Pressure reduction system and pressure reduction control method for shield tool changing operation under pressure

Abstract

The invention discloses a shield under-pressure tool changing operation pressure reduction system and a pressure reduction control method.The shield under-pressure tool changing adopts unsaturated high-pressure operation, the pressure reduction system comprises a mixed gas distribution system, a human cabin, a mouth-nose mask respirator and a thin film hood, the mixed gas distribution system is used for preparing helium, nitrogen and oxygen ternary mixed gas, the nitrogen partial pressure is larger than the helium partial pressure, and the human cabin is used for storing the helium, nitrogen and oxygen ternary mixed gas; the prepared helium-nitrogen-oxygen ternary mixed gas is stored in a mixed gas tank, a human cabin is in butt joint with a muddy water cabin, a mixed gas distribution system is connected to a mouth-nose mask respirator located in the human cabin through a high-pressure hose, a film hood is connected with an oxygen supply device, and an operator enters the muddy water cabin from the human cabin to conduct tool changing operation. And after tool changing is completed, returning to the human cabin for pressure reduction, and after the pressure is reduced to the set pressure, taking down the mouth-nose mask respirator and adopting the film hood for breathing. A traditional living cabin and a shuttle cabin are omitted, operators directly return to the human cabin for pressure reduction after completing under-pressure tool changing operation, and safety and high efficiency in the pressure reduction process are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of shield construction, and particularly relates to a decompression system and a decompression control method for shield pressure - maintained cutter changing operation. Background Art

[0002] At present, the commonly used methods in the field of shield pressure - maintained cabin opening mainly include two operation modes: air pressure - maintained and helium - oxygen saturation pressure - maintained. Specifically, in a relatively shallow operation environment, a high - pressure air operation method is usually adopted, and trained high - pressure workers operate in a diving decompression chamber; in a medium - depth environment, a conventional air diving method is used, and specially trained air divers operate, also relying on a diving decompression chamber, but the operation time is significantly limited. In a deeper operation environment, a helium - oxygen saturation diving operation mode is adopted, and specially trained mixed - gas divers and saturation divers carry out the operation. At this time, a saturation diving chamber, a transfer chamber and corresponding diving equipment need to be equipped. Moreover, due to the large demand for helium, the economic cost is relatively high. Taking CN112943270A as an example, it discloses a method for large - diameter shield cutter changing operation under ultra - high water pressure. Helium - oxygen mixed gas is used for air replacement between the personnel cabin and the slurry chamber. The operators gradually adapt to the pressure increase through the living chamber, then enter the operation area through the shuttle chamber, and return to the living chamber after the operation is completed, and a long - time stepped decompression is implemented.

[0003] However, the above - mentioned traditional methods have many defects, seriously affecting the safety and efficiency of the cutter changing operation. On the one hand, saturation operation requires the configuration of multiple functional cabins, with a complex operation process, occupying a large amount of space inside the shield. And for personnel entering and leaving the cabin, multiple pressure equalizations and pressure regulations are required, making the operation organization difficult. On the other hand, the decompression process is extremely long and relies on precise control. If there is a slight oversight, it is extremely easy to cause physiological risks such as decompression sickness, threatening the life and health of the operators. In addition, in deep - depth high - pressure operations, the consumption of helium is large and the cost is high. Coupled with the complex process of desaturation of helium - oxygen mixed gas in the body, it further exacerbates the difficulty of decompression control. Therefore, when the prior art conducts pressure - maintained cutter changing operations in deep - buried high - pressure tunnel environments, it is urgently faced with a series of technical bottlenecks such as complex decompression procedures, long time, high safety risks, and high operation costs. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention proposes a decompression system and a decompression control method for shield pressure - maintained cutter changing operation, which cancel the traditional living chamber and shuttle chamber structures. After the operators complete the pressure - maintained cutter changing operation in the slurry chamber, they directly return to the personnel cabin for decompression, improving the safety and efficiency of the decompression process, and being applicable to the non - saturated high - pressure operation mode in deep - buried high - pressure tunnel environments.

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

[0006] A decompression system for 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 comprises 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 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, 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, and after decompressing 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 inlet and outlet air 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 a 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 comprises 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, and 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 changing 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 to perform decompression operations;

[0014] S2, determine the decompression depth of the first station according to the nitrogen partial pressure in the configured helium-nitrogen-oxygen ternary gas mixture;

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

[0016] S4, Based on the decompression depth of the first stage, control the residence pressure and time of each decompression stage according to the air decompression table and operating time;

[0017] S5, When the pressure in the personnel cabin is reduced below 1.8 bar, the operator removes the nose and mouth mask respirator and wears a thin film hood to breathe pure oxygen. After each continuous oxygen inhalation for 30 minutes, take a 5-minute air break and then continue oxygen inhalation until decompression to atmospheric pressure. Preferably, in the step S2, the method for determining the decompression depth of the first stage includes the following steps:

[0018] S21, Obtain the nitrogen partial pressure P 氮 in the mixed gas and the operating pressure P 总 , in units of ATA. Through the formula P 空 = P 氮 / 0.78, the air pressure equivalent to the operation under this nitrogen partial pressure can be obtained;

[0019] S22, Calculate the reference values h1 and h2 of the decompression water depth of the first stage, in units of m: h1 = (P 空 - 1) × 10, h2 = ((P 总 - 1) / 2) × 10;

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

[0021] S24, Finally determine the decompression water depth h of the first stage = max(h1, h2) + (3 - 6), in units of m.

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

[0023] Preferably, it further includes step S6. After the decompression in the personnel cabin is completed, enter the micro-pressure oxygen cabin within 10 minutes, and then breathe oxygen at a pressure of 1.3 ATA for 1 hour.

[0024] The beneficial effects of the present invention are as follows: Firstly, the present invention adopts a non-saturated high-pressure operation mode, eliminating the redundant living cabin and shuttle cabin structures in traditional saturated operations. The operators can complete the whole process of pressurization, operation, and decompression only through the personnel cabin, significantly simplifying the operation process, reducing the space occupied by equipment, and lowering the system complexity and operation and maintenance costs. Secondly, by using a ternary helium-nitrogen-oxygen mixed gas and combining the physical property that the nitrogen partial pressure is greater than the helium partial pressure, a decompression curve is formulated based on the nitrogen partial pressure, simplifying the control logic, improving the desaturation efficiency, and reducing the risk of decompression sickness. In particular, in the decompression control method, after the operators complete the operation in the slurry chamber, they first continue to wear a nose and mouth mask respirator to breathe the ternary mixed gas. After decompressing to below 1.8 bar, they switch to wearing a thin film hood to inhale oxygen, and adopt an intermittent oxygen inhalation strategy. This staged decompression method fully considers the desaturation law of human tissues to inert gases. In the initial stage of high pressure, the ternary mixed gas is used to avoid premature high-oxygen inhalation causing oxygen toxicity; in the middle and later stages, a partial pressure gradient is established through high-concentration oxygen to accelerate the discharge of nitrogen, shorten the decompression time, and prevent lung damage caused by long-term oxygen inhalation by intermittent air inhalation, improving the decompression safety and comfort. In addition, the present invention also precisely controls the gas supply flow by setting an intelligent flow regulating valve. The thin film hood adopts a mechanical oxygen supply and discharge structure, automatically adjusting the oxygen discharge amount according to the oxygen supply amount to ensure stable oxygen concentration and prevent oxygen accumulation. Combining the data recording device and the alarm device, the status of the operators and the key data of the decompression process can be monitored in real time, improving the informatization management level and emergency response ability of the whole process. While ensuring the safety of high-pressure operations, the present invention effectively simplifies the decompression path, shortens the decompression time, improves the efficiency, reduces the helium consumption and system burden, and is applicable to the pressure-equipped cutter changing operation in the shield construction environment of deep burial, high pressure, and long distance, with significant engineering adaptability and popularization and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 FIG. is an overall schematic diagram of the decompression system for the pressure-equipped cutter changing operation of the shield in the embodiment of the present invention.

[0026] Figure 2 FIG. is a schematic flow chart of the decompression control method of the decompression system for the pressure-equipped cutter changing operation of the shield in the embodiment of the present invention.

[0027] Figure 3 FIG. is a schematic flow chart of the determination method of the decompression depth at the first station in the embodiment of the present invention.

[0028] Reference numerals: 1 - mixed gas distribution system; 2 - personnel cabin; 3 - nose and mouth mask respirator; 4 - thin film hood; 5 - mixed gas cylinder; 6 - high-pressure hose; 7 - pressurizing device; 8 - outlet valve; 9 - intelligent flow regulating valve; 10 - oxygen supply and discharge control module; 11 - data recording device; 12 - alarm device; 13 - control room; 14 - micro-pressure oxygen chamber. Detailed implementation manners

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part rather than all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention belong to the present invention.

[0031] In addition, the described features, structures or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of the embodiments of the present application. However, those skilled in the art will realize that the technical solutions of the present application can be practiced without one or more of the specific details, or other methods, components, devices, steps, etc. can be adopted. In other cases, well-known methods, devices, implementations or operations are not shown or described in detail to avoid obscuring various aspects of the present application.

[0032] Please refer to Figure 1, This embodiment provides a shield pressure-reducing system for knife-changing operation under pressure. The shield pressure-reducing knife-changing adopts non-saturated high-pressure operation. Non-saturated high-pressure operation means that the operator does not enter the saturated diving state under high-pressure environment, and the operation duration is much shorter than the time required for the complete saturation of tissue gas, thereby significantly shortening the pressurization and decompression cycle, reducing the physiological burden, and improving the overall operation efficiency. The decompression system includes a mixed gas distribution system 1, a human cabin 2, a mouth-nose mask respirator 3, and a film head cover 4. The mixed gas distribution system 1 is used to configure a helium-nitrogen-oxygen ternary mixed gas, in which the nitrogen partial pressure is greater than the helium partial pressure. Nitrogen, as the main inert gas, determines the decompression strategy, and helium can be quickly discharged at the beginning of decompression due to its low partial pressure. The configured helium-nitrogen-oxygen ternary mixed gas 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 the continuous gas supply demand during the whole decompression process. The human cabin 2 is docked with the mud and water tank. The human cabin 2 is the key cabin for the operator to pressurize, prepare for knife-changing 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 delivery. 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 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 body. 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 the oronasal mask respirator 3 and enters the initial pressurization and work preparation stage. Then, the operator enters the mud and water tank from the man cabin 2 to change the tool. During the operation, the oronasal mask respirator 3 is kept supplied with air. After completing the tool change, the operator returns to the man cabin 2 for decompression. After decompression to the set pressure, the oronasal mask respirator 3 is removed and the film hood 4 is used for breathing. Using the film hood 4 to breathe 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.

[0033] 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 an 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 a preset decompression table. The air outlet valve 8 can achieve staged exhaust by program control to ensure a steady decompression rate and a natural transition, thereby avoiding physiological discomfort or the risk of decompression sickness caused by rapid pressure difference.

[0034] In this embodiment, the thin-film hood 4 includes a transparent sealing cover body, which is used to completely enclose the head and neck of the operator. The transparent sealing cover body has good airtightness and visibility, can prevent gas exchange with the outside, and is convenient for observing the facial state of the operator from the outside. The thin-film hood 4 has mechanical automatic oxygen supply and mechanical automatic oxygen discharge functions. The mechanical automatic oxygen supply can provide a constant flow of oxygen into the hood without manual adjustment. The mechanical automatic oxygen discharge function automatically discharges excess gas according to the internal air pressure to prevent the accumulation of oxygen and cause a hyperoxic environment. The thin-film hood 4 includes an oxygen supply and discharge control module 10. The oxygen supply and discharge control module 10 automatically adjusts the oxygen discharge amount according to the oxygen supply flow rate. The oxygen supply and discharge control module 10 can implement a dynamic adjustment logic of more supply and more discharge, no supply and no discharge, so as to make the utilization of the internal gas of the hood more efficient and ensure smooth breathing and gas component safety during the oxygen inhalation and discharge process.

[0035] In addition, a data recording device 11 and an alarm device 12 are arranged in the personnel 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, gas supply flow rate, decompression time node and the feedback information of the operator, which is convenient for subsequent review and medical evaluation. The alarm device 12 is used to identify the working state of the operator and upload the working state information to the control room 13. Specifically, the alarm device 12 can monitor indicators such as the operator's posture, breathing frequency, and static time through sensors. When abnormal states such as loss of consciousness and long-term stillness are detected, an alarm signal is sent to the control room 13 in time to realize remote real-time monitoring and emergency response of operation safety.

[0036] In this embodiment, the personnel cabin 2 includes a hatch door 15. The operator directly enters the personnel cabin 2 from the shield machine through the hatch door 15. After the hatch door 15 is opened, the operator can directly enter the personnel cabin 2 without passing through the living cabin and the shuttle cabin, thus effectively simplifying the traditional multi-cabin series operation process. Since there is no need to set up a living cabin and a shuttle cabin, the equipment layout space is saved, and the tool changing preparation efficiency is also significantly improved. A sealing door 16 is arranged between the personnel cabin 2 and the slurry chamber. The sealing door 16 is used to ensure the airtightness between the two cabins, and can maintain the pressure difference balance between the personnel cabin 2 and the slurry chamber after decompression is completed, preventing the leakage of compressed gas or the backflow of slurry. When the operator performs operations such as tool replacement and mud cake removal in the slurry chamber, the operator always wears a nose and mouth mask respirator 3 to breathe a helium-nitrogen-oxygen ternary mixture. As an auxiliary inert gas, the concentration of nitrogen needs to be strictly controlled. During the operation process, the concentration of nitrogen in the ternary mixture is monitored, and the change of the mixture composition is fed back in real time through a gas analysis device to ensure that the nitrogen partial pressure does not exceed the safety threshold, so as to ensure the breathing safety of the operator during long-term operation in a high-pressure environment.

[0037] Please refer to Figure 2, Another embodiment of the present invention also discloses a decompression control method for a decompression system for shield pressure - maintained tool changing operation based on the above, including the following steps:

[0038] S1, After the operators complete the tool changing operation in the mud chamber and return to the personnel cabin 2, they continue to wear the nose - mouth mask respirator 3 to breathe the helium - nitrogen - oxygen ternary mixture, and start to perform the decompression operation. Instead of immediately changing the oxygen inhalation method after the operators return to the personnel cabin 2, they continue to breathe the ternary mixture, which can ensure the steady release of inert gas in the initial decompression stage and avoid the risk of oxygen toxicity caused by premature oxygen inhalation.

[0039] S2, Determine the decompression depth of the first stage according to the nitrogen partial pressure in the configured helium - nitrogen - oxygen ternary mixture. The nitrogen partial pressure is the key parameter for controlling the desaturation of inert gas, and the setting of the decompression depth of the first stage determines the safety and rationality of subsequent staged decompression.

[0040] S3, Decompress from the operating pressure to the decompression depth of the first stage at a steady rate. The decompression rate needs to be combined with the physiological tolerance range of the operators and the pressure control ability of the cabin structure to ensure that the pressure change process is continuous and gentle, avoiding decompression sickness caused by excessive pressure difference. For example, a decompression rate of 7 m / min can be selected for decompression.

[0041] S4, Based on the decompression depth of the first stage, control the stay pressure and time of each decompression stage according to the air decompression table and the operation time. The air decompression table provides a safe decompression plan, and the air decompression table can refer to the existing diving decompression table to achieve the safe release of inert gas.

[0042] S5, When the pressure in the personnel cabin 2 drops below 1.8 bar, the operators remove the nose - mouth mask respirator 3 and wear the thin - film hood 4 to breathe pure oxygen. After each continuous oxygen inhalation for 30 min, they breathe air for 5 min intervals and then continue to inhale oxygen until decompression to normal pressure. The thin - film hood 4 provides high - concentration pure oxygen supply, accelerates the escape of nitrogen from the body by establishing a strong oxygen - nitrogen partial pressure gradient, and cooperates with the strategy of intermittent air breathing to avoid oxygen poisoning caused by long - term oxygen inhalation, realizing a fast, safe and stable decompression process.

[0043] In a specific embodiment, the preset operating pressure is 5.7 bar, the nitrogen partial pressure in the ternary mixture is set to 2.9 ATA, the oxygen partial pressure is 1.6 ATA, and the helium partial pressure is 2.2 ATA. The partial pressures of the three gases are precisely controlled, and the nitrogen partial pressure is strictly controlled below 4.0 ATA to effectively avoid the risk of high - pressure nitrogen narcosis. The oxygen partial pressure is maintained within the safe range of human metabolism, and the helium partial pressure is used to reduce the density and breathing resistance of the mixture. The operation stay time is 70 min, that is, the continuous operation time of the operators in the high - pressure mixture breathing environment in the mud chamber. This time is set in combination with the tool changing operation task volume and the personnel pressure tolerance, avoiding overtime exposure while ensuring the completion of the task.

[0044] In this embodiment, the ratio of the helium-nitrogen-oxygen ternary mixture during decompression not only takes into account the breathing safety during the operation and the control of nitrogen narcosis risk, but also comprehensively considers the decompression efficiency after the operation. Specifically, nitrogen is used as the basis for the inert gas to judge the most adverse water depth in the mixture ratio, that is, the nitrogen partial pressure is used as the control factor for the dissolution and release of tissue gas in the decompression plan. Compared with the traditional decompression model that uses helium as the basis for the most adverse water depth, it can significantly shorten the decompression time. Since the diffusion rate of helium is faster and the tissue saturation and desaturation processes are more sensitive, if helium is used as the benchmark for decompression design, a longer time is required for stepwise decompression to avoid the precipitation of bubbles and cause decompression sickness. However, by reasonably controlling the nitrogen partial pressure (for example, restricting it to below 4.0 ATA) in the present invention, nitrogen narcosis is effectively avoided, and the release control intensity of the most adverse tissue gas is reduced in the decompression path planning, thereby shortening the decompression duration, improving the overall operation efficiency and the recovery speed of personnel after the operation.

[0045] Please refer to Figure 3 , further, in step S2, the method for determining the first-stage decompression depth includes the following steps:

[0046] S21, obtain the nitrogen partial pressure P 氮 and the operating pressure P 总 , in units of ATA, and the equivalent air pressure of the operation under this nitrogen partial pressure can be obtained through the formula P 空 = P 氮 / 0.78. P 空 represents the equivalent air pressure corresponding to the nitrogen content of 78% in the air, which is used to convert the actual nitrogen partial pressure in the ternary mixture environment into the reference pressure value under the traditional air diving condition, so as to borrow the existing air decompression experience.

[0047] S22, calculate the reference values h1 and h2 of the first-stage decompression water depth, in units of m: h1 = (P 空 - 1) × 10, h2 = ((P 总 - 1) / 2) × 10. Among them, h1 represents the equivalent decompression water depth converted according to the nitrogen partial pressure, and h2 represents the conservative decompression depth estimated according to half of the total operating pressure. Both take into account the initial pressure difference required for gas desaturation and the depth buffer requirements.

[0048] S23, obtain the larger value of the above two results h1 and h2. Select a higher decompression water depth to ensure safety and prevent the formation of bubbles or uneven tissue saturation caused by too fast decompression.

[0049] S24. Finally, determine the first-stage decompression water depth h = max(h1, h2) + (3 - 6), with the unit of m. By adding a safety redundancy of 3 - 6 meters on the basis of the maximum reference value, it can effectively prevent individual differences, operation errors or potential abnormal physiological reactions, and improve the safety and reliability of the entire decompression process.

[0050] Taking the preset operating pressure as 5.7 bar (6.7 ATA) and the ternary mixture gas with 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 as an example for calculation: P 空 = P 氮 / 0.78 ≈ 3.72 ATA; h1 = (3.72 - 1) × 10 = 27.2 m; h2 = (6.7 - 1) / 2 × 10 = 28.5 m; finally, h = max(27.2, 28.5) + (3 - 6) = 31.5 - 34.5 m. That is, the decompression plan can be determined based on this height and operation time.

[0051] Furthermore, the oxygen supply amount of the thin-film hood 4 can be selected as 12 - 15 L / min. 12 - 15 L / min is the recommended oxygen supply range determined according to the oxygen absorption and metabolism requirements of the human body in the later stage of decompression, which can not only meet the continuous oxygen supply requirements of the lungs, but also avoid the risk of oxygen toxicity caused by excessive oxygen supply or uneven load of the supply and exhaust system. The oxygen-absorbing personnel can adjust the appropriate oxygen supply amount according to their actual situation to obtain a comfortable breathing state and meet the requirements of denitrification efficiency. The greater the oxygen supply amount, the slower the desaturation rate of inert gas. Excessive oxygen supply will increase the oxygen partial pressure in the alveoli and reduce the nitrogen excretion rate, prolonging the desaturation process; if the oxygen supply amount is too small, there will be a feeling of stuffiness, and insufficient oxygen supply will lead to unsmooth inhalation and even cause hypoxic symptoms.

[0052] This embodiment also includes step S6. After the decompression in the human cabin 2 is completed, after all the pressurized operation personnel leave the cabin and are examined by a diving doctor and found to be normal, they enter the hyperbaric oxygen chamber 14 within 10 minutes, and then breathe oxygen at a pressure of 1.3 ATA for 1 hour. After the decompression is completed, entering the hyperbaric oxygen chamber 14 for continuous oxygen inhalation treatment can further remove the residual inert gas in the body. The pressure level of 1.3 ATA is close to the slightly increased state of the ground atmospheric pressure, which helps to continue the denitrification effect and stabilize the physiological state. The 1-hour oxygen inhalation process can provide sufficient post-treatment time, reduce the occurrence probability of delayed decompression sickness, and improve the recovery safety after high-pressure operation.

[0053] In the present invention, the operator wears a nose-mouth mask respirator 3 in the personnel cabin 2 to breathe a helium-nitrogen-oxygen ternary mixture or wears a thin-film hood 4 to inhale oxygen. The partial pressure of the in-vivo gas generated during the breathing process decreases synchronously with the gradual decrease of the environmental pressure in the personnel cabin 2. As the personnel cabin 2 is gradually depressurized at a set rate through the air outlet valve 8, the air pressure in the cabin continuously decreases. The inert components (such as nitrogen and helium) in the gas inhaled by the operator maintain a partial pressure gradient synchronized with the outside world between the alveoli and the blood, so as to realize that the "internal decompression" process in the operator's body is consistent with the "external decompression" process in the personnel cabin 2. During the decompression process, the gas dissolution amount and the escape rate change synchronously, which can effectively avoid the precipitation of bubbles caused by the imbalance of the internal and external pressure differences, and ensure the physiological stability during the decompression process and the safety of the operator.

[0054] In summary, the present invention discloses a decompression system and a decompression control method for shield pressure-assisted tool changing operations. The decompression system adopts a non-saturated high-pressure operation mode, cancels the traditional living cabin and shuttle cabin structures, and realizes the whole process of personnel pressurization, operation and decompression through the personnel cabin 2. The decompression system includes a mixed gas distribution system 1, a personnel cabin 2, a nose-mouth mask respirator 3 and a thin-film hood 4, configures a helium-nitrogen-oxygen ternary mixture as the breathing gas during operation, stores the mixed gas in a mixed gas cylinder 5, and connects it to the nose-mouth 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 the air supply regulation. In the latter stage of decompression, the thin-film hood 4 is used to inhale oxygen to accelerate the discharge of inert gases. The thin-film hood 4 is connected to the oxygen supply and discharge control module 10 to realize automatic oxygen supply and discharge control. The personnel cabin 2 is connected to a pressurizing device 7 for pressure regulation, and is subjected to staged decompression control through an air outlet valve 8. The system also includes a data recording device 11 and an alarm device 12, which are respectively used to record decompression parameters and identify the 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 a specified time and continue to inhale oxygen at 1.3 ATA to complete the after-treatment. In the decompression control method, by calculating the equivalent air pressure corresponding to the nitrogen partial pressure and combining the total operation pressure, the decompression depth of the first stage is determined, and the desaturation efficiency of inert gases is improved by means of staged decompression and intermittent oxygen inhalation, the decompression time is shortened, the risk of decompression sickness is reduced, and the safety and controllability of the decompression process are ensured. The decompression system provided by the present invention has a compact structure and a clear control strategy, takes into account both physiological safety and improves the high-pressure operation efficiency, and has good engineering adaptability and practical operability. Especially in shield pressure-assisted tool changing operations in deep-buried and high-pressure environments, it can effectively replace the traditional saturation operation mode, reduce helium consumption, and reduce the decompression time and economic cost, and has significant popularization value and application significance.

[0055] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; under the idea of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above. For the sake of brevity, they are not provided in detail; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A shield machine pressure relief system for tool change operation under pressure, characterized in that: The shield machine tool change under pressure adopts non-saturated high-pressure operation. The decompression system comprises a mixed gas distribution system (1), a man cabin (2), an oronasal mask respirator (3), and a thin 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 man cabin (2) is connected to the mud and water tank. The mixed gas distribution system (1) is connected to the oronasal mask respirator (3) located in the man cabin (2) through a high-pressure hose (6). The thin film hood (4) is connected to an oxygen supply device. After entering the man cabin (2), the operator wears the oronasal mask respirator (3), and then enters the mud and water tank from the man cabin (2) to perform a tool change operation. After completing the tool change, the operator returns to the man cabin (2) to decompress. After the pressure is reduced to a set pressure, the oronasal mask respirator (3) is removed and the thin film hood (4) is used to breathe.

2. The shield machine pressure relief system for tool change operation under pressure according to claim 1 is characterized in that: The man cabin (2) is connected to a pressurizing device (7) provided with the shield machine. The pressurizing device (7) adjusts the pressure in the cabin by filling the man cabin (2) with compressed air. The man cabin (2) includes an air outlet valve (8) to establish an air inlet and outlet balance in 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 a preset decompression table.

3. The shield machine pressure relief system for tool change operation under pressure according to claim 1 is characterized in that: The high-pressure hose (6) is provided with an intelligent flow regulating valve (9), and the supply flow rate of the ternary mixed gas of the oronasal mask respirator (3) is regulated by the intelligent flow regulating valve (9).

4. The shield machine pressure relief system for tool change operation under pressure according to claim 1, characterized in that: The thin 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 the functions of mechanical automatic oxygen supply and mechanical automatic oxygen exhaust.

5. The shield machine pressure relief system for tool change operation under pressure according to claim 4 is characterized in that: 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 shield machine pressure relief system for tool change operation under pressure according to claim 1, characterized in that: 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 response of the operator during the decompression process; and 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. A decompression control method for a shield machine with pressure cutter changing operation decompression system according to any one of claims 1 to 6, characterized in that: The following steps are involved: 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-oxygen ternary gas mixture, and starts to perform the decompression operation; S2, determine the decompression depth of the first station according to the nitrogen partial pressure in the configured helium-nitrogen-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 stay 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 mouth-nose mask respirator (3), wears a thin film hood (4) and breathes pure oxygen. After breathing oxygen continuously for 30 minutes each time, the operator breathes air for 5 minutes, and then continues to breathe oxygen until the pressure is reduced to normal pressure.

8. The decompression control method of the shield machine pressure-changing tool changing operation decompression system according to claim 7, characterized in that: In step S2, the method for determining the first station decompression depth includes the following steps: S21, obtain the nitrogen partial pressure P in the mixed gas 氮 and operating pressure P 总 , in ATA, by 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 ~ 6), the unit is m.

9. The decompression control method of the shield machine pressure-changing tool changing operation decompression system according to claim 8, characterized in that: The oxygen supply of the thin film head cover (4) is (12-15) L / min.

10. The decompression control method of the shield machine pressure-changing tool changing operation decompression system according to claim 9, characterized in that: The step also includes step S6, wherein after the decompression in the human cabin (2) is completed, the human 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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