A decompression system and decompression control method for shield machine tool change operation under pressure

Abstract

The present invention discloses a decompression system and a decompression control method for shield machine tool pressurized tool changing operations. The shield machine tool pressurized tool changing operations adopt non-saturated high-pressure operations. The decompression system includes a mixed gas distribution system, a man cabin, an oronasal mask respirator, and a film hood. The mixed gas distribution system is used to configure a helium-nitrogen-oxygen ternary gas mixture, wherein the nitrogen partial pressure is greater than the helium partial pressure. The configured helium-nitrogen-oxygen ternary gas mixture is stored in a mixed gas tank. The man cabin is docked with a mud and water tank. The mixed gas distribution system is connected to the oronasal mask respirator located in the man cabin through a high-pressure hose. The film hood is connected to an oxygen supply device. The operator enters the mud and water tank from the man cabin to perform the tool changing operation. After completing the tool changing, he returns to the man cabin for decompression. After the pressure is reduced to the set pressure, the oronasal mask respirator is removed and the film hood is used for breathing. The present invention eliminates the traditional living cabin and shuttle cabin. After completing the tool changing operation under pressure, the operator directly returns to the man cabin for decompression, thereby improving the safety and efficiency of the decompression process.

Description

Technical Field

[0001] The present invention relates to the technical field of shield construction, and in particular to a shield pressure-reducing system for cutter-changing operations under pressure and a pressure-reducing control method. Background Art

[0002] Currently, the commonly used methods for shield tunneling under pressure include air pressure and helium-oxygen saturation pressure. Specifically, in shallower operating environments, high-pressure operations are usually used, with trained high-pressure workers working in a diving decompression chamber. In medium-depth environments, conventional air diving is used, with specially trained air divers operating. This also relies on a diving decompression chamber, but the operating time is significantly limited. In deeper operating environments, helium-oxygen saturation diving is used, with specially trained mixed gas divers and saturation divers carrying out the operation. This requires a saturation diving chamber, a transfer chamber, and corresponding diving equipment. Due to the high demand for helium, the economic cost is high. For example, CN112943270A discloses a method for performing large-diameter shield cutter changes under ultra-high water pressure. The method uses a helium-oxygen mixture to replace the air in the manhole and mud water chambers. The workers gradually adjust to the pressure in the living chamber, then enter the working area through the shuttle chamber. After the operation is completed, they return to the living chamber and implement a long-term step-by-step decompression.

[0003] However, the above-mentioned traditional methods have many defects, which seriously affect the safety and efficiency of the tool changing operation. On the one hand, saturation operations require the configuration of multiple functional cabins, the operation process is complicated, and a large amount of space inside the shield is occupied. In addition, personnel entering and exiting the cabin need to be flattened and pressure-adjusted many times, which makes the operation organization difficult. On the other hand, the decompression process is extremely long and relies on precise control. If there is any negligence, it is very easy to cause physiological risks such as decompression sickness, threatening the life and health of the workers. In addition, in deep high-pressure operations, helium consumption is large and the cost is high. In addition, the desaturation process of helium-oxygen mixed gas in the body is complicated, which further aggravates the difficulty of decompression control. Therefore, when the existing technology carries out pressurized tool changing operations in a deep-buried high-pressure tunnel environment, it is urgently faced with a series of technical bottlenecks such as complex decompression process, long time, high safety risks, and high operating costs. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention proposes a decompression system and decompression control method for shield tunneling under pressure cutter changing operations, which eliminates the traditional living cabin and shuttle cabin structure. After completing the pressurized cutter changing operation in the mud and water cabin, the operators directly return to the human cabin for decompression, thereby improving the safety and efficiency of the decompression process. It is suitable for the non-saturated high-pressure operation mode in the deep-buried high-pressure tunnel environment.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A decompression system for a shield machine tool changing operation under pressure, wherein the shield machine tool changing under pressure adopts non-saturated high-pressure operation, and the decompression system includes a mixed gas distribution system, a man cabin, an oronasal mask respirator, and a thin film hood. The mixed gas distribution system is used to configure a helium-nitrogen-oxygen ternary gas mixture, wherein the nitrogen partial pressure is greater than the helium partial pressure. The configured helium-nitrogen-oxygen ternary gas mixture is stored in a mixed gas tank, the man cabin is docked with a mud and water tank, the mixed gas distribution system is connected to the oronasal mask respirator located in the man cabin through a high-pressure hose, and the thin film hood is connected to an oxygen supply device. After entering the man cabin, the operator wears the oronasal mask respirator, and then enters the mud and water tank from the man cabin to perform the tool changing operation. After completing the tool changing, the operator returns to the man cabin to decompress. After the pressure is reduced to the set pressure, the oronasal mask respirator is removed and the thin film hood is used to breathe.

[0007] Preferably, the man cabin is connected to the pressurizing device of the shield machine, and the pressurizing device adjusts the pressure in the cabin by filling compressed air into the man cabin. The man cabin includes an air outlet valve to establish an air inlet and outlet balance of the man cabin. The air outlet valve is opened during the decompression process so that the air pressure in the man cabin is reduced according to the preset decompression table.

[0008] Preferably, the high-pressure hose is provided with an intelligent flow regulating valve, through which the supply flow of the ternary mixed gas of the oronasal mask respirator is regulated.

[0009] Preferably, the thin film head cover includes a transparent sealing cover body, which is used to completely seal the head and neck of the operator and has the functions of mechanical automatic oxygen supply and mechanical automatic oxygen exhaust.

[0010] Preferably, the thin film head cover includes an oxygen supply and exhaust control module, and the oxygen supply and exhaust control module automatically adjusts the oxygen exhaust volume according to the oxygen supply flow rate.

[0011] Preferably, a data recording device and an alarm device are provided in the man cabin. The data recording device is used to record the residence time of each pressure stage and the subjective reaction of the operator during the decompression process. The alarm device is used to identify the working status of the operator and upload the working status information to the control room.

[0012] On the other hand, the present invention also discloses a decompression control method based on the above-mentioned shield pressure-changing tool operation decompression system, comprising the following steps:

[0013] S1: After completing the tool change operation in the mud tank, the operator returns to the man cabin, continues to wear a mouth-nose respirator and breathes a helium-nitrogen-oxygen ternary gas mixture, and begins decompression operations;

[0014] S2, determine the decompression depth of the first stop based on the nitrogen partial pressure in the configured helium, nitrogen and oxygen ternary gas mixture;

[0015] S3, decompression at a steady rate from the operating pressure to the decompression depth of the first station;

[0016] S4, based on the decompression depth of the first station, controlling the pressure and time of each decompression stage according to the air decompression table and the operation time;

[0017] In step S5, when the cabin pressure drops below 1.8 bar, the operator removes the oronasal mask respirator and wears a thin film hood to breathe pure oxygen. Each time, the operator breathes oxygen continuously for 30 minutes, followed by a 5-minute interval of breathing air, and then continues to breathe oxygen until the pressure is reduced to normal. Preferably, in step S2, the method for determining the first decompression depth includes the following steps:

[0018] S21, obtain the nitrogen partial pressure P in the mixed gas 氮 and operating pressure P 总 , the unit is ATA, through the formula P 空 =P 氮 / 0.78 can be used to obtain the equivalent air pressure under the nitrogen partial pressure;

[0019] S22, calculate the reference values ​​h1 and h2 of the first station decompression depth, in meters: h1=(P 空 -1)×10,h2=((P 总 -1) / 2)×10;

[0020] S23, obtaining the larger value of the above two results h1 and h2;

[0021] S24, finally determine the first station decompression water depth h = max (h1, h2) + (3 ~ 6), unit is m.

[0022] Preferably, the oxygen supply of the thin film hood is (12-15) L / min.

[0023] Preferably, the method further includes step S6, wherein after the decompression in the human cabin is completed, the human enters the micro-pressure oxygen chamber within 10 minutes, and then breathes oxygen at a pressure of 1.3 ATA for 1 hour.

[0024] The present invention has the following beneficial effects: First, it employs a non-saturated, high-pressure operation method, eliminating the redundant living and shuttle cabin structures used in traditional saturated operations. Operators can complete the entire pressurization, operation, and decompression process solely through the man cabin, significantly simplifying the operation process, reducing equipment footprint, and lowering system complexity and maintenance costs. Second, by using a helium-nitrogen-oxygen ternary gas mixture and combining the physical property that nitrogen partial pressure is greater than helium partial pressure, a decompression curve is developed based on nitrogen partial pressure, simplifying control logic, improving desaturation efficiency, and reducing the risk of decompression sickness. In particular, in the decompression control method, after the operator completes the mud and water tank operation, he first continues to wear a mouth and nose mask respirator to breathe the ternary mixed gas. After the pressure is reduced to below 1.8 bar, he switches to wearing a thin film hood to inhale oxygen and adopts an intermittent oxygen inhalation strategy. This staged decompression method fully considers the desaturation law of human tissue to inert gases. In the early high-pressure stage, the ternary mixed gas is used to avoid premature high oxygen inhalation causing oxygen toxicity; in the middle and late stages, a partial pressure gradient is established by high-concentration oxygen to accelerate nitrogen discharge, shorten the decompression time, and intermittent air inhalation is used to prevent long-term oxygen inhalation from causing lung damage, thereby improving the safety and comfort of decompression. In addition, the present invention also accurately controls the air supply flow by setting an intelligent flow control valve. The thin film hood adopts a mechanical oxygen supply and exhaust structure, which automatically adjusts the oxygen exhaust according to the oxygen supply to ensure stable oxygen concentration and prevent oxygen accumulation. Combined with a data recording device and an alarm device, the operator's status and key data of the decompression process can be monitored in real time, improving the information management level and emergency response capabilities of the entire process. While ensuring the safety of high-pressure operations, the present invention effectively simplifies the decompression path, shortens the decompression time, improves efficiency, reduces helium consumption and system burden, and is suitable for pressurized tool changing operations in deep-buried, high-pressure, and long-distance shield construction environments. It has significant engineering adaptability and promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is an overall schematic diagram of the shield machine pressure relief system for cutter changing operation under pressure according to an embodiment of the present invention.

[0026] Figure 2 It is a flow chart of a decompression control method of a shield machine pressure-controlled cutter-changing operation decompression system according to an embodiment of the present invention.

[0027] Figure 3 4 is a flow chart of a method for determining the first-stop decompression depth according to an embodiment of the present invention.

[0028] Figure numerals: 1-mixed gas distribution system; 2-personnel cabin; 3-oral and nasal mask respirator; 4-film hood; 5-mixed gas tank; 6-high-pressure hose; 7-pressurization device; 8-exhaust valve; 9-intelligent flow regulating valve; 10-oxygen supply and exhaust control module; 11-data recording device; 12-alarm device; 13-control room; 14-micro-pressure oxygen chamber. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the present invention.

[0030] In addition, described feature, structure or characteristic can be combined in one or more embodiments in any suitable manner.In the following description, many specific details are provided so as to provide a full understanding of the embodiments of the present application. However, it will be appreciated by those skilled in the art that the technical scheme of the present application can be put into practice without one or more of the specific details, or other methods, components, devices, steps etc. can be adopted. In other cases, known methods, devices, implementations or operations are not shown or described in detail to avoid blurring the various aspects of the application.

[0031] See also Figure 1This embodiment provides a decompression system for shield machine tool change operations under pressure. The shield machine tool change under pressure adopts non-saturated high-pressure operation. Non-saturated high-pressure operation means that the operator does not enter a saturated diving state under high-pressure conditions. The operation duration is much shorter than the time required for complete saturation of tissue gas, thereby significantly shortening the pressurization and decompression cycle, reducing physiological burden, and improving overall operation efficiency. The decompression system includes a mixed gas distribution system 1, a human cabin 2, an oral and nasal mask respirator 3, and a thin film hood 4. The mixed gas distribution system 1 is used to configure a helium, nitrogen, and oxygen ternary gas mixture, in which the nitrogen partial pressure is greater than the helium partial pressure. Nitrogen, as the main inert gas, determines the decompression strategy, while helium, due to its lower partial pressure, can be quickly discharged at the beginning of decompression. The configured helium, nitrogen, and oxygen ternary gas mixture is stored in a mixed gas tank 5. The mixed gas tank 5 is a high-pressure container with stable output and pressure regulation functions to ensure continuous gas supply requirements throughout the decompression process. The human cabin 2 is connected to the mud and water tank. The human cabin 2 serves as the key cabin for the operator to pressurize, prepare for tool change, and return to decompression. It is directly connected to the mud and water tank to form a high-pressure operation closed-loop system. The mixed gas distribution system 1 is connected to the oronasal mask respirator 3 located in the human cabin 2 through a high-pressure hose 6. The high-pressure hose 6 is used to transmit the ternary mixed gas and has pressure resistance and corrosion resistance to ensure safe and reliable gas transmission. An intelligent flow regulating valve 7 is also provided on the high-pressure hose 6, and the gas supply flow of the ternary mixed gas of the oronasal mask respirator 3 is adjusted by the intelligent flow regulating valve 7. Specifically, the intelligent flow regulating valve 7 can automatically adjust the gas supply of the mixed gas according to the breathing state of the operator to ensure a stable gas supply and smooth breathing. The film hood 4 is connected to the oxygen supply device. The film hood 4 is a closed head and neck hood. The oxygen supply device can provide a constant flow of pure oxygen and has an automatic oxygen exhaust function, which is used to replace the mixed gas supply at the end of the decompression stage. After entering the man cabin 2, the operator wears an oronasal mask respirator 3 and enters the initial pressurization and operation preparation stage. Then, he enters the mud and water tank from the man cabin 2 to perform the tool changing operation. During the operation, the oronasal mask respirator 3 is kept supplied with air. After completing the tool changing, the operator returns to the man cabin 2 for decompression. After decompression to the set pressure, the operator removes the oronasal mask respirator 3 and uses the film hood 4 to breathe. Using the film hood 4 to inhale oxygen in the latter stage of decompression can promote the accelerated discharge of inert gas, reduce the risk of decompression sickness and shorten the decompression period.

[0032] Furthermore, the man cabin 2 is connected to the pressurizing device 7 of the shield machine. The pressurizing device 7 adjusts the pressure in the cabin by filling compressed air into the man cabin 2. The pressurizing device 7 is used to establish an initial operating pressure environment in the man cabin 2. The man cabin 2 includes an air outlet valve 8. The air outlet valve 8 is used to establish the inlet and outlet air balance of the man cabin 2. The air outlet valve 8 is opened during the decompression process so that the air pressure in the man cabin 2 is reduced according to the preset decompression table. The air outlet valve 8 can be used to achieve staged exhaust in a program-controlled manner to ensure a smooth decompression rate and a natural transition, thereby avoiding the risk of physiological discomfort or decompression sickness caused by rapid pressure difference.

[0033] In this embodiment, the thin film hood 4 includes a transparent sealed hood body, which is used to completely seal the head and neck of the operator. The transparent sealed hood body has good airtightness and visibility, can prevent the exchange of air with the outside, and is convenient for external observation of the operator's facial condition. The thin film hood 4 has mechanical automatic oxygen supply and mechanical automatic oxygen exhaust functions. The mechanical automatic oxygen supply can provide a constant flow of oxygen into the hood without manual adjustment. The mechanical automatic oxygen exhaust function automatically exhausts excess gas according to the internal air pressure to prevent oxygen accumulation from causing a high oxygen environment. The thin film hood 4 includes an oxygen supply and exhaust control module 10. The oxygen supply and exhaust control module 10 automatically adjusts the oxygen exhaust volume according to the oxygen supply flow rate. The oxygen supply and exhaust control module 10 can realize a dynamic adjustment logic of multiple supply and multiple exhaust, no supply and no exhaust, so that the gas utilization inside the hood is more efficient, ensuring smooth breathing and safe gas composition during the oxygen inhalation and exhaust process.

[0034] In addition, a data recording device 11 and an alarm device 12 are provided in the human cabin 2. The data recording device 11 is used to record the residence time of each pressure stage and the subjective reaction of the operator during the decompression process. Specifically, the data recording device 11 can automatically record the cabin pressure, air supply flow, decompression time node and operator feedback information, which is convenient for subsequent review and medical evaluation. The alarm device 12 is used to identify the working status of the operator and upload the working status information to the control room 13. Specifically, the alarm device 12 can monitor the operator's posture, breathing rate, stillness time and other indicators through sensors. When an abnormal state is detected, such as loss of consciousness, long-term stillness, etc., an alarm signal is sent to the control room 13 in time to realize remote real-time monitoring and emergency response of operation safety.

[0035] In this embodiment, the man cabin 2 includes a door 15. Workers enter the man cabin 2 directly from the shield machine through door 15. Once door 15 is opened, workers can enter the man cabin 2 directly without passing through the living and shuttle cabins. This effectively simplifies the traditional multi-chamber tandem operation process. By eliminating the need for living and shuttle cabins, equipment layout space is saved and tool change preparation efficiency is significantly improved. A sealed door 16 is provided between the man cabin 2 and the mud and water tank. This ensures airtightness between the two compartments. After decompression is complete, it maintains a pressure balance between the man cabin 2 and the mud and water tank, preventing compressed gas leakage or mud and water backflow. While performing tool changes and mud cake removal operations in the mud and water tank, workers wear an oronasal respirator 3 and breathe a helium-nitrogen-oxygen ternary gas mixture. Nitrogen, an auxiliary inert gas, must be strictly controlled in concentration. The nitrogen concentration in the ternary gas mixture is monitored during operation, and a gas analyzer provides real-time feedback on changes in the gas mixture's composition to ensure that the nitrogen partial pressure does not exceed a safe threshold, thereby ensuring respiratory safety for workers working in high-pressure environments for extended periods.

[0036] See also Figure 2Another embodiment of the present invention further discloses a decompression control method based on the above-mentioned shield pressure-changing tool change operation decompression system, comprising the following steps:

[0037] After completing the tool change in the mud tank, the operator returns to man cabin 2 and continues to wear a mouth-and-nasal respirator 3 to breathe a helium-nitrogen-oxygen ternary gas mixture, commencing decompression. Upon returning to man cabin 2, the operator does not immediately switch to a new oxygen inhalation method, but instead continues to breathe the ternary gas mixture. This ensures a steady release of inert gas during the initial decompression phase and avoids the risk of oxygen toxicity from premature oxygen inhalation.

[0038] S2: The first decompression depth is determined based on the nitrogen partial pressure in the configured helium-nitrogen-oxygen mixture. Nitrogen partial pressure is a key parameter for controlling inert gas desaturation. The first decompression depth setting determines the safety and rationality of subsequent staged decompression.

[0039] S3: Decompression at a steady rate from the operating pressure to the first decompression depth. The decompression rate must be considered in conjunction with the operator's physiological tolerance and the control capabilities of the cabin structure to ensure a continuous and gentle pressure change and avoid decompression sickness caused by excessive pressure differentials. For example, a decompression rate of 7 m / min can be selected.

[0040] In S4, based on the decompression depth of the first stop, the pressure and duration of each decompression stage are controlled according to the air decompression table and the operation time. The air decompression table provides a safe decompression plan. The air decompression table can refer to existing diving decompression tables to ensure the safe release of inert gas.

[0041] At step S5, when the pressure in cabin 2 drops below 1.8 bar, the operator removes the oronasal mask respirator 3 and dons the film hood 4 to breathe pure oxygen. Each time, they breathe oxygen continuously for 30 minutes, followed by a 5-minute interval of breathing air, and then continue breathing oxygen until the pressure is reduced to normal. The film hood 4 provides a high-concentration pure oxygen supply, establishing a strong oxygen-nitrogen partial pressure gradient to accelerate the escape of nitrogen from the body. Combined with the intermittent breathing of air, this strategy prevents oxygen toxicity caused by prolonged oxygen inhalation, achieving a rapid, safe, and smooth decompression process.

[0042] In one specific embodiment, the preset operating pressure is 5.7 bar, and the ternary gas mixture is set to a nitrogen partial pressure of 2.9 ATA, an oxygen partial pressure of 1.6 ATA, and a helium partial pressure of 2.2 ATA. The partial pressures of the three gases are precisely controlled, with the nitrogen partial pressure strictly controlled below 4.0 ATA to effectively avoid the risk of high-pressure nitrogen narcosis, the oxygen partial pressure remaining within a safe range for human metabolism, and the helium partial pressure used to reduce the density of the mixture and respiratory resistance. The operating dwell time is 70 minutes, which is the continuous working time that the operator maintains the high-pressure mixed gas breathing environment in the mud and water tank. This time is determined by combining the tool change task volume and the operator's pressure tolerance to ensure task completion while avoiding excessive exposure.

[0043] In this embodiment, the ratio of the helium-nitrogen-oxygen ternary gas mixture during the decompression process not only considers respiratory safety and nitrogen narcosis risk control during the operation, but also comprehensively considers decompression efficiency after the operation. Specifically, nitrogen is used as the inert gas basis for determining the most unfavorable water depth in the gas mixture. That is, the nitrogen partial pressure is used as the control factor for tissue gas dissolution and release in the decompression plan. Compared with traditional decompression models that use helium as the basis for the most unfavorable water depth, this significantly shortens decompression time. Due to the faster diffusion rate of helium and the more sensitive tissue saturation and desaturation processes, decompression design based on helium requires longer step-by-step decompression to prevent bubble precipitation and decompression sickness. However, by rationally controlling the nitrogen partial pressure (for example, limiting it to below 4.0 ATA), the present invention not only effectively avoids nitrogen narcosis, but also reduces the intensity of control over the release of the most unfavorable tissue gas during decompression path planning, thereby shortening decompression time, improving overall operation efficiency, and the speed of personnel recovery after the operation.

[0044] See also Figure 3 Furthermore, in step S2, the method for determining the first decompression depth includes the following steps:

[0045] S21, obtain the nitrogen partial pressure P in the mixed gas 氮 and operating pressure P 总 , the unit is ATA, through the formula P 空 =P 氮 / 0.78 can be used to obtain the equivalent air pressure under the nitrogen partial pressure. 空 Indicates the equivalent air pressure when the nitrogen content of air is 78%. It is used to convert the actual nitrogen partial pressure in a ternary gas environment to a reference pressure value under traditional air diving conditions, thereby drawing on existing air decompression experience.

[0046] S22, calculate the reference values ​​h1 and h2 of the first station decompression depth, in meters: h1=(P 空 -1)×10,h2=((P 总 -1) / 2)×10. Here, h1 represents the equivalent decompression depth calculated based on nitrogen partial pressure, and h2 represents the conservative decompression depth calculated based on half of the total operating pressure. Both take into account the initial pressure differential and depth buffer requirements for gas desaturation.

[0047] S23, obtaining the larger value of the two results h1 and h2. Selecting a higher decompression depth to ensure safety and prevent bubble formation or uneven tissue saturation due to rapid decompression.

[0048] S24: Finalize the first decompression depth (h = max(h1, h2) + (3-6) meters) in meters. By adding a safety margin of 3-6 meters to the maximum reference value, this effectively mitigates individual differences, operational errors, or potential abnormal physiological reactions, improving the safety and reliability of the entire decompression process.

[0049] Take the preset operating pressure of 5.7 bar (6.7 ATA), the ternary gas mixture setting nitrogen partial pressure 2.9 ATA, oxygen partial pressure 1.6 ATA, helium partial pressure 2.2 ATA as an example to calculate: P 空 =P 氮 / 0.78≈3.72 ATA; h1=(3.72-1)×10=27.2 meters; h2=(6.7-1) / 2×10=28.5 meters; finally, h=max(27.2, 28.5)+(3-6)=31.5-34.5 meters. This altitude and operation time can be used to determine the decompression plan.

[0050] Furthermore, the oxygen supply of the film hood 4 can be selected to be 12 to 15 L / min. 12 to 15 L / min is the recommended oxygen supply range determined based on the human body's oxygen metabolism needs in the late stage of decompression. It can not only meet the continuous oxygen supply needs of the lungs, but also avoid the risk of oxygen toxicity or uneven load on the supply and exhaust system due to excessive oxygen supply. Oxygen-inhaling personnel can adjust the appropriate oxygen supply according to their actual situation to obtain a comfortable breathing state and meet the requirements of denitrification efficiency. The greater the oxygen supply, the slower the desaturation rate of the inert gas. Excessive oxygen supply will increase the oxygen partial pressure in the alveoli and reduce the nitrogen discharge rate, prolonging the desaturation process; if the oxygen supply is too small, there will be a feeling of stuffiness, and insufficient oxygen supply will lead to poor inhalation and even cause hypoxia symptoms.

[0051] This embodiment also includes step S6. After the decompression in the human cabin 2 is completed, all pressure workers are checked by the diving physician for physical abnormalities after leaving the cabin. Then, they enter the micro-compression oxygen chamber 14 within 10 minutes, and then breathe oxygen at a pressure of 1.3ATA for 1 hour. After the decompression is completed, they enter the micro-compression oxygen chamber 14 for continued oxygen inhalation treatment, which can further remove residual inert gases in the body. The pressure level of 1.3ATA is close to the slightly increased atmospheric pressure on the ground, which helps to continue the denitrification effect and stabilize the physiological state. The 1-hour oxygen inhalation process can provide sufficient post-processing time, reduce the probability of delayed decompression sickness, and improve the recovery safety after high-pressure work.

[0052] In the present invention, the operator breathes a helium-nitrogen-oxygen ternary gas mixture or oxygen through a thin film hood 4 in the human cabin 2 by wearing an oronasal mask respirator 3. The partial pressure of the gas in the body generated during the breathing process decreases synchronously with the gradual decrease of the ambient pressure of the human cabin 2. As the human cabin 2 gradually depressurizes at a set rate through the outlet valve 8, the air pressure in the cabin continues to decrease. The inert components (such as nitrogen and helium) in the gas inhaled by the operator maintain a partial pressure gradient between the alveoli and the blood that is synchronized with the outside world, thereby achieving consistency between the "internal decompression" process in the operator's body and the "external decompression" process in the human cabin 2. The gas dissolution amount and escape rate change synchronously during the decompression process, which can effectively avoid bubble precipitation caused by imbalance of the internal and external pressure difference, and ensure the physiological stability of the decompression process and the safety of the operator.

[0053] In summary, the present invention discloses a shield machine pressure-changing tool change operation decompression system and decompression control method. The decompression system adopts a non-saturated high-pressure operation mode, eliminates the traditional living cabin and shuttle cabin structure, and realizes the entire process of personnel pressurization, operation and decompression through the human cabin 2. The decompression system includes a mixed gas distribution system 1, a human cabin 2, an oral and nasal mask respirator 3 and a thin film hood 4. A helium-nitrogen-oxygen ternary mixed gas is configured as the breathing gas during the operation. The mixed gas is stored in a mixed gas tank 5 and connected to the oral and nasal mask respirator 3 through a high-pressure hose 6. At the same time, an intelligent flow regulating valve 9 is set on the high-pressure hose 6 to realize gas supply regulation. In the latter stage of decompression, the thin film hood 4 is used to absorb oxygen to accelerate the discharge of inert gas. The thin film hood 4 is connected to the oxygen supply and exhaust control module 10 to realize automatic oxygen supply and exhaust control. The human cabin 2 is connected to the pressurizing device 7 for pressure regulation, and the outlet valve 8 implements staged decompression control. The system also includes a data recording device 11 and an alarm device 12, which are respectively used to record decompression parameters and identify personnel status, and communicate with the control room 13. After the decompression is completed, the operator can enter the micro-pressure oxygen chamber 14 within the specified time and continue to breathe oxygen at 1.3ATA to complete the post-processing. In the decompression control method, the decompression depth of the first station is determined by calculating the equivalent air pressure corresponding to the nitrogen partial pressure and combining it with the total operating pressure, and the decompression efficiency of the inert gas is improved by staged decompression and intermittent oxygen inhalation, thereby shortening the decompression time, reducing the risk of decompression sickness, and ensuring the safety and controllability of the decompression process. The decompression system provided by the present invention has a compact structure and a clear control strategy. It not only takes into account physiological safety, but also improves the efficiency of high-pressure operations, and has good engineering adaptability and practical operability. In particular, in shield pressure-driven tool changing operations in deep buried and high-pressure environments, it can effectively replace the traditional saturation operation mode, reduce helium consumption, reduce decompression time and economic costs, and has significant promotion value and application significance.

[0054] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the present invention as described above. For the sake of simplicity, they are not provided in detail. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in this field should understand that it is still possible to modify the technical solutions described in the above embodiments, or to make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A decompression control method based on a shield machine pressure-changing tool change operation decompression system, characterized in that: The shield machine adopts non-saturated high-pressure operation for tool change under pressure, and does not need to set up a living cabin and a shuttle cabin. The decompression system includes a mixed gas distribution system (1), a human cabin (2), an oral nasal mask respirator (3), and a film hood (4). The mixed gas distribution system (1) is used to configure a helium-nitrogen-oxygen ternary mixed gas, wherein the nitrogen partial pressure is greater than the helium partial pressure. The configured helium-nitrogen-oxygen ternary mixed gas is stored in a mixed gas tank (5). The human cabin (2) is docked with the mud and water tank. The mixed gas distribution system (1) is connected to the oral nasal mask respirator (3) located in the human cabin (2) through a high-pressure hose (6). The film hood (4) is connected to an oxygen supply device. After entering the human cabin (2), the operator wears the oral nasal mask respirator (3), and then enters the mud and water tank from the human cabin (2) to perform tool change operation. After completing the tool change, the operator returns to the human cabin (2) to decompress. After the pressure is reduced to the set pressure, the operator removes the oral nasal mask respirator (3) and uses the film hood (4) to breathe. The decompression control method includes the following steps: S1, after completing the tool changing operation in the mud and water tank, the operator returns to the man cabin (2), continues to wear the mouth and nose mask respirator (3) to breathe the helium, nitrogen and oxygen ternary gas mixture, and begins to perform the decompression operation; S2, determine the decompression depth of the first stop based on the nitrogen partial pressure in the configured helium, nitrogen and oxygen ternary gas mixture; S3, decompression at a steady rate from the operating pressure to the decompression depth of the first station; S4, based on the decompression depth of the first station, controlling the pressure and time of each decompression stage according to the air decompression table and the operation time; S5, when the pressure in the cabin (2) drops below 1.8 bar, the operator removes the oral and nasal mask respirator (3), wears a film hood (4) and breathes pure oxygen. Each time, the operator breathes oxygen continuously for 30 minutes, then breathes air for 5 minutes, and then continues to breathe oxygen until the pressure is reduced to normal pressure. In step S2, the method for determining the first decompression depth includes the following steps: S21, obtain the nitrogen partial pressure P in the mixed gas 氮 and operating pressure P 总 , the unit is ATA, through the formula P 空 =P 氮 / 0.78 can be used to obtain the equivalent air pressure under the nitrogen partial pressure; S22, calculate the reference values ​​h1 and h2 of the first station decompression depth, in meters: h1=(P 空 -1)×10,h2=((P 总 -1) / 2)×10; S23, obtaining the larger value of the above two results h1 and h2; S24: Finally determine the first station decompression water depth h = max (h1, h2) + (3 to 6), in meters.

2. The pressure reduction control method according to claim 1, wherein: The man cabin (2) is connected to a pressurizing device (7) provided with the shield machine. The pressurizing device (7) regulates the pressure in the cabin by injecting compressed air into the man cabin (2). The man cabin (2) includes an air outlet valve (8) to establish an air inlet and outlet balance of the man cabin (2). During the decompression process, the air outlet valve (8) is opened so that the air pressure in the man cabin (2) is reduced according to a preset decompression table.

3. The pressure reduction control method according to claim 1, wherein: The high-pressure hose (6) is provided with an intelligent flow regulating valve (9), and the supply flow of the ternary mixed gas of the oronasal mask respirator (3) is regulated by the intelligent flow regulating valve (9).

4. The pressure reduction control method according to claim 1, wherein: The film head cover (4) comprises a transparent sealing cover body, which is used to completely seal the head and neck of the operator and has mechanical automatic oxygen supply and mechanical automatic oxygen exhaust functions.

5. The pressure reduction control method according to claim 4, wherein: The thin film head cover (4) comprises an oxygen supply and exhaust control module (10), and the oxygen supply and exhaust control module (10) automatically adjusts the oxygen exhaust volume according to the oxygen supply flow rate.

6. The pressure reduction control method according to claim 1, wherein: A data recording device (11) and an alarm device (12) are provided in the man cabin (2). The data recording device (11) is used to record the dwell time at each pressure stage and the subjective reaction of the operator during the decompression process. The alarm device (12) is used to identify the working status of the operator and upload the working status information to the control room (13).

7. The pressure reduction control method according to claim 1, wherein: The oxygen supply capacity of the thin film hood (4) is (12-15) L / min.

8. The pressure reduction control method according to claim 7, characterized in that: The step S6 is also included, wherein after the decompression in the human cabin (2) is completed, the person enters the micro-pressure oxygen cabin (14) within 10 minutes, and then breathes oxygen at a pressure of 1.3 ATA for 1 hour.

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