Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
  • F16L53/00—Heating of pipes or pipe systems; Cooling of pipes or pipe systems
  • F16L53/30—Heating of pipes or pipe systems
  • F16L53/34—Heating of pipes or pipe systems using electric, magnetic or electromagnetic fields, e.g. using induction, dielectric or microwave heating

Definitions

• This invention relates to a method for heating a transport pipeline.
• the invention also relates to a transport pipeline with heating.
• the invention is developed in connection with so-called multiphase transport, i.e. transport of mixtures of gas, oil and water through pipelines.
• multiphase transport has increasingly been regarded as more attractive over longer distances. The main reason is the desire to be able to reduce the number of platforms in the sea and/or the size of them. In this way, it will be economically viable to develop more oil and gas fields.
• Heating of pipelines can take place in several ways:
• the present invention aims at using inductive heating, particulary combined with the use of conventional laying methods, so-called S- and J-laying, combined with thermal insulation of the pipeline.
• a method for heating a transport pipeline by induction, and the method is characterized in that a magnetic field is provided, which magnetic field in the case of induction generates heat in the transport pipeline, in such a way that mutual, preferably parallel conductors are utilized as induction wires.
• the power supply can be single-phase or three-phase and the frequency either available grid frequency (50 or 60 Hz) or an optimized frequency provided by a particular converter.
• the physical basis for the calculation of heat generation in the pipes is Maxwell's equations expressed in differential form. These equations provide the relation between electric and magnetic quantities.
• the arrangement of the conductor in or on the surface of the insulation coating will be determined by such considerations as maximum heat development and laying technique.
• a transport pipeline with inductive heating is also suggested, which transport pipeline is characterized in that it is thermally insulated on the outside and on the outside of the thermal insulation there are mutually preferably parallel extending electric electrical conductors without metallic screen or protection.
• the pipeline should preferably be made of a ferromagnetic material or be produced as a composite pipe with at least one layer of ferromagnetic material. It has been seen to be particularly advantageous to utilize a coating with a very good electrical conductivety on the outside of the ferromagnetic steel pipe.
• a suitable coating material can be aluminium. Calculations and practical tests show that the heating will be considerably improved. This means that induced power increases with an aluminium coating on a steel pipe. Maximum effect is achieved for various thicknesses of aluminium coating for different steel pipe dimensions.
• maximum effect for an 8" (approx. 200 mm) steel pipe occurs with an aluminium coating thickness of 0,8 mm, and the effect will be approximately four times the effect without coating.
• the invention makes possible a preferred utilisation of the conventional laying methods, namely S- and J-laying.
• the invention can be implemented in that such a pipe or such a transport pipeline which is to be layed, is insulated thermally in suitable lengths (usually 12 m) on land.
• suitable lengths usually 12 m
• the joints are thermally insulated after welding and inspection are completed.
• electric wires are mounted on the outside of the pipe insulation. This can take place after the pipeline has passed through the usual rectifying/braking devices on the laying ramp. The electric wires or cables will therefore not be in the way during this part of the process.
• the mentioned- electric conductors are connected to an electric system. When connected to the electric system, the electric conductors will provide a magnetic field which due to induction will generate heat in the pipeline.
• the electric conductors or cables must not have a magnetic screen which hinders expansion of the magnetic field, or low impedance screen where currents are created which in turn counteract the magnetic field from the conductor.
• a particular advantage is that the electric cables do not need to penetrate the insulation coating around the pipe, where in such a situation there would be an increased danger of water penetration and reduction of the thermal properties of the insulation.
• Another advantage is that a cable placed outside the pipe insulation will not be a hindrace during application of insulation.
• fig. 1 shows an example of a transport pipeline according to the invention, in the form of a cross-section of the pipeline with external insulation and electric wires placed on the outside of this
• fig. 2 shows a cross-section of a modified conductor embodiment, with an aluminium coating on the pipe made of steel
• fig. 3 shows a cross-section of a modified cable placing.
• fig. 4 shows a diagram where induced power is plotted as a function of the distance between electricity conductor and pipe, for a single-phase system
• fig. 5 shows a diagram where induced power is drawn as a function of the distance between electric conductor and pipe, for a three-phase system
• fig. 6 shows a diagram where induced power is drawn as a function of the thickness of an aluminium coating
• fig. 7 shows a diagram where total induced power is drawn as a function of the central angle ⁇ between the electric conductors in a single-phase system
• fig. 8 shows a cross-section through a typical cable embodiment which can be utilized
• fig. 9 shows the maximum current in an underwater cable for various areas of cross-section of a copper conductor which is exposed to seawater with a temperature of 5 C.
• a pipeline 1 of a suitable steel material is shown.
• a heat insulation 2 is applied to the outside of the pipe 1.
• Two electric wires 3 and 4 are mounted on the outside of the heat insulation, in this case diametrically opposite to each other and along the pipeline.
• These electric cables 3 and 4 are placed on the outside of the heat insulation 2 immediately prior to the pipe leaving a laying-barge, and after the pipe has passed through the rectifying/braking devices mounted on the lay ramp.
• the transport pipeline can therefore, as anyone skilled in the art will understand, be immediately laid by means of conventional laying methods, since the electric cables will not interfere.
• the electric cable 3 can be forward conductor and the electric cable 4 can be return conductor for the current.
• Fig. 1 shows a two-conductor configuration. Use of three cables and three-phase system can also be considered. For redundance, extra conductors can be considered for use.
• alternating current For electricity, alternating current is utilized. A frequency of 50 Hz or 60 Hz is usually used. Higher frequencies are sometimes advantageous when power generation increases. Due to low depth of penetration, electric currents will not run on the internal surface of the pipe. Increased corrosion will therefore not occur on the inside by using the new heating method.
• the field strength of the steel will naturally be of importance. As is known, the field strength decreases with increased distance between electric conductor and the steel pipe. Tests have shown that necessary generation of power will be attained in distances which allow mounting of an adequate thermal insulation 2 between pipe 1 and the induction cables 3,4. In the table provided below the results from the tests are shown.
• the pipe shown in cross-section in fig. 2 is designed as the pipe in fig.l, but with the important exception that the steel pipe 1 has a coating 5 of aluminium.
• the insulation is, as in fig. 1, indicated with 2 , and the electric conductors with 3 and 4.
• the thickness of the coating 5 is indicated with & A ⁇ - Fig. 3 shows electric wires which are placed in grooves 6 which are made in the thermal insulation. Shorter distance between the conductors and steel pipe causes increased efficiency.
• the conductors acquire, since they in this case are incorporated in the periphery of the pipe, a position less exposed to mechanical damage.
• the cables can be secured in the grooves and protected by beeing covered with a sticky and possibly auto-vulcanizing material.
• Fig. 4 shows in the diagram induced power in an 8" steel pipe as a function of the distance from conductor to pipe.
• Two cables 3 and 4 (single-phase system) are assumed placed 180 apart at equal distances from the pipe. The calculations are based upon a steel pipe design without aluminium coating fully drawn curves- and a steel pipe design with an aluminium coating with a thickness of d equal to 0,8 mm - stippled curves. Resistivity for
• Fig. 5 shows a diagram as in fig. 4, for the same pipeline embodiment, but with three cables (three-phase system) mounted at angles of 120 between each other. A clear difference is seen here also, between pipes with and pipes without aluminium coating regarding induced power. The frequency is also in this case of great importance to power generation in the pipe.
• Induced effect is a function of the thickness of the aluminium coating. This is shown in fig. 6. Stippled curves represent a single-phase system and unbroken curves a three-phase system. The results in fig. 4-6 apply to 8" pipes. For other pipe dimensions the values will be otherwise. For example a 22" pipe will achieve maximum power generation for an aluminium coating with a thickness of approximately 0,35 mm. The induced effect with this thickness will be more than twice the effect induced in a steel pipe without aluminium coating.
• the cable has a simpler construction than a conventional underwater cable. This is because basically the cable is to be secured to a pipeline and steel reinforcement will not be necessary.
• the construction can be based on a standard PEX-insulated cable for a voltage range from 12 kV to 52 kV with a copper conductor.
• the cable in fig. 8 is assembled with a central conductor 10 with a conductor screen 11 (semi-conductor layer) . This is followed by an electric insulation 12 (cross-linked polyethylene) and then an insulation screening 13 (semi-conductive layer) . On the outside of this is an outer protection 14.
• Fig. 9 shows the maximum current as function of the cross-sectional area of a copper conductor, for a voltage range of from 12 kV - 24 kV and a frequency of 50 Hz, with an ambient water temperature of 5°C.
• a power generation of 200 W/m will require a cable current of 1,0 kA - 1,3 kA.
• a cable with a copper conductor cross-section of about 400 mm 2 - 600 mm2 will be suitable.

Landscapes

• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Mechanical Engineering (AREA)
• Pipe Accessories (AREA)
• Pipeline Systems (AREA)
• Rigid Pipes And Flexible Pipes (AREA)
• Heat Treatment Of Articles (AREA)
• Laying Of Electric Cables Or Lines Outside (AREA)
• Heat Treatment Of Strip Materials And Filament Materials (AREA)
• Pusher Or Impeller Conveyors (AREA)
• General Induction Heating (AREA)

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ID=19891380

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• 1988
  • 1988-10-31 NO NO884850A patent/NO884850D0/no unknown
• 1989
  • 1989-10-30 DE DE89911899T patent/DE68912605D1/de not_active Expired - Lifetime
  • 1989-10-30 WO PCT/NO1989/000113 patent/WO1990005266A1/en active IP Right Grant
  • 1989-10-30 EP EP89911899A patent/EP0441814B1/en not_active Expired - Lifetime
  • 1989-10-30 US US07/678,990 patent/US5241147A/en not_active Expired - Fee Related
  • 1989-10-30 AU AU44832/89A patent/AU631152B2/en not_active Ceased
  • 1989-10-30 AT AT89911899T patent/ATE100547T1/de not_active IP Right Cessation
  • 1989-10-30 BR BR898907749A patent/BR8907749A/pt not_active IP Right Cessation
• 1991
  • 1991-04-12 NO NO911440A patent/NO174068C/no not_active IP Right Cessation
  • 1991-04-22 DK DK199100732A patent/DK173871B1/da not_active IP Right Cessation

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