A device for testing evaporation loss of shield tail sealing grease

Abstract

The application discloses a kind of shield tail sealing grease evaporation loss testing device, through the sample tray in the device can be rotated in dynamic condition simulates shield grease operating condition, weighing sensor can carry out real-time quality monitoring and feedback to grease sample on sample tray, heater can carry out all-around heating simulation evaporation environment to grease sample on sample tray, and realistically solves the key problems such as low efficiency, poor accuracy, poor working condition reproducibility of existing shield tail sealing grease evaporation loss testing.

Description

Technical Field

[0001] This utility model relates to the technical field of oil performance testing equipment, specifically a shield tail seal oil evaporation loss testing device. Background Technology

[0002] Shield tunneling technology is a primary method for infrastructure construction, including urban rail transit, municipal utility tunnels, and river-crossing and sea-crossing passages. It is widely used in long-distance tunnel excavation projects in complex geological environments. During shield tunneling, to ensure the continuity and airtightness of the cutterhead advance and subsequent lining ring assembly, a shield tail sealing system must be installed at the shield tail to prevent soil media such as mud, mortar, etc., from intruding into the existing tunnel structure from the tail of the shield machine.

[0003] The shield tail sealing system typically consists of a wire brush, an elastic retaining ring, and sealing grease. The sealing grease (shield tail grease) is the key functional material, acting directly on the gap between the shield tail and the tunnel lining segments. It provides long-term sealing, waterproofing, and lubrication under complex mechanical and thermal environments, and its performance plays a decisive role in the safety of shield tunneling and the effectiveness of the sealing system. Among these, the volatility (evaporation stability) of the grease is one of the core indicators for evaluating its high-temperature durability and sealing continuity. Under conditions of high temperature, high shear, and continuous motion, low-molecular-weight components may volatilize or decompose, leading to grease quality loss, decreased consistency, and reduced sealing capacity, which can then cause engineering accidents such as leakage and mud / water intrusion.

[0004] Currently, domestic and international testing methods for the volatility of oils and fats mainly rely on standards such as ASTM D972 and DIN 51808, employing a static constant-temperature oven method to heat the oils and fats, weigh them, and calculate the mass loss rate. However, these methods have significant limitations: Lack of operating condition simulation capability: Traditional testing devices are mostly static heating environments, which cannot simulate the temperature rise and shear effects caused by factors such as rotational friction in actual operation of the shield tail grease, resulting in deviations between the test results and actual operating conditions.

[0005] Uneven heating of samples: Traditional heat sources are mostly single-sided heating or natural convection modes. Uneven heating leads to inconsistent volatilization rates, affecting the reproducibility and accuracy of the test.

[0006] Data acquisition lag: Most existing testing devices can only weigh the oil before and after the test, and cannot monitor the dynamic changes in the mass of the oil during the heating process in real time, nor can they obtain the trend of the rate of change of oil evaporation, which affects the judgment of its thermal stability and lifespan.

[0007] Low testing efficiency and excessive manual intervention: Existing methods have cumbersome operation procedures and low automation. When conducting comparative analysis of multiple oil samples, they lack parallel testing capabilities and fine control methods.

[0008] Therefore, to address the aforementioned issues, it is essential to develop an evaporation loss testing device that can dynamically simulate the shield tunneling operating environment, achieve uniform heating of the grease, and possess real-time quality monitoring capabilities. This would allow for a more accurate assessment of the grease's performance under high temperature and dynamic operating conditions, providing a more scientific basis for grease formulation optimization, shield tunneling selection, and engineering risk assessment. Summary of the Invention

[0009] The purpose of this invention is to provide a shield tail sealing grease evaporation loss testing device, which can simulate the shield grease operation under dynamic conditions, achieve uniform heating of the grease sample through a heater, and has a real-time quality monitoring function, thus solving the problems in the prior art.

[0010] The technical solution adopted by this utility model to solve its technical problem is as follows: a shield tail sealing grease evaporation loss testing device, including a test chamber, a drive motor installed on the test chamber, a vertically arranged central shaft on the output shaft of the drive motor, a sample tray installed at one end of the central shaft extending into the test chamber, the rotation of the central shaft can drive the sample tray to rotate synchronously, a weighing sensor is also installed at the bottom of the sample tray, the weighing sensor can measure the weight of the sample tray, heaters are installed on the side walls inside the test chamber, the heaters can heat the grease on the sample tray, an openable and closable insulated door is installed on the front side of the test chamber, the insulated door is equipped with a heat-resistant glass window, a control panel, a temperature control button and a rotation control button are installed on one side of the test chamber, an expansion interface and a power supply are installed on the rear side of the test chamber, the temperature control button, the rotation control button, the drive motor and the weighing sensor are all connected to the control panel through control lines. The heater is a hot air heating assembly, each including a high-temperature resistant ceramic shell. A hot air nozzle is installed on one side of the high-temperature resistant ceramic shell, and a connected internal hot air duct is installed on the other side. A thermocouple and a temperature control module are also installed on the high-temperature resistant ceramic shell, with the temperature control module connected to the control panel via control circuitry. Corresponding to the position of each hot air heating assembly, a connecting seat is installed on the inner wall of the test chamber. A universal joint and an electric push rod are installed between the connecting seat and the high-temperature resistant ceramic shell. The two ends of the electric push rod are hinged to the connecting seat and the high-temperature resistant ceramic shell, respectively. The extension and retraction of the electric push rod can adjust the position of the hot air nozzle relative to the sample tray. A blower is located on one side of the test chamber, and several connected external hot air ducts are installed at the blower's outlet. Each external hot air duct is connected to a corresponding internal hot air duct. The load cell is mounted at the bottom of the central shaft. A first permanent magnet ring is provided on the upper surface of the load cell. A second permanent magnet ring is connected to the bottom of the sample tray through a viscous damping layer. The first and second permanent magnet rings are arranged with the same polarity opposite each other. A sleeve that mates with the central shaft is provided at the center of the sample tray. Both the sleeve and the central shaft have matching keyways, and positioning keys are installed in the keyways. The keyway in the sleeve is longer than the keyway on the central shaft. A detachable limiting ring is bolted to the top surface of the sleeve, which limits the height position of the sample tray on the central shaft. An encoder is provided on the outer periphery of the load cell. A cavity is provided inside the central shaft. A PLC integrated sensor is mounted on the drive motor. The PLC integrated sensor contains a temperature sensor module and a gravity sensor module. The control circuits of the load cell and encoder pass through the cavity of the central shaft and are connected to the gravity sensor module. The control circuit of the heater is connected to the temperature sensor module. The PLC integrated sensor is connected to the control panel through control circuitry. The test chamber has a multi-layer composite structure, including an inner high-temperature ceramic fiber insulation layer, a middle stainless steel support plate, and an outer cold-rolled steel plate shell.The bottom of the sample tray is equipped with several counterweights arranged in a circle, and the test box at the bottom of the sample tray is also equipped with a detachable anti-falling tray.

[0011] The positive effects of this utility model are as follows: The purpose of this utility model is to provide a shield tail sealing grease evaporation loss testing device. The device uses a rotatable sample tray to simulate the shield grease operation under dynamic conditions. The weighing sensor can monitor and provide feedback on the quality of the grease sample on the sample tray in real time. The heater can heat the grease sample on the sample tray from all directions to simulate the evaporation environment. This device effectively solves the key problems of low efficiency, poor accuracy, and poor reproducibility of the shield tail sealing grease evaporation loss test in the prior art.

[0012] Compared to traditional front and rear weighing methods, this device provides more continuous and accurate data, precisely reflecting the evaporation trend and instantaneous evaporation rate of grease at different heating times, with a lower overall measurement error rate. It effectively simulates the dynamic shearing and centrifugal disturbance of the grease caused by the rotation of the tunnel boring machine's main shaft, making the test conditions closer to actual engineering conditions. The arrangement of the heaters can improve the localized overheating or uneven heat distribution of the grease caused by traditional single-point heating, further reducing test errors and meeting the needs of laboratory research and engineering quality control. The more accurate grease evaporation loss rate data obtained through this device can be used to: optimize the tail grease formulation (such as high-temperature stability additives); guide the selection of sealing materials in different temperature zones; build an industry database of grease volatility performance; and formulate more reasonable grease replenishment cycles and selection standards for engineering projects. This device not only improves the accuracy, repeatability, and efficiency of testing, but also provides reliable support for the research and development, performance evaluation, and quality control of tunnel boring machine sealing grease products. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the structure of this utility model; Figure 2 This is a rear view of the present invention; Figure 3 This is a diagram showing the status of the insulated door after it has been turned on; Figure 4 yes Figure 1 A side sectional view; Figure 5 This is a schematic diagram of the structure of the heater, which is a hot air heating component; Figure 6 This is a schematic diagram of the structure in which the sample tray and weighing sensor are mounted at the bottom of the central shaft; Figure 7 yes Figure 6 Half-section view of the middle structure; Figure 8 This is a simplified schematic diagram of the viscous damping layer. Detailed Implementation

[0014] The shield tail sealing grease evaporation loss testing device described in this utility model, such as Figure 1-4 As shown, the test chamber 1 is equipped with a drive motor 2. The output shaft of the drive motor 2 is provided with a vertically arranged central shaft 3. A sample tray 4 is installed at one end of the central shaft 3 that extends into the test chamber 1. The sample tray 4 is used to place the sealing grease to be tested. The rotation of the central shaft 3 can drive the sample tray 4 to rotate synchronously to simulate the rotation of the sealing grease inside the tunnel boring machine.

[0015] A weighing sensor 5 is also installed at the bottom of the sample tray 4. The weighing sensor 5 can measure the weight of the sample tray 4. That is, during the process of rotating the sample tray 4 to simulate actual working conditions, the weight of the grease remaining on the sample tray 4 can be measured in real time by the weighing sensor 5. Heaters are installed on the side walls inside the test chamber 1. The heaters can heat the grease on the sample tray 4. Compared with the traditional single-point heating method, it can provide all-round heating coverage for the grease to be tested, and more accurately simulate the heating conditions under actual working conditions.

[0016] The weighing sensor 5 may include a weighing module and an A / D conversion module. The weighing module can be an existing Mettler Toledo sensor with an accuracy of 0.001g and a maximum capacity of 300g. The A / D conversion module can use a 24-bit high-precision ADC chip, such as the ADS1232, to convert the weighing analog signal into a digital signal and output it. The heater can be an existing infrared heater, electric heating plate heater, fan circulation heater, or electromagnetic induction heater, with the aim of uniformly heating the test grease on the sample tray 4.

[0017] In the shield-tail sealed grease evaporation loss testing device: it is necessary to monitor the weight change of the grease sample in real time during the heating process. The weighing module outputs a small voltage analog electrical signal; this analog signal is converted into a digital signal by a high-precision A / D conversion module and then sent to the main control chip or host computer system. The higher the conversion accuracy, the more accurate the collected mass change data, thus more realistically reflecting the evaporation rate of the grease. It supports high-frequency real-time acquisition of ≥10Hz, and the data is processed by a filtering algorithm before being transmitted to the host computer system. Unlike the traditional single-point front and rear weighing mode, it can realize real-time continuous measurement of grease mass over time, obtaining highly timely evaporation loss rate and mass change curves.

[0018] Sample tray 4 can be made of rigid aluminum alloy, which has high thermal conductivity and mechanical stability. It is equipped with axial support bearings and radial limiting devices to ensure concentricity and stability at high speeds. The rotation of the sample agitates the grease surface, enhancing heating uniformity. At the same time, it can accelerate the movement and volatilization of grease molecules under heating, simulating the dynamic evaporation process of sealing grease in the shield tunneling environment.

[0019] To facilitate the handling of grease on the sample tray 4, an openable and closable insulated door 6 is installed on the front side of the test chamber 1. When the insulated door 6 is closed, a relatively sealed space is formed inside the test chamber 1, ensuring that the heat inside is fully heated to the grease to be tested. The insulated door 6 is equipped with a heat-resistant glass window 7, allowing the operator to observe the grease inside the test chamber 1 during the test.

[0020] A control panel 8, a temperature control button 9, and a rotation control button 10 are installed on the test chamber 1 on one side of the insulated door 6. An expansion interface 11 and a power supply 12 are installed on the rear side of the test chamber 1. The temperature control button 9, the heater, the rotation control button 10, the drive motor 2, and the weighing sensor 5 are all connected to the control panel 8 through control lines.

[0021] The control panel 8 can be equipped with an LCD touchscreen for inputting test parameters and displaying the current weight, temperature, and rotation speed. Internally, it can house a PLC or STM32 microcontroller chip to coordinate motor drive, temperature control signal acquisition, weighing data acquisition, and data storage. All components can be connected to the signal and control terminals of the main control chip via signal and control lines. The measured data can be transmitted to a host computer or other devices via an external data cable connected to the expansion interface 11. Rotating the temperature control button 9 allows for real-time adjustment of the temperature inside the test chamber 1, while rotating the rotation control button 10 controls the rotation speed of the sample tray 4 and the sealing grease.

[0022] When testing the evaporation loss of the shield tail sealing grease using the shield tail sealing grease evaporation loss testing device described in this utility model, firstly, set the heating temperature, rotation speed, and test duration on the control panel 8. Open the insulated door 6 and place a quantitative grease sample onto the sample tray 4. After the sample is placed, close the insulated door 6, the system starts, the heater heats up to the set value, and the sample tray 4 rotates the sample grease at a uniform speed to simulate the working conditions of the sealing grease inside the tunnel boring machine. During the test, the grease weight change, temperature, and time are recorded in real time, with sampling occurring once every 10 seconds. After heating and rotation are stopped, all test data are saved, analyzed, and an evaporation loss rate curve is exported and generated.

[0023] The following data are from tests conducted using the apparatus described in this invention on conventional mineral-based shield tail sealing grease. The initial sample mass was 5.000 g, the temperature setting was 150°C, the rotation speed was 150 rpm, the heating time was 60 minutes, the remaining mass after evaporation was 3.745 g, and the evaporation loss rate was (5.000 - 3.745) / 5.000 = 25.1%. In a comparative test using a traditional static sample without rotation, the evaporation loss rate was only 17.3% under the same temperature and time. This demonstrates that the rotational operation simulates shear and airflow disturbance, making the grease evaporation loss more closely resemble the real engineering environment.

[0024] Furthermore, in order to ensure that the sample oil can be continuously heated at all angles during rotation, the heater is a hot air heating component. The hot air heating component is arranged around the outer periphery of the sample tray 4, and no less than four sets of hot air heating components can be arranged and evenly distributed in a central stacking manner.

[0025] like Figure 5 As shown, each hot air heating component includes a high-temperature resistant ceramic shell 13. A hot air nozzle 14 is installed on one side of the high-temperature resistant ceramic shell 13, and a connected internal hot air duct 15 is installed on the other side of the high-temperature resistant ceramic shell 13. A thermocouple 16 and a temperature control module 17 are also installed on the high-temperature resistant ceramic shell 13, wherein the temperature control module 17 is connected to the control panel 8 via control lines. The thermocouple 16 can be an existing K-type thermocouple, which can heat the gas transported inside the high-temperature resistant ceramic shell 13. The temperature control module 17 can be an existing PID closed-loop temperature control module, such as the Omron E5C series. The PID module can communicate with the PLC of the controller via an RS485 interface to achieve closed-loop temperature control. The PID closed-loop temperature control module includes three control modes: proportional, integral, and derivative. The combination of these three modes allows the control system to respond quickly while avoiding oscillations and deviations, achieving stable and precise control. The heater output power is adjusted using a PID algorithm to gradually approach and stabilize the temperature within the set value, improving temperature control accuracy within a specified range. Temperature control accuracy: ±0.5°C; temperature can be set from room temperature to 200°C.

[0026] To facilitate adjustment of the spray angle of each hot air heating component onto the sample grease on the sample tray 4, a connecting seat 18 is installed on the inner wall of the test chamber 1 corresponding to the position of each hot air heating component. A universal joint 19 and an electric push rod 20 are installed between the connecting seat 18 and the high-temperature resistant ceramic shell 13. The two ends of the electric push rod 20 are respectively hinged to the connecting seat 18 and the high-temperature resistant ceramic shell 13. The extension and retraction of the electric push rod 20 can adjust the position of the hot air nozzle 14 relative to the sample tray 4.

[0027] To adjust the airflow speed of the hot air from the hot air heating component, a blower 21 is installed on one side of the test chamber 1. Several interconnected external hot air ducts 22 are installed at the outlet of the blower 21, each corresponding to an internal hot air duct 15. The blower 21 has multi-speed adjustable functions, with an airflow range of 0-3 m / s. The spray angle of the hot air can be adjusted between 30° and 60° by extending and retracting the electric push rod 20, based on the different diameters of the oil sample and the target thermal field. A heater can also be installed on the external hot air ducts 22 to heat the blown gas.

[0028] The aforementioned modules can simulate the combined heat and fluid environment created by the advancement of the tunnel boring machine (TBM) during the operation of the shield tail grease under different hot air parameters. Multi-point heating ensures the stability and uniformity of the temperature field, avoiding localized overheating or volatilization distortion of the sample.

[0029] The mounting connection between the load cell 5 and the sample tray 4 allows for both rotation following the central shaft 3 and measurement of the weight of the sample oil on the sample tray 4 via the load cell 5. In scenarios where high dynamic accuracy is not required, a bearing or buffer suspension structure can be installed between the load cell 5 and the sample tray 4. To improve the accuracy of oil weight testing and reduce weighing errors caused by vibration from mechanical friction, such as... Figure 6-8 As shown, the weighing sensor 5 is installed at the bottom of the central shaft 3. A first permanent magnet ring 23 is provided on the upper surface of the weighing sensor 5. A second permanent magnet ring 25 is connected to the bottom of the sample tray 4 through a viscous damping layer 24. The first permanent magnet ring 23 and the second permanent magnet ring 25 are arranged opposite each other with the same polarity to form a magnetic levitation structure, so that the weighing sensor 5 and the sample tray 4 are independent of each other and there is a repulsive force between them, which can effectively reduce the interference of mechanical disturbance on the weight measurement.

[0030] The first permanent magnet ring 23 and the second permanent magnet ring 25 are opposite each other with the same pole, which can provide a low-height equivalent spring without contact to isolate high-frequency vibration. 2-3 mm of silicone or nitrile can be set in the viscous damping layer 24, and rigid vibration isolation springs are arranged at intervals inside to dissipate the remaining energy and suppress the resonance peak of the magnetic spring.

[0031] To enable the sample tray 4 to be mounted on the central shaft 3, a sleeve 26 that mates with the central shaft 3 is provided at the center of the sample tray 4. Both the sleeve 26 and the central shaft 3 are provided with matching keyways 27. A positioning key 28 is installed in the keyway 27. The positioning key 28 allows the central shaft 3 to synchronously drive the sample tray 4 to rotate. The keyway 27 in the sleeve 26 is longer than the keyway 27 on the central shaft 3, which allows the sample tray 4 to be adjusted within a certain range of height for sample oils of different weights.

[0032] A detachable limiting ring 29 is bolted to the top surface of the sleeve 26. The limiting ring 29 can limit the height position of the sample tray 4 on the central shaft 3. When the above structure needs to be installed, firstly, the positioning key 28 is inserted into the keyway 27 of the central shaft 3. The sample tray 4 is installed from the bottom position of the central shaft 3 and moved up to the keyway 27 in the sleeve 26 to cooperate with the positioning key 28. Then, the limiting ring 29 is installed from the upper part of the central shaft 3 and fixedly connected to the sleeve 26. Finally, the weighing sensor 5 with the first permanent magnet ring 23 is installed at the bottom of the central shaft 3.

[0033] Furthermore, the outer periphery of the weighing sensor 5 may be provided with an encoder 30, and a cavity is opened in the central shaft 3. A PLC integrated sensor 31 is installed on the drive motor 2. The PLC integrated sensor 31 is provided with a temperature sensor module and a gravity sensor module. The control lines of the weighing sensor 5 and the encoder 30 are both passed through the cavity of the central shaft 3 and connected to the gravity sensor module. The control line of the heater is connected to the temperature sensor module. The PLC integrated sensor 31 is connected to the control panel 8 through the control line.

[0034] The encoder 30 can be used to provide feedback on the rotational speed or angle of the load cell 5 during its rotation, enabling the load cell 5 to achieve dynamic weighing even under rotational load. The cavity inside the central shaft 3 not only provides an installation channel for the pipeline but also, to some extent, avoids the pulling interference of pipeline sway on the load cell 5.

[0035] The advantages of the magnetic levitation structure composed of the first permanent magnet ring 23 and the second permanent magnet ring 25 are: it can simultaneously meet the requirements of 0-300rpm rotational operation simulation and high-precision real-time weighing with a resolution of 0.001g and an error of ≤0.4%. Ordinary bearings, due to their mechanical contact characteristics, will generate high-frequency impact vibration, frictional heat, and speed fluctuations. They will also suffer from poor long-term stability due to wear, directly causing the real-time weighing and operation simulation functions to fail. Magnetic levitation, on the other hand, can cut off vibration transmission through a non-contact magnetic levitation tray combined with a self-rotating bearing. With the addition of a viscous damping layer for further vibration reduction, there is no additional temperature rise or speed fluctuation due to the absence of friction, and the absence of mechanical wear ensures long-term accuracy, thus simultaneously meeting the requirements of dynamic operation simulation and high-precision weighing.

[0036] Furthermore, to ensure the thermal insulation performance of the test chamber 1, the shell of the test chamber 1 has a multi-layer composite structure, including an inner high-temperature ceramic fiber insulation layer, a middle stainless steel support plate, and an outer cold-rolled steel plate shell. A lighting fixture can also be installed corresponding to the position of the heat-resistant glass window 7 to provide a bright field of vision for observation. A mechanically interlocked door opening structure can also be provided on the insulated door 6, automatically cutting off power after the insulated door 6 is opened to ensure operational safety. The test chamber 1 can be equipped with multiple temperature sensors; if a set threshold is exceeded, heating will stop and an alarm will sound, providing thermal protection and structural protection during operation, preventing the leakage of high-temperature hot air, and ensuring the safety of personnel and equipment.

[0037] Furthermore, to ensure the rotational stability of the sample tray 4, several counterweights 32 are arranged circumferentially at the bottom of the sample tray 4. The grease to be tested is generally in a paste-like, non-fluid state, and the outer periphery of the sample tray 4 has an upwardly protruding folded edge, which effectively prevents the grease from being thrown out of the sample tray 4. To prevent grease from falling and contaminating the test chamber 1 during the grease replacement process after the test, a detachable anti-falling tray 33 is also installed inside the test chamber 1 at the bottom of the sample tray 4.

[0038] The test chamber 1 also has a safety ventilation structure. The internal cavity is used to form a stable and controllable experimental space to prevent heat loss and external interference. The safety ventilation structure is used to automatically depressurize under abnormal temperature or pressure conditions, thereby improving the safety of the test device.

[0039] The device described in this invention can be used for comparative tests of the evaporation performance of various types of shield tail sealing greases under different temperature, wind speed, and rotation speed conditions. It can guide the selection of sealing greases and the evaluation of their suitability for different operating conditions in shield tunneling projects. It can save testing time and labor costs, improve grease usage efficiency, reduce unnecessary waste, enhance the safety and reliability of tunnel construction sealing systems, and indirectly reduce maintenance frequency and failure rate. In summary, this invention not only possesses innovation and practicality in its technical principles and structural design, but also achieves significant technical, economic, and social benefits in industrial applications, and has broad prospects for promotion.

[0040] The technical solution of this utility model is not limited to the scope of the embodiments described herein. All technical contents not described in detail herein are publicly known technologies.

Claims

1. A device for testing the evaporation loss of grease in a shield tail seal, characterized in that: The test chamber includes a test chamber (1), on which a drive motor (2) is installed. A vertically arranged central shaft (3) is provided on the output shaft of the drive motor (2). A sample tray (4) is installed at one end of the central shaft (3) that extends into the test chamber (1). The rotation of the central shaft (3) can drive the sample tray (4) to rotate synchronously. A weighing sensor (5) is also provided at the bottom of the sample tray (4). The weighing sensor (5) can measure the weight of the sample tray (4). Heaters are installed on the side walls inside the test chamber (1). The heaters can remove grease from the sample tray (4). Heating is performed. The front side of the test chamber (1) is equipped with an insulated door (6) that can be opened and closed. The insulated door (6) is equipped with a heat-resistant glass window (7). The test chamber (1) on one side of the insulated door (6) is equipped with a control panel (8), a temperature control button (9) and a rotation control button (10). The rear side of the test chamber (1) is equipped with an expansion interface (11) and a power supply (12). The temperature control button (9), heater, rotation control button (10), drive motor (2) and weighing sensor (5) are all connected to the control panel (8) through control lines.

2. The shield tail sealing grease evaporation loss testing device according to claim 1, characterized in that: The heater is a hot air heating assembly. Each hot air heating assembly includes a high-temperature resistant ceramic shell (13). A hot air nozzle (14) is installed on one side of the high-temperature resistant ceramic shell (13), and an internal hot air duct (15) is installed on the other side of the high-temperature resistant ceramic shell (13). A thermocouple (16) and a temperature control module (17) are also installed on the high-temperature resistant ceramic shell (13). The temperature control module (17) is connected to the control panel (8) through a control line. Corresponding to the position of each hot air heating assembly, a connecting seat (18) is also installed on the inner wall of the test chamber (1). A universal joint (19) and an electric push rod (20) are installed between the connecting seat (18) and the high-temperature resistant ceramic shell (13). The two ends of the electric push rod (20) are respectively hinged to the connecting seat (18) and the high-temperature resistant ceramic shell (13). The extension and retraction of the electric push rod (20) can adjust the position of the hot air nozzle (14) relative to the sample tray (4).

3. The shield tail sealing grease evaporation loss testing device according to claim 2, characterized in that: The test box (1) is equipped with a blower (21) on one side. Several external hot air ducts (22) are connected to each other at the air outlet of the blower (21). Each external hot air duct (22) is connected to an internal hot air duct (15).

4. The shield tail sealing grease evaporation loss testing device according to claim 1, characterized in that: The weighing sensor (5) is installed at the bottom of the central shaft (3). A first permanent magnet ring (23) is provided on the upper surface of the weighing sensor (5). A second permanent magnet ring (25) is connected to the bottom of the sample tray (4) through a viscous damping layer (24). The first permanent magnet ring (23) and the second permanent magnet ring (25) are arranged opposite each other with the same polarity. A sleeve (26) that cooperates with the central shaft (3) is provided at the center of the sample tray (4). Both the sleeve (26) and the central shaft (3) are provided with matching keyways (27). A positioning key (28) is installed in the keyway (27). The keyway (27) in the sleeve (26) is longer than the keyway (27) on the central shaft (3). A detachable limiting ring (29) is installed on the top surface of the sleeve (26) by bolts. The limiting ring (29) can limit the height position of the sample tray (4) on the central shaft (3).

5. The shield tail sealing grease evaporation loss testing device according to claim 4, characterized in that: The weighing sensor (5) is provided with an encoder (30) on its outer periphery and a cavity is provided in the central shaft (3). A PLC integrated sensor (31) is installed on the drive motor (2). The PLC integrated sensor (31) is provided with a temperature sensor module and a gravity sensor module. The control lines of the weighing sensor (5) and the encoder (30) pass through the cavity of the central shaft (3) and are connected to the gravity sensor module. The control line of the heater is connected to the temperature sensor module. The PLC integrated sensor (31) is connected to the control panel (8) through the control line.

6. The shield tail sealing grease evaporation loss testing device according to claim 1, characterized in that: The shell of the test chamber (1) is a multi-layer composite structure, including an inner high-temperature ceramic fiber insulation layer, a middle stainless steel support plate, and an outer cold-rolled steel plate shell.

7. The shield tail sealing grease evaporation loss testing device according to claim 1, characterized in that: The bottom of the sample tray (4) is provided with several counterweights (32) arranged in a circle, and the test box (1) at the bottom of the sample tray (4) is also equipped with a detachable anti-falling tray (33).

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