An early warning system and method for internal leakage of hydraulic cylinders in aluminum electrolysis cranes

Abstract

This invention discloses an internal leakage early warning system and method for hydraulic cylinders of aluminum electrolysis overhead cranes, relating to the field of hydraulic cylinder monitoring technology. It includes a pressure acquisition module, a working condition identification module, an internal leakage determination module, and an early warning module. The pressure acquisition module is used to acquire the pressure signal of the rod chamber in real time. The working condition identification module is used to identify whether the hydraulic cylinder is in the pressure-holding state, and outputs a monitoring start signal when the hydraulic cylinder is identified to have entered the pressure-holding state. The internal leakage determination module is electrically connected to the pressure acquisition module and the working condition identification module, and initiates the internal leakage determination process in response to the monitoring start signal. The early warning module is electrically connected to the internal leakage determination module and is used to issue an alarm according to the internal leakage early warning command. This invention provides online monitoring and early warning of internal leakage risks in the hydraulic cylinders of overhead cranes to ensure continuous and stable operation of the equipment.

Description

Technical Field

[0001] This invention relates to the field of hydraulic cylinder monitoring technology, and in particular to an early warning system and method for internal leakage in the hydraulic cylinder of an aluminum electrolysis crane. Background Technology

[0002] The aluminum electrolysis overhead crane is a core production piece in the aluminum electrolysis workshop. Its hydraulic cylinders need to be reset to their upper limit position after each work cycle and maintain pressure for an extended period to ensure positioning accuracy and operational stability. Due to the harsh working conditions in the aluminum electrolysis workshop, including high-temperature radiation, heavy-load impact, dust corrosion, and strong electromagnetic interference, the hydraulic cylinder seals are prone to wear and aging, and the balance valve may also experience internal leakage. This leads to a continuous decrease in pressure in the rod chamber, potentially causing the cylinder to slide down or fail, affecting production safety and continuity. Several solutions have been proposed in existing technologies for detecting internal leakage in hydraulic cylinders.

[0003] Patent CN201920565793.X discloses a detection device for quickly detecting internal leakage in hydraulic cylinders. This device constructs an independent oil circuit through an external hydraulic supply device and a pressure regulating valve, which are respectively connected to the inlet and return cylinder chambers of the hydraulic cylinder. The pressure of the two chambers is obtained by pressure gauges on the inlet and return pipes, and a pressure difference is formed by the pressure regulating valve to observe whether the piston rod moves to determine internal leakage. It has a simple structure, is convenient for detection, and is suitable for rapid troubleshooting in engineering sites.

[0004] Patent CN201220013263.2 discloses a large hydraulic servo cylinder internal leakage detection device, which uses a metering cylinder in conjunction with a displacement sensor to quantitatively detect the internal leakage by measuring the minute displacement changes caused by leakage, and the detection accuracy is high.

[0005] Patent application CN201711153639.3 discloses a method and device for detecting leakage in excavator hydraulic cylinders. The method, under the condition of the excavator as a whole, collects the pressure data of the rodless chamber and the pressure data of the rod chamber of the hydraulic cylinder, as well as the tilt angle data of the corresponding robotic arm. Under the predetermined working conditions of the bucket being loaded, the robotic arm being suspended, the main directional valve being in the neutral position, and the hydraulic pump being closed, the method performs regular matching based on the changes in the pressure difference between the two chambers and the changes in the tilt angle, thereby achieving qualitative diagnosis of internal leakage, external leakage, and combined internal and external leakage without disassembling the hydraulic cylinder.

[0006] While the existing detection solutions described above can detect routine hydraulic cylinder leaks, they still have significant limitations in adapting to the operating conditions of aluminum electrolysis overhead cranes: external pressure testing requires shutdown and offline operation, making online monitoring impossible. Displacement measurement methods can only detect visible leaks and cannot identify early micro-internal leaks. Multi-parameter diagnostics requires specific shutdown conditions, focuses on fault classification rather than early warning, and has a complex structure.

[0007] Therefore, there is an urgent need for a hydraulic cylinder internal leakage early warning system that can adapt to the harsh working conditions of aluminum electrolysis cranes and has early warning capabilities, so as to identify the risk of internal leakage in the cylinder in advance and ensure the continuous and stable operation of the equipment. Summary of the Invention

[0008] To address the shortcomings of the existing technology, this invention provides an early warning system and method for internal leakage of hydraulic cylinders in aluminum electrolysis overhead cranes. This system is used to monitor and provide early warning of internal leakage risks in the hydraulic cylinders of overhead cranes under harsh working conditions such as high temperature, heavy load, high dust levels, and strong electromagnetic interference in aluminum electrolysis workshops, thereby ensuring the continuous and stable operation of the equipment.

[0009] The specific technical solution is as follows: The first aspect discloses an internal leakage early warning system for the hydraulic cylinder of an aluminum electrolysis overhead crane. The hydraulic cylinder of the aluminum electrolysis overhead crane resets to its upper limit and enters a pressure-holding state after each work cycle, including: The pressure acquisition module includes a pressure sensor installed in the rod chamber of the hydraulic cylinder, used to acquire the pressure signal of the rod chamber of the hydraulic cylinder in real time; The working condition identification module is used to identify whether the hydraulic cylinder is in the pressure holding state, and outputs a monitoring start signal when the hydraulic cylinder is detected to have entered the pressure holding state; The internal leakage determination module is electrically connected to the pressure acquisition module and the working condition identification module. The internal leakage determination module responds to the monitoring start signal to start the internal leakage determination process: taking the pressure signal acquired at the beginning of the pressure holding state as the reference pressure value, during the duration of the pressure holding state, continuously calculating the pressure drop value of the currently acquired pressure signal relative to the reference pressure value and the attenuation rate of the pressure signal within a preset time window, and generating an internal leakage early warning command when the pressure drop value reaches a first preset threshold and the attenuation rate reaches a second preset threshold; The early warning module is electrically connected to the internal leakage determination module and is used to issue an alarm according to the internal leakage early warning command.

[0010] Preferably, the operating condition identification module includes at least one of the following identification methods: By acquiring the neutral position signal of the main directional valve of the aluminum electrolysis crane hydraulic system, it can be identified whether the hydraulic cylinder is in the pressure-holding state. By determining whether the fluctuation amplitude of the pressure signal within a preset stability determination time is less than a preset stability threshold, it can be identified whether the hydraulic cylinder is in the pressure holding state.

[0011] Preferably, the internal leakage determination module, while generating the internal leakage early warning command, records the reference pressure value, pressure drop value, decay rate, the start time of the pressure holding state, and the corresponding cylinder number to form an internal leakage event record.

[0012] Preferably, the first preset threshold is 10% of the reference pressure value, the second preset threshold is 0.3 MPa / min; the reference pressure value ranges from 16 MPa to 35 MPa, and the duration of the preset time window is no more than 10 minutes.

[0013] Preferably, if the working condition identification module outputs a signal that the hydraulic cylinder has exited the pressure holding state during the continuous pressure holding state, the internal leakage determination module terminates the current internal leakage determination process and waits for the next monitoring start signal.

[0014] Preferably, the pressure acquisition module includes multiple pressure sensors installed in the rod chambers of multiple hydraulic cylinders of the aluminum electrolysis crane. The internal leakage determination module independently executes the internal leakage determination process for each hydraulic cylinder and identifies the number of the hydraulic cylinder at risk of internal leakage in the internal leakage warning instruction.

[0015] Preferably, the pressure sensor is a high-temperature resistant and impact-resistant pressure sensor with a protection level of not less than IP69 and an anti-electromagnetic radio frequency interference function; the pressure sensor is installed in the pressure detection interface of the rod chamber of the hydraulic cylinder through a threaded sealing connection, and the connection between the pressure sensor and the rod chamber of the hydraulic cylinder is provided with a high-temperature resistant sealing gasket; the pressure sensor is covered with a stainless steel dustproof and impact-resistant protective cover.

[0016] Preferably, the working condition identification module and the internal leakage determination module are integrated into a PLC controller, and the PLC controller is electrically connected to the pressure sensor through a shielded cable; The PLC controller is also connected to a visual interaction module, which is a dustproof touch screen used to display the values ​​of various parameters and supports custom settings for the first preset threshold and the second preset threshold.

[0017] Preferably, it also includes an extended communication module, which is electrically connected to the internal leakage determination module and has an industrial bus interface for communicating with the main control room of the aluminum electrolysis workshop, so as to transmit the pressure signal, internal leakage early warning command and internal leakage event record to the main control room of the aluminum electrolysis workshop.

[0018] The second aspect discloses a method for early warning of internal leakage in the hydraulic cylinder of an aluminum electrolysis crane, including the following steps: Real-time acquisition of pressure signals from the rod chamber of the hydraulic cylinder of the aluminum electrolysis crane; The system identifies whether the hydraulic cylinder is in the upper limit pressure holding state, and when the hydraulic cylinder is identified to have entered the pressure holding state, the internal leakage determination process is initiated by using the pressure signal collected at the start of the pressure holding state as the reference pressure value. During the pressure holding period, the pressure drop of the currently acquired pressure signal relative to the reference pressure value and the attenuation rate of the pressure signal within a preset time window are continuously calculated. When the pressure drop reaches a first preset threshold and the attenuation rate reaches a second preset threshold, an internal leakage warning is triggered. When the hydraulic cylinder exits the pressure-holding state, the current internal leakage determination process is terminated.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention automatically identifies whether the hydraulic cylinder has entered a pressure-holding state through a working condition identification module. Upon confirmation of entering the pressure-holding state, the actual pressure signal collected at that moment is used as a dynamic reference pressure value to initiate an internal leakage judgment process. During the pressure-holding period, the pressure drop value of the current pressure relative to the reference pressure value and the decay rate within a preset time window are continuously calculated. When the pressure drop value reaches a first preset threshold and the decay rate reaches a second preset threshold, an internal leakage early warning command is generated, triggering the early warning module to issue an alarm. Therefore, this invention achieves online monitoring and early warning of internal leakage risks in overhead crane hydraulic cylinders, ensuring the continuous and stable operation of the equipment.

[0020] This invention employs a dynamic benchmark of initial pressure holding combined with dual criteria of pressure drop and decay rate. The dynamic benchmark eliminates judgment biases caused by load and oil pressure fluctuations. The dual criteria can distinguish between true internal leakage pressure drop and normal pressure fluctuations caused by temperature. This allows for early warning of potential internal leakage before a visible cylinder failure occurs, effectively reducing false alarm rates and improving monitoring reliability. Attached Figure Description

[0021] Figure 1 This is a block diagram of the system functions of the present invention; Figure 2 This is a schematic diagram showing the installation and connection of the pressure sensor of the present invention with the hydraulic cylinder of the aluminum electrolysis crane; Figure 3 This is a schematic diagram of the hardware composition and layout of the present invention; Figure 4 This is a schematic diagram of the workflow of the system of the present invention; In the attached diagram, 1-hydraulic cylinder, 2-balance valve, 3-pressure test connector, 4-pressure sensor, 5-controller, and 6-main control room. Detailed Implementation

[0022] The embodiments of the invention will be described in further detail below with reference to the accompanying drawings, so that the objectives, technical solutions and technical effects of the invention will be more clearly presented.

[0023] The internal leakage early warning system for the hydraulic cylinder of the aluminum electrolysis crane proposed in this invention is used to monitor and provide early warning of the risk of internal leakage of the hydraulic cylinder of the crane in the harsh working conditions of high temperature, heavy load, high dust and strong electromagnetic interference in the aluminum electrolysis workshop, so as to ensure the continuous and stable operation of the equipment.

[0024] As the core production equipment in the aluminum electrolysis workshop, the overhead crane mainly undertakes key operations such as anode replacement, shell breaking, slag removal, and insulation material addition. Its hydraulic cylinder, as the core actuator, must be reset to the upper limit and enter a pressure-holding state after each work cycle to maintain equipment positioning accuracy and operational stability. When the hydraulic cylinder is in the upper limit pressure-holding state, the hydraulic oil in the rod chamber is sealed within a closed cavity by the balance valve and piston seal, maintaining a relatively constant pressure within the cavity. This pressure value is typically in the range of 16MPa to 35MPa, depending on the crane load and system setting parameters.

[0025] The working mechanism upon which this invention is based is as follows: When the cylinder seals wear or age due to long-term use, or when the balance valve experiences internal leakage, the high-pressure hydraulic oil in the rod chamber slowly migrates to the low-pressure side through the damaged sealing interface or internal leakage channel, causing the rod chamber pressure to show a continuous decreasing trend. This pressure decrease process precedes the perceptible mechanical slippage or external leakage of the cylinder. If the characteristics of abnormal pressure changes can be captured at this stage, an early warning can be issued before the fault evolves into a production accident. Based on this mechanism, this invention proposes an internal leakage early warning system that can automatically identify pressure-holding conditions, dynamically determine judgment criteria, and adopt a dual-condition joint judgment logic.

[0026] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.

[0027] Reference Figure 1 This is a block diagram of the system functions of the present invention. The internal leakage early warning system for the hydraulic cylinder of the aluminum electrolysis crane disclosed in this invention includes a pressure acquisition module, a working condition identification module, an internal leakage judgment module, and an early warning module. These modules work together to complete a full monitoring chain from pressure signal acquisition, working condition identification, internal leakage judgment to early warning output.

[0028] The pressure acquisition module is used to acquire the pressure signal of the rod chamber of the hydraulic cylinder in real time. The pressure acquisition module is a pressure sensor installed in the rod chamber of the hydraulic cylinder of the aluminum electrolysis crane. The pressure sensor converts the measured pressure into an electrical signal for subsequent processing and analysis.

[0029] The operating condition identification module is used to identify whether the hydraulic cylinder is in a pressure-holding state, and outputs a monitoring start signal when the hydraulic cylinder is detected to have entered the pressure-holding state. The operating condition identification module automatically determines the start time of the internal leakage judgment, ensuring that the system only executes the judgment logic when the cylinder is in a stable pressure-holding state, which can avoid the judgment result being interfered with by drastic pressure changes caused by the normal operation of the cylinder.

[0030] The internal leakage detection module is electrically connected to the pressure acquisition module and the operating condition identification module, receiving pressure signals and monitoring start signals. The internal leakage detection module initiates the internal leakage detection process in response to the monitoring start signal. The internal leakage detection process uses the pressure signal acquired at the start of the pressure holding state as the reference pressure value. During the pressure holding state, it continuously calculates the pressure drop of the currently acquired pressure signal relative to the reference pressure value, as well as the attenuation rate of the pressure signal within a preset time window. When the pressure drop reaches a first preset threshold and the attenuation rate reaches a second preset threshold, an internal leakage warning command is generated. This dual-condition joint detection method can effectively distinguish between rapid, continuous pressure drops caused by internal leakage from seals and balance valves and normal, gradual pressure changes caused by temperature changes and load fluctuations, reducing false alarms and achieving early warning of internal leakage.

[0031] The early warning module is electrically connected to the internal leakage detection module and is used to issue an alarm based on the internal leakage early warning command, so as to remind on-site or remote maintenance personnel to intervene and handle the situation in a timely manner.

[0032] Reference Figure 2 This diagram illustrates the installation and connection of a pressure sensor to the hydraulic cylinder of an aluminum electrolysis overhead crane. The existing hydraulic cylinder 1 of the aluminum electrolysis overhead crane is equipped with a balance valve 2. The balance valve 2 is used to lock the rod chamber oil circuit when the cylinder is in pressure-holding condition to maintain the piston position. A pressure testing connector 3 is located on the rod chamber side of the hydraulic cylinder 1. This connector 3 is a standard pressure detection interface reserved in the hydraulic system. The pressure sensor 4 is installed at the pressure detection interface of the rod chamber through the pressure testing connector 3, using an M14×1.5 threaded seal connection to ensure no leakage under high-pressure conditions. A high-temperature resistant sealing gasket is installed at the connection point. This high-temperature resistant sealing gasket is made of fluororubber or polytetrafluoroethylene and can withstand the continuous high-temperature radiation in the aluminum electrolysis workshop without sealing failure.

[0033] The pressure sensor 4 is encased in a 316L stainless steel dustproof and shockproof protective cover. This cover can withstand temperatures no lower than 125℃, protecting it from alumina dust, electrolyte dust, and impacts from splashes that may occur during heavy-duty operations. This system uses a pressure sensor specifically designed for aluminum electrolysis overhead cranes, with a protection rating ≥IP69, capable of withstanding high-temperature and high-pressure washing. The medium temperature range is -55℃ to 125℃, able to withstand the instantaneous high temperatures of hydraulic oil under heavy-duty operations. The sensor's operating temperature range is -40℃ to 85℃, suitable for workshop environments of 50℃ to 80℃. It also possesses 10G peak impact resistance in the 20~2000Hz frequency band and 100V / m RF anti-interference capability, effectively resisting strong electromagnetic interference in the workshop and ensuring accurate and stable pressure signal acquisition and transmission. The pressure sensor's acquisition frequency is ≥2Hz, suitable for the 0~40MPa hydraulic cylinder working pressure range, and can acquire the rod chamber pressure in real time and convert it into a 4-20mA standard current signal output.

[0034] Considering that aluminum electrolysis overhead cranes are typically equipped with multiple hydraulic cylinders—for example, the crane lifting mechanism can be equipped with 2 to 4 cylinders, and the shell-breaking mechanism and slag-removing mechanism are also equipped with independent cylinders—the pressure acquisition module accordingly includes multiple pressure sensors 4 installed in the rod chamber of each hydraulic cylinder. Each pressure sensor 4 independently acquires the pressure signal of its corresponding cylinder and transmits it through its own independent shielded cable channel.

[0035] Reference Figure 3 This is a schematic diagram of the hardware composition and layout of the system of the present invention. The pressure sensor transmits a 4-20mA analog signal to the PLC controller via a shielded cable. The shielding layer of the shielded cable is grounded at a single point on the controller end to effectively suppress electromagnetic coupling interference. The PLC controller is installed in the overhead crane control cabinet, which is lined with stainless steel for corrosion protection and equipped with wear-resistant and high-temperature resistant protection devices to cope with the high temperature radiation in the workshop and possible mechanical impacts.

[0036] The PLC controller uses an industrial-grade PLC, such as the S7-200 SMART G2 PLC slave module, which is equipped with a 6ES7288-3AI08-0AA0 analog input module, supporting simultaneous access of multiple 4-20mA signals. The controller 5 integrates operating condition identification and internal leakage detection functions; that is, the functional logic of the aforementioned operating condition identification and internal leakage detection modules is implemented and integrated into the PLC controller through programming.

[0037] The operating condition identification module is used to automatically determine whether the hydraulic cylinder has entered the upper limit pressure holding state. To achieve reliable identification, at least one of the following two methods can be used.

[0038] The first identification method is to obtain the neutral position signal of the main directional valve in the hydraulic system of the aluminum electrolysis crane. In the crane's hydraulic system, the lifting and lowering movements of the hydraulic cylinders are controlled by the main directional valve. When the main directional valve is in its neutral position, the pressure port, return port, and working port connecting the two chambers of the cylinder are all closed, and the rod-side and rodless chambers of the cylinder are in a locked pressure-holding state. Therefore, by connecting the neutral position detection switch signal of the main directional valve or reading the neutral position status in the control system, it can be directly determined that the cylinder has entered the pressure-holding state.

[0039] The second identification method is based on the characteristics of the pressure signal itself. After the hydraulic cylinder resets to its upper limit, the pressure in the rod chamber undergoes a brief dynamic adjustment process before stabilizing. If, within a preset stabilization judgment period, the fluctuation amplitude of the pressure signal remains less than a preset stabilization threshold, the hydraulic cylinder is deemed to have entered a stable pressure-holding state. Specifically, the stabilization judgment period can be set to 5 to 15 seconds, preferably 8 seconds; the stabilization threshold can be set to 0.1 MPa to 0.5 MPa, preferably 0.2 MPa. Within this judgment period, if the peak-to-peak value of the pressure sensor reading never exceeds 0.4 MPa, the hydraulic cylinder is considered to have established a stable pressure-holding state.

[0040] In practical applications, either the midpoint signal identification method or the pressure stability determination method can be used alone, or a combination of both can be used to balance identification speed and reliability. For example, during the commissioning phase or when obtaining a midpoint signal is inconvenient, the pressure stability determination method can be used first; when a midpoint signal is available, it can be used as the primary criterion, supplemented by the pressure stability criterion for secondary confirmation, improving identification robustness. When the operating condition identification function confirms that the cylinder has entered the pressure holding state, it outputs a monitoring start signal, triggering the subsequent internal leakage determination process.

[0041] In the early warning system for internal leakage detection, upon receiving the monitoring start signal, the initial actual pressure of the hydraulic cylinder during a single pressure holding cycle is used as the dynamic reference pressure, ranging from 16MPa to 35MPa, replacing the traditional manually fixed threshold. The reference pressure value is adaptively updated according to the single pressure holding condition, eliminating judgment deviations caused by load, oil temperature, and system pressure fluctuations, and improving the consistency and accuracy of judgment.

[0042] During the pressure holding period, the internal leakage detection function continuously performs the following calculations and comparisons: First, calculate the pressure drop of the current pressure signal relative to the reference pressure value, which is the difference between the reference pressure value and the current pressure value. Second, calculate the attenuation rate of the pressure signal within a preset time window, which is the total pressure drop within the preset time window divided by the length of the window. The preset time window is set to be no more than 10 minutes, preferably 5 to 10 minutes, to ensure timely judgment while avoiding false judgments triggered by instantaneous pressure fluctuations.

[0043] When the pressure drop reaches a first preset threshold and the attenuation rate simultaneously reaches a second preset threshold, the internal leakage detection function generates an internal leakage warning command. The first preset threshold is preferably set to 10% of the reference pressure value. Taking a typical reference pressure of 25 MPa as an example, the pressure drop condition is met when the pressure drops by 2.5 MPa (i.e., the current pressure drops to 22.5 MPa). The second preset threshold is preferably set to 0.3 MPa / min, meaning that the attenuation rate condition is met when the pressure drops by an average of no less than 0.3 MPa per minute within a preset time window. Both conditions must be met simultaneously for a warning command to be generated.

[0044] This invention employs a dual-condition joint judgment logic: the pressure drop value represents the cumulative oil loss due to leakage, and the decay rate represents the real-time development degree of the leakage. Single parameter exceeding limits is mostly due to normal disturbances such as temperature drop, pressure contraction, and external vibration. The combined verification of these two factors can accurately distinguish between genuine internal leakage and operational fluctuations, reducing the false alarm rate from the ground up. The 0.3 MPa / min rate threshold can detect early leakage risks before the cylinder experiences mechanical slippage, reserving sufficient maintenance window time.

[0045] The internal leakage detection module generates an internal leakage early warning command and simultaneously performs an event logging operation. Recorded parameters include the baseline pressure value, the pressure drop value triggered by the early warning, the calculated decay rate, the start time of the pressure holding state, and the corresponding cylinder number. These parameters together constitute an internal leakage event record, which is stored in the data storage module. In actual production, the data storage module has a storage capacity of no less than 32GB and supports data retention for periods exceeding one year, with a retention period set to no less than two years. The recorded data supports categorized querying and export based on timestamps, crane numbers, cylinder numbers, and other criteria, providing detailed data for post-event fault tracing, root cause analysis, and equipment health status assessment.

[0046] The internal leakage detection module performs a dual-condition judgment cyclically during the cylinder pressure holding phase. If the operating condition identification module detects that the cylinder has exited the pressure holding state, the main directional valve has disengaged from the neutral position, or the pressure surge exceeds the allowable operating range, the judgment process is immediately terminated and calculated variables such as pressure drop and decay rate are reset to zero. The judgment is restarted based on the new reference pressure after the next pressure holding start signal arrives. This mechanism limits the judgment to operation only during the stable pressure holding window, avoiding false alarms caused by large pressure fluctuations due to cylinder movement.

[0047] When the system is applied to an overhead crane equipped with multiple hydraulic cylinders, the PLC controller independently executes the above-mentioned judgment process for each cylinder. Each cylinder has its own independent reference pressure value, pressure drop value, and decay rate calculation channel, which do not interfere with each other. When a cylinder reaches the warning condition, the generated internal leakage warning command carries the cylinder's identification information, enabling subsequent alarm display and fault location to be accurate to the specific cylinder.

[0048] In one embodiment, the PLC controller is also connected to a visual interaction module, which is a dustproof touchscreen mounted on the control cabinet panel. The touchscreen display shows the pressure values, pressure holding status indicators, and alarm information of each cylinder in real time, and provides a parameter setting interface, allowing authorized maintenance personnel to customize the first and second preset thresholds to meet the personalized needs of different overhead crane models, different process conditions, or different risk control strategies.

[0049] Here, the early warning module includes a high-temperature resistant audible and visual alarm, which is electrically connected to the controller. The audible and visual alarm can be installed in a prominent position inside the overhead crane operating room and next to the control cabinet to ensure that operators and on-site inspectors can detect it in a timely manner. When the controller generates an internal leakage early warning command, the audible and visual alarm will be activated immediately, emitting a high-decibel alarm sound and a high-penetration flashing light, until manual confirmation and reset.

[0050] In one embodiment, an extended communication module is also included, integrated into the control unit where the controller is located. The extended communication module has a reserved industrial bus interface, supporting mainstream industrial communication protocols such as Modbus RTU, Modbus TCP, and Ethernet. Through this module, real-time pressure signals, internal leakage early warning commands, and internal leakage event records can be transmitted to the SCADA system or equipment management platform in the main control room of the aluminum electrolysis workshop, enabling remote centralized monitoring.

[0051] Reference Figure 4 This is a schematic diagram of the system workflow, illustrating the monitoring and early warning process of this system: After the aluminum electrolysis overhead crane completes its current work cycle, the hydraulic cylinder resets to the upper limit position, and the main directional valve returns to the neutral position. Once the operating condition identification module automatically determines that the cylinder has entered the pressure-holding state, the internal leakage determination module uses the pressure value at the start of the pressure-holding process as the reference pressure value to initiate the internal leakage determination procedure.

[0052] During the pressure holding period, the current pressure value is acquired in real time, and the pressure drop and decay rate are continuously calculated. The pressure drop value is compared with a first preset threshold, and the decay rate is compared with a second preset threshold. When both reach or exceed their respective thresholds, an internal leakage early warning command is generated, triggering the audible and visual alarm, recording the internal leakage event data, and optionally uploading the alarm information to the SCADA system in the main control room.

[0053] If, during the pressure holding period, the operating condition identification function detects that the hydraulic cylinder has exited the pressure holding state, the current judgment process will be terminated, and the process will wait for the next pressure holding state to arrive.

[0054] If the hydraulic cylinder remains in a pressure-holding state and no warning is triggered, monitoring will continue until the pressure-holding state ends.

[0055] The following example, using the overhead crane lifting mechanism of an aluminum electrolysis plant as a case study, further illustrates the actual implementation of this system.

[0056] The overhead crane lifting mechanism is equipped with three hydraulic cylinders. The workshop operating temperature ranges from 55℃ to 75℃, and the normal holding pressure of the hydraulic cylinders is approximately 25MPa. Pressure acquisition modules install pressure sensors at the rod-side pressure testing joints of each cylinder. These sensors transmit pressure signals to the controller via shielded cables. The control cabinet is installed within the overhead crane control compartment. The operating condition identification function uses a combination of the main directional valve's neutral position signal and pressure stability criteria to confirm the holding pressure status. The data storage module has a capacity of 32GB, the visual interaction module uses a dustproof touchscreen, and the extended communication module communicates with the workshop's main control room SCADA system via the Modbus TCP protocol.

[0057] After the overhead crane completes its work cycle and resets to the upper limit, the main directional valve returns to the neutral position, and the hydraulic cylinder enters the pressure-holding state. Once the controller confirms the pressure-holding state, it uses the pressure value at the start of the pressure-holding process as the reference pressure value and initiates internal leakage detection. Assuming a hydraulic cylinder's reference pressure is 25.0 MPa, during operation, due to early wear of the piston seal, the rod chamber pressure drops from 25.0 MPa to 22.4 MPa within 8 minutes. The controller calculates a pressure drop of 2.6 MPa, exceeding the reference pressure value by 10%, with a decay rate of 0.325 MPa / min, reaching the 0.3 MPa / min threshold. This triggers an internal leakage warning command, audible and visual alarms, and simultaneously records the reference pressure value, pressure drop value, decay rate, pressure-holding start time, and cylinder number. The alarm information is then uploaded to the main control room. Maintenance personnel locate the faulty cylinder based on the alarm indication and perform repairs before the cylinder experiences significant slippage. After replacing the seal, the system returns to normal.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the patent application of the present invention. All equivalent changes, substitutions or modifications made within the technical spirit and principles indicated by the present invention should be included within the scope of patent protection covered by the present invention.

Claims

1. A hydraulic cylinder internal leakage early warning system for an aluminum electrolysis overhead crane, wherein the hydraulic cylinder of the aluminum electrolysis overhead crane resets to the upper limit position and enters a pressure-holding state after each working cycle, characterized in that, include: The pressure acquisition module includes a pressure sensor installed in the rod chamber of the hydraulic cylinder, used to acquire the pressure signal of the rod chamber of the hydraulic cylinder in real time; The working condition identification module is used to identify whether the hydraulic cylinder is in the pressure holding state, and outputs a monitoring start signal when the hydraulic cylinder is detected to have entered the pressure holding state; The internal leakage determination module is electrically connected to the pressure acquisition module and the working condition identification module. The internal leakage determination module responds to the monitoring start signal to start the internal leakage determination process: taking the pressure signal acquired at the beginning of the pressure holding state as the reference pressure value, during the duration of the pressure holding state, continuously calculating the pressure drop value of the currently acquired pressure signal relative to the reference pressure value and the attenuation rate of the pressure signal within a preset time window, and generating an internal leakage early warning command when the pressure drop value reaches a first preset threshold and the attenuation rate reaches a second preset threshold; The early warning module is electrically connected to the internal leakage determination module and is used to issue an alarm according to the internal leakage early warning command.

2. The early warning system for internal leakage of hydraulic cylinders in aluminum electrolysis cranes according to claim 1, characterized in that: The operating condition identification module includes at least one of the following identification methods: By acquiring the neutral position signal of the main directional valve of the aluminum electrolysis crane hydraulic system, it can be identified whether the hydraulic cylinder is in the pressure-holding state. By determining whether the fluctuation amplitude of the pressure signal within a preset stability determination time is less than a preset stability threshold, it can be identified whether the hydraulic cylinder is in the pressure holding state.

3. The early warning system for internal leakage of hydraulic cylinders in aluminum electrolysis cranes according to claim 1, characterized in that: While generating the internal leakage warning command, the internal leakage determination module records the reference pressure value, pressure drop value, decay rate, the start time of the pressure holding state, and the corresponding cylinder number to form an internal leakage event record.

4. The early warning system for internal leakage of hydraulic cylinders in aluminum electrolysis cranes according to claim 1, characterized in that: The first preset threshold is 10% of the reference pressure value, and the second preset threshold is 0.3 MPa / min; the reference pressure value ranges from 16 MPa to 35 MPa, and the duration of the preset time window is no more than 10 minutes.

5. The early warning system for internal leakage of hydraulic cylinders in aluminum electrolysis cranes according to claim 1, characterized in that: If, during the pressure holding period, the internal leakage determination module outputs a signal from the working condition identification module indicating that the hydraulic cylinder has exited the pressure holding state, the current internal leakage determination process is terminated, and the module waits for the next monitoring start signal.

6. The early warning system for internal leakage of hydraulic cylinders in aluminum electrolysis cranes according to claim 1, characterized in that: The pressure acquisition module includes multiple pressure sensors installed in the rod chambers of multiple hydraulic cylinders of the aluminum electrolysis crane. The internal leakage determination module independently executes the internal leakage determination process for each hydraulic cylinder and identifies the number of the hydraulic cylinder at risk of internal leakage in the internal leakage warning instruction.

7. The early warning system for internal leakage of hydraulic cylinders in aluminum electrolysis cranes according to claim 1, characterized in that: The pressure sensor is a high-temperature resistant and impact-resistant pressure sensor with a protection level of not less than IP69 and anti-electromagnetic radio frequency interference function. The pressure sensor is installed in the pressure detection interface of the rod chamber of the hydraulic cylinder through a threaded sealing connection. The connection between the pressure sensor and the rod chamber of the hydraulic cylinder is provided with a high-temperature resistant sealing gasket. The pressure sensor is covered with a stainless steel dustproof and impact-resistant protective cover.

8. The early warning system for internal leakage of hydraulic cylinders in aluminum electrolysis cranes according to claim 1, characterized in that: The operating condition identification module and the internal leakage determination module are integrated into a PLC controller, and the PLC controller is electrically connected to the pressure sensor through a shielded cable. The PLC controller is also connected to a visual interaction module, which is a dustproof touch screen used to display the values ​​of various parameters and supports custom settings for the first preset threshold and the second preset threshold.

9. The early warning system for internal leakage of hydraulic cylinders in aluminum electrolysis cranes according to claim 1, characterized in that: It also includes an extended communication module, which is electrically connected to the internal leakage determination module and has an industrial bus interface for communicating with the main control room of the aluminum electrolysis workshop, so as to transmit the pressure signal, internal leakage early warning command and internal leakage event record to the main control room of the aluminum electrolysis workshop.

10. A method for early warning of internal leakage in the hydraulic cylinder of an aluminum electrolysis crane, characterized in that: Includes the following steps: Real-time acquisition of pressure signals from the rod chamber of the hydraulic cylinder of the aluminum electrolysis crane; The system identifies whether the hydraulic cylinder is in the upper limit pressure holding state, and when the hydraulic cylinder is identified to have entered the pressure holding state, the pressure signal collected at the start of the pressure holding state is used as the reference pressure value to start the internal leakage determination process. During the pressure holding period, the pressure drop of the currently acquired pressure signal relative to the reference pressure value is continuously calculated, as well as the attenuation rate of the pressure signal within a preset time window; When the pressure drop reaches a first preset threshold and the attenuation rate reaches a second preset threshold, an internal leakage warning is triggered. When the hydraulic cylinder exits the pressure-holding state, the current internal leakage determination process is terminated.

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