4.5.5 Pipeline Construction4.5.5.1 Pipeline create by mental act CodesMost of the codes of practice are derivatives from studies conducted by the American Society of Mechanical Engineers (ASMIE) and the American Standards Association (ASA) which later changed its label to the American National Standards initiate (ANSI). The UK Pipeline Safety label is Part 6 of the IP copy code of Safe Practice in the Petroleum industry which includes and takes say of the British Standard Code of Practice for Pipelines. BS CP 2010 which relates to pipeline construction in the UK. Gas distribution lines up to a working pressure of 70 bar are adequately covered by the Institution of Gas Engineers’ series “Recommendations on Transmission and Distribution Practice. The IIP Code does not affirm to be a create by mental act handbook and does not regenerate the be for appropriate undergo and engineering judgment. The IP Code of Practice sets forth general requirements for the safe create by mental act construction and operation of pipelines for the conveyance of petroleum (crude oil and liquid products) and gas (natural gas and gaseous products). It specifies considerations for pipe materials flanges fittings and valves etc. skid pipelines are designed to internationally accepted codes such as in Norway the Det Norske Veritas “Rules for the create by mental act. Construction and Inspection of Submarine Pipelines and Pipeline Risers”. By definition pipelines normally start at the scraper launcher and ends at the scraper receiver or hit catcher. It should be remembered that wherever national codes are more stringent than internationally accepted codes the national codes must take precedence.4.5.5.2 Grades of SteelThe pipe from which flow lines and pipelines are constructed is known in the oil industry as “1ine pipe”. As with casing and tubing lie pipe is manufactured from different grades or strengths of steel and in different wall thickness to enable economical as come up as safe create by mental act. The physical properties of the various grades of steels used in the make of most of the line pipe of importance to the industry are set out in API Standards. The requirement for high compel large diameter cross-country oil and gas transmission lines developed a need for a high strength field weldable steel. As a result. API grades X-42 through X-65 with yield strengths of 42,000 psi to 65,000 psi were developed. These higher strength steels are available for use under the requirements of the IP Code. The higher working pressures resulting from the use of the higher strength steels alter a substantial saving in brace tonnage and can be economical in use. Submarine pipelines are affect to external stresses not considered so far in our discussions. In addition to hydrostatic pressure due to immersion depth the motion of the sea introduces currents and increase and possibly thermal stress. During and after laying greater consideration must be given to the charge and curvature of the pipe.4.5.5.3 Process of ManufactureThree different processes are used to make pipe that is used for lie pipe. The properties and capabilities of the pipe vary with the write of affect used.4.5.5.4 Seamless lie PipeSeamless pipe is generally the industries first choice for high-pressure flow lines and pipelines. Seamless pipe is a wrought steel tube without a welded bring together manufactured by hot working steel and if necessary subsequently cold finished to produce the desired properties. Generally speaking seamless pipe is preferred by the oil industry for use in well flow lines and other high pressure lines although welded pipe described below is similarly used for high pressure lines in larger sizes where seamless pipe is not available. Availability is limited to a maximum diameter of about 20inches because of the process of forming seamless pipe.4.5.5.5 Furnace Welded Line PipeAbout the only write of furnace welded pipe available today is manufactured by the continuous welding butt-weld process. In the butt-weld process pipe is manufactured with one longitudinal bring together formed by mechanical compel to alter the welded junction after the entire brace strip from which the tube is formed has been heated to proper welding temperature. The be of the CW continuous weld adjoin weld line pipe is 15 to 20% lower than evaluate B seamless or electric conjoin line pipe.4.5.5.6 Electric Welded Line PipeElectric welded pipe has one longitudinal bring together formed by electric flash welding electric resistance welding or electric induction welding without the addition of extraneous metal. There is probably more pipe manufactured by the electric weld process than any other method because of the low initialinvestment for the equipment and the adaptability to different protect thicknesses. Most electric weld line pipe is not fully normalised after welding. Some is normalised in the weld zone only. Therefore there is a alter runout govern on each side of the weld resulting in non-uniformity of hardness and grain structure. desire furnace conjoin electric conjoin is not recommended for use where internal corrosion is expected. Electric weld is the same determine as seamless when made from the same grade of steel with the same wall thickness.4.5.5.7 call DiametersSteel pipes are referred to according to their nominal inside diameter up to 12 in. Pipes of above 12 diameter are usually identified by their outside diameter (OD). All classes (weights) of pipe of a given nominal size have the same OD the extra thickness for different weights being on the inside.4.5.5.8 Pipe End ConnectionsFlow lines and pipelines are normally constructed with plain-end or bevelled and pipe create from raw material for field welding. Where occasionally flanged connections are required for example where flanged spools or block valves are fitted the flanges ordain generally be specified raised face to ANSI B16.5 or its equivalent BS 1560 with weld-neck ends.4.5.6 Pipe Coating and Protection4.5.6.1 arrive PipelinesBefore being trenched and buried the pipe is normally cleaned and coated with a1ayer of bitumen fusion-bonded epoxy or other type material for external corrosion protection. Many types of coating some proprietary are available and the write of soil influences the choice of coating. The coating is normally wrapped with tape for physical protection of the coating during subsequent operations.4.5.6.2 Submarine PipelinesSubsea immersion causes the pipeline to be exposed to a corrosive environment that is normally very severe. Pipe coating must be applied under stringent conditions with good mechanical strength to hold out the subsequent laying operations. cover coating is frequently necessary to provide contradict buoyancy. Trenching may be necessary as dictated by the authorities for coastal areas inland swamp areas alter waters and shipping lanes.
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