An external pressure expansion joint with leakage monitoring function

Abstract

An external pressure expansion joint with a leakage monitoring function includes an external pressure expansion joint and a leakage monitoring device, wherein the leakage monitoring device includes an outer leakage detection component and a middle detection component, wherein the outer leakage detection component is composed of a liquid detector 1 attached to the inner wall of the innermost tube blank of the external pressure expansion joint bellows and a sensor 1 arranged outside the external pressure expansion joint, wherein the liquid detector 1 is connected to the sensor 1 through a signal line, and the middle detection component is composed of a liquid detector 2 and a sensor 2 arranged outside the external pressure expansion joint, wherein the liquid detector 2 is arranged between the innermost layer and the second inner layer tube blank of the external pressure expansion joint bellows, and the liquid detector 2 is connected to the sensor 2 through a signal line. The corrosion rate of the bellows can be indirectly measured to avoid economic losses to the user unit caused by sudden failure accidents, improve the long-term operation reliability and functional value of the bellows, and ensure the long-term safe operation of the system pipe network.

Description

Technical Field

[0001] The invention relates to the technical field of expansion joints, in particular to an external pressure expansion joint with a leakage monitoring function. Background Art

[0002] According to statistics: corrosion is the main cause of bellows expansion joint failure, accounting for about 80% of the total failure types. Since expansion joints in high temperature, high pressure, and corrosive environments are mostly made of iron-nickel-based alloys and high-nickel alloys, they are mainly damaged by pitting, stress corrosion, high-temperature oxidation, etc., and the initiation of corrosion cracks is concentrated at the crests where liquid is easily accumulated, which is sudden and harmful.

[0003] At present, the expansion joints used in the fields of petrochemicals and coal chemical industry are generally of internal pressure type. By adopting the concept of "single-layer pressure bearing, double-layer design", and setting a negative pressure gauge and pre-vacuuming between the layers of the bellows, the leakage of the inner and outer tube blanks of the bellows can be indicated according to the change of the pressure indication number in actual operation. In the field of urban centralized heating, since the heating pipeline network is mostly located in the soil, the expansion joints are generally of external pressure type. In the actual operation process, the bellows of the external pressure expansion joint are extremely susceptible to corrosion damage induced by external corrosion effusion, which adds a certain degree of uncertainty to the safe operation of the heating pipeline network.

[0004] The leakage monitoring system of buried heating pipe network has been widely used in Europe in the early years. In recent years, with the promulgation of CJ / T254-2016 "Technical Specifications for Leakage Monitoring System of Direct Buried Hot Water Pipeline for Urban Heating", impedance or resistance leakage monitoring technology, distributed optical fiber leakage monitoring technology, temperature capsule monitoring technology, and negative pressure wave leakage monitoring technology have been applied or tested in corresponding thermal engineering projects, and the measurement results have shown a certain degree of reliability. However, the above technologies are based on the premise that the pipeline has been damaged and the internal medium has entered the surrounding environment of the pipeline, and are not suitable for corrosion leakage monitoring of expansion joints.

[0005] "Quantitative detection device for leakage of external pressure expansion joint" (patent number: CN 106287237 A) provides a method for judging whether an external pressure expansion joint is leaking by using a liquid sensor and liquid accumulation tanks of different heights. "A fully enclosed bypass external pressure balanced expansion joint with online detection" (patent number: CN 208169794 U) provides a structure and method for monitoring the leakage of the working bellows and the balancing bellows of the bypass external pressure balanced expansion joint. "A double-layer metal expansion joint online leakage monitoring device and method" (patent number: CN 110345330 A) provides a double-layer metal expansion joint online leakage monitoring device and method, which can realize online monitoring of the damage of any single layer of the double-layer metal expansion joint. "A state monitoring device and method for a heating pipeline expansion joint based on a distributed optical fiber temperature sensing system" (patent number: CN 108896203 A) provides a state monitoring device and method for a heating pipeline expansion joint based on a distributed optical fiber temperature sensing system. None of the existing public technologies or products involve the early warning function of leakage. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides an external pressure expansion joint with a leakage monitoring function, which can indirectly measure the corrosion rate of the bellows, avoid sudden failure accidents from causing economic losses to the user unit, improve the long-term operation reliability and functional value of the bellows, and promptly guide the user unit to actively take corresponding solutions based on the corrosion feedback results to ensure the long-term safe operation of the system pipeline network.

[0007] In order to achieve the above technical objectives, the technical scheme adopted is: an external pressure type expansion joint with a leakage monitoring function, comprising an external pressure type expansion joint and a leakage monitoring device, the leakage monitoring device is arranged at the lowest point of the innermost tube blank of the external pressure type expansion joint bellows, the leakage monitoring device comprises an outer leakage detection component and a middle detection component, the outer leakage detection component is composed of a liquid detector one attached to the inner wall of the innermost tube blank of the external pressure type expansion joint bellows and a sensor one arranged on the outside of the external pressure type expansion joint, the liquid detector one is connected to the sensor one through a signal line, the middle detection component is composed of a liquid detector two and a sensor two arranged on the outside of the external pressure type expansion joint, the liquid detector two is arranged between the innermost layer and the second inner layer tube blank of the external pressure type expansion joint bellows, and the liquid detector two is connected to the sensor two through a signal line.

[0008] The first liquid detector is a monitoring line, the first sensor is a resistance sensor, and a small hole is machined on the surface where the monitoring line contacts the inner wall wave crest of the innermost tube blank of the corrugated pipe.

[0009] The second liquid detector is a sacrificial anode sheet, which is insulated from the innermost layer and the second innermost layer of the bellows. The second sensor is a current sensor.

[0010] Liquid detector - fixed by water-absorbing material.

[0011] The sacrificial anode sheet covers an area within 60° of the bottom of the expansion joint.

[0012] The beneficial effects of the present invention are as follows: the external pressure expansion joint with corrosion monitoring function of the present invention can be applied to heating pipe networks laid in the form of buried, trenched, pipe gallery and other similar applications, and is particularly suitable for the occasions where external accumulated liquid is corrosive to a certain extent and accumulation at the wave crest of the corrugated pipe is easy to cause leakage of the pipe blank. It can effectively improve the service safety and reliability of the expansion joint itself, and when there is a significant change in product performance, it can issue an early warning to the user unit before leakage, so as to avoid emergency shutdown caused by sudden accidents. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a structural schematic diagram of the leakage monitoring device of the present invention;

[0014] Figure 2 It is a structural schematic diagram of the present invention;

[0015] Figure 3 It is a schematic structural diagram of the outlet end ring and the end pipe of the present invention.

[0016] In the figure: 1. limit ring, 2. bellows, 3. monitoring line, 4. water-absorbing material, 5. sacrificial anode plate, 6. end pipe, 7. connecting pipe, 8. signal line, 9. data acquisition controller, 10. inlet end pipe, 11. guide tube, 12. outer pipe, 13. outlet pipe, 6-1. connecting pipe outlet hole, 6-2. anode plate connecting hole, 6-3. lead-out wire connecting hole. DETAILED DESCRIPTION

[0017] like Figure 1 As shown in Figure 2, an external pressure expansion joint with a leakage monitoring function includes an external pressure expansion joint and a leakage monitoring device. The external pressure expansion joint includes an inlet end pipe 10, a guide tube 11, a bellows 2, an outer pipe 12, an outlet pipe 13, an outlet end ring 14, an end pipe 6 and a limit ring 1.

[0018] The leakage monitoring device is arranged at the lowest point of the innermost tube blank of the external pressure expansion joint bellows, and the leakage monitoring device comprises an outer leakage detection component and a middle detection component; the leakage monitoring device is also applicable to the case where two or three groups of bellows are connected in series.

[0019] The external leakage detection component is composed of a liquid detector 1 attached to the innermost inner wall of the external pressure expansion joint bellows and a sensor 1 arranged outside the external pressure expansion joint. The external leakage detection component realizes early warning judgment on whether there is corrosion accumulation at the crest position of the bellows. The liquid detector 1 is connected to the sensor 1 through a signal line, and the liquid detector 1 is arranged on the non-medium contact side of the bottom of the bellows. The liquid detector 1 is the monitoring line 3, and the sensor 1 is a resistance sensor. The surface of the monitoring line 3 and the inner wall crest of the innermost tube blank of the bellows are machined with small holes. When there is no accumulation of liquid, the monitoring line 3 is insulated from the metal cylinder of the expansion joint; once there is accumulation of liquid, the resistance between the monitoring line and the metal cylinder of the expansion joint will decrease; the digital acquisition controller applies power excitation between the lead-out end of the monitoring line and the exposed metal, and according to the size of the feedback current, it can be judged whether there is accumulation of liquid.

[0020] The middle detection component is used to monitor whether the innermost tube blank of the bellows is corroded and penetrated. The middle detection component consists of a liquid detector 2 and a sensor 2 arranged outside the external pressure expansion joint. The liquid detector 2 is arranged between the innermost and second inner tube blanks of the external pressure expansion joint bellows. The liquid detector 2 is connected to the sensor 2 through a signal line. The liquid detector 2 is a sacrificial anode sheet 5, which is insulated from the innermost and second inner tube blanks of the bellows. The sensor 2 is a current sensor. By utilizing the electrode potential difference between the built-in anode sheet 5 and the different metals of the bellows 2, when there is effluent conductive liquid, a current loop will be formed, and the built-in anode sheet 5 with a lower potential will be corroded, and a corrosion current will also be generated. By monitoring whether there is current signal feedback, information on whether the first layer of tube blank is damaged can be obtained.

[0021] Through the outer leakage detection component and the middle detection component, the time difference from the existence of the corrosion effusion to the penetration of the first layer of the tube blank can indirectly infer the corrosion severity of the corrosion effusion.

[0022] The device with the functions of resistance sensor and current sensor is used as the digital acquisition controller 9, which can collect resistance signal and current signal and has display and alarm functions. After receiving the resistance and current signals, the digital acquisition controller 9 can be connected, processed and transmitted with the surrounding signal acquisition system, and the monitored signal changes can be fed back to the user end in time, helping the user to understand the intact condition of the product in time and formulate the best early warning disposal measures.

[0023] like Figure 3As shown, the end tube connected to the bellows is processed with a monitoring line lead-out hole and an embedded part hole, which establishes a connection channel between the bellows monitoring element and the external sensor; and can meet the strength requirements and manufacturing requirements of each component of the product. To facilitate the lead-out of the signal line, a connecting pipe through hole 6-1, an anode plate connecting hole 6-2, and a lead-out line connecting hole 6-3 are processed on the end tube 6. The monitoring line 3 and the sacrificial anode plate 5 are respectively connected to the signal line 8, and are connected to the digital acquisition controller 9 through the lead-out line connecting hole 6-3, the anode plate connecting hole 6-2, and the connecting pipe through hole 6-1 channels set on the outlet end ring and the end tube. To protect the signal line, the signal line can be placed in a connecting tube 7 fixed on the outlet end ring 14 and the end tube 6.

[0024] The liquid detector is fixed by a water-absorbing material 4, which can be polyurethane foam or water-absorbing fiber.

[0025] The sacrificial anode sheet covers a 60° range from the bottom of the expansion joint, within which better monitoring can be performed.

[0026] The above structure and method for online corrosion monitoring can effectively improve the service safety and reliability of external pressure expansion joints. When there is a significant change in product performance, an early warning can be issued to the user in a timely manner to avoid emergency shutdown of the entire device piping system due to sudden corrosion damage, thereby reducing the economic losses of the user.

[0027] The expansion joint structure and monitoring method thereof of the present invention have reliable functions, compact structure, strong reference value and are easy to expand.

Claims

1. An external pressure expansion joint with leakage monitoring function, characterized in that: It includes an external pressure expansion joint and a leakage monitoring device, the leakage monitoring device is arranged at the lowest point of the innermost tube blank of the external pressure expansion joint bellows, the leakage monitoring device includes an outer leakage detection component and a middle detection component, the outer leakage detection component is composed of a liquid detector 1 attached to the inner wall of the innermost tube blank of the external pressure expansion joint bellows and a sensor 1 arranged outside the external pressure expansion joint, the liquid detector 1 is connected to the sensor 1 through a signal line, the middle detection component is composed of a liquid detector 2 and a sensor 2 arranged outside the external pressure expansion joint, the liquid detector 2 is arranged between the innermost layer and the second inner layer of the external pressure expansion joint bellows, and the liquid detector 2 is connected to the sensor 2 through a signal line; The first liquid detector is a monitoring line (3), the first sensor is a resistance sensor, and a small hole is machined on the surface where the monitoring line (3) contacts the inner wall wave crest of the innermost layer of the corrugated tube; The second liquid detector is a sacrificial anode sheet (5), the sacrificial anode sheet (5) is insulated from the innermost layer and the second innermost layer of the bellows, and the second sensor is a current sensor.

2. An external pressure expansion joint with leakage monitoring function as claimed in claim 1, characterized in that: The liquid detector is fixed by a water-absorbing material (4).

3. The external pressure expansion joint with leakage monitoring function as claimed in claim 1, characterized in that: The sacrificial anode sheet covers an area within 60° of the bottom of the expansion joint.

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