JPH0115995B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to electrically heated pipelines. More specifically, the present invention relates to an electrically heated pipeline previously proposed by the present inventor that includes at least one electrically heated tube unit in which the inner and outer tubes are used as reciprocating conductors to generate heat and the inner tube is used as a circular feed tube. Tokukai Akira
No. 55-142200) relates to improvements in the invention of "Electrical heating pipeline with temperature equalizer".

[Conventional technology] The prior art will be explained below with reference to the drawings.

FIG. 1 is a longitudinal cross-sectional view of a specific example of the pipeline of the disclosed invention, and FIG. 2 is an enlarged view of section A in FIG. 1.

In these figures, the inner pipe 1 is a conductive pipe that transports a fluid 23, and 2 is its outer pipe,
It is made of steel tube, which is a ferromagnetic material. Reference numerals 3 and 3' denote an AC power supply, one of which is directly connected to the outer tube 2, preferably at approximately the center 5, and the other terminal is a sealed insulating pushing 1 provided on the outer tube.
It is connected by a conductor 7 passing through 1 to a terminal 4 provided preferably approximately in the center of the inner tube.
The gap between the inner and outer tubes is provided with an insulating spacer 20 to prevent electrical short circuits. Although FIG. 1 shows two units powered by AC power supplies 3 and 3', the number of units may be one or many. The length of one unit is usually from several tens of meters to several hundred meters. The inner and outer layers of each unit are electrically connected at both ends (at 17 and 18 for the power supply 3 unit and at 18 and 19 for the power supply 3' unit).

In such an electric circuit, a current 10 from an AC power source 3 is divided into two parts, 8 and 9, using the inner and outer tubes as a circuit. In this case, the power supply voltage can be lowered compared to the case where power is supplied from the end of one unit, and the potentials of adjacent ends of adjacent units are made equal, so that each unit can be connected one after another without an insulating flange. Can be electrically connected.

[Problem to be solved by the invention]

However, the invention disclosed in the application is
As is clear from the structure of the terminal section enlarged in the figure, the total current 10 from the current is the sum of the current 8 flowing to the right and the current 9 flowing to the left from the terminal in FIG. Although it is possible, needless to say, it is not possible to measure the respective distribution amounts of the currents 8 and 9. And these current values 8, 9
If this remains unknown, it is not only unclear whether the heat generation amount on the left and right sides of the terminals is as designed, but also in the unlikely event that insulation failure or breakdown occurs between the inner tube 1 and outer tube 2. Even if the increase in current value of 10 is known, it is impossible to discover where the defective or destructive point is.

It is an object of the present invention to provide a structure in which the values of these currents 8 and 9 can be measured, respectively, in a branch type double-tube electric heating tube unit for a pipeline as described above.

[Means for Solving the Problems] According to the present invention, an electrically conductive outer pipe is provided with a tubular gap approximately concentrically with an electrically conductive inner pipe through which a fluid that needs to be heated and kept warm is passed. Both ends of the tube are electrically connected, one of the inner and outer tubes is provided with a terminal, a means is provided for connecting this terminal to one terminal of an AC power source, and the other of the inner and outer tubes is provided with a terminal of the AC power source. In an electric heating pipeline including at least one unit of a branch type double electric heating tube provided with means for supplying power from one terminal of the other, the other of the inner and outer tubes is mechanically connected perpendicularly to the length direction of the tube. The two opposite ends of the divided tubes are connected with an electrical insulator interposed between them, and electrically independent terminals are provided on each of the tubes on both sides of the dividing point, and these terminals are The gist of the pipeline is that it is connected to another terminal of the alternating current power supply by a connecting means including electric wire portions connected to each of the electric wire portions, and each of the connecting electric wire portions is provided with a current measuring means.

[Effect]

According to the present invention, electrically independent terminals are provided on each of the divided tubes on both sides with an electrical insulator placed therebetween, and these terminals are connected to each other including electric wire portions to be connected to each other. Since the electric wire is connected to one terminal of the AC power supply by a means and a current measuring means is provided on each of the connected electric wire parts, it is easy to know whether the amount of heat generated on the left and right sides of the terminal is in accordance with the designed value. Not only can this be done, but when dielectric breakdown occurs in the double electric heating tube section including any of the divided tubes, the current passing through the connecting wire section changes, and the location of the breakdown can be estimated.

〔Example〕

FIG. 3 is a schematic longitudinal cross-sectional view of the pipe of one embodiment of the pipeline including the dual electric heating tube unit of the present invention; , represents the same thing as Figure 2.

Now, in the present invention, unlike the disclosed invention shown in FIG. 1, the outer tube 2 is cut perpendicularly to the length direction of the tube 2 through an insulating flange 28 as shown in FIG. It is mechanically and electrically divided into '' parts.

Terminals 5 and 5' are provided on both sides of the dividing point. Then, the total current 10 from the power source 3 passes through the electric wire 7 and the connecting terminal 4 to reach the inner tube 1, and is divided into a current 8 to the right and a current 9 to the left. 11 is an insulating bushing. Current 8 passes through wire 6' from connecting terminal 5, and current 9 passes through wire 6'' from connecting terminal 5'.
and returns to the power supply 3 through the wire 6 with a total current 10 at the connection 29.

Therefore, if necessary, a current transformer 24,
24' is provided, and currents 8 and 9 are measured by ammeters 25 and 2.
Read with 5'. Reference numeral 26 indicates a differential relay that is activated when there is an abnormality in either of the currents 8 and 9.

In such a structure, if dielectric breakdown occurs in any of the spacers 20 and a short circuit occurs at that point, the current 8 or 9 will change, and the change will be related to the distance from the connection terminal 4 to the position of the broken spacer 20. do.
Therefore, by measuring the values of these currents 8 and 9 and knowing the changes in these currents, the location of the breakdown can be estimated.

In the heating tube of the present invention, the length of the unit is 400 to 500 m when the power supply voltage is 100V. Therefore, if the structure of the present invention is not used and the invention disclosed in the application is maintained, the appearance of the outer tube 2 will change. Even more so, when there is a heat insulating layer on the outside of the outer tube 2 (not shown), it is almost impossible to discover the dielectric breakdown point from its appearance. Therefore, the effectiveness of the present invention should be easily estimated.

In FIG. 3, the insulating flange 28 is provided on the outer tube 2, but theoretically it may be provided on the inner tube 1, or on both the inner and outer tubes. However, considering the structure of the heating tube, it is best to provide it in the outer tube 2 in terms of ease of assembly, maintenance, durability, etc. Furthermore, when the insulating flange is provided on the inner tube, it goes without saying that the fluid 23 to be transported within the inner tube must be electrically non-conductive.

Next, the voltage applied to the insulating flange 28, that is, the voltage between the terminals 5, 5' is
Since they are connected at this point, we can consider the potential difference from this point. This potential difference is related to the power consumed by the ammeters 25, 25', which are loads on the current transformers 24, 24', and the differential relay 26, but since this is about 10W in total, the currents 8, 9 If it were 300A, it would be less than 0.1V, which is extremely small. That is, the insulating flange 28 may be electrically extremely simple.

However, the fluid 23 has a small flow rate or has stopped, and although not shown, the heat insulating layer on the outside of the outer tubes 2' and 2'' is uneven in the length direction of the tube, resulting in uneven tube temperature. In order to prevent
When flowing liquid 13' through 2 (described in detail later),
Packing of insulating flange 28 (electrical insulator)
Of course, 28' must be capable of preventing leakage of this liquid.

Furthermore, although the insulating bushing 11 and the flange 28 are placed at different positions in FIG. 3, it would be more convenient for maintenance if they were not far apart.

In addition to the structure shown in FIG. 3, it is also possible to measure the currents 8 and 9 flowing left and right in the branch type electric heating tube unit by using the structure schematically shown in FIG. 4. In FIG. 4, the same numbers as in FIG. 3 have the same meaning. That is, in FIG. 3, there is one insulating flange 28, but in FIG. 4, there are two insulating flanges as shown at 38 and 39, and terminals 51, 51' and 52,
52' are provided, and electric wires 48, 49 connecting these terminals are provided.
If current measuring devices 25, 25' are provided as in FIG. 3, it is possible to measure the currents 8, 9 flowing to the left and right of the heating tube unit. In the structure shown in FIG. 4, the left part of the connection point 29 of the part 2 of the outer tube 2 sandwiched between the insulating flanges 38 and 39 corresponds to the electric wire 6'' in FIG. 3 together with the electric wire 48, and the right part corresponds to the electric wire 49 can be considered to correspond to the electric wire 6' in FIG. 3.Therefore, the structure shown in FIG. 4 can be seen as a modification of the structure shown in FIG. This corresponds to the electric wire 6 in FIG.

When comparing the inventions shown in Figures 3 and 4, the fourth
The invention shown in the figure has the disadvantage that there are two dividing points compared to the invention shown in Fig. 3, but if a bellows is provided in this part to avoid thermal stress due to the temperature difference between the inner and outer tubes, the invention shown in Fig. 4 would be more advantageous.

In the present invention, the outer tubes 2, 2', 2'' can be made of ferromagnetic tubes, such as steel tubes. In this case, the wall thickness t (cm), the resistivity ρ (Ωcm), the magnetic permeability μ, When the power supply frequency is f (Hz), the relationship between the skin depth S (cm) of alternating current and the blown value S = 5030√ (cm) (1) is t>2S (2). The alternating current flowing through the outer tube 2, etc., concentrates only near the inner skin of the tube, and virtually no voltage appears on the outer surface of the tube, even if the outer surface is grounded or metal-contacted at numerous points. In these respects, no current is generated that is harmful to humans or livestock or that may ignite combustible gas.Therefore, there is an advantage that the pipe can be laid as is without the need to provide an insulating layer around the outer periphery of the pipe.

In the present invention, when heating the fluid 23 from a cold state, the heat generated in the inner tube 1 can be used as is for heating and keeping warm, but the heat generated in the outer tube 2 is transferred to the fluid 23. In order to use
This must be passed through the gap 22 between the inner and outer tubes. Therefore, there is a temperature difference between the inner and outer tubes 1 and 2. In order to minimize this temperature difference and the distortion caused by it, the gap 22 (usually 10 to 30 mm) is used.
It is desirable to fill the chamber with a material that is electrically insulating but has better heat conductivity than air. Also,
If there is a large temperature difference between the inner and outer tubes, distortion will occur between the inner and outer tubes, so in order to prevent this, it is desirable to fill the gap 22 with the above-mentioned material. The type of filling material varies depending on the pipeline's holding temperature, power supply voltage, etc., but it may be solid such as heat transfer cement if the power supply voltage is relatively low, up to several tens of volts. If the holding temperature is relatively low, below 100℃, and the voltage is high, over several hundred volts, transformer oil can be used.If the holding temperature is above 100℃, known liquid heat media such as ethylene glycol or silicone oil can be used. Available.
The thermal conductivity of these liquids is around 0.2 KCal/mh°C, which is not very high, but at high temperatures, the apparent thermal conductivity becomes much larger than the above value due to the aid of convection.

Although omitted in FIG. 3, such pipelines usually have a heat insulating layer on the outside of the outer tube 2. This heat insulation layer is inevitably uneven along the length of the pipeline, and even when the pipeline is above ground over its entire length and the ambient temperature is uniform, there is a temperature difference of about ±10% along the length of the pipeline. Can be done.
Such temperature fluctuations can cause problems in sulfur pipelines where the transportable temperature range is as small as 140 to 160°C, especially when the flow is stagnant. Therefore, in order to avoid such temperature fluctuations, the material filling the gap 22 is made into a liquid 13', and as illustrated in FIG. 15, a certain amount of heating can be done if necessary.
Device 21 capable of purifying or storing liquid
The temperature difference along the length of the pipeline can be reduced by refluxing the fluid through the pump 12. 27 is a hole drilled in the connection 17 for the passage of the liquid 13'.

The crossover pipe 16 is defective if it has holes that allow fluid to pass through the electrical connection means 17. However, when assembling a pipeline by connecting prefabricated units, it may be convenient to make connections using such crossover piping possible. In addition, if a heat-resistant liquid medium is used as the heat transfer material in the gap, the holding temperature of the pipeline can be increased to 350℃.
It can far exceed the upper limit of about 200℃ for conventional electric heating pipelines.

Note that in the disclosed invention, the outer tube 2 is limited as expressed by equation (2), but in the present invention, when the length of the tube unit is as short as 100 m or less, preferably several tens of meters or less, Since the power supply voltage can be set to 30V or less, a simple insulating layer may be provided on the outside of the outer tube 2 instead of the restriction in equation (2).

〔effect〕

As described above, the device of the present invention can completely eliminate the drawbacks of the disclosed invention, namely, that it was impossible to detect insulation defects or breakdown points between the inner and outer tubes, and furthermore, It can also have the advantages of published inventions.

[Brief explanation of drawings]

FIG. 1 is a schematic longitudinal cross-sectional view of a pipeline according to the invention disclosed in Japanese Patent Application Laid-Open No. 142200/1982, and FIG. 2 is an enlarged view of section A in FIG. 1. 3 and 4 are schematic longitudinal cross-sectional views of a pipeline according to one embodiment of the present invention, respectively. In these drawings, the numbers represent the following: 1 is an inner tube for transporting fluid, 2 is an outer tube that becomes part of the current path, 3, 3' are AC power sources, 4, 5, 5', 5'',
51, 51', 52, 52' are connection terminals, 6, 6',
6″, 46, 48, 49, 7 are connection conductors, 8, 9,
10 is a current from an AC power supply, 11 is a sealed insulating bushing, 12 is a circulation pump, 13 is its piping,
14 and 15 are connection points between the pipe 13 and the outer pipe, 16 is a circulating fluid transfer pipe, 17, 18, and 19 are the inner and outer pipes 1,
2 electrical connection, 20 an insulating spacer, 21 a circulating fluid storage tank/cleaning device/heating device, 22 an annular gap,
23 is a fluid to be transported, 24, 24' are current transformers, 25,
25' is an ammeter, 26 is a differential relay, 27 is a hole,
28, 38, 39 are insulating flanges, and 29 is a connection point.

Claims (1)

[Scope of Claims] 1. A conductive inner tube 1 through which a fluid that needs to be heated and kept warm is provided, and a conductive outer tube 2 is provided approximately concentrically with a tubular gap therebetween, and both ends of the inner and outer tubes are A terminal 4 is provided on one of the inner and outer tubes, means 7 is provided for connecting this terminal to one terminal of an AC power source, and the other of the inner and outer tubes is provided with a terminal 4, and the other of the inner and outer tubes is provided with a terminal 4. In an electric heating pipeline including at least one unit of a branch type double electric heating tube provided with means for supplying power from the other terminal of the The opposite ends of the divided tubes are connected with an electrical insulator interposed between them, and the tubes 2' on both sides of the dividing point are
2″ electrically independent terminals 5,
5'; 51, 52 are provided, and these terminals are connected to wire portions 6', 6''; 48, 49, respectively.
The connecting wire portions 6', 6'';
8 and 49, each of which is provided with a current measuring means. 2. The pipeline according to item 1, wherein the terminals provided on the tubes on both sides of the dividing point are located at adjacent tube ends of the tubes on both sides. 3. Means for connecting the terminals 5, 5'; 51, 52 provided on the tubes 2', 2'' on both sides of the dividing point to the other terminal of the AC power supply is provided by the connecting wire portions 6',
6″; a common conductor portion 6 in a portion closer to the other one terminal of the AC power source than 48, 49;
4. The pipeline according to claim 1 or 2, characterized in that the pipeline comprises: 46. 4 The common conductor portion 6 is mechanically separated from the tubes 2' and 2'' on both sides of the dividing point, and an electrical insulator is interposed between the two opposing end portions. This is an electric wire 46 that connects the point 29 on the pipe 2, which is connected and installed, and one other terminal of the AC power source, and this electric wire 46, the pipe portions on the left and right of the point 29, and the respective pipes provided thereon. terminal 51',
52' and terminals 51, 52 provided on the tubes 2', 2'' on both sides of the dividing point, respectively. 5. The pipeline according to item 3, characterized in that the pipeline constitutes means for connecting the heating tube unit 52 to another terminal of an AC power source. The pipeline according to any one of paragraphs 6 to 6, wherein the outer tube or the inner tube and the outer tube of the double electric heating tube unit are made of ferromagnetic tubes, and the wall thickness of this tube is
6. The pipeline according to any one of items 1 to 5, wherein the depth is at least twice the skin depth of the alternating current.