CN115523140A - Vacuum system and method for obtaining high vacuum of large-scale low-temperature valve box - Google Patents

Vacuum system and method for obtaining high vacuum of large-scale low-temperature valve box Download PDF

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Publication number
CN115523140A
CN115523140A CN202210849177.3A CN202210849177A CN115523140A CN 115523140 A CN115523140 A CN 115523140A CN 202210849177 A CN202210849177 A CN 202210849177A CN 115523140 A CN115523140 A CN 115523140A
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China
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vacuum
valve
low
valve box
temperature
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CN202210849177.3A
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王金坤
倪清
赵乾坤
汪义
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Shanghai Advanced Research Institute of CAS
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Shanghai Advanced Research Institute of CAS
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C18/00—Rotary-piston pumps specially adapted for elastic fluids
    • F04C18/08—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing
    • F04C18/12—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type
    • F04C18/126—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with radially from the rotor body extending elements, not necessarily co-operating with corresponding recesses in the other rotor, e.g. lobes, Roots type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C29/00—Component parts, details or accessories of pumps or pumping installations, not provided for in groups F04C18/00 - F04C28/00
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C29/00—Component parts, details or accessories of pumps or pumping installations, not provided for in groups F04C18/00 - F04C28/00
    • F04C29/12—Arrangements for admission or discharge of the working fluid, e.g. constructional features of the inlet or outlet
    • F04C29/124—Arrangements for admission or discharge of the working fluid, e.g. constructional features of the inlet or outlet with inlet and outlet valves specially adapted for rotary or oscillating piston pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D19/00—Axial-flow pumps
    • F04D19/02—Multi-stage pumps
    • F04D19/04—Multi-stage pumps specially adapted to the production of a high vacuum, e.g. molecular pumps
    • F04D19/042—Turbomolecular vacuum pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
    • F16K27/00—Construction of housing; Use of materials therefor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
    • F16K27/00—Construction of housing; Use of materials therefor
    • F16K27/12—Covers for housings
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
    • F16L59/00—Thermal insulation in general
    • F16L59/06—Arrangements using an air layer or vacuum
    • F16L59/065—Arrangements using an air layer or vacuum using vacuum
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17D—PIPE-LINE SYSTEMS; PIPE-LINES
    • F17D1/00—Pipe-line systems
    • F17D1/02—Pipe-line systems for gases or vapours
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17D—PIPE-LINE SYSTEMS; PIPE-LINES
    • F17D1/00—Pipe-line systems
    • F17D1/02—Pipe-line systems for gases or vapours
    • F17D1/065—Arrangements for producing propulsion of gases or vapours
    • F17D1/07—Arrangements for producing propulsion of gases or vapours by compression
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17D—PIPE-LINE SYSTEMS; PIPE-LINES
    • F17D3/00—Arrangements for supervising or controlling working operations
    • F17D3/01—Arrangements for supervising or controlling working operations for controlling, signalling, or supervising the conveyance of a product
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin
    • Y02E30/10—Nuclear fusion reactors

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Details Of Valves (AREA)

Abstract

The invention relates to a vacuum system for acquiring high vacuum of a large-scale low-temperature valve box, which comprises two low-temperature valve boxes connected in parallel, wherein the low-temperature valve boxes are connected with a vacuum pump set through a main vacuum pipeline, the main vacuum pipeline is respectively connected with a first air pumping branch and a second air pumping branch, a liquid nitrogen cold trap is arranged on the first air pumping branch, an air source steel cylinder and vacuum leak detection equipment which are connected in parallel are arranged on the second air pumping branch, and the liquid nitrogen cold trap is connected with the vacuum pump set through the first air pumping branch. The invention can quickly replace and obtain high vacuum in the low-temperature valve box cavity, can maintain the required ultrahigh vacuum operation environment for a long time, and ensures that the requirement of a test platform on a cooling medium is met under the condition of minimum cooling loss.

Description

Vacuum system and method for obtaining high vacuum of large-scale low-temperature valve box
Technical Field
The present invention relates to thermally insulated vacuum systems, and more particularly to a vacuum system and method for obtaining high vacuum for large cryogenic valve boxes.
Background
The hard X-ray free electron laser apparatus consists of multiple parts, mainly including an injector, a main accelerator, an undulator line, a beam line and a laboratory station. The injector and the main accelerator are mainly composed of 77 low-temperature modules, and a superconducting cavity in the injector and the main accelerator is cooled in a 2K super-current helium soaking mode. A valve box is arranged between the low-temperature module and the cold box, the helium flow is sent to the distribution valve box by the transmission pipeline, and the valve box distributes and adjusts the helium flow according to the requirement of a cooling object and then transmits the helium flow to each cooling object so as to meet the cooling requirement of each test platform. The vacuum level of the low-temperature valve box is one of the key conditions for ensuring the operation of the whole system.
At present, a low-temperature valve box on the market is simple in structure, a matched vacuum system is not available, and follow-up operation is maintained only by sealing vacuum, so that the vacuum degree is poor, heat leakage is large, a reliable low-temperature vacuum environment cannot be provided for a test, and the requirement of a test platform on a cooling medium cannot be met. Therefore, in order to reduce the loss of cold energy of the low-temperature working medium in the low-temperature valve box, a set of vacuum system with high reliability needs to be built to obtain and maintain better vacuum.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a vacuum system and a method for obtaining high vacuum of a large-scale low-temperature valve box, which can obtain and maintain high vacuum in a cavity of the low-temperature valve box, and ensure that the requirement of a test platform on a cooling medium is met under the condition of minimum cooling loss.
The invention provides a vacuum system for acquiring high vacuum of a large-scale low-temperature valve box, which comprises two low-temperature valve boxes connected in parallel, wherein the low-temperature valve boxes are connected with a vacuum pump set through a main vacuum pipeline, the main vacuum pipeline is respectively connected with a first air pumping branch and a second air pumping branch, a liquid nitrogen cold trap is arranged on the first air pumping branch, an air source steel cylinder and vacuum leak detection equipment which are connected in parallel are arranged on the second air pumping branch, and the liquid nitrogen cold trap is connected with the vacuum pump set through the first air pumping branch.
Further, the low temperature valve box comprises a shell, a vacuum cavity, a cold shield and a low temperature pipeline from outside to inside in sequence, wherein the outer surface of the cold shield and the outer surface of the low temperature pipeline are wrapped with heat insulation multilayer materials.
Furthermore, a vacuumizing interface is arranged on a shell of the low-temperature valve box and connected with the vacuum main pipeline, and a vacuum electromagnetic valve is arranged at the joint of the vacuumizing interface and the vacuum main pipeline.
Furthermore, a measuring interface is arranged above the vacuumizing interface and is connected with vacuum monitoring equipment through an angle valve.
Further, the vacuum monitoring device comprises a composite vacuum gauge and a residual gas analyzer, and the angle valve, the composite vacuum gauge and the residual gas analyzer are connected through a three-way structure.
Further, the vacuum pump set comprises a Roots pump set for a rough vacuum stage and a molecular pump set for a long-term high vacuum stage.
Furthermore, the vacuum main pipeline is formed by combining and connecting a corrugated pipe and a vacuum hard steel pipe through a knife edge flange, and the inner diameter of the vacuum main pipeline is at least the diameter of an inlet of the vacuum pump set.
Furthermore, a liquid nitrogen cold trap is arranged on the first air exhaust branch, and first isolating valves are respectively arranged in front of and behind the liquid nitrogen cold trap.
Furthermore, a baffle valve is arranged on the vacuum main pipeline, a second isolating valve is arranged on the second air pumping branch, and the air source steel cylinder and the vacuum leak detection equipment are respectively connected with a third isolating valve and a fourth isolating valve.
The invention also provides a method for obtaining high vacuum of a large-scale low-temperature valve box, which comprises the following steps:
step S1, providing a vacuum system for obtaining high vacuum of a large-scale cryogenic valve box according to claims 1-9;
s2, starting a Roots pump set in the vacuum pump set, and pumping the vacuum degree of a vacuum cavity of the low-temperature valve box to 1.0 multiplied by 10 -1 Pa magnitude and below, and detecting leakage with helium leak detector until the leakage rate of the vacuum cavity is less than or equal to 1.0 × 10 -9 Pa·m 3 The roots pump set is closed;
s3, opening a second isolating valve on a second air exhaust branch and a third isolating valve connected with an air source steel cylinder, and filling high-purity nitrogen gas at 70-80 ℃ into the vacuum cavity until the vacuum degree of the vacuum cavity reaches 10000Pa;
s4, closing the second isolating valve and the third isolating valve, starting the Roots pump set again, sequentially opening a baffle valve and a vacuum electromagnetic valve, vacuumizing the vacuum cavity to reduce the vacuum degree of the vacuum cavity to 1Pa, and closing the Roots pump set;
s5, judging whether the vacuum degree of the vacuum cavity reaches 1.0 multiplied by 10 -1 If Pa, entering step S6; if not, repeating the step S3 to the step S4;
s6, opening a first isolating valve on the first air exhaust branch, starting a molecular pump set and a liquid nitrogen cold trap in a vacuum pump set, and heating and baking the low-temperature valve box to enable the absolute pressure in the vacuum cavity to be increased to 1 x 10 -1 Pa；
S7, baking the low-temperature valve box at constant temperature, wherein when the vacuum degree of the vacuum cavity is less than 1 multiplied by 10 -3 When Pa, closing the vacuum electromagnetic valve, the baffle valve, the first isolating valve, the liquid nitrogen cold trap and a molecular pump group in the vacuum pump group in sequence, and stopping pumping out in a high vacuum stage;
step S8, during the period of stopping the evacuation in the high vacuum stage, monitoring the vacuumDynamic vacuum degree of the vacuum cavity, if the dynamic vacuum degree is more than 1 multiplied by 10 -3 Pa, vacuum maintenance is performed.
The invention utilizes the different vacuumizing limits of the molecular pump set and the auxiliary rough pump to work in different vacuum ranges in stages, can quickly replace and obtain high vacuum in the low-temperature valve box cavity, can maintain the required ultrahigh vacuum operating environment for a long time, and can meet the requirement of a test platform on a cold supply medium under the condition of minimum cold loss through the heat insulation effect of the high vacuum.
Drawings
Fig. 1 is a schematic diagram of a vacuum system for obtaining high vacuum of a large cryogenic valve box according to the present invention.
Detailed Description
The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
As shown in fig. 1, the vacuum system for obtaining high vacuum of a large-scale cryogenic valve box provided by the invention comprises two cryogenic valve boxes 1 connected in parallel, the cryogenic valve boxes 1 are connected with a vacuum pump unit 3 through a main vacuum pipeline 21, the main vacuum pipeline 21 is respectively connected with a first air pumping branch 22 and a second air pumping branch 23, a liquid nitrogen cold trap 4 is arranged on the first air pumping branch 22, a gas source steel cylinder 5 and a vacuum leak detection device 6 which are connected in parallel are arranged on the second air pumping branch 23, and the liquid nitrogen cold trap 4 is connected with the vacuum pump unit 3 through the first air pumping branch 22.
The low-temperature valve box 1 sequentially comprises a shell 111, a vacuum cavity 112, a cold shield 113 and a low-temperature pipeline 114 from outside to inside, and the outer surfaces of the cold shield 113 and the low-temperature pipeline 114 are wrapped with heat insulation multilayer materials 115 so as to reduce heat loss. The heat-insulating multilayer material 115 is a combination of reflecting materials and spacers which are alternated, the heat-insulating multilayer material 115 wrapped by the cold shield 113 is 30-40 layers, the heat-insulating multilayer material 115 wrapped by the low-temperature pipeline 114 is 10-20 layers, and the layer density is kept at about 20 layers/cm. The wrapping of the multilayer heat-insulating material 15 is carried out in a clean assembly room, the multilayer heat-insulating material is heated and dried for more than 24 hours before wrapping, and the surface of the material is ensured to be free from impurities such as oil stains; after the drying treatment is finished, sealing the multilayer heat-insulating material for standby use by using vacuum or nitrogen filling, wherein the standby time is not more than 12 hours; after all the heat-insulating materials are wound and wrapped, the heat-insulating materials are bound and fixed by nylon ropes approximately every other meter. The operation improves the vacuum-pumping efficiency and maintains the high vacuum degree between the interlayers on the premise of ensuring the excellent and stable heat insulation performance of the low-temperature transmission line.
The middle lower parts of the shells of the two low-temperature valve boxes 1 are respectively provided with a vacuumizing interface 121, the vacuumizing interface 121 is connected with a vacuum main pipeline 21 so as to enable the low-temperature valve boxes 1 to be communicated with a vacuum pump group 3, and a vacuum electromagnetic valve 131 is arranged at the connection position of the vacuumizing interface 121 and the vacuum main pipeline 21. A measurement interface 122 is provided above the evacuation interface 121, and the measurement interface 122 is connected to the vacuum monitoring apparatus 7 through an angle valve 132. The vacuum monitoring device 7 comprises a composite vacuum gauge 71 and a residual gas analyzer 72, wherein the composite vacuum gauge 71 is used for monitoring dynamic and static pressures in a vacuum cavity 112 of the low-temperature valve box 1, and the measurement range is 10 -6 Pa～10 5 Pa, residual gas analyzer 72 is used to monitor gas composition and gas concentration in the vacuum chamber 112 on-line. The angle valve 132, the composite vacuum gauge 71 and the residual gas analyzer 72 are connected through a three-way structure, specifically, the air inlet of the angle valve 132 is connected with the measurement interface 122, the air outlet is connected with the three-way structure, and the three-way structure is connected with the composite vacuum gauge 71 and the residual gas analyzer 72.
The vacuum pump unit 3 comprises a Roots pump unit and a molecular pump unit with high pumping speed, the Roots pump unit and the molecular pump unit are respectively connected with the vacuum main pipeline 21 under different vacuum pressures, namely the Roots pump unit is used in a rough vacuum stage, and the molecular pump unit is used in a long-term high vacuum stage. Because the pumping vacuum limits of the Roots pump set and the molecular pump set are different, the Roots pump set and the molecular pump set work in stages, not only can the high enough vacuum degree be achieved, but also the pumping time is effectively shortened.
The vacuum main pipeline 21 is formed by combining and connecting a corrugated pipe and a vacuum hard steel pipe through a knife edge flange, and the inner diameter of the vacuum main pipeline 21 is not smaller than the inlet diameter of the vacuum pump unit 3, so that the flow resistance loss generated by the pipeline is reduced.
Set up liquid nitrogen cold trap 4 on first branch road 22 of bleeding, set up liquid nitrogen cold trap 4 between low temperature valve box 1 and vacuum pump package 3 promptly, borrow the ultra-low temperature that the liquid nitrogen provided, make gas molecule adsorb on the cold trap wall to improve vacuum and help the pump package to bleed, can adsorb vapor, oil vapor fast, shorten the time of managing to find time, and reduce the impact of steam to the pump body, improve vacuum system's life.
The main vacuum pipeline 21 is provided with a baffle valve 211 for controlling and communicating or separating the main vacuum pipeline 21 and the vacuum pump group 3. The liquid nitrogen cold trap 4 on the first air exhaust branch 22 is provided with a first isolating valve 212 in front and at the back, and the second air exhaust branch 23 is provided with a second isolating valve 213 on one side close to the main vacuum pipeline 21 for controlling the connection or isolation of the air exhaust branch and the main vacuum pipeline. Meanwhile, the gas source steel cylinder 5 and the vacuum leak detection device 6 are respectively connected with a third block valve 214 and a fourth block valve 215, and are used for controlling communication or blocking a pumping branch and the device per se so as to independently control the gas source steel cylinder 5 and the vacuum leak detection device 6. In addition, a pressure gauge 231 is further arranged on the second air exhaust branch 23 and used for detecting the leakage rate of the system.
It should be noted that the interfaces of the above-mentioned devices and devices, including the evacuation interface 121, the measurement interface 122, the vacuum main pipe interface, the suction branch interface, etc., are knife-edge flange interfaces, and this connection mode is convenient to install and has a good sealing effect. And the leakage rate at all the interfaces is less than 1 multiplied by 10 -9 pa·m 3 And/s to reduce absolute pressure deterioration due to external gas entering the chamber.
Based on the vacuum system for obtaining the high vacuum of the large-scale low-temperature valve box, the invention also provides a method for obtaining the high vacuum of the large-scale low-temperature valve box, which comprises the following steps:
and S1, providing the vacuum system for obtaining the high vacuum of the large-scale low-temperature valve box.
S2, starting a Roots pump set in the vacuum pump set 3, and pumping the vacuum degree of the vacuum cavity 112 of the low-temperature valve box 1 to 1.0 multiplied by 10 -1 Pa or below, and detecting leakage with helium leak detector until the leakage rate of the vacuum cavity 112 is less than or equal to 1.0 × 10 -9 Pa·m 3 And s, closing the Roots pump set.
And S3, opening a second isolating valve 213 on the second pumping branch 23 and a third isolating valve 214 connected with the gas source steel cylinder 5, and filling high-purity nitrogen gas at 70-80 ℃ into the vacuum cavity 112 of the distribution valve box 1 until the vacuum degree of the vacuum cavity 112 reaches 10000Pa.
And S4, closing the second isolating valve 213 and the third isolating valve 214, starting the Roots pump set again, sequentially opening the flapper valve 211 and the vacuum solenoid valve 131, vacuumizing the vacuum cavity 112 of the low-temperature valve box 1 to reduce the vacuum degree of the vacuum cavity 112 to 1Pa, and closing the Roots pump set.
Step S5, judging whether the vacuum degree of the vacuum cavity 112 reaches the limit vacuum degree of the Roots pump set of 1.0 multiplied by 10 -1 If so, entering step S6; if not, repeating the step S3-the step S4. Generally, the above-mentioned hot nitrogen gas replacement evacuation is repeated 3 to 4 times to realize the limit evacuation of the rough evacuation stage of the chamber.
Step S6, opening the first isolating valve 212 on the first air extraction branch 22, opening the molecular pump group and the liquid nitrogen cold trap 4 in the vacuum pump group 3, wrapping the outside of the low-temperature valve box 1 by a heating belt for heating and baking, so that the temperature in the vacuum cavity 112 of the low-temperature valve box 1 is kept within the range of the process requirement, and the absolute pressure in the vacuum cavity 112 continuously rises to 1 × 10 along with the continuous rise of the temperature in the cavity -1 Pa。
S7, baking the low-temperature valve box 1 for several days at constant temperature, and when the vacuum degree of the vacuum cavity body 112 is less than 1 multiplied by 10 -3 And Pa, closing the vacuum electromagnetic valve 131, the baffle valve 211, the first isolating valve 212, the liquid nitrogen cold trap 4 and the molecular pump group of the vacuum pump group 3 in sequence, and stopping the evacuation in the high vacuum stage.
Step S8, during the period of stopping evacuation in the high vacuum stage, monitoring the dynamic vacuum degree of the vacuum chamber 112, if the dynamic vacuum degree is greater than 1 × 10 -3 Pa, vacuum maintenance is performed.
Because the evacuation has been carried out for a long time several times, the vacuum is maintained without heating and without adsorption by a cold trap, and the high vacuum state can be completely maintained only by the molecular pump set. The above vacuum maintenance includes two cases:
1) Vacuum maintenance at room temperature
At room temperature, pumping the absolute vacuum degree of the low-temperature valve box 1 to<10 -3 And Pa, cooling and operating. In the cooling process, the vacuum solenoid valve 131 is in a closed state. The vacuum degree of the low-temperature valve box 1 is judged by the vacuum monitoring equipment 7, if the vacuum degree of one low-temperature valve box 1 is more than 10 -3 Pa, opening the corresponding vacuum electromagnetic valve 131 and the baffle valve 211, and starting the molecular pump set; degree of vacuum<10 -3 Pa, the corresponding vacuum solenoid valve 131 and flapper valve 211 are closed and the molecular pump set is shut down. If the other low-temperature valve box detects that the vacuum degree is more than 10 -3 And Pa, after the current low-temperature valve box is completely pumped out, opening the corresponding vacuum electromagnetic valve 131 and the corresponding baffle valve 211, and starting the molecular pump group.
2) Vacuum degree destruction maintenance
When the low-temperature valve box is in a low-temperature state, the vacuum degree is generally 10 -6 Pa, at which time the vacuum solenoid valve 131 closes. If the vacuum degree of a certain low-temperature valve box monitored by the vacuum monitoring equipment 7 is more than 10 -3 Pa, indicating leakage, and possibly generating leakage holes by long-term cold and heat shock of the welding seam of the internal pipeline. To ensure that the test is performed, the corresponding vacuum solenoid valve 131 and flapper valve 211 are opened and the molecular pump set is started. If the vacuum monitoring device 7 monitors that the vacuum degree of the valve box continuously rises to be more than 10 -1 Pa, at which time the molecular pump stack is shut down by closing vacuum solenoid valve 131 and flapper valve 211 in order to protect the molecular pump stack from shock. In this case, if the test is not stopped, the mode is switched to the rough pumping mode, the vacuum solenoid valve 131 and the flapper valve 211 are opened, and only the roots pump set is started to maintain the evacuation.
In the steps, because the two parallel low-temperature valve boxes share one set of vacuum system, one vacuum system can be used for pumping out and then pumping out the other vacuum system, and the two vacuum systems can be used for simultaneous treatment. Also, in the above step, the absolute pressure in the low temperature valve box may be read in real time by the complex vacuum gauge 71.
The invention effectively meets the requirement of multipurpose vacuum degree of a valve box vacuum system, enables the valve box vacuum system to operate in a high vacuum environment all the time, and can monitor parameters such as the working state of a vacuum cavity of equipment, gas partial pressure and the like in real time, thereby ensuring the safe operation of the equipment. The invention adopts the auxiliary rough pumping Roots pump set with large pumping speed in the rough vacuum range, effectively shortens the operation time of the large cavity air-pumping replacement and leakage detection of the low-temperature valve box and improves the working efficiency. The high vacuum adopts the combined operation of a molecular pump set and a liquid nitrogen cold trap, the high vacuum is quickly realized, and the service life of a vacuum system is prolonged. The invention has the advantages of simple and convenient matching of all parts, easy maintenance, stable system and high reliability. When the power is cut off accidentally, the vacuum electromagnetic valve has short reaction time and quick action, and can better protect the vacuum cavity from being influenced by backflow. The cold shield and the inner pipe of the low-temperature valve box adopt an optimized heat-insulating multilayer material wrapping process, so that heat leakage can be effectively reduced, and the material outgassing rate can be reduced by a heat treatment process. In addition, the nitrogen replacement process and the cavity heating and baking process in the evacuation process can enable the indexes of the cavity, such as the vacuum degree, the leakage air release rate and the like, to reach higher requirements in a shorter time.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and various modifications may be made to the above-described embodiment of the present invention. All simple and equivalent changes and modifications made according to the claims and the content of the specification of the present application fall within the scope of the claims of the present patent application. The invention has not been described in detail in order to avoid obscuring the invention.

Claims (10)

1. The utility model provides a vacuum system for obtaining large-scale low temperature valve box high vacuum, its characterized in that, includes two parallelly connected low temperature valve boxes, the low temperature valve box passes through the main vacuum line and is connected with vacuum pump group, the main vacuum line is bled branch road with first branch road, second respectively and is connected, first bleeding is equipped with the liquid nitrogen cold-trap on the branch road, be equipped with parallelly connected air supply steel bottle and vacuum leak hunting equipment on the branch road of bleeding of second, just the liquid nitrogen cold-trap passes through first bleeding branch road with vacuum pump group connects.
2. The vacuum system for obtaining high vacuum of the large-scale low-temperature valve box according to claim 1, wherein the low-temperature valve box comprises a shell, a vacuum cavity, a cold shield and a low-temperature pipeline from outside to inside in sequence, and the outer surfaces of the cold shield and the low-temperature pipeline are wrapped with heat-insulating multilayer materials.
3. The vacuum system for obtaining the high vacuum of the large-scale low-temperature valve box according to claim 1, wherein a vacuum pumping interface is arranged on a shell of the low-temperature valve box, the vacuum pumping interface is connected with the vacuum main pipeline, and a vacuum solenoid valve is arranged at the connection position of the vacuum pumping interface and the vacuum main pipeline.
4. The vacuum system for obtaining high vacuum of the large-scale low-temperature valve box according to claim 1, wherein a measurement interface is arranged above the vacuumizing interface, and the measurement interface is connected with a vacuum monitoring device through an angle valve.
5. The vacuum system for obtaining high vacuum of a large cryogenic valve box according to claim 4, wherein the vacuum monitoring device comprises a compound vacuum gauge and a residual gas analyzer, the angle valve, the compound vacuum gauge and the residual gas analyzer being connected by a three-way structure.
6. The vacuum system for obtaining high vacuum of large cryogenic valve boxes of claim 1, wherein the vacuum pump set comprises roots pump set for rough vacuum stage and molecular pump set for long term high vacuum stage.
7. The vacuum system for obtaining high vacuum of the large-scale cryogenic valve box according to claim 1, wherein the main vacuum pipeline is formed by combining and connecting a corrugated pipe and a hard vacuum steel pipe through a knife edge flange, and the inner diameter of the main vacuum pipeline is at least the diameter of an inlet of the vacuum pump set.
8. The vacuum system for obtaining the high vacuum of the large-scale low-temperature valve box according to claim 1, wherein a liquid nitrogen cold trap is arranged on the first air exhaust branch, and first isolating valves are respectively arranged in front of and behind the liquid nitrogen cold trap.
9. The vacuum system for obtaining high vacuum of a large-scale cryogenic valve box according to claim 1, wherein a flapper valve is disposed on the main vacuum pipeline, a second block valve is disposed on the second pumping branch, and the gas source steel cylinder and the vacuum leak detection device are respectively connected to a third block valve and a fourth block valve.
10. A method for obtaining high vacuum for a large cryogenic valve box, comprising:
step S1, providing a vacuum system for obtaining high vacuum of a large-scale cryogenic valve box according to claims 1-9;
s2, starting a Roots pump set in the vacuum pump set, and pumping the vacuum cavity of the low-temperature valve box to the vacuum degree of 1.0 multiplied by 10 - 1 Pa magnitude and below, and detecting leakage with helium leak detector until the leakage rate of the vacuum cavity is less than or equal to 1.0 × 10 - 9 Pa·m 3 The roots pump set is closed;
s3, opening a second isolating valve on a second air exhaust branch and a third isolating valve connected with an air source steel cylinder, and filling high-purity nitrogen gas at 70-80 ℃ into the vacuum cavity until the vacuum degree of the vacuum cavity reaches 10000Pa;
s4, closing the second isolating valve and the third isolating valve, starting the Roots pump set again, sequentially opening a baffle valve and a vacuum electromagnetic valve, vacuumizing the vacuum cavity to reduce the vacuum degree of the vacuum cavity to 1Pa, and closing the Roots pump set;
s5, judging whether the vacuum degree of the vacuum cavity reaches 1.0 multiplied by 10 -1 If Pa, entering step S6; if not, repeating the step S3 to the step S4;
s6, opening a first isolating valve on the first air extraction branch, opening a molecular pump set and a liquid nitrogen cold trap in a vacuum pump set, and feeding the low-temperature valve boxHeating and baking to raise the absolute pressure inside the vacuum cavity to 1 × 10 -1 Pa；
S7, baking the low-temperature valve box at constant temperature, wherein when the vacuum degree of the vacuum cavity is less than 1 multiplied by 10 -3 When Pa, closing the vacuum electromagnetic valve, the baffle valve, the first isolating valve, the liquid nitrogen cold trap and a molecular pump group in the vacuum pump group in sequence, and stopping pumping out in a high vacuum stage;
s8, monitoring the dynamic vacuum degree of the vacuum cavity in the evacuation stopping period of the high vacuum stage, and if the dynamic vacuum degree is more than 1 multiplied by 10 -3 Pa, vacuum maintenance is performed.
CN202210849177.3A 2022-07-19 2022-07-19 Vacuum system and method for obtaining high vacuum of large-scale low-temperature valve box Pending CN115523140A (en)

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