Vacuum degree keeping device

Abstract

The utility model relates to the technical field of liquefied natural gas sampling, in particular to a vacuum degree keeping device. The device comprises a first vacuum orifice, a first on-off switch, a first pressure monitoring unit, a control unit and a vacuum pump, wherein the first vacuum orifice is used for being connected with an external first sampling probe capable of collecting liquefied natural gas; the vacuum pump is connected with the first vacuumizing opening; the first on-off switch and the first pressure monitoring unit are both arranged on a connecting pipeline of the first vacuumizing opening and the vacuum pump, and the first pressure monitoring unit is located between the first vacuumizing opening and the first on-off switch and used for monitoring a first pressure value in the first sampling probe in real time and transmitting the first pressure value to the control unit; the control unit is connected with the first on-off switch and the vacuum pump and used for comparing the first pressure value with a preset value and controlling the first on-off switch and the vacuum pump to be connected or disconnected according to the first comparison result. According to the invention, the function of automatically keeping the vacuum degree in the first sampling probe can be realized, and the reliability is relatively high.

Description

Technical Field

[0001] This utility model relates to the field of liquefied natural gas sampling technology, and in particular to a vacuum maintenance device. Background Technology

[0002] Accurate sampling and analysis are crucial for trade measurement, quality control, and safe operation during the receiving, storage, and transportation of liquefied natural gas (LNG), such as sampling and analysis of LNG transported by ship. To prevent premature vaporization of the sample, it is necessary to maintain subcooling during the LNG sampling process, ensuring a vacuum environment inside the LNG sampling probe.

[0003] Currently, maintaining a vacuum environment inside the sampling probe involves manually evacuating the liquefied natural gas (LNG) sampling probe. However, this method cannot maintain the vacuum level inside the sampling probe in real time, which can easily lead to sealing problems due to excessively low vacuum during LNG sampling. This can cause partial vaporization of the sample, severely affecting its representativeness and resulting in significant errors in trade measurement results. Therefore, the existing method of maintaining a vacuum environment inside LNG sampling probes has low reliability. Utility Model Content

[0004] The technical problem to be solved by this utility model embodiment is to provide a vacuum maintaining device to solve the problem of low reliability of the existing method of maintaining a vacuum environment in liquefied natural gas sampling probes.

[0005] This utility model discloses a vacuum level maintaining device, including a first vacuum port, a first on / off switch, a first pressure monitoring unit, a control unit, and a vacuum pump, wherein...

[0006] The first vacuum port is used to connect to an external first sampling probe capable of collecting liquefied natural gas;

[0007] The vacuum pump is connected to the first vacuum port;

[0008] The first on / off switch and the first pressure monitoring unit are both located on the connecting pipe between the first vacuum port and the vacuum pump, and the first pressure monitoring unit is located between the first vacuum port and the first on / off switch. The first pressure monitoring unit is used to monitor the first pressure value in the first sampling probe in real time and transmit it to the control unit.

[0009] The control unit is connected to the first on / off switch and the vacuum pump. The control unit is used to compare the first pressure value with a preset value and control the first on / off switch and the vacuum pump to be turned on or off according to the first comparison result.

[0010] Optionally, the vacuum maintaining device further includes a heat preservation cabinet, in which the first on / off switch, the first pressure monitoring unit and the vacuum pump are all located, the first vacuum extraction port is located on the heat preservation cabinet and exposed outside the heat preservation cabinet, and the heat preservation cabinet is provided with an exhaust port connected to the vacuum pump.

[0011] Optionally, the vacuum maintaining device further includes a cooler disposed on the heat preservation cabinet and a heater disposed inside the heat preservation cabinet. The cooler is used to reduce the temperature inside the heat preservation cabinet when the temperature inside the heat preservation cabinet is higher than a first preset temperature value, and the heater is used to increase the temperature inside the heat preservation cabinet when the temperature inside the heat preservation cabinet is lower than a second preset temperature value.

[0012] Optionally, the vacuum maintaining device further includes a temperature control valve and a first gas source interface. The temperature control valve is connected to the cooler, and the first gas source interface is connected to the control terminal of the temperature control valve. The temperature control valve is located inside the insulation cabinet, and the first gas source interface is located on the insulation cabinet and exposed outside the insulation cabinet.

[0013] Optionally, the vacuum maintaining device further includes a second vacuum port, a second pressure monitoring unit and a second on / off switch located inside the insulation cabinet. The second vacuum port is located on the insulation cabinet and exposed outside the cabinet. The second vacuum port is used to connect to an external second sampling probe capable of collecting liquefied natural gas. The vacuum pump is also connected to the second vacuum port. The second on / off switch and the second pressure monitoring unit are both located on the connecting pipeline between the second vacuum port and the vacuum pump. The second pressure monitoring unit is located between the second vacuum port and the second on / off switch. The second pressure monitoring unit is used to monitor the second pressure value inside the second sampling probe in real time and transmit it to the control unit. The control unit is also used to compare the second pressure value with a preset value and control the connection or disconnection of the second on / off switch and the vacuum pump according to the second comparison result.

[0014] Optionally, the first on / off switch is a first pneumatic valve, the second on / off switch is a second pneumatic valve, and the vacuum maintaining device further includes a second air source interface and a first solenoid valve and a second solenoid valve disposed inside the insulation cabinet. The second air source interface is disposed on the insulation cabinet and exposed outside the insulation cabinet. The control terminals of the first pneumatic valve and the second pneumatic valve are both connected to the second air source interface. The first solenoid valve is disposed on the connection pipeline between the control terminal of the first pneumatic valve and the second air source interface to connect or disconnect the air supply of the first pneumatic valve. The second solenoid valve is disposed on the connection pipeline between the control terminal of the second pneumatic valve and the first air source interface to connect or disconnect the air supply of the second pneumatic valve. The control terminals of the first solenoid valve and the second solenoid valve are both connected to the control unit.

[0015] Optionally, the vacuum maintaining device further includes a first filter pressure reducer disposed inside the heat preservation cabinet, wherein the first filter pressure reducer is disposed on the connecting pipeline between the first gas source interface and the control end of the temperature control valve.

[0016] Optionally, the vacuum maintaining device further includes a second filter pressure reducer disposed inside the heat preservation cabinet, wherein the second filter pressure reducer is disposed on the connection pipeline between the first solenoid valve and the second solenoid valve and the first gas source interface.

[0017] Optionally, the vacuum maintaining device further includes a human-machine interface connected to the control unit. The human-machine interface is provided with a manual trigger button, which can be clicked to trigger the connection or disconnection of the first on / off switch, the second on / off switch, and the vacuum pump.

[0018] Optionally, the vacuum maintaining device further includes a first ball valve and a second ball valve, wherein the first ball valve is disposed on the connecting pipeline between the first vacuum port and the first sampling probe, and the second ball valve is disposed on the connecting pipeline between the second vacuum port and the second sampling probe.

[0019] Compared with the prior art, the beneficial effects of the vacuum maintaining device provided in this utility model embodiment are as follows: By setting a first vacuum port, a first on / off switch, a first pressure monitoring unit, a control unit, and a vacuum pump, the first pressure monitoring unit can monitor the first pressure value inside the first sampling probe that can collect liquefied natural gas in real time and transmit the first pressure value to the control unit. The control unit compares the first pressure value with a preset value and controls the first on / off switch and the vacuum pump to be turned on or off according to the first comparison result. When the first pressure value is higher than the preset value, the first on / off switch is turned on, the connecting pipeline between the first vacuum port and the vacuum pump is connected, the vacuum pump is turned on, and the first sampling probe is evacuated so that the pressure inside the first sampling probe is restored to the preset value, realizing the automatic vacuum maintaining function inside the first sampling probe. It has high reliability, improves the stability and reliability of the liquefied natural gas sampling system, reduces the possibility of sample vaporization, ensures the representativeness of the sample taken, and improves the measurement accuracy. Attached Figure Description

[0020] The technical solution of this utility model will be further described in detail below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0021] Figure 1 This is a schematic diagram of the electrical principle of the vacuum maintaining device provided in this embodiment of the utility model;

[0022] Figure 2 This is a simplified schematic diagram of the human-machine interface provided in an embodiment of this utility model.

[0023] The labels for the attached figures are as follows:

[0024] 110. First vacuum port; 120. First on / off switch; 121. First pneumatic valve; 130. First pressure monitoring unit; 140. Control unit; 150. Vacuum pump; 160. Insulation cabinet; 170. Exhaust port; 180. Cooler; 190. Heater; 210. Temperature control valve; 220. First air source interface; 230. First filter pressure reducer; 240. Second vacuum port; 250. Second pressure monitoring unit; 260. Second on / off switch; 261. Second pneumatic valve; 270. Second air source interface; 280. First solenoid valve; 290. Second solenoid valve; 310. Second filter pressure reducer; 320. First ball valve; 330. Second ball valve; 340. Human-machine interface; 341. Manual trigger button. Detailed Implementation

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The preferred embodiments of this utility model will now be described in detail with reference to the accompanying drawings.

[0026] This utility model embodiment provides a vacuum degree maintaining device, such as Figure 1 As shown, the vacuum maintaining device includes a first vacuum port 110, a first on / off switch 120, a first pressure monitoring unit 130, a control unit 140, and a vacuum pump 150.

[0027] The first vacuum port 110 is used to connect to the first external sampling probe for collecting liquefied natural gas.

[0028] The vacuum pump 150 is connected to the first vacuum port 110, which can perform vacuuming operation on the first sampling probe.

[0029] The first on / off switch 120 and the first pressure monitoring unit 130 are both located on the connecting pipe between the first vacuum port 110 and the vacuum pump 150. The first pressure monitoring unit 130 is located between the first vacuum port 110 and the first on / off switch 120. The first pressure monitoring unit 130 is used to monitor the first pressure value in the external sampling probe in real time and transmit the first pressure value to the control unit 140.

[0030] The control unit 140 is connected to the first on / off switch 120 and the vacuum pump 150. The control unit 140 is used to compare the first pressure value with the preset value, and control the first on / off switch 120 and the vacuum pump 150 to be turned on or off according to the first comparison result.

[0031] The vacuum maintaining device in this embodiment of the application includes a first vacuum port 110, a first on / off switch 120, a first pressure monitoring unit 130, a control unit 140, and a vacuum pump 150. The first pressure monitoring unit 130 can monitor the first pressure value inside the first sampling probe for liquefied natural gas in real time and transmit the first pressure value to the control unit 140. The control unit 140 compares the first pressure value with a preset value and controls the first on / off switch 120 and the vacuum pump 150 to be turned on or off according to the first comparison result. When the first pressure value is higher than the preset value, the control unit turns on the first on / off switch 120, connects the connecting pipeline between the first vacuum port 110 and the vacuum pump 150, and turns on the vacuum pump 150 to evacuate the first sampling probe so that the pressure inside the first sampling probe returns to the preset value. This achieves the automatic vacuum maintaining function inside the first sampling probe, which has high reliability, improves the stability and reliability of the liquefied natural gas sampling system, reduces the possibility of sample vaporization, ensures the representativeness of the sample, and improves the accuracy of measurement.

[0032] Specifically, when the first pressure monitoring unit 130 detects that the first pressure value inside the sampling probe has returned to the preset value, the control unit 140 controls the first on / off switch 120 to disconnect the connecting pipe between the first vacuum port 110 and the vacuum pump 150, and shuts down the vacuum pump 150 to stop the vacuuming operation. When the pressure value of the sampling probe exceeds the preset value again, the control unit 140 reconnects the first on / off switch 120, reconnects the connecting pipe between the first vacuum port 110 and the vacuum pump 150, and controls the vacuum pump 150 to start vacuuming, so that the sampling probe is always in a high vacuum state.

[0033] The preset value can be set according to actual needs. The control unit 140 can use an existing programmable logic controller to compare the first pressure value with the preset value. For example, the programmable logic controller integrates a comparator to compare the first pressure value with the preset value and output a level signal as the first comparison result.

[0034] In an optional embodiment of this application, the first pressure monitoring unit 130 may be a pressure transmitter. The pressure transmitter converts the measured pressure into an electrical signal and transmits it to the control unit 140 to monitor the pressure inside the sampling probe in real time and monitor the vacuum level inside the sampling probe.

[0035] refer to Figure 1 In an optional embodiment of this application, the vacuum maintaining device further includes a heat preservation cabinet 160, a first on / off switch 120, a first pressure monitoring unit 130 and a vacuum pump 150 are all located inside the heat preservation cabinet 160, a first vacuum port 110 is located on the heat preservation cabinet 160 and exposed outside the heat preservation cabinet 160, and an exhaust port 170 connected to the vacuum pump 150 is provided on the heat preservation cabinet 160.

[0036] By setting up the heat preservation cabinet 160, heat transfer can be reduced, thus minimizing the impact of external temperature on the first on / off switch 120, the first pressure monitoring unit 130, and the vacuum pump 150, enabling the entire vacuum maintenance device to adapt to different environmental conditions. The first vacuum port 110 can be a connector, which can be connected to the first sampling probe via a connecting pipe. After the first on / off switch 120 and the vacuum pump 150 are turned on, the vacuum pump 150 can evacuate the first sampling probe, and the gas is discharged through the exhaust port 170.

[0037] refer to Figure 1 In an optional embodiment of this application, the vacuum maintaining device further includes a cooler 180 disposed on the heat preservation cabinet 160 and a heater 190 disposed inside the heat preservation cabinet 160. The cooler 180 is used to reduce the temperature inside the heat preservation cabinet 160 when the temperature inside the heat preservation cabinet 160 is higher than a first preset temperature value, and the heater 190 is used to increase the temperature inside the heat preservation cabinet 160 when the temperature inside the heat preservation cabinet 160 is lower than a second preset temperature value.

[0038] By configuring the cooler 180 and heater 190, when the temperature inside the insulation cabinet 160 exceeds a first preset temperature value, the cooler 180 can be activated to lower the temperature inside the insulation cabinet 160. When the temperature inside the insulation cabinet 160 falls below a second preset temperature value, the heater 190 can be activated to raise the temperature inside the insulation cabinet 160. The combination of the cooler 180 and heater 190 effectively controls the temperature inside the insulation cabinet 160, maintaining it within the required range. This ensures that all components inside the insulation cabinet 160 operate at a suitable ambient temperature, improving the environmental adaptability of the entire vacuum maintenance device and preventing the vaporization of liquefied natural gas. The first and second preset temperature values ​​can be set according to actual needs.

[0039] Furthermore, the vacuum holding device also includes a temperature control valve 210 and a first gas source interface 220. The temperature control valve 210 is connected to the cooler 180, and the first gas source interface 220 is connected to the control terminal of the temperature control valve 210. The temperature control valve 210 is located inside the heat preservation cabinet 160, and the first gas source interface 220 is located on the heat preservation cabinet 160 and exposed outside the heat preservation cabinet 160.

[0040] By setting the temperature control valve 210, the flow rate of the fluid in the cooler 180 can be adjusted, thereby controlling the outlet temperature of the cooler 180 and achieving precise temperature control of the cooler 180. The first air source interface 220 can be connected to an external air source such as instrument air or compressed air. The temperature control valve 210 is driven by the air source as a power source, making the overall control simple and maintenance easy.

[0041] Furthermore, the vacuum maintaining device also includes a first filter pressure reducer 230 located inside the heat preservation cabinet 160. The first filter pressure reducer 230 is located on the connecting pipeline between the first gas source interface 220 and the control end of the temperature control valve 210.

[0042] By setting the first filter pressure reducer 230, impurities such as moisture, oil and dust in the air source can be effectively filtered to ensure that the gas entering the control end of the temperature control valve 210 is clean. This is crucial for protecting the temperature control valve 210 and preventing blockage or damage caused by impurities. In addition, the first filter pressure reducer 230 can also regulate the pressure of the air output from the first air source interface 220 to the temperature control valve 210 to avoid damage to the temperature control valve 210 due to excessive pressure.

[0043] refer to Figure 1In an optional embodiment of this application, the vacuum maintaining device further includes a second vacuum port 240 and a second pressure monitoring unit 250 and a second on / off switch 260 disposed within the insulation cabinet 160. The second vacuum port 240 is disposed on and exposed within the insulation cabinet 160. The second vacuum port 240 is used to connect to an external second sampling probe capable of collecting liquefied natural gas. The vacuum pump 150 is also connected to the second vacuum port 240. The second on / off switch 260 and the second pressure monitoring unit 250 are both disposed on the connecting pipeline between the second vacuum port 240 and the vacuum pump 150. The second pressure monitoring unit 250 is located between the second vacuum port 240 and the second on / off switch 260. The second pressure monitoring unit 250 is used to monitor the second pressure value inside the second sampling probe in real time and transmit the second pressure value to the control unit 140. The control unit 140 is also used to compare the second pressure value with a preset value and control the connection or disconnection of the second on / off switch 260 and the vacuum pump 150 according to the second comparison result.

[0044] By setting up a second pressure monitoring unit 250 and a second on / off switch 260, the second pressure monitoring unit 250 can monitor the pressure inside the sampling probe in real time. The control unit 140 receives the second pressure value transmitted by the second pressure monitoring unit 250, and when the second pressure value is higher than a preset value, it opens the second on / off switch 260, connects the pipeline between the second vacuum port 240 and the vacuum pump 150, and starts the vacuum pump 150 to evacuate the second sampling probe, so that the second sampling probe maintains a suitable vacuum level. The control unit 140 can use an existing programmable logic controller to compare the second pressure value with the preset value. For example, the programmable logic controller integrates another comparator to compare the second pressure value with the preset value and outputs a level signal as the second comparison result.

[0045] When the second pressure monitoring unit 250 detects that the second pressure value inside the second sampling probe has returned to the preset value, the control unit 140 controls the second on / off switch 260 to disconnect the connection between the second vacuum port 240 and the vacuum pump 150, and shuts down the vacuum pump 150 to stop the vacuuming operation. When the pressure value of the second sampling probe is higher than the preset value again, the control unit 140 turns on the second on / off switch 260, reconnects the connection between the second vacuum port 240 and the vacuum pump 150, and controls the vacuum pump 150 to start vacuuming, so that the second sampling probe maintains a high vacuum state.

[0046] In practical applications, both the first and second sampling probes can be used to collect liquefied natural gas (LNG). The second sampling probe can serve as a backup; if the first sampling probe fails, the second probe can be used to collect LNG. Vacuum-related devices that can be connected to the second sampling probe can maintain it in a high-vacuum state, ensuring the reliability of LNG sampling.

[0047] In an optional embodiment of this application, the connecting pipeline from the vacuum pump 150 to the first vacuum port 110 and the second vacuum port 240 can be made of 316LSS material. 316LSS material is an ultra-low carbon austenitic stainless steel with excellent corrosion resistance. It can maintain good mechanical properties and corrosion resistance in high and low temperature environments, thereby improving the stability of the vacuum level maintenance device.

[0048] In an optional embodiment of this application, the second pressure monitoring unit 250 may also be a pressure transmitter to monitor the pressure inside the second sampling probe.

[0049] refer to Figure 1 In an optional embodiment of this application, the first on / off switch 120 is a first pneumatic valve 121, the second on / off switch 260 is a second pneumatic valve 261, and the vacuum maintaining device further includes a second air source interface 270 and a first solenoid valve 280 and a second solenoid valve 290 disposed in the heat preservation cabinet 160. The second air source interface 270 is disposed on the heat preservation cabinet 160 and exposed outside the heat preservation cabinet 160. The control terminals of the first pneumatic valve 121 and the second pneumatic valve 261 are both connected to the second air source interface 270. The first solenoid valve 280 is disposed on the connecting pipeline between the control terminal of the first pneumatic valve 121 and the second air source interface 270 to connect or disconnect the air supply of the first pneumatic valve 121. The second solenoid valve 290 is disposed on the connecting pipeline between the control terminal of the second pneumatic valve 261 and the first air source interface 220 to connect or disconnect the air supply of the second pneumatic valve 261. The control terminals of the first solenoid valve 280 and the second solenoid valve 290 are both connected to the control unit 140.

[0050] The second air source interface 270 can be connected to an external air source such as instrument air or compressed air. A pneumatic valve is used as the on / off switch. Driven by the air source, the pneumatic valve can complete the switching operation in a short time, with fast response, no electrical dependence, high safety, relatively simple structure, low failure rate, and convenient maintenance. A solenoid valve is used to control the air supply to the pneumatic valve, with fast response and rapid switching, allowing for more precise control of fluid flow and improving the overall system efficiency. The solenoid valve is directly controlled by the control unit 140, reducing manual intervention and improving operational convenience and safety. The solenoid valve has a relatively simple structure, is easy to maintain, and has a long service life.

[0051] Optionally, both the first solenoid valve 280 and the second solenoid valve 290 are explosion-proof solenoid valves. Explosion-proof solenoid valves can effectively prevent explosion accidents caused by electrical sparks, electric arcs or high temperatures, ensuring safety in flammable and explosive environments such as liquefied natural gas.

[0052] Furthermore, the vacuum maintaining device also includes a second filter pressure reducer 310 located inside the heat preservation cabinet 160. The second filter pressure reducer 310 is located on the connecting pipeline between the first solenoid valve 280, the second solenoid valve 290, and the first air source interface 220.

[0053] By setting the second filter pressure reducer 310, impurities such as moisture, oil, and dust in the air source can be effectively filtered. This is crucial for protecting downstream precision equipment such as the first solenoid valve 280, the second solenoid valve 290, the first pneumatic valve 121, and the second pneumatic valve 261. It can prevent impurities from entering the equipment, avoiding blockage or damage, thereby extending the service life of the equipment and improving the stability of the vacuum maintaining device and its application system. In addition, the second filter pressure reducer 310 can also regulate the pressure of the air output from the second air source interface 270 to the first solenoid valve 280 and the second solenoid valve 290, preventing excessive pressure from damaging the first solenoid valve 280 and the second solenoid valve 290.

[0054] In an optional embodiment of this application, the vacuum maintaining device further includes a first ball valve 320 and a second ball valve 330. The first ball valve 320 is disposed on the connecting pipe between the first vacuum port 110 and the first sampling probe, and the second ball valve 330 is disposed on the connecting pipe between the second vacuum port 240 and the second sampling probe.

[0055] By setting the first ball valve 320 and the second ball valve 330, when the first vacuum port 110 and the second vacuum port 240 are connected to the corresponding sampling probes, the user can rotate the first ball valve 320 and the second ball valve 330 to disconnect the connection between the first vacuum port 110 and the first sampling probe, and disconnect the connection between the second vacuum port 240 and the second sampling probe, so as to maintain the vacuum level maintaining device.

[0056] refer to Figure 1 and Figure 2 In an optional embodiment of this application, the vacuum maintaining device further includes a human-machine interface 340 connected to the control unit 140. The human-machine interface 340 is provided with a manual trigger button 341, which can be clicked to trigger the connection or disconnection of the first on / off switch 120, the second on / off switch 130 and the vacuum pump 150.

[0057] By setting up the human-machine interface 340, users can operate the human-machine interface 340 and the manual trigger button 341 on the human-machine interface 340 to connect or disconnect the first on / off switch 120, the second on / off switch 130 and the vacuum pump 150, thereby manually starting or stopping the vacuum pumping.

[0058] In addition, the HMI 340 can also display vacuum pressure values, vacuum pump status, etc. A simplified schematic diagram of the HMI 340 is shown below. Figure 2 As shown.

[0059] In an optional embodiment of this application, the vacuum maintaining device may further include an explosion-proof power supply box (not shown) for supplying power to the entire vacuum maintaining device. The explosion-proof power supply box adopts a special explosion-proof structure and materials, which can effectively isolate the internal electrical components from direct contact with the external flammable and explosive environment, prevent explosion accidents caused by electrical sparks, arcs or high temperatures, and improve the safety of the system.

[0060] In an optional embodiment of this application, the vacuum maintaining device may further include a mounting skid (not shown), on which the heat preservation cabinet 160 is mounted.

[0061] It should be understood that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Those skilled in the art can modify the technical solutions described in the above embodiments, or make equivalent substitutions for some of the technical features; and all such modifications and substitutions should fall within the protection scope of the appended claims of this utility model.

Claims

1. A vacuum degree maintaining device, characterized in that, It includes a first vacuum port, a first on / off switch, a first pressure monitoring unit, a control unit, and a vacuum pump, wherein, The first vacuum port is used to connect to an external first sampling probe capable of collecting liquefied natural gas; The vacuum pump is connected to the first vacuum port; The first on / off switch and the first pressure monitoring unit are both located on the connecting pipe between the first vacuum port and the vacuum pump, and the first pressure monitoring unit is located between the first vacuum port and the first on / off switch. The first pressure monitoring unit is used to monitor the first pressure value in the first sampling probe in real time and transmit it to the control unit. The control unit is connected to the first on / off switch and the vacuum pump. The control unit is used to compare the first pressure value with a preset value and control the first on / off switch and the vacuum pump to be turned on or off according to the first comparison result.

2. The vacuum maintaining device according to claim 1, characterized in that, The vacuum maintaining device also includes a heat preservation cabinet. The first on / off switch, the first pressure monitoring unit, and the vacuum pump are all located inside the heat preservation cabinet. The first vacuum extraction port is located on the heat preservation cabinet and exposed outside the heat preservation cabinet. The heat preservation cabinet is provided with an exhaust port connected to the vacuum pump.

3. The vacuum maintaining device according to claim 2, characterized in that, The vacuum maintaining device further includes a cooler disposed on the heat preservation cabinet and a heater disposed inside the heat preservation cabinet. The cooler is used to reduce the temperature inside the heat preservation cabinet when the temperature inside the heat preservation cabinet is higher than a first preset temperature value, and the heater is used to increase the temperature inside the heat preservation cabinet when the temperature inside the heat preservation cabinet is lower than a second preset temperature value.

4. The vacuum maintaining device according to claim 3, characterized in that, The vacuum maintaining device further includes a temperature control valve and a first gas source interface. The temperature control valve is connected to the cooler, and the first gas source interface is connected to the control terminal of the temperature control valve. The temperature control valve is located inside the insulation cabinet, and the first gas source interface is located on the insulation cabinet and exposed outside the insulation cabinet.

5. The vacuum maintaining device according to any one of claims 2-4, characterized in that, The vacuum maintaining device further includes a second vacuum port, a second pressure monitoring unit, and a second on / off switch located inside the insulation cabinet. The second vacuum port is located on the insulation cabinet and exposed outside the cabinet. The second vacuum port is used to connect to an external second sampling probe capable of collecting liquefied natural gas. The vacuum pump is also connected to the second vacuum port. The second on / off switch and the second pressure monitoring unit are both located on the connecting pipeline between the second vacuum port and the vacuum pump. The second pressure monitoring unit is located between the second vacuum port and the second on / off switch. The second pressure monitoring unit is used to monitor the second pressure value inside the second sampling probe in real time and transmit it to the control unit. The control unit is also used to compare the second pressure value with a preset value and control the connection or disconnection of the second on / off switch and the vacuum pump according to the second comparison result.

6. The vacuum maintaining device according to claim 5, characterized in that, The first on / off switch is a first pneumatic valve, and the second on / off switch is a second pneumatic valve. The vacuum maintaining device also includes a second air source interface and a first solenoid valve and a second solenoid valve disposed inside the insulation cabinet. The second air source interface is disposed on the insulation cabinet and exposed outside the insulation cabinet. The control terminals of the first pneumatic valve and the second pneumatic valve are both connected to the second air source interface. The first solenoid valve is disposed on the connecting pipeline between the control terminal of the first pneumatic valve and the second air source interface to connect or disconnect the air supply of the first pneumatic valve. The second solenoid valve is disposed on the connecting pipeline between the control terminal of the second pneumatic valve and the second air source interface to connect or disconnect the air supply of the second pneumatic valve. The control terminals of the first solenoid valve and the second solenoid valve are both connected to the control unit.

7. The vacuum maintaining device according to claim 4, characterized in that, The vacuum maintaining device further includes a first filter pressure reducer installed inside the heat preservation cabinet. The first filter pressure reducer is installed on the connecting pipeline between the first gas source interface and the control end of the temperature control valve.

8. The vacuum maintaining device according to claim 6, characterized in that, The vacuum maintaining device further includes a second filter pressure reducer installed inside the heat preservation cabinet. The second filter pressure reducer is installed on the connecting pipeline between the first solenoid valve, the second solenoid valve and the first gas source interface.

9. The vacuum maintaining device according to claim 5, characterized in that, The vacuum maintaining device also includes a human-machine interface connected to the control unit. The human-machine interface is provided with a manual trigger button, which can be clicked to trigger the connection or disconnection of the first on / off switch, the second on / off switch, and the vacuum pump.

10. The vacuum maintaining device according to claim 6, characterized in that, The vacuum maintaining device further includes a first ball valve and a second ball valve. The first ball valve is disposed on the connecting pipe between the first vacuum port and the first sampling probe, and the second ball valve is disposed on the connecting pipe between the second vacuum port and the second sampling probe.

Images