JPH0972489A - Heat insulation pipe for feeding steam with leakage sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably detect steam leakage without being influenced by high temperature steam. SOLUTION: A steam pipe 11 is covered with an adiabatic heat insulation layer 13 and the outside thereof is covered with a sheathing pipe 14 through a spacer to produce a heat insulation pipe for feeding steam having an air space formed around the adiabatic heat insulation layer 13. A leakage detecting sensor 12 is arranged lower than the central line of the surface if the adiabatic heat insulation layer 13 throughout an overall length in the direction of the length thereof in such a state to place it in a porous protection conduit 15. The sensor 12 is hardly influenced by high temperature steam by dint of the adiabatic heat insulation layer 13. When a pinhole is generated in the steam pipe 11 and steam leaks, dew is condensed on the upper surface of the adiabatic heat insulation layer 13, and the dew condensation is detected by the sensor 12 to announce the generation of a pin hole. The leakage position thereof is detected through comparison and computation of the electric resistance values thereof in such a way that the sensor 12 is formed of a plurality of electrode wires.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam supply heat insulating pipe having a function of detecting a leak and detecting a leak position.

[0002]

2. Description of the Related Art In district heating / cooling / plant equipment and the like, a heat insulating pipe is laid from a supply center to a customer and steam or hot water is supplied. The adiabatic pipes used here are unavoidable from corrosion due to corrosion progressing over the years, and if pinholes occur, they must be repaired or replaced early to lose heat energy, Or, a problem of hygiene occurs due to the backflow of groundwater containing impurities. Therefore, it is necessary to detect it at an early stage, detect its position, and repair it. A means for detecting this pinhole and detecting the generation position is proposed in Japanese Patent Publication No. 58-17422, but in this method, the supply of the fluid is once stopped and the reaction gas is sent to the outer space of the pipe, The reaction-coloring cord is inserted in advance in the pipe, the reaction-coloring cord is colored by the reaction gas entering the pipe from the pinhole, and the cord is retrieved to determine the position of the pinhole. Therefore, it takes time and labor to detect a pinhole and detect its position, which is not satisfactory.

Therefore, the inventors of the present invention filed Japanese Utility Model Application No. 5-904.
No. 8 (Actual Kaihei No. 6-62282), assuming that the fluid flowing through the heat insulation pipe is hot water of 100 ° C. or less as shown in FIG. 11, “two conductors and electricity higher than electric resistance of the conductors” A leak sensor 2 which is braided and insulated from a conductive wire having a resistance value, and which is provided with a protective braid on the outer periphery thereof is additionally provided in the lengthwise direction immediately above the service pipe 1 to insulate it. A "heat-insulating pipe with a leak detection sensor" that was covered with the material 3 was proposed and a certain evaluation was obtained.

[0004]

However, not only hot water but also steam is naturally used as the supply fluid for district heating. In this case, the environment in which the sensor is installed greatly changes, that is, steam is much more hot than hot water. Due to the high temperature, the temperature of the electrode wire (conductive wire) becomes high and the electric resistance of the sensor wire becomes high. As a result, it is doubtful whether the leak position can be accurately detected by the resistance comparison calculation of the closed circuit. Also, since the fluid is steam, if leakage occurs, there is a concern that the leakage steam may spread considerably in the length direction and the leakage position may not be accurately detected. Development was delayed.

Further, since the structure of the hot water supply pipe and that of the steam supply pipe are largely different, and the contents of the pipe laying work also change greatly, it is necessary to devise a construction method that matches them.

In view of the above, it is an object of the present invention to immediately detect a steam leak in a steam supply pipe laid in a district heating and cooling system and to accurately detect the leak location.

[0007]

[Means for Solving the Problems] In order to solve the above problems,
The present invention, in a steam supply pipe provided with an outer tube through an air space around a steam pipe provided with an insulating heat insulating layer on the outer periphery, on the surface of the heat insulating heat insulating layer of the steam pipe over the entire length in the length direction. The configuration is such that a sensor for detecting leakage of steam is added (claim 1).

In this structure, the sensor may be one in which an electrode wire in which a high resistance conductor and a low resistance conductor are respectively insulated so as to allow water to pass through and a conductor in which a low resistance conductor is impervious to water are arranged in parallel. It is possible (Claim 2), and the sensor is arranged below the center horizontal line of the steam pipe (Claim 3), and a large number of the heat insulating layer of the steam pipe is provided over the entire surface in the longitudinal direction. A protective conduit having a hole formed along its entire length may be added and inserted into the protective conduit (claim 4).

[0009]

In the present invention constructed as described above, since the sensor is attached to the surface of the heat insulating and heat insulating layer, it is not easily affected by high temperature steam, and if a pinhole is generated in the steam pipe,
When the steam leaks, dew condensation forms on the surface of the heat insulation layer, and the sensor can detect dew condensation to detect the occurrence of pinholes. At this time, if the sensor is composed of a high and low resistance conductor, the pinhole occurrence position can be immediately detected by performing a comparative calculation of the electric resistance of the closed circuit shown in FIG. 7 or the like (see the embodiment). Also, if the sensor is located below the center horizontal line of the steam pipe, the dew condensation of the steam leaking from the pinhole will drop down along the surface of the adiabatic heat insulation layer, and it will be detected. Others are less likely to be detected, and malfunctions can be prevented.

Further, if the sensor is inserted into the porous protective conduit, the sensor is sufficiently protected, and the electrode wire of the sensor is sequentially inserted and extended while laying and extending the unit of the heat insulating pipe for vapor supply. be able to.

[0011]

Embodiments of the present invention will now be described with reference to the drawings. 1 to 3 are vertical cross-sectional views of a steam supply heat insulating pipe P with a leak sensor according to the present invention, and FIG. 1 shows one steam pipe 11 having a heat insulating and heat insulating layer 13 made of foamed resin or the like as an outer tube 14.
FIG. 2 shows two steam pipes 11 each having an adiabatic heat insulation layer 13 arranged inside the jacket tube 14, and FIG. 3 shows one steam pipe 11 having an adiabatic heat insulation layer 13 and other heat insulation. The steam pipe 11 or the drain pipe having no heat insulating layer 13 is arranged in the outer tube.

FIGS. 4a to 4g show standard shapes of the heat insulating pipes P and P'for supplying steam. a is a straight pipe, b is an elbow, c is a tee,
d is a standard anchor, e is an elastic loop that absorbs thermal expansion,
f is an end seal and g is a gland seal, both of which have a porous protective conduit 15 attached to the surface of the heat insulating and heat insulating layer 13 over the entire length in the lengthwise direction, and those having standard shapes are manufactured in advance in a factory. It is supplied to the construction site, and at the construction site these are combined and constructed. In the figure, D is a concrete block, 17 is an anchor plate, and 18
Is an exhaust socket, 19 is a drain socket, 21 is a seal plate, 20 is a drain plate, 21 'is a gland seal, 22 is a sleeve, and 23 is a seal material.

At the bent portions of the elbow, the tee and the expansion / contraction loop, the perforated protective conduit 15 is diverted or attached in a loop shape to increase the curvature so that the sensor 12 can be easily inserted. Further, the air space S between the outer jacket tube 14 and the heat insulating and heat insulating layer 13 is formed by fitting a spacer 16 shown in FIG.

In order to lay the heat-insulating pipe P for steam supply manufactured at the factory as described above at the construction site, first, as shown in FIG. 5, the steam pipe 11 is welded a and subjected to rust prevention treatment (see Fig. A), the part is covered with the heat insulating heat insulating material 30 for the joint, and the fixing band 31 is tightened (b, c in the same figure), and the outer jacket tube 32 for the joint having a slit inserted in the longitudinal direction which has been previously inserted is joined. The pull-back points are welded to the respective parts (Fig. 4 (d)). The joint portion is covered with asphalt coating or polyethylene heat shrink cover 33 (e in the figure).

At this time, in the case of a straight pipe, the insertion of the sensor 12 into the porous protective conduit tube 15 can be performed collectively by using a lead wire after laying several units P ...
When the elbow, the tee, and the expansion / contraction loop are interposed, the sensor 12 is inserted every time each unit P, P ′ is laid so that the sensor 12 is not damaged.

In this embodiment, the steam supply heat insulating pipe P,
After laying P ′, the sensor 12 was inserted into the porous protective conduit tube 15. However, in the factory production of the units P and P ′ shown in FIG.
If 2 is attached and a connector is set at the end of each sensor 12 (see FIG. 11), the labor at the construction site can be reduced and the porous protective conduit 15 can be omitted.

When laying the heat-insulating pipe P for supplying steam, it is desirable that the sensor 12 is located below the horizontal line passing through the central axis of the steam pipe 11 except for the rising and falling portions of the pipe P.

The porous protective conduit tube 15 of the present embodiment is a metal tube having a rectangular cross section provided with a large number of holes. However, the shape and material are not limited to this, and the leaked vapor that has condensed is used as a sensor. Any structure can be used as long as it can reach, and any material can be used as long as it can withstand the temperature in the surface length direction of the heat insulating and heat insulating layer 13. Further, the perforated protective conduit 15 used for the curved portion has a corrugated tube or a portion corresponding to the spine in the lengthwise direction as shown in FIG. 6a, and a large number of circular rib portions are circumferentially provided from the spine portion. If they are provided adjacent to each other, the bending process is easy.

Next, the structure of the leak detection sensor 12 will be described. As shown in FIG. 7, three electrode wires in which the electric copper conductor 12a and the conductor 12b of the nichrome wire are respectively braided and insulated by polyester fiber, and an electrode wire in which the electric copper conductor 12c is insulated by polytetrafluoroethylene are three. Are arranged in parallel (three twists in this embodiment). In this embodiment, polyester fiber is used for braid insulation, but any other electrically insulating fiber can be used. Although a nichrome wire is used for one of the electrode wires, the nichrome wire is used for better detection of the leakage position, and the material is not limited to this.

The detection of the leak position by the sensor 12 will be described with reference to FIG.
When the conductive state RW is established between a and 12b, a → b → c → d
Current flows in the direction of. At this time, the current (I), the voltage (E), and the resistance (Rs1) between cd are in the relation of formula. Rs1 = E / I ... Further, when the combined resistance per unit length of the conductors 12a and 12b is (Rs), the leakage position (Lp) is given by an equation. Lp (between cd) = Rs1 / Rs ... Therefore, the leakage position can be detected based on the above equation.

FIG. 8 shows a circuit capable of detecting the disconnection of the electrode wire 12b of the leak detection sensor 12, and the constant current source shown in the drawing is
As shown in FIG. 10, the resistance R of FIG.
A constant current i _C can be flown up to the value of Rx, and when it exceeds (Rx <R), ic decreases (i ′ c << ic). In the figure, Vab is a voltmeter, Vref
Is a reference voltmeter, and Rref is a reference resistance.

When detecting leakage / disconnection in this circuit, as shown in Table 1, first, (Rs ₁ + Rs ₂ ) · ic and Rref · ic are in a proportional relationship in a state where no leakage / disconnection occurs. Therefore, the total length of the sensor is L
(Known) If the equivalent sensor length of Rref is set to Lr, connecting the relay RY to the contact C ₂ as shown by a chain line results in Va.
b / Vref = {(Rs ₁ + Rs ₂ ) · ic = L · i
c} / Lr · ic, equivalent sensor length Lr = L · Vre
f / Vab is obtained.

Next, in order to detect the leakage and its position, the relay RY is connected to the contact c ₁ as shown by the solid line, and if there is no leakage, the above R≈∞, and in this state, the leakage occurs. When RW occurs, R <Rx and constant current ic
Flows through Rw, Rs ₂ , and Rref. Therefore, Va
b = ic · Rs ₂ , Vref = ic · Rref,
A voltage corresponding to the constant current ic appears on the reference voltmeter Vref, and the leak is detected. Also, L ₂ = Vab / V
ref x (Rref equivalent sensor length: Lr), and L ₁
= L-L ₂ , the distance L from the detection point to the leak point RW
₁ can be detected.

On the other hand, in order to detect the disconnection of the conductor (electrode wire) 12b, the relay RY is connected to the contact c ₂ like a chain line, and when the disconnection does not occur, R <Rx and Rs ₁ , Rs
A constant current ic flows through s ₂ and Rref, and Vab,
A reference voltage is shown in Vref. In this state, if the conductor 12b is broken, R> Rx and Rref
Only a small current ic 'flows through the reference voltmeter, and the value of the reference voltmeter at this time becomes Vref', and Vref '= ic'.R
ref << ic · Rref, and a disconnection is detected.

[0025]

[Table 1]

In order to detect the disconnection of the conductor 12a, as shown in FIG. 9, one plastic insulated wire 12c 'is added to the leak detection sensor 12 and both electrodes are added to the voltmeter Vab. Lines 12b, 12c or 12a, 12
A changeover switch Q capable of selectively connecting c ′ may be provided. However, the switching of c ₁ and c ₂ of RY is reversed. That is, the broken line detects leakage and the solid line detects disconnection.

[0027]

As described above, according to the present invention, when a steam leak occurs in a steam supply heat insulating pipe in which a steam pipe covered with a heat insulating and heat insulating layer is wrapped with an outer tube through an air space. It can be detected immediately and the leak position can be accurately detected.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of one embodiment.

FIG. 2 is a longitudinal sectional view of another embodiment.

FIG. 3 is a vertical sectional view of another embodiment.

FIG. 4 is an explanatory diagram of each standard unit according to the embodiment.

[Fig. 5] Construction explanatory diagram

FIG. 6A is a perspective view of an example of a porous protective conduit, and b is a perspective view of a spacer.

FIG. 7: Leakage position detection equivalent circuit diagram

FIG. 8 is an equivalent circuit diagram for determining a leakage position and disconnection.

FIG. 9 is an equivalent circuit diagram for determining other leakage positions and disconnection.

FIG. 10 is an explanatory view of the action of the constant current source.

FIG. 11 is a cross-sectional view of a conventional example.

[Explanation of symbols]

 11 Steam Pipe 12 Leak Detection Sensor 12a, 12c Electric Copper Conductor 12b Nichrome Wire Conductor 13 Adiabatic Insulation Layer 14 Outer Tube 15, 15 'Perforated Protective Conduit 16 Spacer P, P'Adiabatic Pipe for Steam Supply

Front Page Continuation (72) Inventor Keiho Mishima 3 1-3 Nihombashi Muromachi, Chuo-ku, Tokyo Kubota Tokyo Head Office (72) Inventor Yumitsu Kosuge 3 1-3 Nihombashi Muromachi, Chuo-ku, Tokyo Kubota Tokyo Head Office (72) Inventor Kunihiko Onishi 1-12-4 Hamamatsucho, Minato-ku, Tokyo Within Rickwill Japan (72) Inventor Kenji Kojima 2-10-5 Ryogoku, Sumida-ku, Tokyo Mitsui Inside the Metal Engineering Co., Ltd. (72) Inventor Tamotsu Kobori 2-3-1 Iwata-cho, Higashi-Osaka City Tatsuta Electric Wire Co., Ltd. (72) Inventor Kihachi Ohnishi 2-3-1 Iwata-cho, Higashi-Osaka City Tatsuta Electric Line Co., Ltd.

Claims (4)

[Claims] 1. A heat-insulating pipe for steam supply, wherein a jacket pipe is provided around the steam pipe having a heat-insulating heat-insulating layer on the outer periphery through an air space. A steam supply adiabatic pipe with a leak sensor, characterized in that a sensor for detecting a leak of steam is attached to the pipe. 2. The sensor is characterized in that an electrode wire in which a high resistance conductor and a low resistance conductor are respectively insulated so as to allow water to pass therethrough, and a conductor in which a low resistance conductor is impervious to water are arranged in parallel. The steam supply heat insulating pipe with a leak sensor according to claim 1. 3. The heat-insulating pipe for steam supply with a leak sensor according to claim 1, wherein the sensor is located below a center horizontal line of the steam pipe. 4. A protective conduit having a large number of holes perforated along the entire length in the lengthwise direction is provided on the surface of the heat insulation layer of the steam pipe, and the sensor is inserted therein. The steam supply adiabatic pipe with a leak sensor according to any one of claims 1 to 3, characterized in that: