Liquefied gas leak detection system

Abstract

This system provides a liquefied gas leak detection system that can quickly and accurately detect localized liquefied gas leaks and identify liquefied gas leaks. [Solution] A liquefied gas leak detection system A1 is used in plants and facilities for filling liquefied gas tanks and tank trucks with liquefied gas, and detects leaks of liquefied gas. The system comprises a metal plate 3 positioned below a pipe connection 2 provided in a liquefied gas pipe L1, a temperature sensor 4 for measuring the temperature of the metal plate, and a control unit 5 for acquiring temperature data measured by the temperature sensor at predetermined time intervals. The system determines that a liquefied gas leak has occurred when the difference between the most recently acquired temperature and the previously acquired temperature is less than a predetermined threshold set in advance for the predetermined time interval.

Description

TECHNICAL FIELD

[0001] The present invention relates to a liquefied gas leakage detector used in plants and facilities for filling liquefied gas into liquefied gas tanks and tank trucks. BACKGROUND ART

[0002] In liquefied gas filling equipment for filling liquefied gas into liquefied gas tanks and tank trucks, it is important to quickly detect leakage of liquefied gas caused by detachment of a hose during filling or the like to ensure the safety of surrounding facilities and workers.

[0003] As a prior art, there is an apparatus in which a temperature sensor is attached to a flange (connection part) of a liquefied gas supply pipe to detect leakage from the flange based on a temperature drop. (Patent Document 1) PRIOR ART DOCUMENTS PATENT DOCUMENTS

[0004] Patent Document 1 Published Utility Model Application No. Sho 56-146239

[0005] However, since liquefied gas supply devices are often installed outdoors, they are easily affected by the surrounding environment. For example, when liquefied gas leaks into the atmosphere, the liquefied gas is quickly warmed and vaporized, making it difficult to detect the leakage with a thermometer.

[0006] In addition, when a temperature sensor is installed at a single spot on the supply pipe, the temperature of the supply pipe and its surroundings has already decreased due to heat transfer from the cryogenic liquefied gas inside the pipe. Therefore, a temperature drop cannot be detected unless the liquefied gas itself comes into contact with the sensor.

[0007] Furthermore, when it comes to measuring atmospheric and environmental ambient temperature, there are no measuring instruments that can handle the extremely low temperatures of -196°C for liquid nitrogen. Even using a thermometer that converts the pressure drop caused by a CO2-filled tube into temperature, it is difficult to detect temperature drops in a very limited area, such as the connectors of liquefied gas-filled hoses, pipe flanges, or directly below valves.

[0008] In addition, using a typical system that issues an alarm when the temperature falls below a certain threshold, there is a problem in that if the ambient temperature gradually decreases due to weather conditions, the system may mistakenly judge that there is a "leak" even if there is no actual leak, simply because the temperature falls below the set threshold, leading to false alarms. [Overview of the project] [Problems that the invention aims to solve]

[0009] This invention provides a liquefied gas leak detection system that can quickly and accurately detect localized liquefied gas leaks and identify liquefied gas leaks. [Means for solving the problem]

[0010] The inventor discovered that by installing a metal plate directly beneath connection points in piping prone to leaks, such as connectors, fittings (flanges), and valves of liquefied gas filling hoses, acquiring temperature data within a limited area at predetermined time intervals, and calculating the difference between the most recent temperature measurement and the previous temperature measurement, it is possible to detect liquefied gas leaks. This disclosure includes, for example, the following aspects: [1] A liquefied gas leak detection system for detecting leaks of liquefied gas, A metal plate is positioned below the pipe connection, separated from the pipe connection provided in the liquefied gas piping, A temperature sensor for measuring the temperature of the aforementioned metal plate material, The system includes a control unit that acquires temperature data measured by the temperature sensor at predetermined time intervals, The liquefied gas leak detection system is characterized in that the control unit determines that a liquefied gas leak has occurred when the difference between the most recently acquired temperature and the previously acquired temperature is less than a predetermined threshold set in advance for the predetermined time interval. [2] A liquefied gas leak detection system as described in [1], characterized in that the metal plate material is an aluminum checkered steel plate. [3] A liquefied gas leak detection system according to [1] or [2], characterized in that the metal plate has dimensions of up to 40 cm square, and the temperature sensor is mounted at the center of the metal plate. [4] A liquefied gas leak detection system according to any one of [1] to [3], wherein the control unit outputs a signal to stop the operation of the pump supplying the liquefied gas and / or a signal to close the shut-off valve provided in the liquefied gas piping when it determines that a liquefied gas leak has occurred. [5] A liquefied gas leak detection system according to any one of [1] to [4], characterized in that the control unit outputs an alarm signal that activates at least one of a display, a buzzer, and an audio announcement when it determines that a liquefied gas leak has occurred. [6] A liquefied gas leak detection system according to any one of [1] to [5], wherein the liquefied gas is one of liquefied nitrogen, liquefied oxygen, liquefied argon, or liquefied carbon dioxide. [7] A liquefied gas leak detection system according to any one of [1] to [6], wherein the piping connection portion is a flange or a valve.

[0011] (effect) (1) Leakage of liquefied gas can be accurately determined by acquiring temperature data in a limited area such as below the connection parts of pipes where leakage is likely to occur, such as connectors and joints (flanges) of liquefied gas filling hoses and valves, and calculating the temperature drop per predetermined time (predetermined time interval). (2) When filling a tank truck with liquefied gas, the pressure of the liquefied gas in the filling hose is low and it is in a supercooled state, so even a small amount of liquefied gas leakage does not vaporize immediately. The present liquefied gas leakage detection system can determine that liquefied gas has leaked by detecting the liquefied gas dropped onto a metal plate installed below the leakage location. (3) The present liquefied gas leakage detection system measures the temperature of a metal plate at a location away from the liquefied gas leakage site. Since the temperature sensor is not directly attached to the liquefied gas pipe, flange, or valve, false alarms of leakage caused by the cold heat of the liquefied gas pipe itself can be avoided. [BRIEF DESCRIPTION OF THE DRAWINGS]

[0012] [Figure 1] It is a diagram showing an example of the liquefied gas leakage detection system A1 according to Embodiment 1. [Figure 2] An example of a top view of the metal plate 3 according to Embodiment 1 is shown. [Figure 3] It is a diagram showing an example of the alarm unit according to Embodiment 1. [Figure 4] It is a diagram showing an example of the flowchart according to Embodiment 1. [Figure 5] It is a diagram showing an example of measurement by the temperature sensor according to Embodiment 1. [MODE FOR CARRYING OUT THE INVENTION]

[0013] The apparatus according to one embodiment will be described below with reference to the embodiment shown in FIG. 1. However, this is to describe an example of the present disclosure. The present disclosure is not limited in any way to the following embodiments, and also includes various modified embodiments implemented within a range that does not alter the gist of the present disclosure. In addition, not all of the configurations described below are necessarily essential configurations of the present disclosure. The terms upstream and downstream are based on the flow direction of fluid (liquid, gas).

[0014] (Embodiment 1) The liquefied gas leakage detection system A1 according to Embodiment 1 will be described with reference to FIG. 1. The liquefied gas leakage detection system A1 comprises a metal plate 3, a temperature sensor 4, and a control unit 5.

[0015] Liquefied nitrogen (LIN) is stored in a storage tank 1, and one end of a liquefied gas pipe L1 is connected to the storage tank 1. When the filling container is a tank lorry 9, the other end of the pipe L1 is connected to a hose L2 via a pipe connection part (flange 2). In addition to liquid nitrogen, the liquefied gas may be liquefied oxygen, liquefied argon or liquefied carbon dioxide. The filling container may be another type of filling container, and may be connected to a device using liquefied gas. In addition to a flange, the pipe connection part may be various joints such as a threaded joint or a valve.

[0016] In the liquefied gas pipe L1, a shut-off valve 10 and a pump 11 are installed between the storage tank 1 and the flange 2. The pump 11 pressurizes the liquefied gas to a predetermined pressure and delivers it to the filling container. The shut-off valve 10 is installed between the pump 11 and the storage tank 1, and is a valve for closing to cut off the supply when the hose L2 ruptures during filling of the liquefied gas or the liquefied gas leaks from the pipe connection part. The shut-off valve 10 may be a solenoid valve that opens and closes in conjunction with the control unit 5 described later. The liquefied nitrogen in the storage tank 1 is filled into the tank lorry 9 through the liquefied gas pipe L1 and the hose L2. A flow meter (not shown) and other valves (not shown) may be installed in the pipe L1 as necessary.

[0017] Figure 2 shows a top view of the metal plate 3. The metal plate 3 is installed below the pipe connection (flange 2), and a temperature sensor 4 is installed on the top surface of the metal plate 3. The temperature sensor 4 is located below the pipe connection (below the flange 2) and in the center of the metal plate 3. More preferably, it is located directly below the pipe connection and in the center of the metal plate 3. The temperature sensor can be a general-purpose temperature sensor, such as a thermocouple, platinum resistance thermometer, or thermistor. Measurement by the temperature sensor 4 is performed at predetermined time intervals, for example, 10 seconds or 1 minute. The predetermined time interval may be a constant time interval.

[0018] Considering outdoor use, the material of the metal plate 3 is preferably aluminum or stainless steel, which is rust-resistant and has good thermal conductivity. The shape of the metal plate 3 is rectangular, such as a square or rectangle. The size of the metal plate 3 is a plate shape with a thickness of about 0.3 cm, and the length and width are preferably a maximum of 40 cm, with a length of 10 cm and a width of 30 cm being preferable depending on the space below the pipe connection part (flange 2). Furthermore, considering corrosion resistance and anti-slip effect, checker plate is preferred for the metal plate 3. Even if the leaked liquefied gas does not directly come into contact with the temperature sensor, if it falls into the metal plate 3, the metal plate 3 will transfer heat and cold, and the temperature sensor will be able to detect the temperature drop. Furthermore, the distance between the pipe connection (flange 2) and the metal plate 3 should be such that there is no effect of heat transfer (cold or hot), and preferably it should be such that the leaked liquefied gas adheres to the metal plate 3 in a liquid state, and preferably it should be in the range of 5 cm to 100 cm in the vertical direction.

[0019] The temperature sensor 4 detects the heat transferred to the metal plate material 3 and measures the temperature. The measured temperature (detected value) is transmitted as a temperature signal 4a to the control unit 5 via a wired or wireless line.

[0020] The control unit 5 includes a storage unit 6 that stores the detected value from the temperature sensor 4 and various data such as calculation formulas, and a calculation unit 7 that performs calculations based on the detected value and various data to determine whether an alarm is necessary. The calculation unit 7 calculates the difference between the detected value input this time and the previous detected value (for example, the detected value 10 seconds ago). If the difference is less than a preset threshold (for example, -1°C) for a predetermined time interval (for example, 10 seconds), the calculation unit 7 determines that liquefied gas is leaking and sends a signal 5a to the alarm unit 8 to activate the alarm unit 8.

[0021] Figure 3 shows an example of the alarm unit 8. Based on the signal 5a from the calculation unit 7, the alarm unit 8 issues an alarm when a specific situation occurs, informing workers of a gas leak. The alarm may be an audible sound, such as a buzzer or voice announcement, or a visual form, such as an alarm light or a specific screen display. A combination of these forms is also possible. A manual emergency stop switch may be provided to close the shut-off valve 10 or shut off (stop) the pump 11.

[0022] The control unit 5 may send a signal 5b to the shut-off valve 10 to shut off the supply of liquefied gas. The control unit 5 may also send a signal 5c to the pump 11 to stop the operation of the pump 11. Based on this signal, the shut-off valve 10 can be automatically closed and / or the pump 11 can be shut off (stopped).

[0023] Figure 4 shows a flowchart illustrating the procedure leading up to the alarm activation. The temperature sensor 4 measures the temperature at predetermined time intervals. The detected value (temperature data) measured by the temperature sensor 4 is transmitted to the storage unit 6 of the control unit 5. The storage unit 6 stores the most recently received detected value (A) (S1). Here, the storage unit 6 also stores the detected value (B) obtained in the previous measurement. The calculation unit 7 calculates the difference C (C=AB) between A and B in the storage unit 6 (S2). It determines whether the difference C is less than a predetermined value (threshold) (S3). The predetermined value (threshold) is set in advance according to the time interval measured by the temperature sensor 4. For example, the threshold may be -0.5℃ when the measurement time interval is 10 seconds, -1.0℃ when the time interval is 20 seconds, or -3.0℃ when the time interval is 1 minute.

[0024] If the difference C is greater than or equal to the threshold, the calculation unit 7 determines that there is "no leakage" and stores A in the storage unit 6 as B for the next calculation (S5). After that, based on the time interval, it waits until the next measurement and returns to S1. On the other hand, if the difference is less than the threshold, it determines that there is "leakage" and sends signal 5a to the alarm unit 8. The alarm unit receives signal 5a and issues an alarm and / or displays the leakage on a display or the like (S4-1). Furthermore, the calculation unit 7 instructs the shut-off valve 10 on the liquefied gas piping to be closed and / or the pump 11 to be stopped immediately (S4-2).

[0025] (Another embodiment) (1) Unless otherwise specified, pressure regulating devices, flow control devices, etc. may be installed in each piping line to regulate pressure or flow rate. (2) Unless otherwise specified, control valves, gate valves, etc. may be installed in each piping line. (3) Unless otherwise specified, each tower may be equipped with a pressure regulator, a temperature measuring device, etc., and pressure regulation or temperature regulation may be performed.

[0026] (Examples) The experiment was conducted under conditions that mimicked Embodiment 1 (Figure 1). An aluminum metal plate equipped with a temperature sensor at its center was dripped with 50cc of liquid nitrogen, and the temperature drop was observed. The ambient temperature change was also observed. As shown in Figure 5, at an ambient temperature of 27°C, the temperature of an aluminum metal plate exposed to 50cc of liquid nitrogen dropped to 23.4°C after 1 minute and remained almost constant, resulting in a temperature drop of 3.6°C. On the other hand, the ambient temperature changed to 26.8°C after 1 minute and did not drop any further. This experiment demonstrated that by setting the threshold for detecting liquid nitrogen leakage to approximately 0.5-0.6°C / 10 seconds (0.05-0.06°C / second), it is possible to detect liquid nitrogen leakage and communicate the leak to workers via alarms, etc. [Explanation of symbols]

[0027] 1 Storage tank 2 flanges 3 Metal plate material 4. Temperature sensor 5. Control Unit 6 Memory section 7 Calculation part 8 Alarm section 9 Tanker truck 10 Shut-off valve 11 pumps

Claims

1. A liquefied gas leak detection system for detecting leaks of liquefied gas, A metal plate is positioned below the pipe connection, separated from the pipe connection provided in the liquefied gas piping, A temperature sensor for measuring the temperature of the aforementioned metal plate material, The system includes a control unit that acquires temperature data measured by the temperature sensor at predetermined time intervals, The liquefied gas leak detection system is characterized in that the control unit determines that a liquefied gas leak has occurred when the difference between the most recently acquired temperature and the previously acquired temperature is less than a predetermined threshold set in advance for the predetermined time interval.

2. A liquefied gas leak detection system according to claim 1, characterized in that the metal plate material is an aluminum checkered steel plate.

3. A liquefied gas leak detection system according to claim 1 or 2, characterized in that the metal plate material has a maximum size of 40 cm square, and the temperature sensor is mounted at the center of the metal plate material.

4. A liquefied gas leak detection system according to claim 1 or 2, wherein the control unit, when it determines that a liquefied gas leak has occurred, outputs a signal to stop the operation of a pump that supplies liquefied gas to the liquefied gas piping and / or a signal to close a shut-off valve provided in the liquefied gas piping.

5. A liquefied gas leak detection system according to claim 1 or 2, characterized in that the control unit outputs an alarm signal that activates at least one of a display, a buzzer, and an audio announcement when it determines that a liquefied gas leak has occurred.

6. A liquefied gas leak detection system according to claim 1 or 2, wherein the liquefied gas is any of liquefied nitrogen, liquefied oxygen, liquefied argon, or liquefied carbon dioxide.

7. A liquefied gas leak detection system according to claim 1 or 2, wherein the piping connection portion is a flange or a valve.

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