Steam trap internal leakage detection device for steam and drain pipeline

Abstract

The application relates to the technical field of automation detection and control, in particular to a steam drain pipeline drain valve inner leakage detection device. The device comprises a steam pipeline, a drain pipeline connected between a steam pipeline drain pipeline interface and a steam expansion vessel interface, the drain pipeline being provided with a pneumatic drain valve and a manual valve, a pipe wall temperature measurement assembly arranged on the drain pipeline between the pneumatic drain valve and the steam expansion vessel interface and used for collecting the pipe wall temperature of the pipeline downstream of the pneumatic drain valve, and a distributed control system with a signal input end electrically connected to a signal output end of the pipe wall temperature measurement assembly, used for receiving a temperature signal, and a control signal output end of the distributed control system connected to a control end of the pneumatic drain valve, wherein the distributed control system is configured to judge the inner leakage state of the pneumatic drain valve based on the temperature signal. The steam drain pipeline drain valve inner leakage detection device can automatically, continuously and timely and accurately monitor the inner leakage of the drain valve, thereby improving the operation safety and economy of a thermal power plant.

Description

Technical Field

[0001] This application relates to the field of automated detection and control technology, specifically to a device for detecting internal leakage of steam trap valves in steam condensate pipelines. Background Technology

[0002] In modern thermal power plants and other large-scale industrial production processes, the safe and economical operation of the steam system is crucial. To remove condensate generated during steam pipeline startup, low load, and shutdown, or to ensure the steam superheat meets system operating requirements and prevent water hammer or corrosion, drain lines and drain valves are typically installed at the lowest points of the pipelines. However, once the unit is in normal operation, if these drain valves experience internal leakage due to wear, aging, or other reasons, it will lead to a series of serious consequences: not only will it cause continuous leakage and waste of high-quality steam, directly increasing production costs, but the leaked steam will also raise the pressure in the condensate system, interfering with the operation of other equipment. Furthermore, the erosion and corrosion of adjacent pipelines by the steam will accelerate equipment damage, ultimately resulting in a significant decrease in the economic efficiency and reliability of the entire system.

[0003] Regarding the aforementioned issue of internal leakage in steam traps, current detection methods generally rely on manual operation. Common methods include listening to the venting sound, using thermal imaging to scan for temperature anomalies, detecting fluid noise with ultrasonic detectors, observing the flow state inside the sight glass, and judging by the vaporization phenomenon when water is sprayed onto the valve body surface. While these methods can identify internal leaks to some extent, they are all discrete and discontinuous inspection methods. Their effectiveness is highly dependent on the experience and sense of responsibility of the inspectors, and they require carrying specialized equipment close to high-temperature and high-pressure pipeline areas, posing safety risks and efficiency bottlenecks.

[0004] In summary, existing manual detection methods have inherent and insurmountable drawbacks: they cannot achieve continuous, real-time monitoring of steam trap status and struggle to quickly detect early signs of internal leakage. This lag in detection often leads to late discovery of internal leaks, where small defects may have already developed into serious malfunctions. This not only delays maintenance and causes continued expansion of steam losses but also poses a potential threat to the safe and stable operation of the power plant. Therefore, developing a device capable of automatically, continuously, promptly, and accurately monitoring internal leakage in steam traps has become an urgent technical requirement for improving the operational safety and economy of thermal power plants. Summary of the Invention

[0005] In view of this, the present application provides a steam trap internal leakage detection device, which can automatically, continuously, timely and accurately monitor the internal leakage of the steam trap, thereby improving the operational safety and economy of thermal power plants.

[0006] The first aspect of this application provides a steam trap valve internal leakage detection device, comprising: Steam pipes; A condensate drain line is connected between the condensate drain port and the condensate expansion container port of the steam pipe, and the condensate drain line is equipped with a pneumatic condensate drain valve. A pipe wall temperature measuring component is installed on the drain line between the pneumatic steam trap and the drain expansion container interface to collect the pipe wall temperature of the downstream pipeline of the pneumatic steam trap. The distributed control system has a signal input terminal electrically connected to the signal output terminal of the pipe wall temperature measurement component for receiving temperature signals, and the control signal output terminal of the distributed control system is connected to the control terminal of the pneumatic steam trap. The distributed control system is configured to determine the internal leakage status of the pneumatic steam trap based on the temperature signal.

[0007] In one embodiment, the pipe wall temperature measurement assembly includes a heat collection block and a temperature measuring element. The heat collection block is installed on the drain line downstream of the pneumatic drain valve. The temperature measuring element is correspondingly arranged with the heat collection block, and its front end armor wire is inserted into the detection hole in the temperature measuring heat collection block to obtain the pipe wall temperature. The signal output terminal of the temperature measuring element is electrically connected to the signal input terminal of the distributed control system.

[0008] In one embodiment, the hydrophobic conduit includes: The first condensate drain pipe has one end connected to the condensate drain pipe interface of the steam pipe and the other end connected to one end of the second condensate drain pipe. The second drainage pipe is connected at one end to the inlet of the pneumatic drainage valve; The third drainage pipe is connected between the outlet of the pneumatic drainage valve and the interface of the drainage expansion container. The pipe wall temperature measuring component is installed on the third drainage pipe.

[0009] In one embodiment, the third drainage pipe is further provided with a drainage throttling orifice, which is disposed between the pipe wall temperature measuring component and the drainage expansion container interface.

[0010] In one embodiment, a manual drain valve is also included, with the other end of the first drain pipe connected to the inlet of the manual drain valve and the outlet of the manual drain valve connected to one end of the second drain pipe.

[0011] In one embodiment, the signal input terminal of the distributed control system is also connected to the valve status output terminal of the pneumatic steam trap, for receiving a fully open position signal or a fully closed position signal that characterizes the valve status of the pneumatic steam trap.

[0012] In one embodiment, the distributed control system includes a logic delay circuit, a voltage comparator, and a first logic AND circuit. The input of the logic delay circuit is connected to the all-off position signal. One input of the voltage comparator is connected to the signal output of the pipe wall temperature measurement component to receive a temperature voltage signal, and the other input is connected to a preset temperature rise threshold voltage. The outputs of the logic delay circuit and the voltage comparator are respectively connected to the inputs of the first logic AND circuit, and the output of the first logic AND circuit is used to output an alarm signal.

[0013] In one embodiment, the distributed control system further includes an alarm module, the input of which is connected to the output of the first logic AND circuit, for executing an alarm.

[0014] In one embodiment, the distributed control system further includes a first OR gate, a second OR gate, a NOT gate, a second AND logic circuit, and a monostable multivibrator. The input of the first OR gate is connected to the valve opening command and the interlock protection valve opening signal; the input of the second OR gate is connected to the valve closing command and the interlock protection valve closing signal; the output of the first OR gate is connected to one input of the second AND logic circuit; the output of the second OR gate is connected to the other input of the second AND logic circuit through the NOT gate; the output of the second AND logic circuit is connected to the set terminal of the monostable multivibrator; the output of the second OR gate is connected to the reset terminal of the monostable multivibrator; and the output of the monostable multivibrator is connected to the control terminal of the pneumatic steam trap.

[0015] The first aspect of this application provides a steam trap internal leakage detection device. By integrating steam pipelines, drain lines, pipe wall temperature measurement components, and a distributed control system, a complete automated monitoring architecture is constructed. This device utilizes a DCS system to process temperature signals in real time, achieving continuous and automatic judgment of the internal leakage status of pneumatic steam traps, thereby overcoming the discontinuity and lag of traditional manual detection methods. It can promptly repair valves when internal leakage occurs, preventing serious valve damage and improving system safety and economy. It is particularly suitable for large steam systems such as thermal power plants. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of a steam trap internal leakage detection device provided in one embodiment of this application; Figure 2 This is a schematic diagram of the control logic of a steam trap valve internal leakage detection device provided in one embodiment of this application. Detailed Implementation

[0018] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0019] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0020] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0021] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0022] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0023] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0024] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0025] like Figure 1 As shown, thermal power plants have numerous main steam, reheat steam, and turbine extraction steam pipelines equipped with drain pipes and drain valves. Large units may have dozens or even hundreds of these drain pipes. This application embodiment describes one such drain pipe. This application embodiment provides a steam drain pipe drain valve internal leakage detection device, comprising: Steam pipe 1, main steam delivery pipe, with a drain pipe interface 2 installed at the lowest point; A condensate drain line is connected between the condensate drain line interface 2 and the condensate expansion container interface 9 of the steam pipe 1. The condensate drain line is equipped with a pneumatic condensate drain valve 6. The pipe wall temperature measuring component is installed on the drain line between the pneumatic drain valve 6 and the drain expansion container interface 9, and is used to collect the pipe wall temperature of the downstream pipeline of the pneumatic drain valve 6. The distributed control system 41 has its signal input terminal electrically connected to the signal output terminal of the pipe wall temperature measurement component to receive temperature signals, and its control signal output terminal is connected to the control terminal of the pneumatic steam trap 6. The distributed control system 41 is configured to determine the internal leakage status of the pneumatic steam trap 6 based on the temperature signal.

[0026] In this application, a manual drain valve 4 is also installed upstream of the pneumatic drain valve 6. This is used during maintenance and is normally kept open when not under maintenance. The pneumatic drain valve 6 is controlled by the DCS and is used to control condensation during normal operation. During unit startup and low-load operation, the steam pipeline contains condensate due to low superheat or non-superheated steam. By installing a drain pipe at the lowest point of the steam pipeline, the manual valve is normally open when not under maintenance. The DCS system controls the pneumatic drain valve to open, draining the condensate into the drain expansion tank. When the unit load reaches a certain value (typically 10%~30% of rated load for thermal power plants, the specific value is determined based on the pipeline medium parameters), and the steam superheat meets the requirements and the pipeline warm-up is complete, the DCS controls the drain valve to close.

[0027] The pneumatic steam trap is controlled by a single-coil solenoid valve to open and close its power supply. The trap opens when power or air supply is lost to ensure system safety. A pipe wall temperature measuring element (heat collector + RTD) is installed near the pneumatic steam trap (e.g., approximately 20cm away). For vertical pipes, the heat collector can be installed anywhere on the pipe; for horizontal pipes, it is installed below the center line of the horizontal pipe after the steam trap to ensure timely temperature monitoring.

[0028] This application embodiment constructs a complete automated monitoring architecture by integrating steam pipelines, condensate drain lines, pipe wall temperature measurement components, and a distributed control system. The device utilizes a DCS system to process temperature signals in real time, enabling continuous and automatic judgment of the internal leakage status of pneumatic condensate traps, thereby overcoming the discontinuity and lag of traditional manual detection methods. It can promptly repair valves when internal leakage occurs, preventing serious valve damage and improving system safety and economy. It is particularly suitable for large steam systems such as those in thermal power plants.

[0029] In one embodiment, the pipe wall temperature measurement assembly includes a heat collection block 10 and a temperature measuring element 11. The heat collection block 10 is installed on the drain line downstream of the pneumatic drain valve 6. The temperature measuring element 11 is correspondingly arranged with the heat collection block 10. Its front end armor wire is inserted into the detection hole in the temperature measuring heat collection block 10 to obtain the pipe wall temperature. The signal output terminal of the temperature measuring element 11 is electrically connected to the signal input terminal of the distributed control system 41.

[0030] In the application, the heat collector 10 is installed on the pipeline after the pneumatic steam trap and is used in conjunction with the temperature measuring element to detect the pipeline wall temperature. The armored wire at the front measuring end of the temperature measuring element 11 is inserted into the hole of the heat collector, and then the screw is screwed into the reserved hole of the heat collector to press the armored wire in place, for detecting the pipeline wall temperature.

[0031] The pipe wall temperature measurement component of this application includes a heat collection block and a temperature measuring element, which ensures the accuracy and response speed of temperature detection. The heat collection block can efficiently conduct changes in pipe wall temperature, and the temperature measuring element can accurately capture minute temperature fluctuations by being inserted deep into the detection hole, providing a stable and reliable data source for the DCS system and enhancing the sensitivity of internal leakage detection.

[0032] In one embodiment, the drainage conduit includes: The first drainage pipe 3 is connected at one end to the drainage pipe interface 2 of the steam pipe 1, and at the other end to one end of the second drainage pipe 5. The second drainage pipe 5 is connected at one end to the inlet of the pneumatic drainage valve 6; The third drainage pipe 7 is connected between the outlet of the pneumatic drainage valve 6 and the drainage expansion container interface 9. The pipe wall temperature measuring component is installed on the third drainage pipe 7.

[0033] In this embodiment, the drainage pipeline is clearly divided into first, second and third drainage pipelines, and their connection sequence is specified. This segmented design makes the pipeline layout clearer and more reasonable, which not only facilitates installation and maintenance, but also ensures that the temperature measurement component is located in the optimal position downstream of the pneumatic drain valve, so as to reflect the true temperature of the pipeline after the valve in a timely manner and avoid measurement blind spots.

[0034] In one embodiment, the third drainage pipe 7 is further provided with a drainage throttling hole 8, which is located between the pipe wall temperature measuring component and the drainage expansion container interface 9.

[0035] In this embodiment, a condensate throttling orifice is provided on the third condensate pipe. This structure is located downstream of the temperature measurement component and can effectively limit and stabilize the condensate flow rate, preventing pressure shocks or damage to the downstream pipe caused by sudden flow changes. At the same time, it provides a more stable fluid environment for temperature measurement and improves the accuracy of the detection results.

[0036] In one embodiment, a manual drain valve 4 is also included, with the other end of the first drain pipe 3 connected to the inlet of the manual drain valve 4 and the outlet of the manual drain valve 4 connected to one end of the second drain pipe 5.

[0037] This application embodiment adds a manual steam trap and positions it upstream of the pneumatic steam trap, providing important safety redundancy. When the pneumatic steam trap needs maintenance or malfunctions, the manual valve can reliably isolate the upstream steam medium, ensuring the safe conduct of maintenance work without affecting the operation of the entire steam system.

[0038] In one embodiment, such as Figure 2 As shown, the signal input terminal of the distributed control system 41 is also connected to the valve status output terminal of the pneumatic steam trap 6, and is used to receive the fully open position signal or the fully closed position signal that characterizes the valve status of the pneumatic steam trap 6.

[0039] The DCS system in this application receives the valve status signal of the pneumatic steam trap, making the internal leakage judgment logic more intelligent and accurate. The system only starts temperature analysis after confirming that the valve is in the closed state, which effectively avoids the temperature rise caused by normal drainage when the valve is open being misjudged as internal leakage, and reduces false alarms.

[0040] In one embodiment, the distributed control system 41 includes a logic delay circuit 36, a voltage comparator 38, and a first logic AND circuit 39. The input of the logic delay circuit 36 ​​is connected to the all-off position signal. One input of the voltage comparator 38 is connected to the signal output of the pipe wall temperature measurement component to receive a temperature voltage signal, and the other input is connected to a preset temperature rise threshold voltage. The outputs of the logic delay circuit 36 ​​and the voltage comparator 38 are respectively connected to the inputs of the first logic AND circuit 39. The output of the first logic AND circuit 39 is used to output an alarm signal.

[0041] In the application, the DCS system continuously receives the temperature signal 37 from the pipe wall temperature measuring element 11 and the fully open position signal 21 and fully closed position signal 22 from the pneumatic steam trap 6.

[0042] In application, after the unit is running normally, the DCS receives the pneumatic steam trap fully closed position signal 22 and then performs a logical "delay" through the logic delay circuit 36 ​​(the delay time can be set to 15 minutes, which depends on the time required for the pipe wall temperature to drop to the "natural" temperature after the steam trap completes drainage and closes).

[0043] The DCS synchronously detects the pipe wall temperature TE value of 37 after the steam trap. After the voltage comparator 38 performs a temperature rise logic "comparison", the DCS sets the temperature rise of the detected pipe wall temperature measuring element TE (e.g., 5°C) according to the steam pipeline medium pressure and temperature. Then, it performs a logic "AND" operation with the logic "delay" through the first logic AND circuit 39. When the steam trap is closed for a certain period of time and the measured pipe wall temperature rise exceeds the set temperature, its output result is a high level 1. At this time, an alarm ALARM 40 is generated, indicating that an internal leak of the steam trap has been detected, reminding the operators to notify maintenance.

[0044] The DCS can also compare the pipe wall temperature signals of other similar drain valves (e.g., those controlled by the same load to open and close) acquired synchronously. For drain pipes with temperatures higher than other drain pipes by a certain value (e.g., 5°C), it is determined that the pneumatic drain valve has internal leakage. Figure 2 (This was not stated in the original text).

[0045] The DCS in this embodiment includes a logic delay circuit, a voltage comparator, and an AND gate circuit. The delay circuit ensures that the pipeline is fully cooled before detection begins. The comparator performs threshold judgment, and the AND gate circuit integrates the conditions to form a judgment core with fast response and strong anti-interference capability, thereby improving the reliability of detection and control.

[0046] In one embodiment, the distributed control system 41 further includes an alarm module, the input of which is connected to the output of the first logic AND circuit 39, for executing an alarm.

[0047] The alarm module in this application embodiment immediately triggers an audible and visual alarm or other forms of alarm when the internal leakage condition is met, directly notifying the operators, shortening the response time from problem discovery to action, facilitating rapid fault isolation and maintenance scheduling, and preventing damage from escalating.

[0048] In one embodiment, the distributed control system 41 further includes a first OR gate 25, a second OR gate 31, a NOT gate 33, a second AND gate 34, and a monostable multivibrator 27. The input of the first OR gate 25 is connected to the valve opening command and the interlock protection valve opening signal. The input of the second OR gate 31 is connected to the valve closing command and the interlock protection valve closing signal. The output of the first OR gate 25 is connected to one input of the second AND logic circuit 34. The output of the second OR gate 31 is connected to the other input of the second AND logic circuit 34 through the NOT gate 33. The output of the second AND logic circuit 34 is connected to the set terminal of the monostable multivibrator 27. The output of the second OR gate 31 is connected to the reset terminal of the monostable multivibrator 27. The output of the monostable multivibrator 27 is connected to the control terminal of the pneumatic steam trap 6.

[0049] In the application, the operator operates on the HMI and sends the valve opening command, namely the "open" command 23. This command, along with the interlock protection valve opening signal 24, is logically ORed through the first OR gate circuit 25. The valve opening signal 26 is then sent to the reset terminal R of the monostable multivibrator 27. At this time, the set terminal of the monostable multivibrator 27 generates a low-level signal 28 to the single-coil solenoid valve control circuit of the pneumatic steam trap 6, causing the solenoid valve to lose power and cut off the power supply to the pneumatic steam trap. After losing power, the valve is opened by the action of the spring.

[0050] Similarly, when the operator operates the HMI, they send a valve closing command, namely the "close" command 29, which is then logically ORed with the interlock protection valve closing signal 30 through the second OR gate circuit 31 to generate a valve closing signal 32. The valve closing signal 32 and the logical "NOT" output of the valve opening signal 26 are then logically ANDed (this design is to ensure that the valve opening command takes precedence over the valve closing command) to obtain the valve closing command 35, which is sent to the set terminal S of the monostable multivibrator 27. At this time, the monostable multivibrator outputs a high level 1, which energizes the control solenoid valve of the pneumatic steam trap, connecting the air power source of the pneumatic steam trap and causing the valve to close.

[0051] In application, the interlock / protection valve opening signal includes the unit load not exceeding a certain value (this load value differs for the condensate drain lines of high, medium, and low pressure steam pipelines): High-pressure steam pipeline: ≤10% of rated load, mainly used in main steam pipelines and high-pressure bypass systems; Medium-pressure steam pipeline: ≤20% of rated load, mainly used in steam turbine high-pressure cylinder extraction steam pipeline, reheat steam cold section, and medium-pressure bypass system; Low-pressure steam pipeline: ≤30% of rated load, mainly used in other low-level extraction steam pipelines and low-pressure bypass systems of steam turbines.

[0052] Interlock / protection valve opening signals also include unit trip signals.

[0053] Interlock / protection valve closing signals include those indicating that the unit load is higher than a certain value: High-pressure steam pipeline: >11% of rated load Medium-pressure steam pipeline: >21% of rated load Low-pressure steam piping: >31% of rated load The valve control logic circuit in the DCS of this application embodiment, composed of OR gates, AND gates, NOT gates and monostable triggers, ensures that the valve opening command takes precedence over the valve closing command under any circumstances, which complies with the fail-safe principle. In emergency situations, it can force the valve to open to drain water, thus ensuring the safety of steam pipelines and equipment.

[0054] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A device for detecting internal leakage of steam trap valves in steam trap pipelines, characterized in that, include: Steam pipe (1); A condensate drain line is connected between the condensate drain line interface (2) and the condensate expansion container interface (9) of the steam pipe (1), and the condensate drain line is equipped with a pneumatic condensate drain valve (6). A pipe wall temperature measuring component is installed on the condensate line between the pneumatic steam trap (6) and the condensate expansion container interface (9) to collect the pipe wall temperature of the downstream pipeline of the pneumatic steam trap (6). The distributed control system (41) has its signal input terminal electrically connected to the signal output terminal of the pipe wall temperature measurement component for receiving temperature signals. The control signal output terminal of the distributed control system (41) is connected to the control terminal of the pneumatic steam trap (6). The distributed control system (41) is configured to determine the internal leakage status of the pneumatic steam trap (6) based on the temperature signal.

2. The steam trap internal leak detection device of claim 1, wherein, The pipe wall temperature measurement assembly includes a heat collection block (10) and a temperature measuring element (11). The heat collection block (10) is installed on the drain line downstream of the pneumatic drain valve (6). The temperature measuring element (11) is arranged correspondingly to the heat collection block (10). Its front end armor wire is inserted into the detection hole in the temperature measuring heat collection block (10) to obtain the pipe wall temperature. The signal output terminal of the temperature measuring element (11) is electrically connected to the signal input terminal of the distributed control system (41).

3. The steam trap internal leak detection device of claim 1, wherein, The drainage pipeline includes: The first drainage pipe (3) is connected at one end to the drainage pipe interface (2) of the steam pipe (1) and at the other end to one end of the second drainage pipe (5); The second drainage pipe (5) is connected at one end to the inlet of the pneumatic drainage valve (6); The third drainage pipe (7) is connected between the outlet of the pneumatic drainage valve (6) and the drainage expansion container interface (9); The pipe wall temperature measuring component is installed on the third drainage pipe (7).

4. The steam trap internal leak detection device of claim 3, wherein, The third drainage pipe (7) is also provided with a drainage throttling hole (8), which is located between the pipe wall temperature measuring component and the drainage expansion container interface (9).

5. The steam trap internal leak detection device of claim 3, wherein, It also includes a manual drain valve (4), with the other end of the first drain pipe (3) connected to the inlet of the manual drain valve (4) and the outlet of the manual drain valve (4) connected to one end of the second drain pipe (5).

6. The steam trap internal leak detection device of claim 1, wherein, The signal input terminal of the distributed control system (41) is also connected to the valve status output terminal of the pneumatic steam trap (6) to receive the fully open position signal or the fully closed position signal that characterizes the valve status of the pneumatic steam trap (6).

7. The steam trap internal leak detection device of claim 6, wherein, The distributed control system (41) includes a logic delay circuit (36), a voltage comparator (38), and a first logic AND circuit (39). The input terminal of the logic delay circuit (36) is connected to the all-off position signal. One input terminal of the voltage comparator (38) is connected to the signal output terminal of the pipe wall temperature measuring component to receive the temperature voltage signal, and the other input terminal is connected to a preset temperature rise threshold voltage. The output terminals of the logic delay circuit (36) and the voltage comparator (38) are respectively connected to the input terminal of the first logic AND circuit (39). The output terminal of the first logic AND circuit (39) is used to output an alarm signal.

8. The steam trap internal leak detection device of claim 7, wherein, The distributed control system (41) further includes an alarm module, the input of which is connected to the output of the first logic AND circuit (39) for performing an alarm.

9. The steam trap internal leak detection device of claim 6, wherein, The distributed control system (41) further includes a first OR gate (25), a second OR gate (31), a NOT gate (33), a second AND gate (34), and a monostable multivibrator (27). The input of the first OR gate (25) is connected to the valve opening command and the interlock protection valve opening signal. The input of the second OR gate (31) is connected to the valve closing command and the interlock protection valve closing signal. The output of the first OR gate (25) is connected to one input of the second AND logic circuit (34). The output of the second OR gate (31) is connected to the other input of the second AND logic circuit (34) through the NOT gate (33). The output of the second AND logic circuit (34) is connected to the set terminal of the monostable multivibrator (27). The output of the second OR gate (31) is connected to the reset terminal of the monostable multivibrator (27). The output of the monostable multivibrator (27) is connected to the control terminal of the pneumatic steam trap (6).

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