Control type dry gas sealing device with independent backpressure cavity

Abstract

The invention relates to the technical field of mechanical sealing, and discloses a control type dry gas sealing device with an independent backpressure cavity, the control type dry gas sealing device is composed of a rotating ring, a static ring and a spring seat, a displacement sensor is arranged at the position (4) on a base, a pressure sensor is arranged at the position (11), and a sealing medium is injected from the position I, passes through a sealing surface between the rotating ring and the static ring and is discharged from the position III; an O-shaped blocking ring is arranged at the clearance fit position of the outer diameter side of the static ring and the sealing seat, an independent backpressure cavity can be formed in the back face of the static ring, and an external auxiliary air source is injected into the backpressure cavity from the position II. A displacement sensor is arranged outside the static ring to detect displacement of the static ring, signal conditioning is carried out through a filter and a signal amplifier, gas input by a proportional valve is adjusted by calculating gas film thickness deviation through a PLC (programmable logic controller) to generate a control quantity and output an analog signal, so that the pressure of a back pressure cavity is adjusted, and then the gas film thickness is adjusted according to changes of a pressure sensor.

Description

Technical Field

[0001] This invention relates to the field of mechanical seal technology, specifically to a controlled dry gas sealing device with an independent back pressure chamber. Background Technology

[0002] Dry gas seals are widely used in shaft end seals of various rotating machinery. In the current context of increasingly widespread high-pressure applications, the conventional seal inlet and the straight-through back of the stationary ring result in excessive back pressure during startup, potentially leading to poor opening. To address this issue, academia and industry have explored various improvements. The gas film thickness and fluid film stiffness of traditional mechanical seals are primarily limited by unit operating conditions, such as speed, medium viscosity, and pressure. These parameters are usually not adjustable, therefore the design process relies heavily on optimizing the seal structure itself to adapt to changing operating conditions. Several improved seal structures have been proposed in the existing technology. For example, Chinese patent CN1272563C discloses a double-helix angle three-dimensional spiral groove end face sealing device, which enhances fluid film stiffness through a special groove design; CN100427816C proposes a spiral groove end face sealing structure composed of a family of angular microgrooves, further optimizing the end face hydrodynamic pressure effect. In addition, CN101776152A proposes an externally pressurized dynamic and static pressure gas lubrication sealing device, which achieves rapid opening of the sealing end face by introducing external high-pressure gas. However, this solution requires a complex high-pressure gas source system and has high control precision requirements.

[0003] Other research focuses on achieving sealing control by adjusting the closing force. For example, Chinese patent CN104179975A uses an electromagnetic loading device to adjust the air film thickness by regulating the current to change the adhesion force between the sealing rings. However, such solutions usually require a dedicated electromagnetic actuator and a matching control system, resulting in a complex structure, high cost, and response performance limited by the characteristics of the electromagnetic components.

[0004] In summary, while existing technologies have improved the opening capability of dry gas seals to some extent, they still suffer from problems such as complex groove structures, high control precision requirements, reliance on external high-pressure gas sources or electromagnetic components for external systems, and insufficient dynamic response. Therefore, there is an urgent need to develop a dry gas sealing device that is simple in structure, responds quickly, and can automatically adjust the gas film thickness. Summary of the Invention

[0005] To address the problems of complex groove shapes, intricate structures, and difficulty in adaptively and precisely adjusting back pressure in traditional dry gas sealing technologies, this invention provides a controllable dry gas sealing device with an independent back pressure chamber. By using a displacement sensor to detect the gas film thickness in real time, combined with signal conditioning, PID algorithm, and proportional valve adjustment, closed-loop precise control of the gas film thickness is achieved.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a controllable dry gas sealing device with an independent back pressure chamber, comprising a rotating ring, a stationary ring, and a spring seat. The rotating ring and the stationary ring form a sealing surface, and the back of the stationary ring and the spring seat form a back pressure chamber. Unlike traditional dry gas sealing structures, the back pressure chamber is a completely closed structure. A pressure sensor is installed inside to detect the pressure in the back pressure chamber, thereby adjusting the back pressure of the stationary ring. A displacement sensor is installed inside the base mounted on the spring seat to detect the gas film thickness in real time and output an analog signal. Both the pressure sensor and the displacement sensor are electrically connected to the sealing auxiliary system. The system uses a displacement sensor to detect the displacement of the stationary ring. When the rotating ring rotates with the spindle, the resulting opening force pushes the stationary ring, and the resulting displacement distance is measured by the displacement sensor. This allows for real-time detection of the gas film thickness and the output of an analog signal. The displacement sensor detects the gas film thickness, and the signal is filtered and amplified by a filter and signal amplifier before being sent to the PLC controller. The PLC controller performs calculations based on the real-time deviation setpoint minus the actual value, calculating the control quantity—the difference between the set initial film thickness and the real-time film thickness. During the startup phase, the difference is positive and relatively large. This difference is transmitted to the air pump, controlling the air pump to adjust and reduce the back pressure to facilitate startup. When the system detects that the actual film thickness is greater than the set target value, it indicates that the gap between the stationary and rotating rings is too large. At this time, the signal output from the displacement sensor is conditioned and sent to the PLC controller. The PLC calculates the positive deviation and outputs a signal to increase the control quantity through a PID algorithm. This signal drives the proportional control valve to open wider, causing the air pump to inject more gas into the independent back pressure chamber, thus increasing the back pressure. The increased back pressure acts on the back of the stationary ring, pushing it axially towards the rotating ring, thereby reducing the gas film thickness and bringing it back to the set range. Conversely, when the actual film thickness is less than the set target value, it indicates that the sealing end face clearance is too small, posing a risk of contact. The PLC calculates a signal to reduce the control quantity based on the negative deviation, controlling the proportional regulating valve to reduce its opening or even vent, thus reducing the back pressure. After the back pressure decreases, the stationary ring moves slightly backward under the action of the end face gas film opening force, thereby increasing the gas film thickness and avoiding dry friction. This adjustment process continuously and adaptively performs under all operating conditions: during startup, the system actively reduces the back pressure to reduce the closing resistance and help the gas film establish quickly; during operation, it maintains stable film thickness through real-time feedback; during shutdown, it moderately increases the back pressure to allow the stationary ring to smoothly adhere to the rotating ring, achieving a soft landing. The entire system is monitored through "detection..." judge implement The closed-loop mechanism of "feedback" enables precise, dynamic, and adaptive control of the air film thickness.

[0007] As a preferred embodiment of the present invention, an O-ring is provided on the outer diameter side of the stationary ring to block the direct correlation between the back pressure of the stationary ring and the sealing pressure.

[0008] As a preferred embodiment of the present invention, the sealing auxiliary system comprises a displacement sensor, a filter, a signal amplifier, a PLC controller, a proportional regulating valve, and an air pump.

[0009] As a preferred embodiment of the present invention, the displacement sensor is either a capacitive or an inductive non-contact sensor.

[0010] As a preferred embodiment of the present invention, the displacement difference signal at the stationary ring is detected by a displacement sensor and transmitted to the PLC controller after passing through a filter and a signal amplifier.

[0011] As a preferred embodiment of the present invention, the pressure sensor is mounted on a spring seat, and a small opening is provided on the right side of the spring seat for the pressure sensor to pass through, so that the pressure sensor connects the pressure of the back pressure chamber to the sealing auxiliary system.

[0012] As a preferred embodiment of the present invention, the sealing auxiliary system consists of a displacement sensor, a filter, a signal amplifier, a PLC controller, a proportional regulating valve, and an air pump connected by wires in sequence.

[0013] Compared with the prior art, the present invention provides a controlled dry gas sealing device with an independent back pressure chamber, which has the following advantages: This invention injects a sealing medium from point I, passes it through the sealing surface between the rotating ring and the stationary ring, and exits from point III. A back pressure chamber is located on the back side of the stationary ring, and gas is injected into the back pressure chamber from point II. A displacement sensor outside the stationary ring detects its displacement. The signal is conditioned by a filter and a signal amplifier, and a PLC calculates the thickness deviation to generate a control quantity. This outputs an analog signal to adjust the gas input through the proportional valve, thereby regulating the pressure in the sealing chamber. Based on changes in the pressure sensor, the gas film thickness is adjusted, further extending the service life of the mechanical seal and broadening its application range. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the workflow of the present invention.

[0015] In the diagram: 1. Rotating ring; 2. Stationary ring; 3. Spring seat; 4. Displacement sensor; 5. Base; 6. Filter; 7. Signal amplifier; 8. PLC controller; 9. Proportional regulating valve; 10. Air pump; 11. Pressure sensor. Detailed Implementation

[0016] The technical solutions of 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.

[0017] Please see Figures 1-2A controlled dry gas sealing device with an independent back pressure chamber comprises a rotating ring 1 mounted on a main shaft, a stationary ring 2 mounted on a spring seat 3, and the spring seat 3 itself. The rotating ring 1 is mounted on the main shaft, and its inner diameter is slightly smaller than the outer diameter of the bushing or shaft. It is "pressed" into its designed position by applying axial force. This method ensures no relative movement between the rotating ring 1 and the shaft, guaranteeing reliable torque transmission. During operation, it rotates with the main shaft, thereby forming an air film. The stationary ring 2 is located on the stationary component, the spring seat 3. The installation method involves first pre-assembling the stationary ring 2, spring, and O-ring into a complete floating assembly within the spring seat 3, ensuring that the stationary ring 2 can move flexibly axially. Then, the entire assembly is aligned and pushed into the sealing chamber, engaging the anti-rotation pin groove. Finally, it is evenly pressed and fixed with a pressure plate. The rotating ring 1 and the stationary ring 2 form a sealing surface. A back pressure chamber is formed between the back of the stationary ring 2 and the spring seat 3. A pressure sensor 11, mounted on the spring seat 3, is installed inside the stationary ring 2 to detect the pressure in the back pressure chamber. The sensor 11 is installed with a small opening on the right side of the spring seat 3, just large enough for it to pass through. This allows the pressure sensor 11 to connect the pressure in the back pressure chamber to the sealing auxiliary system. The sensor transmits a signal to the PLC controller 8, which controls the air pump 10 to supply gas to the back pressure chamber, thereby adjusting the back pressure of the stationary ring 2. A displacement sensor 4 is installed inside the base 5. When the rotating ring 1 rotates with the spindle, the resulting opening force pushes the stationary ring 2. The displacement distance generated is measured by the displacement sensor 4, used to detect the gas film thickness in real time and output an analog signal. Both the pressure sensor 11 and the displacement sensor 4 are electrically connected to the sealing auxiliary system. The sealing auxiliary system consists of a Micro-Epsilon capacitive NCDT 6110 series (capacitive) displacement sensor 4 and a Texas Instruments (TI) sensor installed inside the base 5. The filter 6 of INA333, the signal amplifier 7 of model ADS1278, the PLC controller 8 of model Siemens *S7-1200*, the proportional control valve 9 of model Festo VPPE-series, and the air pump 10 of model KNFNMP 830 B series are connected in sequence by cables. The filter 6 and the signal amplifier 7 are used to filter and amplify the signal of displacement sensor 4. The sealing medium is injected from point I, passes through the sealing surface between rotating ring 1 and stationary ring 2, and is discharged from point III. There is a back pressure chamber on the back of stationary ring 2, and gas is injected into the back pressure chamber from point II.A displacement sensor 4 is located outside the stationary ring 2 to detect its displacement. When the rotating ring 1 rotates with the main shaft, the resulting opening force pushes the stationary ring 2. The displacement distance generated at this time is measured by the displacement sensor 4, thereby detecting the gas film thickness in real time and outputting an analog signal. The signal is then filtered and amplified by the filter 6 and the signal amplifier 7. The PLC controller 8 calculates the thickness deviation to generate a control quantity and outputs an analog signal to adjust the gas input from the air pump 10 through the proportional regulating valve 9, thereby adjusting the back pressure chamber pressure. Based on the changes in the pressure sensor 11, a signal is sent to the PLC controller 8 to detect the closing force pressure, thereby adjusting the gas film thickness, further improving the service life of the mechanical seal and broadening its application range.

[0018] Furthermore, the rotating ring 1 and the stationary ring 2 form a sealing surface with a gap of h. Unlike traditional dry gas seals that regulate opening force, this device completely seals the back of the stationary ring 2, forming a back pressure chamber. A pressure sensor 11 is installed inside to detect the spatial pressure. A signal is transmitted to the PLC controller 8, which controls the air pump 10 to supply gas to the back pressure chamber, thereby adjusting the back pressure of the stationary ring 2 to create an adjustable back pressure. This device can achieve multiple purposes by adjusting the back pressure. For adjusting the balance force, especially during startup when the opening force is small, the PLC controller 8 can send a signal to the air pump 10 to reduce the gas supply, thus lowering the back pressure and facilitating startup. During normal operation, the back pressure is adaptively adjusted for stable operation. During shutdown, the PLC controller 8 sends a signal to the air pump 10 to increase the gas supply, thus increasing the back pressure and facilitating shutdown. The lead wire of displacement sensor 4 is led out from point III. The pressure sensor 11 is located in the back pressure chamber, and its lead wire can be directly led out, so that displacement sensor 4 and pressure sensor 11 are connected to the sealing auxiliary system, thus forming a complete system.

[0019] When rotating ring 1 is first started, the back pressure causes rotating ring 1 and stationary ring 2 to fit tightly together. The back pressure can be changed by reducing the back pressure chamber pressure through air pump 10, thus facilitating startup. When rotating ring 1 and stationary ring 2 separate, the back pressure chamber pressure can be increased to maintain balance and stabilize operation. The same principle applies during shutdown; reducing the rotational speed and opening force adaptively reduces the back pressure, resulting in a more stable shutdown than traditional methods. For dry gas sealing devices in operation, the auxiliary sealing system can be adjusted to change the back pressure, thereby providing feedback control of the film thickness for intelligent adjustment.

[0020] A displacement sensor 4 is located outside the stationary ring 2 to detect the displacement of the stationary ring 2. When the rotating ring 1 rotates with the main shaft, the resulting opening force pushes the stationary ring 2. The displacement distance generated at this time is measured by the displacement sensor 4, thereby detecting the air film thickness in real time and outputting an analog signal. The signal is detected by the displacement sensor 4 and filtered and amplified by the filter 6 and the signal amplifier 7 before being sent to the PLC controller 8. The PLC controller 8 performs calculations and calculates the control quantity based on the real-time deviation set value minus the actual value, that is, the difference between the set initial film thickness and the real-time film thickness. During the start-up phase, the difference is positive and large. The signal is sent to the air pump 10 to control the gas delivered by the air pump 10 to adjust and reduce the back pressure to facilitate start-up. During the operation phase, the air film thickness is stabilized, and the same applies during the shutdown phase.

[0021] Furthermore, the displacement sensor 4 is a capacitive or inductive non-contact sensor with a detection resolution of not less than 0.1μm; the filter 6 and signal amplifier 7 can effectively suppress high-frequency noise; the parameters of the PLC controller 8 can be tuned online to adapt to different working conditions; the response time of the proportional regulating valve 9 is less than 10ms, ensuring the dynamic performance of the system.

[0022] The core innovation of this invention lies in: (1) Independent back pressure: In this invention, an O-ring is provided at the gap fit position between the outer diameter side of the stationary ring and the sealing seat, thereby forming a closed and independent back pressure chamber on the back side of the stationary ring. This back pressure chamber is connected to an external auxiliary gas source through the gas passage interface located at II, and the chamber pressure is actively adjusted by injecting or venting gas into the chamber. This structure forms a brand-new back pressure regulation mechanism that can be independently controlled and responds quickly.

[0023] (2) Closed-loop feedback mechanism: There is a displacement sensor 4 outside the stationary ring 2 to detect the displacement of the stationary ring 2. When the rotating ring 1 rotates with the main shaft, the opening force generated pushes the stationary ring 2. The displacement distance generated at this time is measured by the displacement sensor 4, which directly measures the thickness of the air film, forming a closed-loop control and significantly improving the control accuracy. (3) Adaptive PLC algorithm: Combined with real-time thickness deviation, the control parameters are dynamically adjusted. The PLC controller 8 calculates the control quantity based on the real-time deviation set value minus the actual value, that is, the difference between the set initial film thickness and the real-time film thickness. When the difference is positive and large during the start-up phase, the signal is sent to the air pump 10 to control the gas delivered by the air pump 10 to adjust and reduce the back pressure to facilitate start-up. During the operation phase, the air film thickness is stabilized. The same applies during the shutdown phase. (4) Fast response design: High bandwidth signal conditioning and high speed proportional valve work together. That is, displacement sensor 4 detects the displacement of stationary ring 2, and sends the signal to filter 6 and signal amplifier 7 to filter and amplify the signal and send it to PLC controller 8. By sending the signal to air pump 10, the back pressure is adjusted by controlling the gas delivered by air pump 10. The response time of proportional regulating valve 9 is less than 10ms, realizing millisecond-level response.

[0024] Example 1: Basic Closed-Loop Control Example This embodiment demonstrates the most basic and complete automatic adjustment workflow of the device.

[0025] System initialization: Upon system startup, the "thickness setting module" in PLC controller 8 sets the target air film thickness (h) set The initial back pressure is set to 5μm. The air pump 10 and the proportional regulating valve 9 start working, injecting gas into the back pressure chamber formed by the back of the stationary ring 2 and the spring seat 3 to establish the initial back pressure.

[0026] Signal detection and acquisition: The spindle begins to rotate, driving the rotating ring 1 to rotate, forming an air film between the sealed end faces. The capacitive displacement sensor 4 begins to detect the axial displacement of the stationary ring 2 in real time, and this displacement directly corresponds to the air film thickness (h). actual It outputs a corresponding analog voltage signal.

[0027] Signal conditioning: The signal output from displacement sensor 4 is first sent to filter 6 to filter out high-frequency noise caused by mechanical vibration or electromagnetic interference. Subsequently, the clean signal enters signal amplifier 7 and is amplified to the standard voltage range (e.g., 0-10V) required by the analog input module of PLC controller 8.

[0028] Control quantity calculation (core process): Deviation calculation: PLC controller 8 reads the actual value of the conditioned air film thickness (h) actual ), and the set value (h) set By comparing the thickness (e(t)) with that of a sample of 5 μm, the real-time thickness deviation e(t) = h was calculated. set - h actual (t). PID algorithm calculation: The PLC's built-in PID control program calculates the deviation e(t). The calculation process is as follows: Proportional (P) element: K p * e(t). Generates a control action proportional to the current deviation, responding quickly to the deviation. Integral (M) element: K i * ∫e(t)dt. Integrating the historical deviation is used to eliminate steady-state error and ensure that the gas film thickness remains stable at the set value over the long term. Differential (D) term: K d* de(t) / dt. Adjustment based on the rate of change of the deviation allows for prediction of future deviation trends, thereby suppressing overshoot and improving system stability. Control quantity synthesis: The outputs of the P, M, and D stages are added together to obtain the final control quantity u(t) = K. p e(t) + K i *∫e(t)dt + K d *de(t) / dt.

[0029] Control Output and Execution: The PLC converts the calculated control quantity u(t) into a standard 4-20mA current signal through its analog output module and outputs it to the proportional control valve 9. This signal controls the opening degree of the proportional control valve 9, thereby precisely regulating the gas flow rate and pressure entering the back pressure chamber from the air pump 10.

[0030] Closed-loop regulation: Changes in back pressure will affect the stationary ring 2, influencing its balance with the rotating ring 1, and thus regulating the film thickness (h). actual Meanwhile, pressure sensor 11 monitors back pressure changes, providing additional feedback to the system. This closed-loop process of "detection-comparison-calculation-execution-feedback" continues, ultimately stabilizing the system's gas film thickness within the range of 5 μm ± 0.2 μm.

[0031] The parameters mentioned above have the following meanings: h set Meaning: Preset target air film thickness. This is the ideal air film thickness value that the operator or system program pre-sets to maintain during stable operation of the sealing device. In this embodiment, this value is set to 5 μm.

[0032] h actual (t): Meaning: The actual measured value of the air film thickness at time t. This is the current air film thickness value detected in real time by displacement sensor 4, and after being conditioned by filter 6 and signal amplifier 7, it is input to PLC controller 8. It is a quantity that changes over time.

[0033] e(t): Meaning: Real-time thickness deviation at time t. This is the difference between the target value and the actual measured value, calculated using the formula e(t) = h. set - h actual e(t) is the input signal of the PID controller and is the basis of the entire control logic. e(t) > 0 indicates that the air film is too thin, and e(t) < 0 indicates that the air film is too thick.

[0034] K p Meaning: Proportional gain coefficient. It determines the strength of the controller's output response to the current deviation e(t). K pThe larger the value, the faster the system responds to deviations, but too large a value can lead to system instability and oscillations.

[0035] K i Meaning: Integral gain coefficient. It is used to eliminate the steady-state error (static error) of the system. By accumulating (integrating) historical deviations, even if the current deviation is small, as long as there were historical deviations, the integral term can produce a continuously increasing control effect until the deviation is completely eliminated.

[0036] K d Meaning: Differential gain coefficient. It reflects the controller's sensitivity to the rate of change of deviation (i.e., the speed of deviation change). K d Its function is to predict the future trend of deviation and apply an inhibitory control in advance, thereby effectively reducing the overshoot of the system, improving stability, and making the process stabilize more quickly.

[0037] ∫e(t)dt: Meaning: The integral of the deviation from time 0 to the current time t. It represents the cumulative sum of all deviations throughout history and is the basis for calculating the integral term (M).

[0038] de(t) / dt: Meaning: The first derivative (differential) of the deviation e(t) at time t. In discrete systems, it is approximately the difference between the current sampling deviation and the previous sampling deviation divided by the sampling time. It represents the instantaneous rate of change of the deviation and is the basis for calculating the differential term (D).

[0039] u(t): Meaning: The output control quantity of the PID controller at time t. It is the weighted sum of the outputs of the proportional, integral, and derivative terms, calculated using the formula u(t) = K p * e(t) + Ki * ∫e(t)dt + K d * de(t) / dt. This calculated value is ultimately converted into a 4-20mA analog signal to drive the proportional control valve 9.

[0040] Example 2: Example of using inductive sensors and remote monitoring The core structure and control flow of this embodiment are exactly the same as those of Embodiment 1. The main difference lies in the type of displacement sensor and the data transmission method.

[0041] Change and Reason: The capacitive displacement sensor in Example 1 is replaced with an inductive displacement sensor. This is done based on considerations of adaptability to different working conditions. Capacitive sensors are sensitive to the dielectric constant of the medium; if the sealed medium or the presence of foreign matter in the environment, it may affect the measurement accuracy. Inductive sensors, on the other hand, are not sensitive to non-conductive media and may have better stability and anti-interference capabilities in environments containing oil or specific gases.

[0042] Implementation and Effects: To achieve this change, the capacitive sensor is replaced with an inductive sensor of the same specification in terms of hardware, and the installation interface is adjusted. In signal processing, the parameters of filter 6 may need to be fine-tuned to match the signal characteristics of the inductive sensor. Furthermore, this embodiment adds a wireless transmission module to send the air film thickness data and system status information collected by the PLC controller 8 to a remote monitoring center. This allows operators to monitor the operating status of multiple sealing devices in real time from the central control room, achieving remote and centralized equipment management, facilitating big data analysis and predictive maintenance.

[0043] Example 3: Example with advanced filtering and dual redundancy safety design Based on the previous two embodiments, this embodiment has made two key upgrades for harsh industrial environments with high reliability requirements (such as high vibration, strong electromagnetic interference, or critical equipment where downtime is not allowed).

[0044] Difference 1: Integration of advanced digital filtering algorithms. Working process and principle: In the signal processing unit of PLC controller 8, in addition to the basic filtering of hardware filter 6, a software digital filtering algorithm is also integrated. The system provides multiple selectable modes, such as: Low-pass filtering: further filtering out noise above a specific frequency. Band-stop filtering: specifically filtering out periodic interference of a specific frequency caused by spindle rotation, etc. Kalman filtering: this is an optimal estimation algorithm that not only relies on the current displacement sensor readings but also combines the system's physical model (such as motion state) to optimally estimate the air film thickness, greatly suppressing random noise and providing smoother, more accurate estimates. How it is implemented: These algorithms are embedded in the PLC as software programs, performing secondary processing on the digital sampling signal sent from signal amplifier 7, and then using the "purified" signal for PID calculation, significantly improving control accuracy and stability in high-noise environments.

[0045] Difference 2: Dual Redundancy Design of Proportional Control Valves. "Dual redundancy" is a safety design concept that configures two completely independent, functionally identical systems for critical components (one primary, one backup). In this embodiment, the system is configured with two parallel proportional control valves 9 and an air source (air pump 10). Working Process and Principle: Under normal circumstances, only the primary proportional control valve 9 and air pump 10 operate, undertaking all the regulation tasks, identical to Embodiments 1 and 2. The system is equipped with a fault detection circuit that continuously monitors the operating status of the primary proportional control valve 9 and air pump 10 (such as current, valve core position, air pressure output, etc.). Once a fault is detected in the primary system (such as valve core jamming, coil burnout, air pump failure), the PLC controller 8 immediately issues a switching command. Through a rapid switching valve or electromagnetic switch, the air path and control signal are switched to the backup path in a very short time (milliseconds), with the backup proportional control valve 9 and air pump 10 taking over the operation. How it's achieved and its effects: This design achieves "fail-safe" capability by adding a backup system, meaning that even if the main system fails, the equipment can continue to operate safely without immediate shutdown. It significantly improves the reliability and availability of the entire dry gas seal device, making it particularly suitable for industrial applications with extremely high requirements for production continuity.

[0046] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and alterations can be made to these embodiments without departing from the principles of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A control type dry gas seal device with independent back pressure cavity, which is composed of a rotating ring (1), a stationary ring (2) and a spring seat (3), characterized in that: The rotating ring (1) and the stationary ring (2) form a sealing surface, the gap between the outer diameter side of the stationary ring (2) and the spring seat is provided with an O-shaped barrier ring (11), thereby forming an independent back pressure cavity at the back of the stationary ring (2), the back pressure cavity is surrounded by the back surface of the stationary ring (2), the end surface and the side wall of the spring seat (3), the back pressure cavity is connected with the external auxiliary gas source through the gas path interface (II) for controlling the back pressure of the stationary ring (2), the pressure sensor (12) is arranged in the back pressure cavity for detecting the pressure of the back pressure cavity in real time, the back pressure cavity is connected with the proportional regulating valve (9) and the air pump (10) through the gas path for injecting or discharging gas to adjust the gas pressure in the back pressure cavity, thereby adjusting the back load of the stationary ring (2), the displacement sensor (4) is installed on the spring seat (3) for detecting the axial displacement of the stationary ring (2), indirectly reflecting the gas film thickness and outputting an analog signal, the pressure sensor (12) and the displacement sensor (4) are electrically connected with the PLC controller (8) to form a closed-loop control system.

2. The control type dry gas seal device with independent back pressure cavity according to claim 1, characterized in that: The outer diameter side of the stationary ring (2) is provided with an O-shaped barrier ring (11) for blocking the direct correlation between the back pressure of the stationary ring (2) and the sealing pressure.

3. The control type dry gas seal device with independent back pressure cavity according to claim 1, characterized in that: The sealing auxiliary system is composed of the displacement sensor (4), the filter (6), the signal amplifier (7), the PLC controller (8), the proportional regulating valve (9) and the air pump (10).

4. The control type dry gas seal device with independent back pressure cavity according to claim 1, characterized in that: The displacement sensor (4) is one of a capacitive or inductive non-contact sensor.

5. The control type dry gas seal device with independent back pressure cavity according to claim 3, characterized in that: The displacement difference signal at the stationary ring (2) is detected by the displacement sensor (4) and transmitted to the PLC controller (8) through the filter (6) and the signal amplifier (7).

6. The control type dry gas seal with independent back pressure cavity of claim 1, wherein: The pressure sensor (12) is installed on the spring seat (3), a small opening is formed on the right side of the spring seat (3) for the pressure sensor (12) to pass through, so that the pressure sensor (12) connects the pressure of the back pressure cavity with the sealing auxiliary system.

7. The sealing assist system of claim 2, wherein: The sealing auxiliary system is sequentially connected by the displacement sensor (4), the filter (6), the signal amplifier (7), the PLC controller (8), the proportional regulating valve (9) and the air pump (10) through wires.

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