DE102015003481A1 - Method for electric accompanying heating of pipelines for fluid transport - Google Patents

Abstract

Process for the electrical accompanying heating of heat-insulated pipelines, in particular underground pipelines for the transport of oil and petroleum products or other transport media to be kept warm over long transport distances, characterized in that a) the specific heating power to be provided along one pipeline section is applied to a plurality of resistance elements installed in parallel along the transport pipeline B) the resistance heating conductors are each provided with electrical jacket insulation, and in each case laid in metal heating tubes are, as they are typical for skin effect heating systems, wherein the heating tubes to achieve a good heat transfer by means of welding or soldering connection with the transport line are connected c) in the area of the connection of two heating tube sections special measures to minimize a possible ingress of water are made, for. B. by means of welded or soldered couplings and / or cable pull-in boxes, the tightness is finally detected by means of suitable leak tests d) the tube material, which forms the outer jacket-shaped part of a heating tube, not, as in skin effect heating systems, is flowed through by the heating current e) the jacket-shaped component of a heating tube itself does not actively contribute to the generation of heat from electrical energy.

Description

The invention relates to a method for electrical accompanying heating of pipelines, in particular underground pipelines for the transport of oil and petroleum products over long transport distances.

1. Overview and problem description

1.1 General

In the course of the transport of fluids, in particular of heavy and high-viscosity oils in long pipelines (eg more than 400 km) results in certain types of crude oil u. a. the task of transporting the crude oil at an elevated temperature relative to the ambient temperature. The fluid to be transported will simplify referred to below as crude oil, but the fundamental considerations may also apply to other fluids, eg. As liquid sulfur, sulfuric acid, if necessary, be applied in accordance with adapted approach.

• a) Um die Temperatur des Rohöls oberhalb des Stockpunkts (Pour Point) zu halten, und somit eine mögliche Verfestigung (Gelierung) des Rohöls während normaler Betriebsphasen einschließlich möglicher Förderstillstände zu vermeiden.
• b) Um die Temperatur des Rohöls oberhalb der Temperatur der beginnenden Wachsabscheidung (englisch: wax appearance temperature) (WAT) zu halten, und somit eventuelle Wachsabscheidungen auf der inneren Oberfläche der Transportleitung zu vermeiden, die ggf. häufig erforderliche Reinigungsmaßnahmen zur Folge hätten.
• c) Um die Viskosität des Erdöls, und damit den Reibungswiderstand und die benötigte Pumpenantriebsleistung während des normalen Transportbetriebs zu verringern,
• d) Um nach einem beabsichtigten oder unbeabsichtigten längeren Förderstillstand den Förderbetrieb mit den zur Verfügung stehenden Pumpen wieder aufnehmen zu können, ohne dass es infolge der Erdöl-Abkühlung zu einer Verfestigung (Gelierung) des transportierten Erdöls kommt, die einen erneuten Start des Förderbetriebs verhindern könnte.

The transport of crude oil at elevated temperatures compared to the ambient temperature may be necessary for the following reasons:

• a) In order to keep the temperature of the crude oil above the pour point (Pour Point), and thus to avoid a possible solidification (gelation) of the crude oil during normal operating phases including possible delivery stoppages.
• b) In order to maintain the temperature of the crude oil above the temperature of the wax appearance temperature (WAT), and thus to avoid any wax deposits on the inner surface of the transport line, which would often result in necessary cleaning measures.
• c) In order to reduce the viscosity of the petroleum, and thus the frictional resistance and the required pump drive power during normal transport operation,
• d) To be able to resume the delivery operation with the available pumps after an intended or unintentional prolonged production shutdown, without it due to the oil cooling to a solidification (gelation) of the transported oil, which could prevent a restart of the production operation ,

To meet the above requirements, the heat losses occurring along the heated crude oil line must be minimized as possible, which z. B. in underground installation by exploiting the heat-insulating property of the soil, and possibly additionally by sheathing the crude oil pipe can be done with a heat-insulating layer, as in an analogous manner z. B. is realized in known district heating transport systems. Furthermore, the unavoidable heat losses must be compensated by means of suitable heating methods.

1.2 Known heating methods

1.2.1 General

Known methods for the heating of transport lines are the method of heating in heating stations / 1, 2, 3 / and the method of tracing heating with electrical energy. Essentially two different methods / 3 / are used in the method of heat tracing with electrical energy: the resistance heating method and the skin effect heating method.

1.2.2 Skin effect heating

The method of skin effect heating, also known as skin effect current trace heating (SECT), skin effect heat tracing system (SEHTS) or skin effect tracing system (STS), is has long been known / 3, 4, 5 / and can be used in sections, especially in longer pipelines.

In such a heat tracing along the pipeline and in close thermal contact with this runs a comparatively thin tube of ferromagnetic material, eg. B. carbon steel with a nominal diameter of z. B. 25 mm, hereinafter 'heating tube' (called 'heating tube'), which operated by the 'skin effect' due to the laid in her isolated electrical line, which are powered by alternating current is heated on its inside and gives off their heat to the oil pipe to be heated. The heating tube is in this case preferably connected by means of welding or soldering with the transport line to be heated.

The aspects associated with planning, specification and installation of such a system are e.g. B. in the literature / 6 / described in detail.

The longest known pipeline heat-tracing system using a skin-effect heating system was implemented on the Mangala Development Pipeline System (MDP) in India on a 670 km long heat-insulated and accompanied crude oil pipeline with a pipeline diameter of approx. 0.6 m ("24"). has / 7 /. The distance between the feed stations is given in / 7 / at approx. 18 km. According to a more detailed description of the case realized skin effect trace heating system of the company. Pentair / 8 / the piping length specific heating power at the design point is about 40 W / m per linear meter with a heating circuit length of 8,210 m and a SEHMS feed voltage of about 3, 3 kV at 50/60 Hz AC voltage. Thus, from a feed-in point, a pipeline length of approx. 16.42 km could be supplied with electrical heating energy.

A similar skin-effect heat tracing system is being offered by Thermon on the market / 9 /.

• • Die Vielzahl der erfolgreichen Anwendungen und die erwiesene Zuverlässigkeit eines solchen Systems
• • Die gute Übertragung der in der Heizröhre erzeugten Wärme auf die zu beheizende Rohölleitung
• • Die Sicherheit der in der Heizröhre verlegten elektrischen Leitung gegen äußere Einflüsse, z. B. gegen Eindringen von Wasser, wenn die Verbindungsstellen der Heizröhren-Abschnitte entsprechend abgedichtet werden.

The advantages of the SECT system can be mentioned in particular:

• • The multitude of successful applications and the proven reliability of such a system
• • The good transfer of the heat generated in the heating tube to the crude oil line to be heated
• • The safety of the electrical cable laid in the heating tube against external influences, eg. As against ingress of water when the joints of the heating tube sections are sealed accordingly.

1.2.3 Resistance heating

1.2.3.1 General description

The method of resistance heating of transport lines has long been known, in particular in the area of above-ground cable laying / 3 /. The required heat is generated here in electrical heating cables according to the principle of electrical resistance heating, the z to be heated to the transport line. B. be attached by means of ribbons / 10 /. In addition, a variant with a laying of heating cables in cable ducts is known / 11 /.

In single-phase resistance heating systems, two parallel heating conductors can be operated along the transport pipeline in series with conductive connection of both heating conductors at the remote ends of the line to the electrical supply point / 11 /. In three-phase resistance heating conductor systems with parallel installation of three heating conductors, these can be connected and operated in star connection at the remote line ends / 12 /. The heating systems of some providers researched on the Internet will be discussed briefly below.

1.2.3.2 Pentair

In their technical documentation / 13 /, Pentair offers flexible Raychem series resistance heating cables that can be used when heating circuit lengths exceed the design limits of conventional parallel resistance cables and a single power source is required.

Series Resistance Heating (SC) cables are available with one or two conductors for single-phase or three-phase systems. The resistance heating conductors are electrically insulated with high temperature resistant, thick walled fluoropolymers surrounded by a grounded shield and a final fluoropolymer jacket.

Maximum continuous temperatures of 250 ° F (121 ° C) and a temperature load of up to 482 ° F (250 ° C) are available. Series resistance heating cables (SC) are capable of providing heating circuit lengths of up to 12,000 feet (3660m) with a feed point and voltages up to 600V AC.

1.2.3.3 Thermon

Thermon / 14 / also offers resistance heating trace heat tracing systems, including grade 825 mineral insulated heating cable (MIQ), an alloy with a high nickel / chromium content that is ideally suited for high temperature applications in accordance with / 14 / and has exceptional resistance to stress corrosion cracking in chloride, acid, saline and alkaline environments. As indicated further in / 14 /, MIQ cables are suitable for use in ordinary (unclassified) and hazardous (classified) areas and are operated at temperatures up to 932 ° F (500 ° C) with an AC voltage of 600V.

1.2.3.4 Heat-Trace Ltd.

With its 'Longline Trace Heating System', the company Heat-Trace / 10 / offers a heating cable system based on the principle of resistance heating, in which the heating cables provided for heating the transport line are designed as single, double or triple heating conductors. These heating cables are drawn into the cable ducts of prefabricated, heat-insulated pipeline sections during the installation of the pipeline system. The cable ducts in this case consist of elongated cable channel elements with a C-shaped cross section, which abut with its two edges on the outside of the transport pipe and thus form an approximately rectangular cable channel. The annular space between the transport line, the cable channels running along it and the outer casing of the transport line is in this case with a suitable heat-insulating material, for. B. filled in polyurethane foam.

The heating cables offered by Fa. Heat-Trace can in this case have different cross-sectional shapes, for. B. as a single electrical line with a circular or flat, approximately rectangular cross-section, or with outer, flat approximately rectangular cross-section and contained therein, separated from each other, insulated heating conductors.

According to Heat-Trace / 10 /, this indicates that their new continuous-flow extrusion facility ("extrusion facility") allows the construction of long-life heating systems ("longline systems") to produce up to 60 kilometers of pipeline heating section length from a single central electrical system Supply point out.

For different heat tracing lengths that can be realized from a single central electrical feed point, the following heat tracing options are listed in / 10 / among others: 0-15 km 2 foil longlines 15-25 km 3 Foil longline 25-30 km Skin trace 30-60 km 3 × 1 foil longline

• • Längere Heizkreise
• • Niedrigere Kapitalkosten
• • Billigere/einfachere Installation
• • Niedrigere Betriebskosten; nach Angaben des Herstellers beträgt der Leistungsfaktor des Skin-Effekt – Heizungssystems 0.85 im Vergleich zu 1 beim ,Longline Trace Heating System'.

For the 'Longline Trace Heating System', the manufacturer sees the following advantages over the skin effect heat tracing system / 10 /:

• • longer heating circuits
• • Lower capital costs
• • Cheaper / easier installation
• • Lower operating costs; According to the manufacturer, the power factor of the skin effect heating system is 0.85 compared to 1 in the Longline Trace Heating System.

2. Problem description

2.1 General

For long, electrically heated crude oil transport systems, eg. As with transport distances of more than 500 km, the assurance of a reliable and trouble-free pipeline operation and thus the minimization of all conceivable caused by construction, installation and operation of possible risks of extreme importance. This is especially true if such an electrically heated transport system is to be built and operated in regions with difficult environmental conditions. In this context, z. B. in particular seasonally occurring rainy seasons with extreme water attack, in which the torrential accumulating rainwater then his way z. B. searches within the pipe trenches along the laid transport pipe, this flushed and submerged and in the course of time by Sandausspülung the problem of seasonal underwater replacement of the transport pipeline aggravated.

In order to achieve optimal safety of the transport system against possible ingress of water and subsequent water spreading, in particular along the electric companion heating, the proposed heat tracing must be designed to be resistant to such effects maximum resistance.

Another extremely important further consideration for minimizing known and possibly unknown risks of a system installation is the use of reliable system technology that has been proven in the past, even if newer technical methods and arrangements promise a cost advantage, but not yet sufficient operating experience for the system expected operating conditions (eg potential underwater pipeline) over a corresponding period of operation.

Another important consideration is especially in remote areas or areas with difficult socio-economic infrastructure, the idea to minimize the number of required for pipeline operation stations, especially feed stations for electrical energy, to minimize, and thus to realize the largest possible station distances to the To minimize the total number of operating and security personnel required for the operation and maintenance of such stations, and thus to maximize overall risk minimization for all operations personnel.

In view of the objectives described above, particular attention will be given below to disadvantages of the previously known pipeline heat tracing systems.

2.2 Skin Effect Heating Systems

• • Die Notwendigkeit des Verschweißens oder Verlötens der Heizröhre mit der Transportleitung, was mit entsprechend erhöhten Investitionskosten verbunden ist
• • Der Wirkungsgrad der elektrischen Begleitheizung nach dem SECT-System, der in der Größenordnung von etwa 90% genannt wird /10/.
• • Die beschränkte Heizkreislänge von ca. 12,5 km bei einer spezifischen Heizleistung von 40 W/m, wodurch der maximal realisierbare Stationsabstand auf etwa 25 km beschränkt wird.

Although electrical heat tracing systems based on the principle of skin effect heating (SECT) have the advantages already mentioned under point 1.2.2, from the applicant's point of view in particular the following possible disadvantages are considered:

• The necessity of welding or soldering the heating tube to the transport line, which entails correspondingly increased investment costs
• • The efficiency of electrical heat tracing after the SECT system, which is on the order of about 90% / 10 /.
• • The limited heating circuit length of approx. 12.5 km with a specific heat output of 40 W / m, which limits the maximum achievable station distance to approx. 25 km.

2.3 Resistance trace heating systems for large heating section lengths

• • Aufgrund der möglichen Spaltenbildung zwischen Transportrohrleitung und den daran angelegten Kabelkanälen könnte sich bei einem Wassereintritt, z. B. im Bereich von Muffen-Verbindungen des die Transportrohrleitung umgebenden Schutzmantels (z. B. HDPE Rohr) das eingetretene Wasser entlang oder innerhalb eines oder mehrerer Kabelkanäle ausbreiten und zu weiteren Folgeschäden, z. B. Korrosion des Transportrohres oder elektrischen Kurzschlüssen im Bereich von Heizleiter-Verbindungsstellen führen.
• • Mögliche Überhitzung der Heizleitungen und ggf. daraus resultierende Heizleitungs-Kurzschlüsse, falls im Bereich von Fehlstellen bei der Montage eines oder mehrerer Kabelkanäle die Wärmeleitung zwischen Kabelkanal und Oberfläche der zu beheizenden Transportleitung deutlich vermindert ist; aufgrund des dann erheblich erhöhten Wärmeübergangswiderstands zwischen Transportleitungsoberfläche und Kabelkanal wird dann die Lufttemperatur im Kabelkanal erheblich ansteigen, gefolgt von einem weiteren erheblichen Temperaturanstieg im Heizkabel selbst, insbesondere aufgrund des erheblichen Wärmeübergangswiderstands zwischen der Luft im Kabelkanal und der Oberfläche der elektrischen Kabelisolation.
• • Deutlich geringere (zumindest öffentlich bekannte) Erfahrungen mit dem Langzeitverhalten eines solchen Begleitheizsystems im Vergleich zu Skin-Effekt-Begleitheizsystemen.

Although electrical heat tracing systems based on the principle of resistance heating for long heating circuit sections have the advantages already mentioned under point 1.2.3.4, in the applicant's view, in particular the following possible disadvantages of such a system are considered:

• • Due to the possible formation of gaps between the transport pipeline and the cable channels attached to it, a water ingress, eg. B. in the range of sleeve joints surrounding the transport pipe protective jacket (eg., HDPE pipe) propagate the water along or within one or more cable channels and further damage, eg. B. lead to corrosion of the transport tube or electrical short circuits in the range of heating conductor connection points.
• • Possible overheating of the heating cables and possibly resulting heating cable short circuits, if the heat conduction between the cable duct and the surface of the transport line to be heated is significantly reduced in the area of defects when installing one or more cable ducts. due to the then significantly increased heat transfer resistance between Transportleitungsoberfläche and cable channel then the air temperature in the cable channel will increase significantly, followed by a further significant increase in temperature in the heating cable itself, in particular due to the significant heat transfer resistance between the air in the cable channel and the surface of the electrical cable insulation.
• • Significantly lower (at least publicly known) experiences with the long-term behavior of such a heat tracing system compared to skin effect heat tracing systems.

2.4 conclusions

• • möglichst hoher Schutz gegen unbeabsichtigten Wassereintritt und Wasserausbreitung im Transport- und Begleitheizungssystem,
• • ausschließliche Verwendung bewährter, zuverlässiger Systemtechnik sowie
• • weitgehende Minimierung der Anzahl der erforderlichen Einspeise-Stationen, und damit verbundene Maximierung der mittels Begleitheizung beheizbaren Transportabschnittslängen

keines der vorstehend genannten Begleitheizsysteme (SECT-System, Widerstands-Heizsystem) als zufriedenstellend empfohlen werden kann.From the point of view of the author, the explanations given in the previous chapters show that, with regard to the requirements set out in Chapter 2.1, the minimization of possible risks associated with the installation and operation of an electrical heat tracing system, such as

• • maximum protection against inadvertent water ingress and water dispersion in the transport and heat tracing system,
• • exclusive use of proven, reliable system technology as well as
• • minimizing the number of required feed stations and maximizing the heatable transport section lengths

none of the above-mentioned heat tracing systems (SECT system, resistance heating system) can be recommended as satisfactory.

As part of the system planning of accompanying long crude oil transport systems, the task was therefore to look for measures with which the requirements set out in Chapter 2.1 can be fulfilled to a large extent in the end.

3. Problem solving

3.1 Description of the problem solution according to the invention

As problem solving according to the invention in the context of this patent application, it is provided to combine the advantages of both described heat-tracing systems and to largely avoid their disadvantages. The advantage of the resistance-tracing heating system is that relatively long heating sections can be realized, in particular, when the specific heating power to be provided along a pipeline section (eg 40 W / m) is divided among a plurality of parallel resistance heating lines (heating conductors). Therefore, according to the invention, the heating pipe system is realized from a plurality of heating conductors laid parallel along the pipe. Preferably, such a system is implemented by three heating conductors, which is operated with 3-phase AC current, the heating conductors are connected to each other in star connection at the lying opposite the 3-phase feed point distant Heizleitungsenden.

In order to ensure good protection of the heating conductors, the heating cables used are those heating cable types which are also used in the proven reliable SECT heat tracing system. In addition, the heating cables are laid in an analogous manner as in the SECT heating system in heating pipes, which are connected to the transport pipe by welding or soldering and thus ensure good heat transfer of the generated heat to be heated in the transport pipeline. In order to minimize a possible ingress of water in the region of the connection of two heating tube sections, the construction of the connection according to the invention takes place in an analogous manner as in the case of the SECT system. In the literature / 15 / this z. For example, it has been described that the heating tubes are welded or brazed together by means of coupler / cable pull boxes, and pneumatically tested to ensure system integrity and, in particular, to provide system security against any external water (e.g. Leakages of sleeve joints of the outer polyethylene protective tube).

Thus, the companion heating system according to the invention is based on the model of known skin-effect heating systems with a plurality along the transport pipe to be heated substantially parallel and connected to the transport pipe by welding or soldering connection 'heating tubes' equipped, in which according to the model of skin effect heating in each case an electrically insulated heating cable, preferably laid as a copper stranded wire, and wherein the heating cables at the opposite the power supply points opposite (far) heating cable ends conductively connected to each other.

As a particularly advantageous implementation variant of a built-up of 3 heat exchanger tubes heating system is considered, in which at the feed point 3-phase alternating current with z. B. 50 Hz or 60 Hz system frequency with comparatively high system voltage, z. B. 5 kV to 6 kV is fed, and their 'remote' ends are connected together as an electrical 'star point'.

Since from an electrical energy feed point two in the opposite direction along the transport pipe arranged line sections can be heated, the doubled feasible distance of the feed stations for electrical energy compared to the determined possible trace heating length.

• • Im Gegensatz zum Prinzip der Skin-Effekt-Beheizung erfolgt kein Stromfluss über die mit der Transportleitung elektrisch verbundene Heizröhren, so dass sämtliche Stromflüsse innerhalb der elektrisch isolierten Heizleiter verbleiben
• • Der Wirkungsgrad der elektrischen Widerstandsheizung liegt nahe bei 1 und ist damit deutlich höher als bei der Skin-Effekt-Heizung.
• • Bei Wahl gleicher Heizleiter-Querschnitte in einem mit 3 Heizleitern ausgestatteten und 3-phasig betriebenen Pipeline-Systemheizabschnitt ergeben sich annähernd gleiche elektrische Ströme in den drei Heizleitern; die erforderliche 3-Phasen-Versorgungsspannung am Einspeisepunkt kann hierbei in einfacher Weise mittels entsprechender Transformatoren bei ausgeglichener Stromaufnahme aus der Drehstrom-Versorgungsquelle (z. B. Stromnetz oder Generator) bereit gestellt werden.

Other advantages of the proposed heat tracing system include:

• • In contrast to the principle of skin effect heating, there is no current flow through the heating pipes electrically connected to the transport line, so that all current flows remain within the electrically insulated heating conductors
• • The efficiency of electrical resistance heating is close to 1 and is therefore significantly higher than in the case of skin effect heating.
• • If the same heating conductor cross-sections are selected in a pipeline system heating section equipped with 3 heating conductors and operated in 3 phases, approximately the same electrical currents will result in the three heating conductors; the required 3-phase supply voltage at the feed point can hereby be provided in a simple manner by means of appropriate transformers with a balanced current consumption from the three-phase supply source (eg power grid or generator).

3.2 Calculation equations

In the following, basic calculation equations for the heating cable design are compiled.

With the system voltage U, the voltage U ₁ between the two ends of a heat conductor 1 in a symmetrical 3-phase system in star connection U ₁ = U / √ 3 (3-1)

The specific heat tracing heat q _{1 of} the heating conductor 1 is q ₁ = q / 3 (3-2) when q denotes the specific heat tracing power in a pipeline section. The heating power Q _{1 of} the heating element 1 is with the length L of the pipeline section to be heated Q ₁ = q ₁ × L (3-3)

The electric current I ₁ in the heating element 1 results to I ₁ = Q ₁ / U ₁ (3-4)

The resistance R _{1 of} the heating conductor 1 is R ₁ = U ₁ / I ₁ (3-5)

With the electrical conductivity ρ, the length L of the heat conductor and with the cross section A of the heating element, the resistance R ₁ results R ₁ = ρ · L / A (3-6)

Conversion of equation (3-6) taking into account equation (3-5)

Solving for A by inserting equation (3-4)

Inserting Equations (3-3) and (3-3) in (3-8) yields

Inclusion of the equation (3-1) in (3-9) gives the heating cable cross-section A.

The heating cable diameter d can then be calculated to

3.3 Calculation examples

Hereinafter, for the assumed case of a required specific heat output of 40 W / m for a crude oil transportation line, calculations are made for the trace heating line design according to the resistance heating principle.

This is based on a 3-phase heating cable system with copper as Heizleitungsmaterial based, which is operated with a system voltage of 6 kV at a mains frequency of 50 Hz or 60 Hz.

The diagram ( 1 ) shows the required cable diameter as a function of the intended heating conductor length for the calculation example described above.

With an intended pipeline heating section length of 50 km and a required specific pipeline heating capacity of 40 W / m, the required conductor diameter per heating cable would be approximately 8.8 mm and the corresponding conductor cross-section would be for a heating conductor system consisting of 3 parallel heating conductors and connected to the heating conductor ends in star connection be about 61 mm ² . With such a solution, section lengths of about 100 km could then be realized between feeding stations for electrical auxiliary heating energy.

4. References

• /1/ Rafael Martínez-Palou et al.: Transportation of Heavy and Extra Heavy Crude Oil by Pipeline: A Review; Journal of Petroleum Science and Engineering 75 (2011) 274-282
• / 2 / GA Nunez, HJ Rivas, DD Joseph: Drive to <produce Heavy Crude Prompts Variety of Transportation Methods; OGJ Special Oct. 26, 1998 Oil and Gas Journal
• / 3 / S. Lechler, J. Kossert and K. Zehl: Planning and construction of the liquid sulfur transport pipeline Voigtei-Barenburg; Petroleum Natural Gas Journal, 93rd ed., July 1977, pp. 235-242
• / 4 / Canadian Patent 1149761 A1 ; Pipelines by Skin-Effect-Current Heating; published 12.07.1983; Inventor: Masao Ando http://www.google.com/patents/CA1149761A1?cl=en
• / 5 / http://www.skin-trace.com/, website downloaded on 01.03.2015
• / 6 / Ben C. Johnson: The Practical Issues Involved in Designing, Specifying and Installing Skin Effect Current Tracing Systems; 2012 Petroleum and Chemical Industry Conference Europe Conference Proceedings (PCIC EUROPE); 1-13
• / 7 / Mangala Development Pipeline (MDP), Rajasthan, Gujarat, India http://www.hydrocarbons-technology.com/projects/mangala-development-pipeline-india-crude-oil/ downloaded from internet on 07-03-2015
• /8th/ F. Chakkalakal, M. Hamill, J. Beres: Building the World's Longest Heated Pipeline - A Technology Application Review; 2014 IEEE Petroleum and Chemical Industry Technical Conference; Paper No. PCIC-2014-52, 8-10 Sep. 2014, San Francisco, CA.
• / 9 / Thermon, downloaded from the Internet on 07.03.2015 http://www.thermon.com/us/products.aspx?prodid=10
• / 10 / Hotfoil EHS, downloaded from the Internet on 08.03.2015 http://www.hotfoilehs.com/images/hotfoil/PDFs/Brochures/Heat_Tracing_Long_Pipelines.pdf
• / 11 / Heat-Trace, downloaded from the Internet on 08.03.2015 http://www.temarsrl.it/index.php/en/download/category/1-cables?start=20

Claims (8)

Process for the electrical accompanying heating of heat-insulated pipelines, in particular underground pipelines for the transport of oil and petroleum products or other transport media to be kept warm over long transport distances, characterized in that a) the specific heating power to be provided along one pipeline section is applied to a plurality of resistance elements installed in parallel along the transport pipeline B) the resistance heating conductors are each provided with electrical jacket insulation, and in each case laid in metal heating tubes are, as they are typical for skin effect heating systems, wherein the heating tubes to achieve a good heat transfer by means of welding or soldering connection with the transport line are connected c) in the region of the connection of two heating tube sections special measures to minimize any water ingress are made, eg. B. by means of welded or soldered couplings and / or cable pull-in boxes, the tightness is finally detected by means of suitable tightness tests d) the tube material, which forms the outer jacket-shaped component of a heating tube, not, as in skin effect heating systems, is flowed through by the heating current e) the jacket-shaped component of a heating tube itself does not actively contribute to the generation of heat from electrical energy. A method according to claim 1, characterized in that the heating conductors have a comparatively low specific electrical resistance in the typical order of copper conductors Method according to one of claims 1 to 2, characterized in that the heating conductors are preferably designed as stranded wire Method according to one of Claims 1 to 3, characterized in that the heating conductors are conductively connected to one another at the (far) heating conductor ends located opposite the current supply points. Method according to one of claims 1 to 4, characterized in that the heat tracing system preferably consists of 3 along the transport pipe arranged in parallel electrically insulated heating conductors, which are each laid in the heating conductors individually associated heating tubes. Method according to one of claims 1 to 5, characterized in that the heat tracing system is operated with 3-phase alternating current Method according to one of claims 1 to 6, characterized in that the heat tracing system is operated with alternating current in the frequency range 50 Hz to 60 Hz. Method according to one of claims 1 to 7, characterized in that the heat tracing system is preferably operated with a relatively high system operating voltage of at least 3 kV.

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