Maintenance method for freezer

Abstract

The present application provides a maintenance method for a freezer, and in particular, for a freezer for a superconducting magnet apparatus having a vacuum vessel. When maintenance is performed on the freezer, after a helium atmosphere is formed around the freezer, a displacer is pulled out from a cylinder. At this time, the temperature in the cylinder is low. In order to avoid condensation of water vapor in air that enters the cylinder, a heating rod is inserted into the cylinder to increase the surface temperature of the cylinder. At this time, even if air enters the cylinder, no condensation will occur. When the surface temperature of the cylinder has risen to a specified preset temperature condition, the heating rod is pulled out, and upon completion of the maintenance of the freezer, a second displacer is inserted into the cylinder.

Description

[0001] This application relates to the field of refrigeration equipment used in superconducting magnet devices, specifically a method for maintaining and repairing a refrigeration unit. Background Art: Superconducting magnets require extremely low temperatures to operate. In the prior art, refrigeration units are often used to cool superconducting magnet devices with vacuum containers, creating a suitable working environment for the magnets. The refrigeration unit has a cylinder and a transfer device housed within it. To prevent malfunctions of the refrigeration unit from affecting the working environment of the superconducting magnets within the device, regular maintenance is required. Considering the high temperature requirements of superconducting magnets, the temperature of the refrigeration unit cylinder and the transfer device housed within it is close to absolute zero. When maintaining the refrigeration unit, the transfer device needs to be removed from the cylinder. At this time, air enters the cylinder, and water vapor in the air precipitates and freezes inside the cylinder under extremely low temperatures, potentially causing problems such as transfer device jamming. In existing technology, to avoid problems such as air entering the cylinder and causing icing on the cylinder walls during refrigeration maintenance, the exposed parts of the refrigeration unit are wrapped in a plastic bag before the air transfer device is removed. The plastic bag is then secured to the vacuum container with tape, ensuring a sealed environment inside the bag. The air transfer device is then removed to prevent outside air from entering the cylinder and icing. However, even with a plastic bag isolating the cylinder from outside air, it is still impossible to completely prevent air from condensing inside the bag within the cylinder. This application aims to provide a method for maintaining and repairing a refrigeration unit, thereby at least solving or mitigating some of the problems existing in the prior art. This application provides a maintenance method for a cryostat. The cryostat has a cylinder and a transfer device housed within the cylinder, used in a superconducting magnet device with a vacuum container. The maintenance method includes: a transfer device removal step, removing the transfer device from the cylinder; a heating rod insertion step, inserting the heating rod into the cylinder; a heating rod temperature control step, controlling and adjusting the output of the heating rod until a predetermined preset temperature condition is reached; a heating rod removal step, removing the heating rod from the cylinder; and a transfer device insertion step, inserting a second transfer device into the cylinder. In an optional technical solution, the predetermined temperature condition is set to achieve a cylinder internal temperature of 290K-300K, which is monitored and managed by a device-side thermometer installed inside the vacuum container. In an optional technical solution, the cryostat maintenance method further includes: a cylinder surface temperature detection step, using a surface thermometer to detect the temperature of the cylinder's internal surface. In an optional technical solution, the cylinder includes: a first cylinder section having a first cylinder diameter; and a second cylinder section having a second cylinder diameter connected to the first cylinder section.In optional technical solutions, the maintenance method for the refrigeration unit further includes: a nitrogen atmosphere formation step, wherein nitrogen is filled to form a nitrogen atmosphere at least within the refrigeration unit area before performing the gas transfer device removal step. In optional technical solutions, the maintenance method for the refrigeration unit further includes: a nitrogen cylinder introduction step, wherein nitrogen is introduced into the cylinder after the heating rod is inserted. In optional technical solutions, the nitrogen introduction flow rate in the nitrogen cylinder introduction step is 3-4 L / min. In optional technical solutions, the maintenance method for the refrigeration unit further includes: a cylinder internal cleaning step, wherein the cylinder interior is cleaned at least after the heating rod is removed. In optional technical solutions, the cylinder internal cleaning step further includes a nitrogen purging step, using nitrogen to purge the cylinder interior. In optional technical solutions, the maintenance method for the refrigeration unit further includes: a heating rod re-insertion step, wherein the heating rod is re-inserted after completing the cylinder internal cleaning step. In optional technical solutions, the maintenance method for the cryostat further includes: a heating rod reheating step, wherein after the heating rod re-insertion step, the heating rod is again subjected to temperature rise control until the specified preset temperature condition is reached. In optional technical solutions, the maintenance method for the cryostat further includes: a nitrogen charging and purging replacement step, wherein after the gas transfer device insertion step, nitrogen is charged and purged inside the cryostat. In optional technical solutions, the nitrogen charging and purging replacement step includes a first charging and purging replacement step under a first nitrogen supply pressure and a second charging and purging replacement step under a second nitrogen supply pressure. Figure 1 is a schematic diagram of the structure of a cryostat installed in a superconducting magnet device according to one embodiment of this application. Figure 2 is a schematic diagram of the execution steps of the maintenance method for the cryostat according to one embodiment of this application. Figure 3 is a schematic diagram of the execution steps of the maintenance method for the cryostat according to one embodiment of this application. Figure 4 is a schematic diagram of the execution steps of the maintenance method for the cryostat according to one embodiment of this application. Figure 5 is a schematic diagram of the execution steps of the maintenance method for the cryostat according to one embodiment of this application. Figure 6 is a schematic diagram of the execution steps of a maintenance method for a refrigeration unit according to one embodiment of this application. Figure 7 is a schematic diagram of the execution steps of a maintenance method for a refrigeration unit according to one embodiment of this application. Reference numerals: Superconducting magnet device 1, Refrigeration unit 11, Vacuum container 12, Motor 111, Cylinder 112, First cylinder section 1121, Second cylinder section 1122, Gas transfer device 113, Plastic bag 2.It should be noted that the following description of the working principle, features, and advantages of the refrigeration equipment according to this application will be illustrated by way of example. However, it should be understood that all descriptions are given for illustrative purposes only and should not be construed as limiting this application in any way. Furthermore, for any single technical feature described or implied in the embodiments mentioned herein, or any single technical feature shown or implied in the accompanying drawings, this application still allows for any combination or deletion of these technical features (or their equivalents) without any technical obstacles, thereby obtaining more other embodiments of this application that may not be directly mentioned herein.

[0002] <First Embodiment> Figure 1 is a schematic diagram of the structure of a cryostat installed in a superconducting magnet device according to one embodiment of this application. As shown in Figure 1, the superconducting magnet device 1 includes a vacuum container 12 with a cryostat 11 installed. The cryostat 11 installed in the superconducting magnet device 1 has a motor 111 protruding from the superconducting magnet device 1 and exposed to the air, a cylinder 112 corresponding to the motor 111 and installed in the superconducting magnet device 1, and a gas transfer device 113 connected to the motor 111 and housed in the cylinder 112. The cylinder 112 further includes a first cylinder portion 1121 with a first cylinder diameter and a second cylinder portion 1122 with a second cylinder diameter communicating with the first cylinder portion 1121. Figure 2 is a schematic diagram of the execution steps of a maintenance method for the cryostat according to one embodiment of this application. The maintenance method for the cryostat according to this embodiment includes: gas transfer device removal step.

[0003] 51. Step S2: Inserting the heating rod; Step S3: Controlling the temperature of the heating rod; Step S4: Pulling out the heating rod; Step S5: Inserting the gas transfer device. In this embodiment, when maintenance of the refrigeration unit is required, in the prior art, a sealed environment is created around the refrigeration unit using a plastic bag (2) and tape (not shown). Step S1 is then performed to pull out the gas transfer device 113 from the cylinder 112. Considering the temperature requirements of the superconducting magnet and the low refrigeration temperature of the refrigeration unit, the temperature in the gas transfer device 113 and cylinder 112 is close to absolute zero. After removing the plastic bag 2, the step of inserting the heating rod is performed.

[0004] 52. A heating rod (not shown) matching the shape of cylinder 112 is inserted into cylinder 112. The heating rod heats the environment entering cylinder 112 and the cylinder wall, raising the internal temperature of cylinder 112. Simultaneously, heating rod temperature control step S3 is executed to control and adjust the output of the heating rod, so that the internal temperature of cylinder 112 reaches the predetermined preset temperature condition. When the internal temperature of cylinder 112 reaches the predetermined preset temperature condition, heating rod removal step S4 is executed to remove the heating rod from cylinder 112. Vacuum transfer device insertion step S5 is executed to insert the second vacuum transfer device 113 into cylinder 112. Through the above implementation method, when maintaining the refrigeration unit, the motor 111 exposed to air is wrapped in a plastic bag 2, and the plastic bag 2 is fixed to the vacuum container 12 with tape to ensure a sealed environment inside the plastic bag 2. Then, the vacuum transfer device 113 is removed from cylinder 112. Although the temperature inside cylinder 112 is low at this time, the sealed environment created by wrapping it with plastic bag 2 prevents ambient air from entering the cylinder 112 when the transfer device 113 is pulled out of the cylinder 112. This reduces the possibility of water vapor in the ambient air entering the cylinder 112 and condensing and adhering to the cylinder 112 wall under the effect of low temperature, thus preventing the transfer device 113 from getting stuck. However, considering that the plastic bag 2 is not a vacuum environment, some air may still enter the cylinder 112. In this case, the plastic bag 2 is removed, the heating rod is inserted into the cylinder 112, and the output of the heating rod is controlled and adjusted until the preset temperature condition is reached. At this point, the temperature in the cylinder 112 rises. Even if air still enters the cylinder 112, when the temperature inside the cylinder 112 reaches the preset temperature condition, such as room temperature, water vapor in the air no longer condenses and precipitates. This avoids the water vapor entering the cylinder 112 condensing and adhering to the inner wall of the cylinder 112, which could potentially cause the gas transfer device 113 to jam. In the preferred embodiment of this application, the preset temperature condition is to make the temperature inside the cylinder 112 reach 290K-300K, and this is monitored and managed by a device-side thermometer (not shown) installed inside the vacuum container 12. It is considered that when the heating rod is inserted to heat the cylinder 112, the internal surface temperature of the cylinder 112 cannot be accurately detected. Therefore, the device side temperature is detected by a device side thermometer installed in the vacuum container 12, and the surface temperature of the cylinder 112 is determined based on the device side temperature to see if it has reached the specified preset temperature condition.Specifically, during the execution of heating rod temperature control step S3, the output of the heating rod is controlled and adjusted to continuously raise the temperature inside cylinder 112. Consequently, the temperature inside the vacuum container 12 near cylinder 112 also rises. When the device-side thermometer installed inside the vacuum container 12 detects a device-side temperature of 290K-300K (approximately 17°C-27°C), i.e., a device-side temperature higher than the freezing point, the water vapor entering cylinder 112 cannot condense into ice. The heating rod is then de-energized and stops outputting, and step S4, removing the heating rod, is executed to prevent further temperature increases in cylinder 112 and vacuum container 12 from affecting the superconducting magnet device 1. In this application embodiment, 290K-300K is used as the specified preset temperature condition. However, this application does not limit its specific value. Different preset temperature conditions can be set according to the cylinder 112 capacity of different refrigerators, the size and power of the heating rod, and external environmental conditions. All such methods should be included within the protection scope of this application. Figure 3 is a schematic diagram of the execution steps of the maintenance method for a refrigeration unit according to one embodiment of this application. Referring to Figure 3, the maintenance method for a refrigeration unit provided by this application further includes: a cylinder surface temperature detection step S6. Specifically, after performing the step of removing the heating rod S4, the cylinder surface temperature detection step S6 is performed. A surface thermometer (not shown) is used to detect the temperature of the internal surface of the cylinder 112 when the heating rod is removed, and the internal surface temperature of the cylinder 112 is compared with a predetermined preset temperature condition. If the comparison result is that the internal surface temperature of the cylinder 112 when the heating rod is removed does not reach the predetermined preset temperature condition, that is, the internal surface temperature of the cylinder 112 is lower than 290K, the time for the next insertion of the heating rod or the output power is appropriately extended so that the internal surface temperature of the cylinder 112 can be increased. If the comparison result shows that the internal surface temperature of cylinder 112 exceeds the specified preset temperature condition when the heating rod is removed (i.e., the internal surface temperature of cylinder 112 is higher than 300K), then the time for inserting the heating rod again or the output power will be appropriately shortened to appropriately reduce the internal surface temperature of cylinder 112 and control it within the specified preset temperature condition range. Through the above method, the temperature of the internal surface of cylinder 112 is detected when the heating rod is removed, and the detection result is compared with the specified preset temperature condition. Based on the comparison result, the specified preset temperature condition is adjusted so that when the refrigeration unit is maintained next time, the internal surface temperature of cylinder 112 after the heating rod is removed reaches or is closer to the specified preset temperature condition.<Second Embodiment> The maintenance method for the refrigeration unit according to the second embodiment of this application is identical to the maintenance method for the refrigeration unit described in the above-mentioned embodiments of this application, and will not be repeated here. Figure 4 is a schematic diagram of the execution steps of the maintenance method for the refrigeration unit according to one embodiment of this application. Referring to Figure 4, the maintenance method for the refrigeration unit provided in this application differs from that in the first embodiment in that it further includes: a nitrogen atmosphere formation step S7 and a nitrogen introduction into the cylinder step S8. In order to further reduce the amount of air that may enter the cylinder 112 during the maintenance of the refrigeration unit, after wrapping the motor 111 exposed to the air with a plastic bag 2, the nitrogen atmosphere formation step S7 is performed first to fill the plastic bag 2 with nitrogen, so as to form a nitrogen atmosphere at least within the refrigeration unit area and reduce the air content inside the plastic bag 2. By employing the above method, after ensuring that a nitrogen atmosphere is formed within the refrigeration unit area inside the plastic bag 2, the step S1 of removing the transfer device is performed. This avoids water vapor in the air encased in the plastic bag 2 from entering the cylinder 112 or contacting the transfer device 113 during the removal step S1, causing condensation on the inner surface of the cylinder 112 or the surface of the transfer device 113, resulting in the transfer device 113 becoming stuck and unable to be removed. It should be noted that this application does not limit the method of filling nitrogen in the nitrogen atmosphere formation step S7. Introducing nitrogen through a conduit, etc., as long as the setup creates a nitrogen atmosphere within the refrigeration unit area, should be included within the scope of protection of this application. As a preferred embodiment of this application, after performing the heating rod insertion step S2 and inserting the heating rod into the cylinder 112, the nitrogen introduction cylinder step S8 is performed, introducing nitrogen into the cylinder 112 through the nitrogen channel (not shown) in the heating rod. Specifically, when the heating rod is inserted into the cylinder 112, the heating rod and the inner surface of the cylinder 112 do not directly form a complete surface contact; a certain space is left in the middle. While the heating rod heats the inner surface of the cylinder 112, nitrogen gas is introduced into the cylinder 112, so that the nitrogen gas fills the gap between the heating plate and the inner surface of the cylinder 112. Nitrogen gas can be used to conduct the heat generated by the heating rod to the inner surface of the cylinder 112, thereby improving the heating efficiency.Through the above implementation method, on the one hand, the nitrogen content in cylinder 112 is increased, so that the gap between the heating rod and the inner surface of cylinder 112 is filled with nitrogen. This avoids the problem of air entering the cylinder 112 when the inner surface temperature of cylinder 112 is still low, causing water vapor in the air to precipitate and remain inside cylinder 112, which would affect the refrigeration unit. On the other hand, the thermal conductivity of air is about 0.0257 W / m « °C, while the thermal conductivity of nitrogen is about 0.1513 W / m « °C, which is higher than that of air. By introducing nitrogen into the cylinder 112, the heat exchange efficiency between the heating rod surface and cylinder 112 is improved, allowing the inner surface temperature of cylinder 112 to reach the specified preset temperature condition more quickly. As a preferred embodiment of this application, in the nitrogen introduction step S8, the nitrogen introduction flow rate is 3-4 L / min. o Through the above implementation method, in the nitrogen introduction cylinder step S8, by controlling the nitrogen introduction flow rate to 3-4 L / min, the nitrogen can completely fill the gap between the heating rod and the inner surface of the cylinder 112. Continuous nitrogen introduction ensures that the nitrogen pressure filling the gap between the heating rod and the inner surface of the cylinder 112 is higher than the external ambient air pressure. This avoids the problem of insufficient nitrogen introduction leading to a negative pressure environment inside the cylinder 112, allowing external air to enter. Simultaneously, by controlling the nitrogen introduction flow rate to 3-4 L / min, excessive nitrogen introduction is avoided, which would cause the nitrogen pressure filling the gap between the heating rod and the inner surface of the cylinder 112 to be too high, resulting in the nitrogen in the cylinder 112 dissipating into the external ambient air at a relatively high speed, and the nitrogen temperature inside the cylinder 112 remaining consistently low, thus reducing the heat exchange efficiency between the heating rod and the inner surface of the cylinder 112. Although this embodiment uses a nitrogen inlet flow rate of 3-4 L / min, this application is not limited to this. Different inlet flow rates may be set according to the cylinder 112 capacity of different refrigerators, the size and power of heating rods, and external environmental conditions, and all such inlet flow rates should be included within the scope of protection of this application.

[0005] <Third Embodiment> The maintenance method for the refrigeration unit according to the third embodiment of this application is the same as the maintenance method for the refrigeration unit in the above-described embodiments of this application, and all use the same names or symbols. Therefore, they are identical in content and will not be repeated here. Figure 5 is a schematic diagram of the execution steps of the maintenance method for the refrigeration unit according to one embodiment of this application. Referring to Figure 5, the maintenance method for the refrigeration unit provided in this application differs from that in the above-described embodiments in that it further includes: a cylinder internal cleaning step S9 and a nitrogen purging step S100. Specifically, when the temperature detected by the device-side thermometer inside the vacuum container 12 reaches a predetermined preset temperature condition, the heating rod removal step S4 is executed. After the heating rod is removed, the cylinder internal cleaning step S9 is executed to clean the inside of the cylinder 112. Through the above implementation method, after the heating rod is removed, the inside of the cylinder 112 is cleaned to prevent impurities from remaining inside the cylinder 112. This avoids the problem that the second gas transfer device 113 may become stuck due to condensation of water vapor or impurities after being inserted into the cylinder 112, or affect the operation of the superconducting magnet device 1. As a preferred embodiment of this application, the cylinder internal cleaning step S9 also includes a nitrogen purging step S10, which uses nitrogen to purge the inside of the cylinder 112. When performing the cylinder internal cleaning step S9, it is preferable to use nitrogen to purge the inside of the cylinder 112. Considering that nitrogen has already been introduced into the inside of the cylinder 112 in the nitrogen atmosphere formation step S7 and the nitrogen introduction cylinder step S8, it is more convenient to use nitrogen to purge the inside of the cylinder 112. Meanwhile, nitrogen has a low melting point of approximately 2K. After purging with nitrogen, even if a low-temperature transfer device 113 is inserted, the nitrogen remaining inside the cylinder 112 will not freeze. This avoids the problem of the cylinder 112's internal temperature dropping rapidly after the transfer device insertion step S5, causing the gas temperature inside the cylinder 112 to sublimate below its melting point, forming a solid and causing the transfer device 113 to jam. Although the above embodiment uses nitrogen purging to clean the inside of the cylinder 112, this application is not limited to this. Other methods of cleaning the inside of the cylinder 112, as long as they can remove impurities from the cylinder 112 and the reduction in the internal temperature of the cylinder 112 does not affect the operation of the refrigeration unit, should be included within the scope of protection of this application.

[0006] <Fourth Embodiment> The maintenance method for the refrigeration unit according to the fourth embodiment of this application is the same as the maintenance method for the refrigeration unit in the above-described embodiments of this application, and all use the same names or symbols for description. Therefore, they are all the same content and will not be repeated here. Figure 6 is a schematic diagram of the execution steps of the maintenance method for the refrigeration unit according to one embodiment of this application. Referring to Figure 6, the difference between the maintenance method for the refrigeration unit provided in this application and the above-described embodiments is that it further includes: a heating rod re-insertion step S11 and a heating rod reheating step S12. After completing the cylinder internal cleaning step S9, the heating rod re-insertion step S11 is performed to re-insert the heating rod. At this point, the heating rod reheating step S12 is executed, and the heating rod is controlled to rise in temperature again. At this time, based on the comparison result of the internal surface temperature of cylinder 112 when the heating rod is first pulled out, obtained from the cylinder surface temperature detection step S6, and the specified preset temperature condition, if the comparison result is that the internal surface temperature of cylinder 112 when the heating rod is first pulled out does not reach the specified preset temperature condition, that is, the internal surface temperature of cylinder 112 is lower than 290K, then in the heating rod reheating step S12, error compensation is performed on the internal surface temperature of cylinder 112. That is, when the device-side thermometer installed in the vacuum container 12 detects that the device-side temperature in the vacuum container 12 reaches 290K, the heating rod is controlled to continue outputting, so that the device-side temperature in the vacuum container 12 continues to rise. The difference between the internal surface temperature of cylinder 112 when the heating rod is first pulled out and the specified preset temperature condition is used to determine that the internal surface temperature of cylinder 112 has reached the specified preset temperature condition, that is, 290K, and the output of the heating rod is stopped and the heating rod is pulled out. For example, suppose that when the heating rod is first removed, the internal surface temperature of cylinder 112 measured by cylinder surface temperature detection step S6 is 285K, which is lower than the preset temperature condition of 290K. Therefore, the internal surface temperature of cylinder 112 has not actually reached the preset temperature condition. Then, in the heating rod reheating step S12, when the device-side thermometer installed inside the vacuum container 12 detects that the device-side temperature inside the vacuum container 12 has reached 295K, it is determined that the internal surface temperature of cylinder 112 has reached the preset temperature condition of 290K. The output of the heating rod is then stopped, and the heating rod is removed.If the comparison result shows that the internal surface temperature of cylinder 112 exceeds the preset temperature condition when the heating rod is first pulled out, that is, the internal surface temperature of cylinder 112 measured by cylinder surface temperature detection step S6 is higher than 300K, then in the heating rod heating step S12, error compensation is performed on the internal surface temperature of cylinder 112. That is, before the device-measured temperature inside vacuum container 101, as detected by the device-side thermometer installed inside vacuum container 101, reaches 300K, the output of the heating rod is stopped and the heating rod is pulled out. For example, assuming that the internal surface temperature of cylinder 112 is 305K when the heating rod is first pulled out, which is higher than 300K, the internal surface temperature of cylinder 112 exceeds the specified preset temperature condition. In the heating rod reheating step S12, when the device-side thermometer inside the vacuum container 101 detects that the device-side temperature inside the vacuum container 101 reaches 295K, it is determined that the internal surface temperature of the cylinder 112 has reached the predetermined preset temperature condition of 300K. The output of the heating rod is then stopped, and the heating rod is pulled out. Through the above implementation method, based on the temperature comparison result when the heating rod is pulled out for the first time (step S4), the control of the heating rod reheating step S12 is adjusted so that the output control adjustment of the heating rod in the heating rod reheating step S12 can be closer to the predetermined preset temperature condition, ensuring that the internal surface temperature of the cylinder 112 after the heating rod is pulled out reaches or is closer to the predetermined preset temperature condition. It should be noted that the preset temperature condition in this application is 290K-300K, but this application does not limit its specific value. Different preset temperature conditions set according to the cylinder 112 capacity, heating rod size and power, and external environmental conditions of different refrigerators should all be included within the protection scope of this application. <Fifth Embodiment> The maintenance method of the refrigerator in the fifth embodiment of this application, which uses the same names or symbols as the maintenance methods of the refrigerator in the above embodiments of this application, is the same content and will not be repeated here.Figure 7 is a schematic diagram of the execution steps of the maintenance method for a refrigeration unit according to one embodiment of this application. Referring to Figure 7, the maintenance method for a refrigeration unit provided in this application differs from that in the above embodiment in that it further includes: a nitrogen charging and purging replacement step S13. After completing the maintenance of the refrigeration unit and inserting the second gas transfer device (not shown) after replacement or cleaning in the gas transfer device insertion step S5, the nitrogen charging and purging replacement step S13 is performed to charge and purge nitrogen in the refrigeration unit, so that the gap between the gas transfer device 113 and the inner wall of the cylinder 112 is filled with nitrogen, thereby preventing external ambient air from entering the cylinder 112 and causing water vapor in the air to condense in the cylinder 112, which would lead to the gas transfer device 113 getting stuck. Through the above implementation method, the inside of cylinder 112 is purged again with nitrogen, avoiding the problem of air entering and remaining inside cylinder 112 during the process of removing the heating rod and inserting the second gas transfer device, which would cause the temperature inside cylinder 112 to drop after the second gas transfer device is inserted, resulting in the condensation of water vapor in the air. As a preferred embodiment of this application, the nitrogen filling and purging replacement step S13 further includes a first filling and purging replacement step S131 under a first nitrogen supply pressure and a second filling and purging replacement step S132 under a second nitrogen supply pressure. Specifically, in the nitrogen filling and purging replacement step S13, by cyclically executing the first filling and purging replacement step S131 and the second filling and purging replacement step S132, nitrogen is filled into the inside of cylinder 112 under different supply pressures, assuming that the first nitrogen supply pressure is greater than the second nitrogen supply pressure. In the first filling and purging step S131, nitrogen gas is used to strongly purge the inside of cylinder 112 under high pressure, discharging impurities inside cylinder 112 into the ambient air. In the second filling and purging step S132, nitrogen gas is slowly filled into cylinder 112 under lower pressure, ensuring that the cylinder 112 is completely filled with nitrogen and maintaining a positive pressure environment inside cylinder 112. This prevents the pressure inside cylinder 112 from being too low, which could allow ambient air to enter and introduce impurities, affecting the operation of the refrigeration unit and the superconducting magnet device 1. The above are merely preferred embodiments of this application and are not intended to limit the application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

Claims 1. A method for maintaining and repairing a refrigeration unit, the refrigeration unit having a cylinder and a gas transfer device housed in the cylinder, used for a superconducting magnet device with a vacuum container, the method being characterized in that... include: The gas transfer device removal step involves removing the gas transfer device from the cylinder. The heating rod insertion step involves inserting the heating rod into the cylinder; The heating rod temperature control step involves controlling and adjusting the output of the heating rod until a predetermined preset temperature condition is reached. The step of removing the heating rod involves pulling the heating rod out of the cylinder. In the gas shifter insertion step, the second gas shifter is inserted into the cylinder.

2. The maintenance method for the refrigeration unit according to claim 1, characterized in that, The specified preset temperature condition is to make the temperature inside the cylinder reach 290K-300K, and the temperature is monitored and managed by a device-side thermometer installed inside the vacuum container.

3. The maintenance method for the refrigeration unit according to claim 2, characterized in that, It also includes a cylinder surface temperature detection step, which uses a surface thermometer to detect the temperature of the internal surface of the cylinder.

4. The maintenance method for the refrigeration unit according to claim 3, characterized in that, The cylinder includes: a first cylinder section having a first cylinder diameter; and a second cylinder section having a second cylinder diameter connected to the first cylinder section.

5. The maintenance method for the refrigeration unit according to claim 1, characterized in that, Also includes: The nitrogen atmosphere formation step involves filling the space with nitrogen to create a nitrogen atmosphere at least within the scope of the refrigeration unit before performing the gas transfer device removal step.

6. The maintenance method for the refrigeration unit according to claim 5, characterized in that, It also includes a nitrogen introduction cylinder step, wherein nitrogen is introduced into the cylinder after the heating rod is inserted. department.

7. The maintenance method for the refrigeration unit according to claim 6, characterized in that, In the step of introducing nitrogen into the cylinder, the nitrogen flow rate is 3-4 L / min.

8. The maintenance method for the refrigeration unit according to claim 7, characterized in that, Also includes: The cylinder internal cleaning step involves cleaning the inside of the cylinder at least after the heating rod is removed.

9. The maintenance method for the refrigeration unit according to claim 8, characterized in that, The cylinder internal cleaning process also includes a nitrogen purging step, in which nitrogen is used to purge the inside of the cylinder.

10. The maintenance method for the refrigeration unit according to claim 9, characterized in that, It also includes a heating rod re-insertion step, in which the heating rod is reinserted after the cylinder internal cleaning step is completed.

11. The maintenance method for the refrigeration unit according to claim 10, characterized in that, It also includes a heating rod reheating step, in which the heating rod is reheated after the heating rod re-insertion step until the specified preset temperature condition is reached.

12. The maintenance method for the refrigeration unit according to claim 11, characterized in that, It also includes a nitrogen purging and purging step, in which nitrogen is purged and purged inside the refrigeration unit after the gas transfer device insertion step.

13. The maintenance method for the refrigeration unit according to claim 12, characterized in that, The nitrogen charging and discharging replacement step includes a first charging and discharging replacement step under a first nitrogen supply pressure and a second charging and discharging replacement step under a second nitrogen supply pressure.

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