Centralized high-capacity hydraulic fracturing system in underground coal mines and its operation method

Abstract

This invention relates to the field of underground roof control technology in coal mines, and discloses a centralized, high-capacity hydraulic fracturing system and its operation method for underground coal mines. The system includes an underground central pump station, a high-pressure pipeline network, a working face control unit, and a centralized control center. The underground central pump station is located within a dedicated chamber complex, and the high-pressure pipeline network connects the underground central pump station to the working face control unit. This invention aggregates work requests through the centralized control center, calculates the total flow load rate using a parallel work load assessment program, and schedules the number of high-power explosion-proof pumps. It utilizes a PID control algorithm to adjust the frequency converter based on the flow difference, achieving on-demand allocation of flow for multiple concurrent operations. By calculating the equipment health degradation index, preventative maintenance work orders are generated, and the control strategy is updated using a parameter optimization algorithm. This solves the problem of limited fluid supply from mobile pump stations, reduces the labor intensity of equipment relocation, and extends the service life of the explosion-proof pumps.

Description

Technical Field

[0001] This invention relates to the field of underground roof control technology in coal mines, specifically to a centralized, high-capacity hydraulic fracturing system for underground coal mines and its operation method. Background Technology

[0002] Current underground hydraulic fracturing operations in coal mines mainly rely on mobile water injection pump stations for on-site fluid supply. These mobile pump stations need to be frequently relocated as the mining face advances. Due to the spatial constraints of the cross-sectional dimensions of underground coal mine roadways, it is difficult to configure high-power pump sets for these mobile pump stations. Consequently, the output flow and pressure of these mobile pump stations cannot meet the demands of high-intensity fracturing operations. During the frequent changes in work locations, the disassembly, transportation, and reinstallation of mobile water injection pump stations consume a significant amount of manpower and time, increasing the difficulty of implementing hydraulic fracturing operations.

[0003] The existing hydraulic fracturing fluid supply system adopts a single-point independent control mode, which lacks a centralized coordination mechanism for the concurrent demand of multiple operation sites. When facing multi-channel concurrent fracturing operation conditions, the single-point independent control mode is difficult to dynamically allocate flow resources according to actual load conditions, resulting in large pressure fluctuations within the pipeline system. Due to the lack of a unified scheduling strategy, fluid supply conflicts or energy waste are likely to occur when multiple devices are running at the same time, which limits the overall scheduling level of hydraulic fracturing operations in mines.

[0004] Conventional hydraulic fracturing fluid supply equipment lacks comprehensive condition monitoring and health assessment functions. Maintenance mainly relies on post-failure repair, which cannot provide early warning and intervention in the early stages of equipment performance degradation. This can easily lead to long-term operation of the equipment with defects and shorten its service life. In addition, existing control systems lack adaptive optimization capabilities based on operating data and cannot automatically adjust control parameters according to the degree of equipment aging or environmental changes, increasing the risk of sudden shutdowns during operation. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a centralized, high-capacity hydraulic fracturing system for underground coal mines and its operation method, which solves the problems of limited fluid supply capacity, frequent equipment movement, and difficulties in coordinated control caused by the dispersed arrangement of pump sets in existing underground hydraulic fracturing operations.

[0006] To achieve the above objectives, the first aspect of the present invention provides a centralized high-displacement hydraulic fracturing system for underground coal mines, including an underground central pump station, a high-pressure pipeline network, multiple working face control units, and a centralized control center.

[0007] The underground central pump station is located in a dedicated chamber complex near the main mining area or the bottom of the well. The physical location of the underground central pump station remains fixed throughout its entire lifecycle. The site is chosen in geologically stable rock formations, close to the underground central substation and the bottom water reservoir. The dedicated chamber complex includes a main pump house, a power distribution chamber, a control chamber, and a liquid storage chamber. The underground central pump station includes multiple high-power explosion-proof pumps installed in the main pump house, providing the fluid power required for fracturing operations. The underground central pump station includes a high-pressure distribution valve assembly. The inlet of the high-pressure distribution valve assembly is connected to the main discharge pipe of the multiple high-power explosion-proof pumps via a high-pressure rigid pipeline. Each outlet of the high-pressure distribution valve assembly is connected to the high-pressure pipeline network via high-pressure unions or flanges. The underground central pump station includes a large liquid storage tank, a pre-boost pump unit, and an explosion-proof online mixing skid. These components are installed inside the liquid storage chamber and connected to the suction main of multiple high-power explosion-proof pumps via supply pipelines. The power distribution chamber is connected to the underground central substation via high-voltage armored cables. Multiple high-voltage vacuum power distribution devices are installed inside the power distribution chamber and connected to multiple high-power explosion-proof pumps via high-voltage shielded power cables.

[0008] The high-pressure pipeline network is laid along the main underground transport roadways of the coal mine, connecting the central underground pumping station with various target work areas. The network is constructed of high-strength seamless steel pipes. It employs either a ring-shaped or branched route. Automatic air vents are installed at the highest points of the network, and drain valves are installed at the lowest points. Industrial ring network optical cables or explosion-proof and flame-retardant communication buses are laid along the pipeline network, forming a communication network.

[0009] Multiple face control units are located near the entrance of each mining face. The inlets of these control units are connected to branch pipes of the high-pressure pipeline network via high-pressure hoses, and the outlets are connected to the fracturing borehole. The face control units are wall-mounted near the face entrance and integrate electrically or hydraulically controlled valves, bypass return valves, flow meters, pressure sensors, and explosion-proof quick connectors. The electrically or hydraulically controlled valves are connected in series to the internal high-pressure pipeline of the face control unit, as are the flow meters and pressure sensors. The fluid outlet of the face control unit is connected to one end of a high-pressure hose via an explosion-proof quick connector, and the other end of the high-pressure hose is connected to the borehole sealer inside the fracturing borehole.

[0010] The centralized control center is located in the control chamber. It is connected to the underground central pump station, the high-pressure pipeline network, and multiple working face control units via a communication network. The centralized control center is used to achieve remote centralized power supply for fracturing operations. It includes an explosion-proof industrial computer, data acquisition cabinets, and a video monitoring server. The data acquisition cabinets are connected to pressure sensors installed on the high-pressure pipeline network via industrial ring network fiber optic cables or explosion-proof flame-retardant communication buses. They are also connected to flow meters installed on the high-pressure pipeline network and to frequency converters of multiple high-power explosion-proof pumps via industrial ring network fiber optic cables or explosion-proof flame-retardant communication buses. The communication network adopts an industrial Ethernet ring network. The central control center is equipped with a mine-use explosion-proof core switch. The mine-use explosion-proof core switch is connected to the mine-use explosion-proof access switches at the entrance of each mining area through mine-use flame-retardant optical cables. The mine-use explosion-proof access switches are cascaded to form a ring network topology through mine-use flame-retardant optical cables. The mine-use explosion-proof access switches are responsible for aggregating the data generated by the working face control unit.

[0011] A second aspect of this invention provides a method for centralized, high-volume hydraulic fracturing operations in underground coal mines, applied to the aforementioned centralized, high-volume hydraulic fracturing system in underground coal mines, comprising the following steps:

[0012] S1. Planning and Infrastructure Construction of Underground Central Pump Station: Determine the optimal theoretical coordinates of the underground central pump station, carry out roadway development operations in the selected area, determine the laying route of the high-pressure pipeline network and lay it, and lay double-circuit high-pressure armored cables and mine flame-retardant optical cables.

[0013] S2. Installation and integration of core equipment for the underground central pump station: Install multiple high-power explosion-proof pumps, install a pre-boost pump set and a working face control unit, and connect sensors to the centralized control center.

[0014] S3. Static commissioning and parameter initialization of the underground central pump station: Measure insulation resistance, test data transmission performance, and configure the operating parameters of the PID control algorithm inside the programmable logic controller.

[0015] S4. Dynamic trial operation and performance calibration: Conduct low-pressure cycle trial operation and full-load test mode.

[0016] S5. Formal large-displacement fracturing operation process, specifically including:

[0017] S501 Operation Preparation and Request Implementation: The central control center receives the operation request signal from the working face control unit. Based on the parameters in the operation request signal, the central control center calculates the minimum fluid reserve required for this fracturing operation. The central control center reads the real-time fluid level sensor data installed in the large fluid storage tank, calculates the currently available fracturing base fluid volume in the large fluid storage tank based on the real-time fluid level sensor data, and compares the currently available fracturing base fluid volume with the calculated minimum fluid reserve. If the currently available fracturing base fluid volume is less than the minimum fluid reserve, the central control center automatically opens the valve on the water supply pipeline connected to the large fluid storage tank to replenish the fluid.

[0018] The implementation of intelligent scheduling and execution in step S502: The centralized control center calculates the optimal number of high-power explosion-proof pumps to be activated based on the target injection flow rate and the rated output flow parameters of multiple high-power explosion-proof pumps. The centralized control center then selects the pumps to perform the specific task based on the calculated optimal number, prioritizing pumps with the shortest cumulative operating time. The centralized control center collects real-time actual flow data from the electromagnetic flowmeter installed at the main outlet of the high-pressure pipeline network, compares the actual flow data with the target injection flow rate, and uses a PID control algorithm to dynamically adjust the operating frequency of the frequency converters connected to the multiple high-power explosion-proof pumps based on the comparison result.

[0019] S503 Real-time Monitoring and Dynamic Adjustment: The centralized control center calculates the instantaneous output power of the pump station based on real-time pressure and injection flow rates. The calculated instantaneous output power is then compared to the rated power threshold of the entire unit. When the instantaneous output power exceeds the preset rated power threshold, the centralized control center automatically sends a frequency reduction command to the frequency converter. The centralized control center also monitors the vibration frequency data of multiple high-power explosion-proof pumps in real time. When the vibration amplitude in a specific frequency band exceeds the fault warning threshold, the centralized control center determines that the corresponding high-power explosion-proof pumps have a mechanical failure risk, immediately stops the pumps with this risk, and automatically increases the output frequency of the remaining normally operating high-power explosion-proof pumps.

[0020] S504 Step-by-Step Operation Switching and Parallel Operation: When the fracturing operation of the first fracturing borehole is completed, the working face control unit automatically closes the electric control valve at the fluid outlet and simultaneously opens the bypass return valve in the fluid circuit. The centralized control center controls multiple high-power explosion-proof pumps to maintain low-speed operation. While the first fracturing borehole operation is still ongoing, the centralized control center receives a concurrent operation request from the second fracturing borehole and initiates the parallel operation load assessment program. The parallel operation load assessment program calculates the total flow load rate, and the centralized control center compares the calculated total flow load rate with the overall maximum safe load threshold. If the total flow load rate is less than or equal to the preset maximum safe load threshold, the centralized control center generates a parallel operation permission instruction and automatically increases the number of operating high-power explosion-proof pumps based on the new total flow demand; if the total flow load rate is greater than the preset maximum safe load threshold, the centralized control center places the concurrent operation request in a waiting queue.

[0021] S6. Maintenance and Data Feedback Optimization: The centralized control center reads vibration intensity data from vibration sensors and bearing temperature data from temperature sensors in real time. It then uses a multi-source data fusion algorithm to calculate the equipment health degradation index for multiple high-power explosion-proof pumps. The centralized control center compares the calculated equipment health degradation index with a preset maintenance alarm threshold. If the equipment health degradation index exceeds the maintenance alarm threshold, the centralized control center automatically generates a preventative maintenance work order. The centralized control center extracts all operational data for this fracturing operation from the historical database and calculates the overall energy efficiency ratio (EER) of this fracturing operation. The centralized control center compares the calculated overall EER with the historical best EER stored in the database. If the overall EER is lower than the historical best EER, the centralized control center initiates a parameter optimization algorithm. The parameter optimization algorithm calculates the control strategy correction factor, and the centralized control center stores the updated control strategy correction factor in the control logic parameter library.

[0022] This invention provides a centralized, high-capacity hydraulic fracturing system for underground coal mines and its operation method. It offers the following advantages:

[0023] 1. This invention solves the problem of insufficient fluid supply capacity caused by the roadway cross-section limitation of traditional mobile pump stations by fixing the underground central pump station in a dedicated chamber group near the main underground mining area or the bottom of the mine. It utilizes the spatial advantages of the dedicated chamber group to install multiple high-power explosion-proof pumps. The invention also constructs a fluid transmission channel by laying a high-pressure pipeline network along the main underground transport roadway and cooperating with the working face control unit arranged near the entrance of the mining face to realize the remote centralized supply of fracturing power. This avoids the cumbersome process of frequently moving large pump sets at the mining face and reduces the labor intensity caused by equipment relocation.

[0024] 2. This invention uses a centralized control center to aggregate work requests from multiple working face control units via a communication network. It applies a parallel work load assessment program to calculate the total flow load rate. Based on the comparison between the total flow load rate and the maximum safe load threshold, it intelligently schedules the number of high-power explosion-proof pumps in operation. The PID control algorithm dynamically adjusts the frequency converter frequency based on the difference between the target injection flow rate and the actual flow rate data. This enables on-demand flow allocation and stable pressure control for multiple concurrent fracturing operations, improving the overall scheduling efficiency of hydraulic fracturing operations in coal mines.

[0025] 3. This invention collects data from vibration and temperature sensors through a centralized control center, calculates the equipment health degradation index using a multi-source data fusion algorithm, and automatically generates preventive maintenance work orders based on the equipment health degradation index, realizing the transformation from post-fault maintenance to preventive maintenance. It calculates the overall energy efficiency ratio of fracturing operations and initiates a parameter optimization algorithm to update the control strategy correction factor. The updated control strategy correction factor is fed back to the control logic parameter library, realizing adaptive iterative optimization of the fracturing system operating parameters and extending the service life of multiple high-power explosion-proof pumps. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the system structure of the present invention;

[0027] Figure 2 This is a schematic diagram of the layout structure of the downhole central pump station of the present invention;

[0028] Figure 3 This is a schematic diagram of the connection between the high-pressure pipeline network fixing and the working face control unit of the present invention;

[0029] Figure 4 This is a flowchart of the method of the present invention;

[0030] Figure 5 This is the formal large-volume fracturing operation flowchart of the present invention.

[0031] The components include: 1. Downhole central pump station; 11. Multiple high-power explosion-proof pumps; 12. High-pressure distribution valve group; 13. Large liquid storage tank; 14. Explosion-proof online mixing skid; 2. High-pressure pipeline network; 21. Pre-embedded anchor bolts; 22. U-shaped clamps; 23. High-strength seamless steel pipes; 3. Working face control unit; 31. Explosion-proof quick connectors; 32. High-pressure hoses; 4. Central control center; 5. Industrial Ethernet ring network; 6. Roadway side; 61. Orifice sealing device; 62. Fracturing borehole. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] See attached document Figure 1 The present invention provides a centralized large-displacement hydraulic fracturing system for underground coal mines, including an underground central pump station 1, a high-pressure pipeline network 2, multiple working face control units 3, and a centralized control center 4.

[0034] The underground central pump station 1 is located in a group of dedicated chambers near the main mining area or the bottom yard. The geological conditions in the dedicated chamber group are stable and the ventilation is good. The dedicated chamber group includes a main pump room, a power distribution chamber, a control chamber and a liquid storage chamber. The high-pressure pipeline 2 is laid along the main underground transport roadway of the coal mine. The high-pressure pipeline 2 connects the underground central pump station 1 with each target operation area. Multiple working face control units 3 are arranged near the entrance of each mining working face. The centralized control center 4 is located in the control chamber. The centralized control center 4 is connected to the underground central pump station 1 through a communication network. The centralized control center 4 is connected to the high-pressure pipeline 2 through a communication network. The centralized control center 4 is connected to the multiple working face control units 3 through a communication network.

[0035] The underground central pump station 1 includes multiple high-power explosion-proof pumps 11, which are installed in the main pump room and fixed according to the design foundation. Vibration damping pads are installed between the multiple high-power explosion-proof pumps 11 and the design foundation. The underground central pump station 1 includes a high-pressure distribution valve group 12. The inlet of the high-pressure distribution valve group 12 is connected to the discharge main of the multiple high-power explosion-proof pumps 11 through a high-pressure rigid pipeline. Each outlet of the high-pressure distribution valve group 12 is connected to the high-pressure pipeline network 2 through a high-pressure union or flange. The underground central pump station 1 includes a large liquid storage tank 13, a pre-boost pump set, and an explosion-proof online mixing skid 14. The large liquid storage tank 13, the pre-boost pump set, and the explosion-proof online mixing skid 14 are installed in the liquid storage chamber. The large liquid storage tank 13, the pre-boost pump set, and the explosion-proof online mixing skid 14 are connected to the suction main of multiple high-power explosion-proof pumps 11 through the liquid supply pipeline. The underground central pump station 1 obtains power through the power distribution chamber, which is connected to the underground central substation through a high-voltage armored cable.

[0036] High-pressure pipeline 2 adopts a ring-shaped or branch-shaped high-pressure pipeline 2 route. High-pressure pipeline 2 is laid with high-strength seamless steel pipes 23. The connection points of high-pressure pipeline 2 are connected by high-pressure flanges, which are tightened to the standard torque. High-pressure pipeline 2 is fixed to the roadway side 6 throughout by pre-embedded anchor bolts 21 and U-shaped clamps 22. An automatic air vent valve is installed at the highest point of high-pressure pipeline 2, and a drain valve is installed at the lowest point of high-pressure pipeline 2. Industrial ring network optical cables or explosion-proof and flame-retardant communication buses are laid along the high-pressure pipeline 2, and the industrial ring network optical cables or explosion-proof and flame-retardant communication buses constitute a data communication network.

[0037] The working face control unit 3 is wall-mounted near the working face inlet. The working face control unit 3 integrates an electric control valve or a hydraulic control valve, a bypass return valve, a flow meter, a pressure sensor, and an explosion-proof quick connector 31. The inlet of the working face control unit 3 is connected to a branch pipe of the high-pressure pipeline 2 via a high-pressure hose 32. The explosion-proof quick connector 31 reserved at the outlet of the working face control unit 3 is used to connect to the fracturing borehole 62.

[0038] The centralized control center 4 includes an explosion-proof industrial computer, a data acquisition cabinet, and a video monitoring server. The data acquisition cabinet of the centralized control center 4 is connected to the pressure sensor via an industrial ring network optical cable or an explosion-proof and flame-retardant communication bus. The data acquisition cabinet of the centralized control center 4 is also connected to the flow meter via an industrial ring network optical cable or an explosion-proof and flame-retardant communication bus. The data acquisition cabinet of the centralized control center 4 is connected to the frequency converters of multiple high-power explosion-proof pumps 11 via an industrial ring network optical cable or an explosion-proof and flame-retardant communication bus. The data acquisition cabinet of the centralized control center 4 is also connected to the valve controller via an industrial ring network optical cable or an explosion-proof and flame-retardant communication bus.

[0039] The centralized large-capacity hydraulic fracturing system in underground coal mines is spatially divided into a power generation area, a fluid transmission network, and a terminal execution area. The power generation area is the dedicated chamber group where the underground central pump station 1 is located. The fluid transmission network is the high-pressure pipeline network 2 distributed along the underground roadway. The terminal execution area is the mining face where the working face control unit 3 is installed.

[0040] The underground central pump station 1 is located at the geometric center or load center of the planned fracturing area. The physical location of the underground central pump station 1 remains fixed throughout its entire life cycle. The site of the underground central pump station 1 is located in a geologically stable rock stratum underground, in an area with an independent ventilation network, and close to the underground central substation and the bottom water tank. The centralized arrangement of the underground central pump station 1 in a dedicated chamber group can remove the restrictions on the size and weight of the fracturing pump group, allowing the use of high-power and high-displacement fracturing pump groups.

[0041] High-pressure pipeline network 2 forms the backbone channel connecting the power generation area and the terminal execution area. It is laid along the main underground transport roadways and the uphill or downhill roadways of the mining area. The pipelines of high-pressure pipeline network 2 extend to the entrance of each planned mining face, forming a ring-shaped or dendritic topology in the underground roadways. As a long-distance transport carrier for fracturing fluid, high-pressure pipeline network 2 transports the high-pressure, high-flow fluid generated by the underground central pump station 1 to any target operation point.

[0042] Multiple working face control units 3 serve as end control nodes, distributed at the entrance of each mining face to be operated. They are connected to the reserved branch interface of the high-pressure pipeline network 2 via high-pressure hoses 32. The position of the working face control unit 3 is locally adjusted as the mining operation progresses. It is responsible for receiving fluid from the high-pressure pipeline network 2 and injecting the fluid into the fracturing borehole 62. Through the layout of fixed underground central pump station 1, wide coverage of high-pressure pipeline network 2, and flexible access of working face control units 3, the centralized large-displacement hydraulic fracturing system in the coal mine realizes the remote centralized supply of power for fracturing operations.

[0043] This invention provides the site selection and chamber layout structure of an underground central pump station 1. The underground central pump station 1 is set in one or more dedicated chamber groups. The dedicated chamber groups are located near the main mining area or the bottom yard of the coal mine. The dedicated chamber groups are located in areas with stable geological conditions, good ventilation, and convenient power supply and drainage. The dedicated chamber groups are located at the center of the planned fracturing area.

[0044] The dedicated chamber complex is formed through underground roadway development operations. The geometric dimensions of the dedicated chamber complex meet the functional zoning requirements of the main pump room, power distribution chamber, control chamber, and liquid storage chamber. The main pump room constitutes the physical space for installing high-power explosion-proof pumps, power distribution equipment, control unit hardware, large liquid storage tank 13, and explosion-proof online mixing skid 14.

[0045] Multiple high-power explosion-proof pumps 11 are installed in the main pump room of the underground central pump station 1. The multiple high-power explosion-proof pumps 11 form a pump group cluster and are fixed in the position determined by the design foundation. Vibration damping pads are installed between the multiple high-power explosion-proof pumps 11 and the design foundation. The vibration damping pads are used to reduce the vibration transmission of the multiple high-power explosion-proof pumps 11 during operation. The fluid suction end of the multiple high-power explosion-proof pumps 11 is connected to the pump group suction main pipe, and the fluid discharge end is connected to the pump group discharge main pipe. The pump group discharge main pipe is used to collect the high-pressure fluid generated by the multiple high-power explosion-proof pumps 11. The motors of the multiple high-power explosion-proof pumps 11 are equipped with frequency converters, which are used to adjust the operating speed of the multiple high-power explosion-proof pumps 11.

[0046] The underground central pump station 1 includes a high-pressure distribution valve group 12, which is installed in the main pump room. The inlet of the high-pressure distribution valve group 12 is connected to the pump group discharge main pipe through a high-pressure rigid pipeline. The pump group discharge main pipe is connected to the fluid discharge end of multiple high-power explosion-proof pumps 11. Each outlet of the high-pressure distribution valve group 12 is connected to the high-pressure pipeline network 2 through a high-pressure union, or each outlet of the high-pressure distribution valve group 12 is connected to the high-pressure pipeline network 2 through a flange.

[0047] See attached document Figure 1 The present invention provides a routing planning structure for a high-pressure pipeline network 2. The routing planning of the high-pressure pipeline network 2 is designed based on the layout of the working face in the mining area. The routing planning of the high-pressure pipeline network 2 is designed as a ring high-pressure pipeline network 2 route, or the routing planning of the high-pressure pipeline network 2 is designed as a branch high-pressure pipeline network 2 route. The main pipeline of the high-pressure pipeline network 2 is laid along the main transportation roadway in the coal mine, and the main pipeline covers all target operation areas.

[0048] The high-pressure pipeline 2 is laid with high-strength seamless steel pipes 23. The connection points between the high-strength seamless steel pipes 23 are connected by high-pressure flanges and tightened according to the standard torque. The entire pipeline is fixed to the roadway side 6 by pre-embedded anchor bolts 21 and U-shaped clamps 22. The pre-embedded anchor bolts 21 and U-shaped clamps 22 restrict the displacement of the high-pressure pipeline 2.

[0049] An automatic air vent valve is installed at the highest point of the high-pressure pipeline 2. The automatic air vent valve is used to release the gas accumulated in the pipeline during the filling process of the high-pressure pipeline 2. A drain valve is installed at the lowest point of the high-pressure pipeline 2. The drain valve is used to drain the fluid remaining in the high-pressure pipeline 2 when maintenance or operation is completed.

[0050] See attached document Figure 3 The working face control unit 3 is fixed to the roadway side 6 near the entrance of the mining working face using a wall-mounted installation method. The working face control unit 3 integrates an electric control valve or a hydraulic control valve, a flow meter, a pressure sensor, and an explosion-proof quick connector 31.

[0051] The fluid inlet of the working face control unit 3 is connected to a branch interface of the high-pressure pipeline network 2 via a high-pressure hose 32. An electric control valve or a hydraulic control valve is installed in series on the internal high-pressure pipeline of the working face control unit 3. A flow meter is installed in series on the internal high-pressure pipeline of the working face control unit 3. A pressure sensor is installed on the internal high-pressure pipeline of the working face control unit 3. The electric control valve or the hydraulic control valve is used to perform opening, closing, or opening adjustment actions. The flow meter is used to monitor the fracturing fluid flow through the working face control unit 3 in real time. The pressure sensor is used to monitor the fluid pressure at the working face control unit 3 in real time. An explosion-proof quick connector 31 is installed at the fluid outlet of the working face control unit 3. The explosion-proof quick connector 31 is used to connect the working face control unit 3 to the high-pressure hose 32 extending toward the fracturing borehole 62.

[0052] The fluid outlet of the working face control unit 3 is connected to one end of the high-pressure hose 32 via an explosion-proof quick connector 31. The other end of the high-pressure hose 32 is connected to the orifice sealer 61 inside the fracturing borehole 62. The high-pressure hose 32 serves as a flexible transmission channel between the working face control unit 3 and the fracturing borehole 62, allowing relative displacement between them. The pressure resistance of the high-pressure hose 32 is not lower than the preset maximum working pressure. A safety chain is provided at the connection between the high-pressure hose 32 and the explosion-proof quick connector 31, and at the connection between the high-pressure hose 32 and the orifice sealer 61. The safety chain is used to limit the swing of the high-pressure hose 32 when the connection is broken.

[0053] See attached document Figure 2 The power distribution chamber is connected to the underground central substation via a dual-circuit high-voltage armored cable. The dual-circuit high-voltage armored cable transmits the high-voltage electrical energy required for the operation of the underground central pump station 1. Multiple high-voltage vacuum power distribution devices are installed in the power distribution chamber. These devices are connected to the dual-circuit high-voltage armored cable. The output side of these devices is connected to multiple high-power explosion-proof pumps 11 in the main pump room via high-voltage shielded power cables, which control the power supply and de-energization of the pumps 11.

[0054] An explosion-proof mobile substation is installed in the power distribution chamber. The high-voltage side of the explosion-proof mobile substation is connected to a high-voltage vacuum power distribution device, which converts high-voltage electrical energy into low-voltage AC power. The low-voltage side is connected to a low-voltage feeder switch, which provides working power to the centralized control center 4 through a low-voltage cable. The low-voltage feeder switch also provides working power to the electric valves and stirring devices in the liquid storage chamber through a low-voltage cable. The centralized control center 4 integrates a mine-use explosion-proof and intrinsically safe uninterruptible power supply, which is used to maintain the operation of the data acquisition cabinet and video monitoring server in the event of an external power outage.

[0055] See attached document Figure 1 The underground centralized high-displacement hydraulic fracturing system constructs an information transmission channel based on an industrial Ethernet ring network 5. The industrial Ethernet ring network 5 is deployed along the laying path of the high-pressure pipeline network 2. The centralized control center 4 is equipped with a mining explosion-proof core switch. The mining explosion-proof core switch is connected to the mining explosion-proof access switch at the entrance of each mining area through mining flame-retardant optical cable. The mining explosion-proof access switches are cascaded with mining flame-retardant optical cables to form a ring network topology. The ring network topology provides redundant data transmission paths when a single point of optical cable breaks.

[0056] The mine explosion-proof access switch is responsible for aggregating the data generated by the working face control unit 3. The working face control unit 3 establishes a connection with the mine explosion-proof access switch installed in the roadway through the explosion-proof and flame-retardant communication bus. The industrial Ethernet ring network 5 transmits the pressure signal monitored by the pressure sensor to the centralized control center 4. The industrial Ethernet ring network 5 transmits the flow signal monitored by the flow meter to the centralized control center 4. The industrial Ethernet ring network 5 transmits the control commands issued by the centralized control center 4 to the working face control unit 3. The mine explosion-proof core switch is connected to the ground production scheduling network through the shaft optical cable. The ground production scheduling network is used to realize the real-time monitoring of underground fracturing operation data from the surface.

[0057] Reference Appendix Figure 4 and attached Figure 5 This invention provides a method for centralized, high-volume hydraulic fracturing operations in coal mines, comprising the following steps:

[0058] S1. Planning and infrastructure construction of the downhole central pump station 1: Determine the optimal theoretical coordinates of the downhole central pump station 1. The optimal theoretical coordinates are calculated based on the geometric center positions of all planned fracturing operation areas and the weighted estimated fracturing water demand of all planned fracturing operation areas. The planar position coordinates of the downhole central pump station 1 are calculated using the center of gravity method model. The calculation formula is as follows:

[0059] ;

[0060] ;

[0061] In the formula, The theoretical x-coordinate represents the location of the underground central pump station 1; The theoretical ordinate represents the location of the underground central pump station 1; Indicates the first The abscissa of the geometric center of the planned fracturing operation area; Indicates the first The geometric center ordinate of the planned fracturing operation area; Indicates the first The estimated total injection volume for each planned fracturing operation area; This indicates the total number of fracturing operation areas covered by the plan.

[0062] The calculated planar coordinates are mapped onto the mine geological map. The actual site selection of the underground central pump station 1 is adjusted in conjunction with the mine geological map. The actual site selection must avoid fault fracture zones, stress concentration zones, and mining-affected zones. The actual site selection is preferably located in stable rock strata near the bottom of the mine or in stable rock strata on both sides of the main transport roadway.

[0063] According to the design dimensions, the selected area is developed into a tunnel. The tunnel is excavated sequentially to form the main pump house chamber, power distribution chamber, control chamber, and liquid storage chamber. The surface of the excavated chambers is supported by a combined support system, which uses high-strength threaded steel anchors in conjunction with metal mesh. A layer of shotcrete is applied to the surface of the combined support system. A reinforced concrete equipment foundation is poured on the bottom slab of the main pump house chamber. The reinforced concrete equipment foundation has pre-drilled holes for anchor bolts and is used to support the weight of the high-power explosion-proof pump unit and its dynamic loads during operation.

[0064] Based on the mine development drawings, technicians determined the laying route of high-pressure pipeline 2. The laying route extends along the main underground transport roadway, avoiding overhead line facilities and train tracks within the transport roadway. Technicians conducted surveying and setting out along the roadway sidewalls along the laying route. The surveying and setting out were used to mark the positions of pipeline fixing points, which were evenly distributed.

[0065] Before the laying operation begins, the wall thickness of the high-strength seamless steel pipe 23 is determined according to the designed working pressure. The wall thickness of the high-strength seamless steel pipe 23 must meet the safety pressure requirements. The calculation formula for the wall thickness of the high-strength seamless steel pipe 23 is as follows:

[0066] ;

[0067] In the formula, This indicates the design wall thickness of the high-strength seamless steel pipe 23; This indicates the maximum design working pressure of high-pressure pipeline network 2; This indicates the outer diameter value of the high-strength seamless steel pipe 23; This indicates the allowable stress value of the high-strength seamless steel pipe material 23; This indicates the weld coefficient of high-strength seamless steel pipe 23; This indicates the wall thickness corrosion allowance of high-strength seamless steel pipe 23.

[0068] Construction workers drill anchor holes at the marked pipe fixing points, install pre-embedded anchor bolts 21 in the anchor holes, install U-shaped clamp bases 22 at the ends of the pre-embedded anchor bolts 21, use lifting equipment to lift the high-strength seamless steel pipe 23 to the installation height, clamp the high-strength seamless steel pipe 23 into the U-shaped clamp bases 22, install the U-shaped clamp cover plate and tighten the fixing nut, and the fixing nut restricts the radial displacement of the high-strength seamless steel pipe 23.

[0069] Construction workers connect the flanges of two adjacent high-strength seamless steel pipes 23, place a metal high-pressure sealing gasket between the sealing surfaces of the flanges, and symmetrically tighten the connecting bolts of the flanges using a torque wrench. The tightening torque of the connecting bolts meets the design standards of the high-pressure flanges. Construction workers construct concrete supports at the bends of the high-pressure pipeline 2. The concrete supports wrap around the bends of the high-pressure pipeline 2 to eliminate the axial impact force generated by the high-pressure fluid. Construction workers install corrugated compensators at regular intervals on the straight sections of the high-pressure pipeline 2. The corrugated compensators are used to absorb the thermal expansion and contraction deformation of the high-strength seamless steel pipes 23.

[0070] Construction workers installed cable hooks along the sides of the main underground transport roadway. The installation density of the cable hooks was determined according to the spacing of the anchor bolts. The cable hooks were used to suspend dual-circuit high-voltage armored cables and mine flame-retardant optical cables.

[0071] Construction workers laid the dual-circuit high-voltage armored cable in the lower hook position of the cable hook and laid the mining flame-retardant optical cable in the upper hook position of the cable hook. The dual-circuit high-voltage armored cable and the mining flame-retardant optical cable are arranged in layers. The layered arrangement structure is used to reduce the interference of the electromagnetic field generated by the dual-circuit high-voltage armored cable on the transmission signal of the mining flame-retardant optical cable.

[0072] During cable laying, construction workers must strictly control the cable tension. Tension control is crucial to prevent excessive sag between adjacent cable hooks. Excessive sag can cause the vertical distance between the dual-circuit high-voltage armored cable and the mining flame-retardant optical cable to fall below the safety threshold. The minimum tension calculation formula for cable laying is as follows:

[0073] ;

[0074] In the formula, This indicates the minimum tension that must be applied during cable laying; This indicates the weight per unit length of the laid cable; This indicates the horizontal span between two adjacent cable hooks; This indicates the maximum allowable sag of the cable between the two cable hooks.

[0075] Construction workers hung warning signs at fixed intervals along the dual-circuit high-voltage armored cables, indicating the voltage level and power supply purpose. They also installed explosion-proof junction boxes at the splicing points of the mine-use flame-retardant optical cables. These junction boxes were fixed in grooves in the roadway walls to prevent damage from transport vehicles. Steel protective sleeves were installed where the dual-circuit high-voltage armored cables and flame-retardant optical cables passed through the chamber walls. The steel protective sleeves were filled with fire-resistant sealing material to isolate airflow between different chambers.

[0076] S2. Installation and integration of core equipment for underground central pump station 1: Construction personnel transported multiple high-power explosion-proof pumps 11 to the main pump room chamber. Using the hoisting equipment in the roadway, the multiple high-power explosion-proof pumps 11 were hoisted onto the reinforced concrete equipment foundation. The installation level of the multiple high-power explosion-proof pumps 11 was finely adjusted by adjusting shims. The installation level deviation was controlled within the tolerance range allowed by the equipment installation specifications. Anchor bolts were inserted into the reserved holes in the base of the multiple high-power explosion-proof pumps 11 and the reserved holes in the reinforced concrete equipment foundation. The nuts of the anchor bolts were tightened in stages according to the diagonal sequence. The final tightening torque of the anchor bolts met the requirements of the equipment installation manual.

[0077] The pre-boost pump unit is installed on the connecting pipeline between the liquid storage chamber and the main pump room chamber. The installation position of the pre-boost pump unit is lower than the lowest liquid level of the liquid storage chamber. This installation method, which is lower than the lowest liquid level of the liquid storage chamber, is used to achieve self-priming of the pre-boost pump unit.

[0078] Multiple high-voltage vacuum power distribution devices are installed in the power distribution chamber, as are explosion-proof mobile substations and multiple low-voltage feeder switches. Data acquisition cabinets, explosion-proof industrial computers, video surveillance servers, and mine explosion-proof core switches are installed in Chamber 4 of the centralized control center. All equipment is fixed to the chamber floor or walls with anchor bolts or expansion bolts, and a safe maintenance distance is maintained between the equipment and the walls.

[0079] Transport the working face control unit 3 to the working position near the fracturing borehole 62, install a wall-mounted fixed bracket on the side of the roadway, and firmly install the working face control unit 3 on the wall-mounted fixed bracket. The installation position is selected in an area where the roadway roof is well supported and there is no water spray. The installation height is convenient for the operator to observe the instrument readings on the working face control unit 3.

[0080] Connect the branch pipeline of high-pressure pipeline 2 to the fluid inlet end of the working face control unit 3. The connection component is a high-pressure hose 32 assembly. Connect the fluid outlet end of the working face control unit 3 to one end of another high-pressure hose 32. The construction personnel connect the other end of this high-pressure hose 32 to the orifice sealer 61 and insert the orifice sealer 61 into the predetermined depth in the fracturing borehole 62. Install anti-detachment safety chains at all joints of high-pressure hose 32 and lock the joints of high-pressure hose 32 with the anti-detachment safety chains.

[0081] Connect the working face control unit 3 to the underground local power supply, check the communication line connection status between the working face control unit 3 and the mine explosion-proof access switch, the mine explosion-proof access switch confirms that the working face control unit 3 has been connected to the industrial Ethernet ring network 5, the central control center 4 reads the equipment status information of the working face control unit 3 through the industrial Ethernet ring network 5, and the construction personnel conduct no-load operation tests on the electric control valves or hydraulic control valves in the working face control unit 3, the no-load operation test confirms that the valve opening and closing actions are accurate.

[0082] A high-precision pressure sensor is installed on the outlet pipe of the high-power explosion-proof pump, an electromagnetic flow meter is installed on the outlet pipe of the high-power explosion-proof pump, a liquid level sensor is installed inside the large liquid storage tank 13 in the liquid storage chamber, a temperature sensor is installed on the bearing seat of the high-power explosion-proof pump, and a vibration sensor is installed on the pump body base of the high-power explosion-proof pump.

[0083] Intrinsically safe shielded cables are used to connect field sensors to the data acquisition cabinet in the central control center. The shielding layer of the intrinsically safe shielded cable is grounded at one end on one side of the data acquisition cabinet. The single-end grounding is used to eliminate electromagnetic interference signals in the downhole environment. The signal line of the intrinsically safe shielded cable is connected to the analog input module of the programmable logic controller inside the data acquisition cabinet.

[0084] Technicians configure the parameters of the analog input module of the programmable logic controller (PLC). This parameter configuration converts the received analog current signal into an actual physical quantity value. The conversion calculation formula for the actual physical quantity value is as follows:

[0085] ;

[0086] In the formula, This indicates the actual physical quantity value read by the control center; This indicates the real-time current signal value received by the analog input module; This indicates the minimum current value within the sensor's output signal range. This indicates the maximum current value within the sensor's output signal range; This indicates the minimum value of the physical quantity that the sensor can measure; This indicates the maximum value of the physical quantity that the sensor can measure.

[0087] Connect the explosion-proof industrial computer to the mining explosion-proof core switch via an industrial Ethernet cable. Connect the video monitoring server to the mining explosion-proof core switch via an industrial Ethernet cable. Connect the large-screen monitor to the video output interface of the explosion-proof industrial computer. Connect the output terminal of the mining explosion-proof and intrinsically safe uninterruptible power supply to the power input terminal of the data acquisition cabinet. Connect the output terminal of the mining explosion-proof and intrinsically safe uninterruptible power supply to the power input terminal of the explosion-proof industrial computer. The mining explosion-proof and intrinsically safe uninterruptible power supply ensures stable operation of the entire system during power grid fluctuations.

[0088] S3. Static commissioning and parameter initialization of the underground central pump station 1: The commissioning personnel used a high-voltage megohmmeter to measure the insulation resistance of the dual-circuit high-voltage armored cable and the insulation resistance of the high-power explosion-proof pump motor winding. The measured insulation resistance value must be higher than the minimum threshold specified in the coal mine electrical equipment handover test standard. The insulation resistance measurement confirms that the power supply network has the conditions for receiving power.

[0089] Close the isolating switch and vacuum circuit breaker of the high-voltage vacuum power distribution device in sequence. The commissioning personnel close the low-voltage feeder switch. The power supply network starts to supply power to the central control center 4. The power supply network starts to supply power to various sensors. Observe the power indicator light of the data acquisition cabinet in the central control center 4. The power indicator light is lit, indicating that the power supply circuit is connected normally.

[0090] The data transmission performance of the industrial Ethernet ring network 5 was tested using a network analyzer. Test data packets were sent to the workface control unit 3, and the data packet loss rate of the communication link was calculated. The formula for calculating the data packet loss rate is as follows:

[0091] ;

[0092] In the formula, This indicates the data packet loss rate of the communication link; This indicates the total number of test data packets sent from the centralized control center 4 to the working face control unit 3; This indicates the number of data packets that the working face control unit 3 successfully received and returned as confirmation signals.

[0093] The communication quality is judged based on the calculated data packet loss rate. The data packet loss rate must be lower than the upper limit of the allowable bit error rate of the industrial control network. The initial values ​​of all sensors are checked on the human-machine interface of the explosion-proof industrial computer. For pressure sensors, calibration operations are performed, and zero-point calibration operations are performed to eliminate the zero-point drift error of the sensor in a static state.

[0094] Technicians start the control logic simulation test program on the human-computer interface of the explosion-proof industrial computer. The control logic simulation test program is used to verify the logical control relationship of the central control center 4 to each functional module. The explosion-proof industrial computer sends simulated action commands to the working face control unit 3. The simulated action commands include valve opening commands and valve closing commands. The explosion-proof industrial computer records the time point when the simulated action commands are sent, receives the action execution status feedback signal returned by the working face control unit 3, and records the time point when the action execution status feedback signal is received.

[0095] The signal transmission and processing response time of the explosion-proof industrial computer control system must be less than the preset maximum allowable delay threshold. The formula for calculating the signal transmission and processing response time is as follows:

[0096] ;

[0097] In the formula, This indicates the overall signal transmission and processing response time of the control system; This indicates the timestamp indicating when the explosion-proof industrial computer receives the action execution status feedback signal; This indicates the timestamp when the explosion-proof industrial computer issues simulated action commands. This represents the inherent network transmission delay constant of an industrial Ethernet ring network 5.

[0098] Technicians verified the safety interlock logic by simulating a pressure value higher than the safety threshold on an explosion-proof industrial computer. The programmable logic controller (PLC) detected that the pressure value exceeded the limit and triggered the emergency shutdown logic. The emergency shutdown logic immediately cut off the control power of multiple high-power explosion-proof pumps 11 and sent a forced shutdown command to the working face control unit 3.

[0099] Technicians verified the overall sequential start-up logic. The sequential start-up logic requires that the fully open signal of the electric control valve or hydraulic control valve must be received first. Only after receiving the fully open signal can the programmable logic controller send the start command of the high-power explosion-proof pump. The sequential start-up logic prevents the high-power explosion-proof pump from starting in a closed pipeline state. The explosion-proof industrial computer automatically compares the actual logic execution result with the preset logic truth table. If the comparison result is completely consistent, the control logic verification is confirmed to be successful.

[0100] Log in with engineer privileges through the human-machine interface of the explosion-proof industrial computer, input the target pressure value for fracturing operations in the parameter setting module, input the target flow rate value for fracturing operations in the parameter setting module, set the overpressure protection threshold for the high-power explosion-proof pump, and set the low liquid level alarm threshold for the large liquid storage tank 13.

[0101] Technicians configure the operating parameters of the PID control algorithm inside the programmable logic controller (PLC). These parameters include proportional, integral, and derivative coefficients. The PID control algorithm automatically adjusts the motor speed of the high-power explosion-proof pump based on the deviation between the target pressure value and the actual pressure value. The formula for calculating the control output of the PID control algorithm is as follows:

[0102] ;

[0103] In the formula, Indicates the first Control output quantity for each sampling period; The proportional coefficient represents the PID control algorithm. Indicates the first Pressure deviation value for each sampling period; Represents the integral coefficient of the PID control algorithm; Indicates the first Pressure deviation value for each sampling period; This represents the sampling time interval of the PID control algorithm; Represents the derivative coefficients of the PID control algorithm; Indicates the first Pressure deviation value for each sampling period.

[0104] All configured operating parameters are downloaded to the programmable logic controller's memory. The programmable logic controller performs a validity check on the input operating parameters. If the validity check confirms that the operating parameters are within the allowable safe range, the system enters a standby state after the validity check is passed. The standby state indicates that the underground central pump station 1 is ready to start operations at any time.

[0105] S4. Dynamic trial operation and performance calibration: The operator remotely opens the bypass return valve of the working face control unit 3. In the centralized control center 4, the frequency of the inverter of the high-power explosion-proof pump is set to the low-speed cruise frequency. The high-power explosion-proof pump starts to operate according to the low-speed cruise frequency, sucks in fracturing base fluid from the large liquid storage tank 13, and injects the fracturing base fluid into the high-pressure pipeline network 2. The fracturing base fluid fills the internal space of the high-pressure pipeline network 2 and returns to the bottom water tank through the bypass return valve. The circulation of the fracturing base fluid carries away the residual air inside the high-pressure pipeline network 2.

[0106] Inspection personnel patrolled the high-pressure pipeline 2, checking for leaks at the flange connections of the high-strength seamless steel pipe 23 and for loose supports. The centralized control center 4 collected real-time pressure data from both the inlet and outlet of the high-pressure pipeline 2. Based on fluid mechanics principles, it calculated the theoretical friction loss of the high-pressure pipeline 2 at the current flow rate. The formula for calculating the theoretical friction loss is as follows:

[0107] ;

[0108] In the formula, This represents the theoretical friction loss along the pressure line of high-pressure pipeline 2; This represents the coefficient of fluid friction resistance inside the high-strength seamless steel pipe 23; This represents the total length of the fluid path through high-pressure pipeline 2; This indicates the inner diameter of the high-strength seamless steel pipe 23; Indicates the fluid density of the fracturing base fluid; This indicates the average flow velocity of the fracturing base fluid inside the pipeline.

[0109] The centralized control center 4 calculates the actual pressure drop value monitored in real time, compares the actual pressure drop value with the theoretical pressure loss along the pipeline, and confirms the smoothness of the high-pressure pipeline 2 by comparing the results. It also eliminates the possibility of serious blockage or large-flow leakage inside the pipeline. The low-pressure circulation test run continues until there are no air bubbles in the discharged fluid. The operator then shuts off the high-power explosion-proof pump and the bypass return valve.

[0110] The operator switches the control mode of the high-power explosion-proof pump to the full-load test mode through the human-machine interface of the explosion-proof industrial computer. The full-load test mode controls the inverter output frequency of the high-power explosion-proof pump to increase to the rated operating frequency. The high-power explosion-proof pump drives the hydraulic end plunger to reciprocate at the rated operating frequency. The reciprocating motion of the hydraulic end plunger outputs the fracturing base fluid with the maximum design flow rate to the high-pressure pipeline 2.

[0111] A high-precision pressure sensor monitors the pipeline pressure value of high-pressure pipeline 2 under full load in real time. The pipeline pressure value must be stable within the preset rated working pressure range. An electromagnetic flow meter monitors the actual output flow of high-pressure pipeline 2 under full load in real time. A temperature sensor monitors the operating temperature of the bearing housing of the high-power explosion-proof pump in real time. A vibration sensor monitors the vibration acceleration of the high-power explosion-proof pump body in real time. The centralized control center 4 records all monitoring data within the continuous operating cycle. The continuous operating cycle is used to verify the overall thermal stability under long-term full load conditions.

[0112] The centralized control center 4 calculates the actual volumetric efficiency of the high-power explosion-proof pump based on monitoring data. The actual volumetric efficiency is used to assess the wear condition of the hydraulic end sealing components. The formula for calculating the actual volumetric efficiency is as follows:

[0113] ;

[0114] In the formula, This indicates the actual volumetric efficiency of a high-power explosion-proof pump; This indicates the actual output flow rate monitored by the electromagnetic flowmeter; This indicates the real-time speed of the high-power explosion-proof pump motor; This represents the theoretical displacement of a single plunger at the hydraulic end; This indicates the total number of plungers at the hydraulic end of a high-power explosion-proof pump.

[0115] Technicians compare the calculated actual volumetric efficiency with the equipment's factory-calibrated efficiency. If the actual volumetric efficiency is lower than the allowable deviation threshold of the equipment's factory-calibrated efficiency, it indicates that there is internal leakage in the sealing component. Based on the comparison results, a decision is made on whether to replace the sealing component. After the full-load performance test is completed, the inverter output frequency is zeroed, and the bypass return valve of the working face control unit 3 is closed to complete the transition from the commissioning state to the standby state.

[0116] S5. Formal large-displacement fracturing operation process.

[0117] S501. Work preparation and request implementation: On-site personnel conduct a final inspection of the sealing quality of the fracturing borehole 62, confirm the safety warning range around the fracturing borehole 62, evacuate all non-essential personnel around the fracturing borehole 62, connect the end interface of the high-pressure pipeline 2 to the fluid inlet of the working face control unit 3, and connect the fluid outlet of the working face control unit 3 to the borehole sealing device 61 of the fracturing borehole 62. After the connection is completed, on-site personnel check the tightness of all high-pressure connections.

[0118] The parameters for this fracturing operation are input through the human-machine interface of the working face control unit 3. The parameters include the target injection flow rate, the design fracturing pressure, and the estimated operation time. The working face control unit 3 sends an operation request signal to the central control center 4. The operation request signal is transmitted to the central control center 4 through the industrial Ethernet ring network 5.

[0119] Upon receiving the operation request signal, the central control center 4 calculates the minimum fluid reserve required for this fracturing operation based on the parameters in the operation request signal. The minimum fluid reserve must meet the continuous injection requirements throughout the entire operation. The formula for calculating the minimum fluid reserve is as follows:

[0120] ;

[0121] In the formula, This indicates the minimum fluid reserve required for this fracturing operation; This indicates the target injection flow rate set in the job request signal; This indicates the estimated job time set in the job request signal; This indicates the safety redundancy factor for preventing accidental liquid loss. This represents the inherent volume required to fill the interior of the high-pressure pipeline 2 with fluid.

[0122] The central control center 4 reads the real-time liquid level sensor data of the large liquid storage tank 13 in the liquid storage chamber, calculates the currently available fracturing base fluid volume in the large liquid storage tank 13 based on the real-time liquid level sensor data, and compares the currently available fracturing base fluid volume with the calculated minimum liquid reserve. If the currently available fracturing base fluid volume is less than the minimum liquid reserve, the central control center 4 automatically opens the valve of the water supply pipeline connected to the large liquid storage tank 13 to replenish the liquid. If the currently available fracturing base fluid volume is greater than the minimum liquid reserve, the central control center 4 sends a ready confirmation signal to the working face control unit 3.

[0123] The centralized control center 4 remotely monitors the stator temperature of the motors of multiple high-power explosion-proof pumps 11, remotely monitors the bearing temperature of multiple high-power explosion-proof pumps 11, confirms that all shut-off valves along the high-pressure pipeline 2 are in the open state, and confirms that all electric control valves along the high-pressure pipeline 2 are in the standby state.

[0124] S502. Implementation of intelligent scheduling and execution: The centralized control center 4 receives the operation request signal sent by the working face control unit 3, parses the target injection flow rate value contained in the operation request signal, calls the rated output flow rate parameters of the high-power explosion-proof pumps stored in the database, and calculates the optimal number of high-power explosion-proof pumps to be activated based on the target injection flow rate value and the rated output flow rate parameters of the high-power explosion-proof pumps. The calculation of the optimal number of pumps aims to maximize the unit's operating efficiency while ensuring the fracturing operation needs. The formula for calculating the optimal number of pumps is as follows:

[0125] ;

[0126] In the formula, This indicates the calculated optimal number of high-power explosion-proof pumps in operation. This represents the round-up operator; This indicates the target injection flow rate value set in the job request signal; This indicates the rated output flow rate parameter of a single high-power explosion-proof pump; This indicates the optimal efficiency load factor for a high-power explosion-proof pump.

[0127] The centralized control center 4 selects high-power explosion-proof pumps to perform specific tasks based on the calculated optimal number of pumps. The selection strategy prioritizes high-power explosion-proof pumps with the shortest cumulative operating time. This strategy aims to balance the lifespan of multiple high-power explosion-proof pumps 11. The centralized control center 4 sends a remote start command to the frequency converter corresponding to the selected high-power explosion-proof pump. The frequency converter drives the high-power explosion-proof pump to start and accelerate to the initial set frequency. The initial set frequency is calculated by the centralized control center 4 based on the target injection flow rate. The formula for calculating the initial set frequency is as follows:

[0128] ;

[0129] In the formula, Indicates the initial set frequency of the frequency converter; Indicates the target injection flow rate; This indicates the number of high-power explosion-proof pumps put into operation; This represents the theoretical displacement per stroke of the hydraulic end plunger in a high-power explosion-proof pump. This indicates the overall volumetric efficiency of the fracturing pump station. This indicates the reference power frequency of the high-power explosion-proof pump motor; This represents the time unit conversion constant.

[0130] The centralized control center 4 collects real-time actual flow data from the electromagnetic flowmeter installed at the main outlet of the high-pressure pipeline 2. It compares the actual flow data with the target injection flow rate and uses a PID control algorithm to dynamically adjust the frequency converter's operating frequency based on the comparison result. This dynamic adjustment of the operating frequency ensures a continuous and stable output of fracturing fluid flow. The control center 4 also monitors the pipeline pressure data of the high-pressure pipeline 2 in real time. When the pipeline pressure data approaches the set safe pressure threshold, the control center 4 automatically reduces the frequency converter's operating frequency. This reduction in operating frequency limits the overall pressure from continuing to rise. The control center 4 also uploads the real-time operating status data of the high-power explosion-proof pump to the ground remote monitoring platform. This real-time operating status data includes motor speed, motor current, bearing temperature, and pump body vibration amplitude.

[0131] S503. Real-time monitoring and dynamic adjustment: The centralized control center 4 collects the real-time pressure value of the high-pressure pipeline 2 at a millisecond sampling frequency through a high-precision pressure sensor, and simultaneously collects the real-time injection flow value of the fracturing base fluid through an electromagnetic flow meter. The real-time pressure value and the real-time injection flow value are plotted into a fracturing operation curve, and the operators monitor the changing trend of the fracturing operation curve through a large screen display.

[0132] The centralized control center 4 calculates the instantaneous output power of the pump station based on real-time pressure and injection flow rates. This calculation is used to prevent overload shutdown of multiple high-power explosion-proof pumps 11 during sudden pressure changes. The formula for calculating the instantaneous output power is as follows:

[0133] ;

[0134] In the formula, This indicates the instantaneous output power of the pumping station; This indicates the real-time pressure value collected by a high-precision pressure sensor. This indicates the real-time injection flow rate value collected by the electromagnetic flowmeter; This represents the unit conversion constant used in hydraulic power calculations. This indicates the mechanical efficiency of the power transmission components of a high-power explosion-proof pump.

[0135] The centralized control center 4 compares the calculated instantaneous output power with the rated power threshold of the whole machine. When the instantaneous output power exceeds the preset rated power threshold, the centralized control center 4 automatically sends a frequency reduction command to the frequency converter. The frequency reduction command reduces the speed of the high-power explosion-proof pump motor. The speed reduction reduces the real-time injection flow rate, and the reduction of the real-time injection flow rate keeps the instantaneous output power within a safe range.

[0136] The centralized control center 4 monitors the vibration frequency data of the high-power explosion-proof pump body in real time. It analyzes the vibration frequency data using a fast Fourier transform algorithm. When the vibration amplitude of a specific frequency band exceeds the fault warning threshold, the centralized control center 4 determines that the corresponding high-power explosion-proof pump has a mechanical failure risk. It immediately stops the high-power explosion-proof pump with mechanical failure risk and automatically increases the output frequency of the remaining high-power explosion-proof pumps that are operating normally. The increase in output frequency compensates for the flow loss caused by the shutdown. The flow compensation operation ensures that the target injection flow rate of the fracturing operation is continuously met.

[0137] S504, Operation Switching and Parallel Operation: When the fracturing operation of the first fracturing borehole 62 is completed, the working face control unit 3 automatically closes the electric control valve at the fluid outlet and simultaneously opens the bypass return valve. The flow direction of the fracturing base fluid changes, returning to the bottom water tank via the bypass return valve. The centralized control center 4 detects the changes in flow rate and pressure and controls the high-power explosion-proof pump to maintain a low-speed operation. The low-speed operation keeps the high-pressure pipeline 2 full of liquid and has a certain basic pressure. The basic pressure prevents air from entering the pipeline network. The switching method that does not require a complete shutdown shortens the process conversion time between different working faces.

[0138] While the first fracturing borehole 62 operation is still ongoing, the central control center 4 receives a concurrent operation request from the second fracturing borehole 62 and initiates a parallel operation load assessment program. This program calculates the total flow load rate, which is used to determine whether the current pump station capacity is sufficient to support multiple simultaneous fracturing operations. The formula for calculating the total flow load rate is as follows:

[0139] ;

[0140] In the formula, Indicates the total flow load factor; This indicates the total number of fracturing boreholes (62) currently requesting parallel operations; Indicates the first The target injection flow rate requested for each fracturing borehole 62; This indicates the total number of high-power explosion-proof pumps currently in use at the underground central pump station 1. This indicates the rated output flow rate of a single high-power explosion-proof pump.

[0141] The centralized control center 4 compares the calculated total flow load rate with the overall maximum safe load threshold. If the total flow load rate is less than or equal to the preset maximum safe load threshold, the centralized control center 4 generates a parallel operation permit instruction. The parallel operation permit instruction is sent to the working face control unit 3 corresponding to the second fracturing borehole 62. The centralized control center 4 automatically increases the number of high-power explosion-proof pumps in operation according to the new total flow demand. Increasing the number of high-power explosion-proof pumps in operation ensures that all parallel operation faces receive sufficient fluid supply.

[0142] If the total flow load rate is greater than the preset maximum safe load threshold, the centralized control center 4 will place the concurrent operation requests into the waiting queue. The waiting queue is sorted according to the operation priority level. When the operation of the first fracturing borehole 62 is completed and the operation capacity is released, the centralized control center 4 will automatically extract the operation request from the waiting queue and start execution. The intelligent scheduling mechanism realizes the maximum utilization of the output capacity of the downhole central pump station 1.

[0143] S6. Maintenance and Data Feedback Optimization: The centralized control center 4 establishes a full lifecycle database for high-power explosion-proof pumps. This database records the cumulative operating time of each pump. The centralized control center 4 reads vibration intensity data from vibration sensors and bearing temperature data from temperature sensors in real time. A multi-source data fusion algorithm is used to calculate the equipment health degradation index of the high-power explosion-proof pumps. This index quantifies the real-time wear and tear and potential failure risks of the equipment. The formula for calculating the equipment health degradation index is as follows:

[0144] ;

[0145] In the formula, This indicates the equipment health degradation index for high-power explosion-proof pumps; The weighting coefficient represents the cumulative running time; This indicates the cumulative operating time of the high-power explosion-proof pump since the last maintenance. This indicates the rated service life of the core components of a high-power explosion-proof pump. Weighting coefficients representing vibration intensity; This indicates the average vibration amplitude of a high-power explosion-proof pump during its most recent operating cycle. This indicates the maximum permissible safe vibration amplitude for a high-power explosion-proof pump; Weighting coefficients representing bearing temperature; This indicates the average bearing temperature of the high-power explosion-proof pump during the most recent operating cycle. This indicates the maximum permissible bearing operating temperature for high-power explosion-proof pumps.

[0146] The centralized control center 4 compares the calculated equipment health degradation index with the preset maintenance alarm threshold. If the equipment health degradation index exceeds the maintenance alarm threshold, the centralized control center 4 automatically generates a preventive maintenance work order. The preventive maintenance work order is sent to the human-machine interface of the explosion-proof industrial computer through the industrial Ethernet ring network 5. The maintenance personnel perform maintenance on the high-power explosion-proof pump according to the contents of the preventive maintenance work order. The maintenance content includes replacing the hydraulic end sealing components and lubricating the power end. After completing the maintenance work, the maintenance personnel reset the cumulative running time through the explosion-proof industrial computer. Resetting the cumulative running time ensures that the equipment health degradation index is calculated accurately for the next cycle.

[0147] The centralized control center 4 extracts all operational data for this fracturing operation from the historical database. This data includes real-time pressure values ​​of the high-pressure pipeline 2, real-time injection flow rates of the fracturing base fluid, and real-time input current values ​​of multiple high-power explosion-proof pumps 11. The centralized control center 4 calculates the overall energy efficiency ratio of this fracturing operation. The overall energy efficiency ratio quantifies the energy conversion efficiency of electrical energy into hydraulic energy. The formula for calculating the overall energy efficiency ratio is as follows:

[0148] ;

[0149] In the formula, This indicates the overall energy efficiency ratio of this fracturing operation; This indicates the total number of sampling points during this fracturing operation; Indicates the first The outlet pressure values ​​of high-pressure pipeline 2 at each sampling point at any given time; Indicates the first The total injection flow rate of fracturing base fluid at each sampling point; This indicates the sampling time interval of the data acquisition module; This indicates the line voltage value of the underground power grid; Indicates the first The sum of the input current of the high-power explosion-proof pump under all operating conditions at each sampling point; This indicates the power factor of a high-power explosion-proof pump motor. This represents the percentage conversion constant.

[0150] Central control center 4 compares the calculated overall energy efficiency ratio with the historical best energy efficiency ratio stored in the database. If the overall energy efficiency ratio is lower than the historical best energy efficiency ratio, central control center 4 initiates a parameter optimization algorithm. The parameter optimization algorithm calculates a control strategy correction factor, which is used to correct the scheduling strategy of the high-power explosion-proof pump in the next fracturing operation. The calculation formula for the control strategy correction factor is as follows:

[0151] ;

[0152] In the formula, This represents the updated control strategy correction factor; This indicates the control strategy correction factor used in this fracturing operation; The learning rate coefficient represents the parameter optimization algorithm. This indicates the best historical energy efficiency ratio; This indicates the overall energy efficiency ratio of this fracturing operation.

[0153] The centralized control center 4 stores the updated control strategy correction factor into the control logic parameter library. The updated control strategy correction factor will be used to calculate the optimal number of high-power explosion-proof pumps in the next operation request response. The centralized control center 4 generates a fracturing operation energy efficiency analysis report and uploads the fracturing operation energy efficiency analysis report to the ground remote monitoring platform through the industrial Ethernet ring network 5. The data closed-loop mechanism realizes continuous iterative optimization of the operation economy.

[0154] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A centralized, high-capacity hydraulic fracturing system for underground coal mines, characterized in that: This includes an underground central pump station, a high-pressure pipeline network, multiple working face control units, and a centralized control center; The underground central pump station is located in a group of dedicated chambers near the main mining area or the bottom of the well. The group of dedicated chambers includes a main pump room, a power distribution chamber, a control chamber, and a liquid storage chamber. The underground central pump station includes multiple high-power explosion-proof pumps installed in the main pump room. The high-pressure pipeline is laid along the main underground transport roadway of the coal mine. The high-pressure pipeline connects the underground central pump station with each target operation area. The high-pressure pipeline is made of high-strength seamless steel pipes. The multiple working face control units are respectively arranged near the entrance of each mining working face. The inlet of the multiple working face control units is connected to the branch pipe of the high pressure network through a high pressure hose, and the outlet of the multiple working face control units is connected to the fracturing borehole. The centralized control center is located in the control chamber. The centralized control center is connected to the underground central pump station through a communication network. The centralized control center is connected to the high-pressure pipeline network through a communication network. The centralized control center is connected to the multiple working face control units through a communication network. The centralized control center is used to realize the remote centralized supply of power for fracturing operations. The centralized control center establishes a full lifecycle database for high-power explosion-proof pumps, recording the cumulative operating time of each pump. The center also reads vibration intensity data from vibration sensors and bearing temperature data from temperature sensors in real time. A multi-source data fusion algorithm is used to calculate the equipment health degradation index for the multiple high-power explosion-proof pumps. The formula for calculating the equipment health degradation index is as follows: ; In the formula, This indicates the equipment health degradation index for high-power explosion-proof pumps; The weighting coefficient represents the cumulative running time; This indicates the cumulative operating time of the high-power explosion-proof pump since the last maintenance. This indicates the rated service life of the core components of a high-power explosion-proof pump. Weighting coefficients representing vibration intensity; This indicates the average vibration amplitude of a high-power explosion-proof pump during its most recent operating cycle. This indicates the maximum permissible safe vibration amplitude for a high-power explosion-proof pump; Weighting coefficients representing bearing temperature; This represents the average bearing temperature of the high-power explosion-proof pump during the most recent operating cycle; Thax represents the maximum allowable bearing operating temperature of the high-power explosion-proof pump. The centralized control center compares the calculated equipment health degradation index with a preset maintenance alarm threshold. If the equipment health degradation index exceeds the maintenance alarm threshold, the centralized control center automatically generates a preventive maintenance work order. The centralized control center extracts all operating data of this fracturing operation from the historical database, calculates the overall energy efficiency ratio of this fracturing operation, and compares the calculated overall energy efficiency ratio with the historical best energy efficiency ratio stored in the database. If the overall energy efficiency ratio is lower than the historical best energy efficiency ratio, the centralized control center starts a parameter optimization algorithm. The parameter optimization algorithm calculates a control strategy correction factor, and the centralized control center stores the updated control strategy correction factor in the control logic parameter library.

2. The centralized high-capacity hydraulic fracturing system for underground coal mines according to claim 1, characterized in that, The underground central pump station includes a high-pressure distribution valve group. The inlet of the high-pressure distribution valve group is connected to the discharge main of the multiple high-power explosion-proof pumps through a high-pressure rigid pipeline. Each outlet of the high-pressure distribution valve group is connected to the high-pressure pipeline network through a high-pressure union or flange. The downhole central pump station includes a large liquid storage tank, a pre-boost pump set, and an explosion-proof online mixing skid. The large liquid storage tank, the pre-boost pump set, and the explosion-proof online mixing skid are installed in the liquid storage chamber. The large liquid storage tank, the pre-boost pump set, and the explosion-proof online mixing skid are connected to the suction main of the multiple high-power explosion-proof pumps through a liquid supply pipeline. The power distribution chamber is connected to the underground central substation via a high-voltage armored cable. Multiple high-voltage vacuum power distribution devices are installed in the power distribution chamber, and these devices are connected to multiple high-power explosion-proof pumps via high-voltage shielded power cables.

3. The centralized high-capacity hydraulic fracturing system for underground coal mines according to claim 1, characterized in that, The high-pressure pipeline network adopts a ring high-pressure pipeline network route or a branch high-pressure pipeline network route. An automatic air vent valve is installed at the highest point of the high-pressure pipeline network, and a drain valve is installed at the lowest point of the high-pressure pipeline network. The high-pressure pipeline is provided with industrial ring network optical cables or explosion-proof and flame-retardant communication buses, and the industrial ring network optical cables or the explosion-proof and flame-retardant communication buses constitute the communication network. The centralized control center includes an explosion-proof industrial computer, a data acquisition cabinet, and a video monitoring server. The data acquisition cabinet is connected to pressure sensors installed on the high-pressure pipeline via the industrial ring network optical cable or the explosion-proof and flame-retardant communication bus. The data acquisition cabinet is also connected to flow meters installed on the high-pressure pipeline via the industrial ring network optical cable or the explosion-proof and flame-retardant communication bus. Furthermore, the data acquisition cabinet is connected to the frequency converters of the multiple high-power explosion-proof pumps via the industrial ring network optical cable or the explosion-proof and flame-retardant communication bus.

4. The centralized high-capacity hydraulic fracturing system for underground coal mines according to claim 1, characterized in that, The working face control unit is wall-mounted near the working face inlet. The working face control unit integrates an electric control valve or a hydraulic control valve, a bypass return valve, a flow meter, a pressure sensor, and an explosion-proof quick connector. The electric control valve or the hydraulic control valve is connected in series on the internal high-pressure pipeline of the working face control unit; the flow meter is connected in series on the internal high-pressure pipeline of the working face control unit; and the pressure sensor is installed on the internal high-pressure pipeline of the working face control unit. The fluid outlet of the working face control unit is connected to one end of a high-pressure hose via the explosion-proof quick connector, and the other end of the high-pressure hose is connected to the borehole sealer inside the fracturing borehole.

5. The centralized high-capacity hydraulic fracturing system for underground coal mines according to claim 1, characterized in that, The physical location of the underground central pump station remains fixed throughout its entire life cycle. The underground central pump station is located in a geologically stable rock stratum and is close to the underground central substation and the bottom water tank. The communication network adopts an industrial Ethernet ring network. The centralized control center is equipped with a mining explosion-proof core switch. The mining explosion-proof core switch is connected to the mining explosion-proof access switches at the entrances of each mining area through mining flame-retardant optical cables. The mining explosion-proof access switches are cascaded to form a ring network topology through the mining flame-retardant optical cables. The mining explosion-proof access switches are responsible for aggregating the data generated by the working face control unit.

6. A centralized, high-volume hydraulic fracturing operation method for underground coal mines, characterized in that: The centralized, high-capacity hydraulic fracturing system applied to any one of claims 1-5 in a coal mine includes the following steps: S1. Planning and infrastructure construction of underground central pump station: determine the optimal theoretical coordinates of the underground central pump station, carry out roadway development operations in the selected area, determine the laying route of the high-pressure pipeline and lay it, and lay double-circuit high-pressure armored cables and mine flame-retardant optical cables. S2. Installation and integration of core equipment of underground central pump station, including installation of multiple high-power explosion-proof pumps, installation of front booster pump group and working face control unit, and connection of sensors to the centralized control center; S3. Static commissioning and parameter initialization of the underground central pump station, measuring insulation resistance, testing data transmission performance, and configuring the operating parameters of the PID control algorithm inside the programmable logic controller; S4. Dynamic trial operation and performance calibration, including low-pressure cycle trial operation and full-load test mode; S5, Formal Large-Dump Fracturing Operation Process: Step S501 Operation Preparation and Request Implementation; Step S502 Intelligent Scheduling and Execution Implementation; Step S503 Real-Time Monitoring and Dynamic Adjustment; Step S504 Operation Switching and Parallel Operation. S6. Maintenance and data feedback optimization: Establish a full lifecycle database and generate preventive maintenance work orders and fracturing operation energy efficiency analysis reports.

7. The method for centralized high-volume hydraulic fracturing operations in coal mines according to claim 6, characterized in that, The S501 step of work preparation and request implementation specifically includes: The centralized control center receives the operation request signal sent by the working face control unit. The centralized control center calculates the minimum fluid reserve required for this fracturing operation based on the parameters in the operation request signal. The centralized control center reads the real-time liquid level sensor data installed in the large liquid storage tank, calculates the currently available fracturing base fluid volume in the large liquid storage tank based on the real-time liquid level sensor data, and compares the currently available fracturing base fluid volume with the calculated minimum fluid reserve. If the currently available fracturing base fluid volume is less than the minimum fluid reserve, the centralized control center automatically opens the water supply pipeline valve connected to the large liquid storage tank to replenish the fluid. The implementation of intelligent scheduling and execution in step S502 specifically includes: The centralized control center calculates the optimal number of high-power explosion-proof pumps to be turned on based on the target injection flow rate and the rated output flow rate parameters of the multiple high-power explosion-proof pumps. The centralized control center then selects the multiple high-power explosion-proof pumps to perform the specific task based on the calculated optimal number of pumps, prioritizing the pumps with the shortest cumulative operating time.

8. The method for centralized high-volume hydraulic fracturing operations in coal mines according to claim 6, characterized in that, The implementation of intelligent scheduling and execution in step S502 also includes: The centralized control center collects the actual flow data fed back by the electromagnetic flowmeter installed at the main outlet of the high-pressure pipeline in real time, compares the actual flow data with the target injection flow value, and uses a PID control algorithm to dynamically adjust the operating frequency of the frequency converter connected to the multiple high-power explosion-proof pumps based on the difference comparison result. The real-time monitoring and dynamic adjustment of step S503 specifically includes: The centralized control center calculates the instantaneous output power of the pump station based on the real-time pressure value and the real-time injection flow rate value. The centralized control center compares the calculated instantaneous output power with the rated power threshold of the whole machine. When the instantaneous output power exceeds the preset rated power threshold, the centralized control center automatically sends a frequency reduction command to the frequency converter. The centralized control center monitors the vibration frequency data of the multiple high-power explosion-proof pumps in real time. When the vibration amplitude of a specific frequency band exceeds the fault warning threshold, the centralized control center determines that the corresponding multiple high-power explosion-proof pumps have a mechanical failure risk, immediately stops the multiple high-power explosion-proof pumps with mechanical failure risk, and automatically increases the output frequency of the remaining high-power explosion-proof pumps that are operating normally.

9. The method for centralized high-volume hydraulic fracturing operations in coal mines according to claim 6, characterized in that, The S504 step of job switching and parallel operation specifically includes: When the fracturing operation of the first fracturing borehole is completed, the working face control unit automatically closes the electric control valve at the fluid outlet and simultaneously opens the bypass return valve in the fluid circuit. The centralized control center controls the multiple high-power explosion-proof pumps to maintain a low-speed operation. While the first fracturing borehole operation is not yet completed, the centralized control center receives a concurrent operation request from the second fracturing borehole, initiates a parallel operation load assessment program, calculates the total flow load rate, and compares the calculated total flow load rate with the overall maximum safe load threshold. If the total flow load rate is less than or equal to the preset maximum safe load threshold, the centralized control center generates a parallel operation permission instruction, and the centralized control center automatically increases the number of operating high-power explosion-proof pumps according to the new total flow demand; if the total flow load rate is greater than the preset maximum safe load threshold, the centralized control center places the concurrent operation request into a waiting queue.

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