within allowable pipe operating temperature; connections should be protected against damage of the seal area, threads and other areas susceptible to damage; pipe should be covered to prevent degradation by ultraviolet radiation; fluids left inside the riser, e.g. pressure test fluid, should be compatible with pipe materials. Precautions should be taken during handling and transportation of flexible pipe to prevent damage. Dragging on the floor or against equipment or unacceptable torsional or bending loading resulting from transfer of the riser should be avoided. Installation ConsiderationsIn certain applications, such as deep water, the flexible riser configuration could be selected based on ease of installation. Flexible pipe installation methods and equipment vary greatly, depending on the application and the environmental conditions. The three most common methods are: winch/chute lay. The flexible pipe is paid out from its storage reel powered by a winch system and launched over the edge of the vessel by an overboarding steel chute having a radius greater than the minimum bending radius of the pipe; horizontal tensioner/sheave lay. The flexible pipe is on a reel or carrousel, and a tensioner is used to provide the laying tension. A sheave is used to overboard the flexible pipe from the laying vessel to minimize the contact pressure and friction forces; vertical tensioner lay. The tensioner is installed vertically, and the flexible pipe is overboarded directly over one side of the installation vessel or through a moonpool. Some of these applications are shown in Figure 22. Flexible pipe is normally laid in a catenary shape, with a small initial deflection from the vertical axis. The pay out rate of the flexible pipe should be coordinated with the movements of the installation support vessel to prevent either overtension or formation of loops or kinks. This is especially important when laying multiple lines. Particular attention should be given to the passage of intermediate connections over a sheave, chute, roller or drum to prevent excessive bending behind the end fitting. The loads imposed during installation can be an important parameter for the design of the flexible riser structure and the selection of the installation equipment and accessories. The two primary installation loads are the pipe tension and the crushing force on the pipe from the tensioning system and the overboarding chute. The installation equipment should be designed or selected considering:
crushing loads exerted on the pipe by the overboarding chute, the installation reel, and/or the tensioner; the variation of pipe outer diameter along its length due to manufacturing tolerances. Typical installation procedures for Steep S, Lazy S and Lazy Wave riser configurations are shown in Figures 23, 24 and 25. After installation, the riser configuration should be checked by divers or an ROV. The selected riser configuration, riser accessories and appurtenances should allow retrieving a riser line, whether single or part of a multiple riser system. Tension in the flexible pipe is usually significantly higher during retrieval than during installation due to friction on overboarding chutes. Depending on the tension and the riser configuration, it may be necessary to void the riser before retrieval. ReinstallationPrior to reinstallation, the riser should be visually inspected for external damage and repairs carried out where required. The riser should also be drifted and hydrostatically tested at its rated operating pressure. On-site testing during and after installation should be carried out according to recommendations given in API RP 17B. Riser components should be tested similarly. Directory: standards standards -> Request for proposal contract form for the transit industry standards -> Indiana Academic Standards Resource Guide Grade 8 United States History – Growth and Development (to 1877) Updated April 2016 standards -> Us history Dictionary Based on the sc state Standards standards -> Integrating Standards Education into the Business School Curriculum standards -> Use of Sprint U301 3G/4g mobile Broadband usb device Installation standards -> International organisation for standardisation organisation internationale de normalisation standards -> Standards of Excellence standards -> Common Core State Standards for Mathematics (ccssm) Download 2.34 Mb. Share with your friends:
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