JPH0321798B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electric heating tube device. More specifically, the present invention relates to an electrically heated pipeline in which the inner and outer tubes are used as reciprocating conductors to generate heat, and the inner tube is used as a transport tube.

[Conventional technology]

The present inventors have proposed the following: A. Regarding improvements to the invention of JP-A-55-142200 "Electric heating pipeline" (hereinafter referred to as the first invention) B. Pipeline" (hereinafter referred to as the second invention), the present invention further relates to an additional and improved invention of the second invention.

The first and second inventions 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 first invention disclosed in the application, and FIG.
The figure is an enlarged view of section A in FIG. 1.

In these figures, the inner tube 1 is an electrically conductive pipe for transporting a fluid 23, and the outer tube 2 is made of a ferromagnetic steel tube. Reference numerals 3 and 3' denote an AC power source, one of which is directly connected 5 to the outer tube 2, preferably at approximately the center thereof, and the other terminal is a sealed insulating bushing 11 provided on the outer tube.
It is connected by a conductor 7 passing through the inner tube to a terminal 4 provided preferably at approximately the center of the inner tube. The gap 22 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 sources 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 tubes of each unit are electrically connected at both ends (17, 18 for the power source 3 unit, 18, 19 for the power source 3' unit).

Now, in such an electric circuit, the current 10 from the AC power supply 3 is divided into 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. It has the advantage that it can be electrically connected.

However, in the first invention disclosed in the application, as is clear from the structure of the terminal portion shown enlarged in FIG. It is the sum of the current 9 flowing to the left and the current 9 flowing to the left, and it goes without saying that it can be measured, but the amount of distribution of each of the currents 8 and 9 cannot be measured. If these current values 8 and 9 remain 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 there is a defect in the insulation between the inner tube 1 and outer tube 2. Or, even if destruction occurs, the location of the failure or destruction point cannot be discovered even if the increase in current value of 10 is known. This is a serious problem because, for example, in such a heating tube, when the power supply voltage is 100 V, the length of one unit is 400 to 500 m.

A second object of the invention is to provide a structure in which the values of these currents 8 and 9 can be measured, respectively, in the above-mentioned pipeline branch type double-pipe electric heating tube unit.

In the second invention, an electrically conductive inner pipe for passing a fluid that needs to be heated and kept warm is provided with an electrically conductive outer pipe with a tubular gap substantially concentric therewith, and both ends of the inner and outer pipes are electrically connected to each other. A terminal is provided on either one of the inner and outer tubes, means is provided for connecting this terminal to one terminal of the AC power source, and power is supplied to the other of the inner and outer tubes from the other terminal of the AC power source. In an electric heating pipeline including at least one unit of a split type double electric heating tube provided with means for Electrically independent terminals are provided on each of the tubes on both sides of the dividing point, and these terminals are connected to the other terminal of the alternating current power source by connecting means including branched wire portions connected to each of the tubes. The gist of the present invention is that the pipeline is connected, and each of the branched connecting wire portions is provided with a current measuring means.

Fig. 3 is a patent application filed in 1983 related to the second invention.
132523 is a schematic longitudinal cross-sectional view of the pipes of an embodiment of the pipeline containing a unit of double electric heating tubes, the numbers appearing in this drawing being the first, except for those newly added. , represents the same thing as Figure 2.

Now, in the second invention, unlike the disclosed invention shown in FIG. 1, as shown in FIG. It is cut vertically in the length direction and mechanically and electrically divided into 2' and 2'' parts.

Terminals 5 and 5' are provided on both sides of the dividing point. Then, the entire 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 power source 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, the fracture position can be estimated from this current change.

FIG. 4 shows another example of the branch type electric heating tube unit shown in the above-mentioned Japanese Patent Application No. 132523/1982. 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 three insulating flanges.
As shown in 8 and 39, there are two terminals, and terminals 51 and 51' and terminals 52 and 52' are provided respectively.
If electric wires 48 and 49 connecting these terminals are provided with current measuring devices 25 and 25' as in FIG. 3, it is possible to measure the currents 8 and 9 flowing to the left and right of the heating tube unit. The structure shown in FIG. 4 has an insulating flange 38,
Connection point 2 of part 2 of outer tube 2 sandwiched between 39
9 can be considered to correspond to the electric wire 6'' in FIG. 3 together with the electric wire 48, and the right side part can be considered to correspond to the electric wire 6' in FIG. 3 together with the electric wire 49. Therefore, FIG. The structure shown in
It can be seen as a variation of the structure shown in the figure. The electric wire 46 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.

[Problem to be solved by the invention]

However, with the structure shown in Figures 3 and 4, it is clear that there is a problem in that it is very difficult to assemble the heating tube, especially to ensure that the connection terminal 4 serves as a current path. Summer.

As mentioned above, this difficulty is caused by the length of one unit, that is, the length of the outer tubes 2' and 2'', which is usually from several tens of meters to several meters.
100 m, and the gap 22 between the inner and outer tubes 1 and 2 is usually 10 m.
This will become even clearer if we consider that it is ~30mm.

The present invention was made primarily to overcome this difficulty.

[Means to solve the problem]

In the present invention, a conductive inner tube 1 through which a fluid that needs to be heated and kept warm is provided with a conductive outer tube 2 with a tubular gap 22 therebetween, and both ends of the inner and outer tubes are electrically connected 17 and 18. , a flange 35 having a diameter that bisects and penetrates the outer tube is provided at a position near the center in the length direction of the inner tube, and a flange 35 having a diameter that passes through the outer tube by dividing the outer tube into two is provided, and a flange 35 is provided that penetrates the outer tube, respectively. A flange 3 with a diameter matching the dimensions of the flange facing the flange
0, 30' are provided, and the inner pipe flange 35 and the outer pipe flange 30, 30' are electrically insulated with insulators 28", 28".
Further, the one inner tube flange is provided with a terminal 50, the two outer tube flanges are each provided with one terminal 5, 5', and the terminal 50 of the inner tube flange is connected to an AC power source. Connect one end of 3, and
The other ends of the AC power source are connected to the terminals 5, 5' of the two outer tube flanges by electric wires 6 having two electric wire branches 6', 6'' corresponding to the respective outer tube terminals,
This heating tube device includes at least one split-flow type dual electric heating tube unit that is capable of independently measuring the current flowing through each branch (6 and 6'') of the electric wire.

[Effect]

According to the structure of the present invention, first, a flange 35 having a diameter that bisects and penetrates the outer tube is provided on the inner tube (the terminal 50 can be easily and reliably provided on this flange); Since it is possible to reliably connect the inner tube and then insert the bisected outer tube to the outside of the content 1, it has conventionally been difficult to make the disconnection terminal to the inner tube reliable as a current path. In addition, it becomes easy to assemble a split-flow type dual electric heating tube device in which the inner and outer tubes serve as current paths.

〔Example〕

The present invention will be explained below with reference to the drawings.

FIG. 5 is a schematic partial cross-sectional view in the longitudinal direction of the heating tube according to the present invention, and FIG.
5 is a conceptual cross-sectional diagram around 5. The term ``conceptual'' is used to facilitate understanding, and indicates that the drawing method is not necessarily in accordance with the diagrammatic method.

Also, among the numbers in Figures 5 and 6, the numbers that have already appeared are number 1.
~4 The numbers have the same meaning as shown in Figure 4.

Now, in the present invention, as shown in FIG. 5, the flange 3 corresponds to the connection terminal 4 in FIGS. 1 to 4.
5 and its weld 36 constitute a terminal.

The order of assembly of the double electric heating tube is as follows: inner tube 1 with flange 35, flange 30,
The outer tube 2', 2'' with 30' is the insulating packing 2.
8'', 28 from the left and right, respectively, and are insulated from each other by the necessary number of insulating bolts 31 and fixed around the flange 35. At this time, in order to create an annular gap 22, The required number of spacers 20 must be inserted.The unit of the outer tube 2' or 2'' is short and the flanges 35, 2
If the length between the 8", 28 part and the connection 17 or 18 does not reach the required length, use the cylindrical cover 32 to add the outer tube 2", 102, for example to add 102 for 2". outside of
The outer tubes 2'', 102 are connected by welds 34, 34'.

At this time, the welding 33 for connecting the inner tube 1 must be performed before welding 34, 34', and the spacer 20' must also have been inserted, as well as having been inspected by X-rays, etc., if desired. Must be.

Next, the flanges 30 and 30 have terminals 5 and 5, respectively.
5' is provided, and the power source 3 is connected by branch wires 6' and 6''.
A terminal 50 is provided on the flange 35 and connected to the other terminal of the power source 3 by an electric wire 7. This electric wire 7 includes a divided outer tube 2',
The sum of currents 9 and 8, 10, flows through 2''.

If necessary, connect ammeters 25 and 25' via current transformers 24 and 24', and the current will be 8.
9 can be measured, and if an abnormal current occurs such as a short circuit due to dielectric breakdown between the inner and outer tubes, differential relay 2 is activated.
Similarly to the second invention, the power supply 3 can be shut off by the switch 6.

In the present invention, the outer tubes 2', 2'', and 102 can be made of ferromagnetic tubes, for example, steel tubes. In this case, the rib thickness t (cm), the resistivity ρ (Ωcm), the magnetic permeability μ, When the power supply frequency is f (Hz), the value called the skin depth S (cm) of alternating current S = 5030√ (cm) (1) When there is a relationship of 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, and even if the outer surface is grounded or contacted with metal at numerous points, no voltage will appear on the outer surface of the tube. In this respect, it does not generate a current that is harmful to human resources or ignites combustible gas.Therefore, it has the advantage that it 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, it is desirable to fill the gap 22 (usually 10 to 30 mm) with a material that is electrically insulating but has better heat conductivity than air. Further, 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 substance. The type of filling material varies depending on the holding temperature of the pipeline, 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°C, and the voltage is high, over several hundred V, transformer oil can be used, and the holding temperature is 100°C or higher.
In the above, known liquid heat media such as ethylene glycol and silicone oil can be used. 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.

In order to prevent these tubes from being damaged due to thermal stress caused by the temperature difference between the inner and outer tubes even after taking the above measures, the cover 32 may be made of a thermally expandable material such as a bellows. good.

Next, the heat insulating layer 37 is inevitably uneven in the length direction of the pipeline, and even when the pipeline is above ground over its entire length and the ambient temperature is uniform, the heat insulating layer 37 is approximately ±10% in the length direction of the pipeline. A temperature difference is created. 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, fill the gap 22 with a liquid 13' and use the pump 12 and piping 13 as shown in FIG. 15, the liquid is returned to the pump 12 through a device 21 which can provide some heating if necessary and which can purify or store the liquid, thereby reducing temperature differences along the length of the pipeline.
27 are holes drilled in the connection 18 and the flange 35 for the passage of the liquid 13'.

The crossover pipe 16 is unnecessary if the electrical connection means 17 has a hole through which fluid passes. 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 heat 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.

In addition, in the first disclosed invention, the outer tube 2 has (2)
Although there are restrictions as shown in the formula,
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, the power supply voltage is
Since it is possible to set the voltage 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).

If the gap 22 between the inner tube and the outer tube does not need to be airtight from the outside air (for example, if the fluid 13' is not filled or flowed, there is no need to make it airtight), then the cover 32 may be If the length is not very long, such as several centimeters or less, the currents 8 and 9 will not flow out of the outer tube even if 32 is simply connected as a current path.

〔effect〕

According to the present invention, the first, which is mostly based on the principle,
The second invention is more specific and easier to manufacture. That is, according to the structure of the present invention, first, a flange 35 having a diameter that bisects and penetrates the outer tube is provided on the inner tube (the terminal 50 can be easily and reliably provided on this flange); Since the flange can be reliably inserted into the outside of the inner tube 1,
Conventionally, it was difficult to ensure that the connection terminal to the inner tube serves as a current path, but this makes it easier to assemble a split-flow type dual electric heating tube device in which the inner and outer tubes serve as current paths. .

Additional Relationships The invention of original patent number 1544385 (Japanese Patent Publication No. 1-15995) is a conductive inner tube through which a fluid that needs to be heated and heat-retained is passed, and a conductive outer tube is provided by placing a tubular gap almost concentrically with the conductive inner tube. , electrically connecting both ends of the inner and outer tubes, and providing a terminal on either one of the inner and outer tubes,
At least a branch type double electric heating tube unit is provided with means for connecting this terminal to one terminal of the AC power supply, and means for supplying power to the other of the inner and outer tubes from the other terminal of the AC power supply. This invention relates to an electric heating pipeline that includes an electric heating pipeline, in which the other of the inner and outer tubes is mechanically and electrically divided vertically in the length direction of the tube, and the tubes on both sides of the dividing point are electrically independent of each other. and connecting these terminals to the other terminal of the alternating current power source by connecting means including branched wire portions connected to each of the terminals, and providing current measuring means for each of the branched connecting wire portions. The main part of this invention is to mechanically and electrically divide the outer tube of a branch type double electric heating tube unit, and to provide terminals on each tube on both sides of the dividing point. The main part includes connecting these to an alternating current power source by means of connection means including branched wire parts, providing current measuring means in each of the branched wire parts, and further including the installation of terminals provided in the inner tube. In order to facilitate the process, a flange 35 is provided on that part of the inner tube, and a terminal is provided on this flange, as specified in the Patent Law.
The relationship is in Article 31, Item 1.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view in the longitudinal direction of an electric heating tube device, which is the first invention disclosed in Japanese Patent Application Laid-Open No. 55-142200, and FIG. 2 is an enlarged view of section A in FIG. 1. Figures 3 and 4 are patent application No. 58-132523, respectively.
FIG. 5 is a schematic cross-sectional view in the longitudinal direction of a specific example of the electric heating tube device according to the second invention described in No. 1, and FIG. The figure is a schematic cross-sectional view of the vicinity of the flange 35 in FIG. 5. In these drawings, the numbers represent the following: 1 is an inner tube for transporting fluid, 2 is an outer tube that becomes a part of the current path, 2', 2'', 2, 102 are tubes that constitute the outer tube 2, 3, 3' are AC power sources, 4, 5, 5 ',5'',
50, 51, 51', 52, 52' are connection terminals,
6, 6', 6'', 46, 48, 49, 7 are connecting conductors, 8, 9, 10 are currents from an AC power source, 11 is a sealed insulating bushing, 12 is a circulation pump, 13
14 and 15 are the connection points between the pipe 13 and the outer pipe, 16 is the circulating fluid crossover pipe, 17, 18, 19
2 is an electrical connection between the inner and outer tubes 1 and 2, 20 is an insulating spacer, 21 is a circulating fluid storage tank/cleaning device/heating device, 2
2 is an annular gap, 23 is a fluid to be transported, 24, 24'
is a current transformer, 25, 25' is an ammeter, 26 is a differential relay, 27 is a hole, 28, 28', 28'', 28,
38, 39 are insulating flanges or packing, 29
is a connection point, 30, 30', 35 are flanges, 32
is the cover, 33 is the inner tube 1, and 36 is the flange 35.
, 34 and 34' are welds of the cover 32, respectively.

Claims (1)

[Claims] 1. An electrically conductive inner pipe 1 through which a fluid that needs to be heated and kept warm is provided with an electrically conductive outer pipe 2 with a tubular gap 22 therebetween, and both ends of the inner and outer pipes are electrically connected 17. ,1
8, a flange 35 having a diameter that divides the outer tube into two and penetrates the inner tube is provided at a position near the center in the longitudinal direction of the inner tube, and the outer tube is also attached to the outer tube divided into two by the penetration. A flange 30, 3 with a diameter corresponding to the dimensions of the flange facing the flange passing through the
0' is provided, and the inner pipe flange 35 and the outer pipe flange 3
0 and 30' are electrically connected via insulators 28'' and 28, and furthermore, a terminal 50 is attached to the one inner tube flange, and one terminal 5, 5' is attached to each of the two outer tube flanges. and a terminal 5 of the inner pipe flange.
0 is connected to one end of the AC power source 3, and the other end of the AC power source is connected to the terminals 5 and 5' of the two outer tube flanges.
It is connected by an electric wire 6 having two electric wire branches 6' and 6'' corresponding to each outer tube terminal, so that the current flowing through each electric wire branch (6' and 6'') can be measured independently. 1. A heating tube device comprising at least one branch type dual electric heating tube unit. 2. The branch type double electric heating tube device according to item 1, wherein two or more of the electric heating tube units are connected in the length direction. 3 The outer tube or both the inner and outer tubes of the double electric heating tube unit are made of ferromagnetic tubes, and the wall thickness of these tubes is at least twice the depth of the skin of the alternating current.
Or the heating tube device according to item 2.