Method for achieving super-slip of mechanical seal sealing end face

Abstract

The application provides a method for realizing super-slip of a mechanical seal sealing end face, comprising the following steps: S1, determining the limit PcV value of different groups of materials, and selecting the group materials of the static ring and the dynamic ring; S2, performing surface texture treatment on the sealing end face of the static ring and the dynamic ring; S3, relatively rotating the static ring and the dynamic ring, applying a certain end face pressure on the sealing end face, and using water as the sealing lubricating medium to form a stable continuous fluid lubrication film on the sealing end face. According to the limit PcV value of the group materials, the materials of the friction pair can be selected, and the group materials of the static ring and the dynamic ring with superior friction performance can be obtained. The surface texture treatment is performed on the sealing end face of the friction pair, the affinity of the sealing end face to the sealing lubricating medium can be improved, and the stable continuous film can be easily formed. The group materials of the friction pair have a small trend of the friction coefficient with the increase of the end face pressure, the friction coefficient can be small by applying a certain end face pressure on the sealing end face, and thus the super-slip state is realized.

Description

Technical Field

[0001] This invention relates to the field of mechanical seal technology, and more specifically, to a method for achieving super-slippery sealing end faces of mechanical seals. Background Technology

[0002] Mechanical seals are a type of sealing technology for relatively moving mechanical components. They play a vital role in various sectors of the national economy and are widely used. Their main structure consists of a pair of annular components—a friction pair. The relatively stationary component is the stationary ring, and the relatively moving component is the rotating ring. The contact surfaces of the rotating and stationary rings are the sealing surfaces, maintaining a thin liquid film between them. Under axial closing force, the rotating and stationary rings remain in constant floating contact, achieving both sealing and lubrication. Due to factors such as deformation of the sealing surfaces and temperature, the friction state of a mechanical seal constantly changes during operation, typically with a friction coefficient between 0.01 and 0.18. An increased friction coefficient leads to increased power consumption and wear of the friction pair, directly affecting energy efficiency and the service life of the mechanical seal. Therefore, how to reduce the friction coefficient while ensuring sealing performance is a crucial concern for technicians in the sealing industry. Summary of the Invention

[0003] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is how to reduce the friction coefficient of mechanical seals and achieve a super-lubricated state.

[0004] This invention provides a method for achieving super-lubricity in mechanical seals, comprising the following steps:

[0005] S1. Determine the limiting PcV values ​​of different material pairs and select the material pairs of stationary and dynamic rings;

[0006] S2. Apply surface texturing to the sealing end faces of the stationary ring and the rotating ring;

[0007] S3. The stationary ring and the moving ring rotate relative to each other, and a certain end face specific pressure (Pc) is applied to the sealing end face. Water is used as the sealing lubricating medium to form a stable and continuous fluid lubricating film on the sealing end face.

[0008] The limiting PcV value is the product of the end-face specific pressure (Pc) and the average linear velocity (V) of the end face when the seal fails. Different friction pair materials will have different friction states, and thus different limiting PcV values. The pair material with a larger limiting PcV value has better sealing friction performance. Therefore, this invention selects the friction pair material according to the limiting PcV value of the pair material, which can obtain a static ring and dynamic ring pair material with excellent friction performance. Surface texturing of the sealing end face of the friction pair can improve the affinity of the sealing end face to the sealing lubricating medium, making it easier to form a stable continuous film. The friction coefficient of the pair material tends to decrease as the end-face specific pressure increases. Applying a certain end-face specific pressure to the sealing end face can reduce the friction coefficient, thereby achieving a super-lubricated state.

[0009] Furthermore, in step S1, materials with a limiting PcV value greater than 50 MPa·m / s are selected as the materials for the stationary and dynamic rings. A higher limiting PcV value indicates better sealing friction performance of the material, commonly referred to as good assembly performance. Therefore, selecting materials with a high limiting PcV value is beneficial for achieving super-lubricity.

[0010] Furthermore, in step S1, for each pair of materials, at least three sets of specimens are used for testing, and then the average limiting PcV value and standard deviation are calculated, with the standard deviation S ≤ 8. The limiting PcV value test uses multiple sets of specimens, and the standard deviation is controlled to ensure the accuracy of the test results.

[0011] Furthermore, in step S1, the selected pair of materials are reaction-bonded silicon carbide and pressureless sintered silicon carbide. Testing showed that the limiting PcV value of reaction-bonded silicon carbide and pressureless sintered silicon carbide (material code: S / SS) is 196.98 MPa·m / s. These materials also have high thermal conductivity, facilitate the conduction of frictional heat, have low temperature rise, and high mechanical strength. Therefore, they are less affected by force and temperature changes, and exhibit minimal end-face deformation, making them suitable materials for friction pair pairings.

[0012] Furthermore, in step S2, the sealing end face of the stationary ring is machined into a bright surface, and the sealing end face of the rotating ring is machined with densely arranged grooves to form a satin surface.

[0013] Furthermore, in step S2, the groove depth Ry on the sealing end face of the rotating ring is 0.50–1.0 μm, the width Rz is 10.0–20.0 μm, and the average roughness Ra is 0.20–0.32 μm. The finished sealing end face, with one side having a bright finish and the other a satin finish, exhibits good water affinity. The satin finish forms extremely shallow, straight, filamentous grooves with a depth in the micrometer range, which easily store the sealing lubricating medium and form a stable, continuous film, while also providing a sealing function.

[0014] Furthermore, in step S3, the end-face specific pressure Pc applied to the sealing end face is 6.5–8.5 MPa. Applying a higher end-face specific pressure can make the coefficient of friction very small.

[0015] Furthermore, in step S3, the water, the sealing lubricating medium, is kept in circulation. This promptly removes frictional heat, ensuring the stability of the sealing lubricating medium at the sealing end face, thereby achieving super-lubricity.

[0016] Furthermore, in step S3, the temperature of the sealing lubricating medium water is maintained at 67–73°C, and the pressure is maintained at 0.25–0.35 MPa. The water temperature and pressure are controlled to ensure the formation of a stable, continuous fluid lubrication film.

[0017] Furthermore, in step S3, the relative rotational speed between the stationary ring and the rotating ring is maintained at 3000–9000 rpm. The rotational speed of the mechanical seal is adjustable, with a maximum speed of 9000 rpm.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] This invention combines material pairing, surface texture treatment of sealing end face, and end face specific pressure control technology. The mechanical seal designed according to the method of this invention can greatly reduce the friction coefficient of the friction pair, achieve a super-lubricated state, reduce energy consumption, and extend the service life of the mechanical seal and equipment.

[0020] When the technology of this invention is applied to the mechanical seal of a stirred tank, the maintenance period is extended from 3 years to 6 years; when the technology of this invention is applied to the mechanical seal of a cooling pump for electric vehicles, the friction coefficient is reduced and the friction power consumption is greatly reduced, thus extending the service life of electric vehicle batteries. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the sealed cavity of the test device in an embodiment of the present invention;

[0022] Figure 2 This is an external view of the dynamic ring sealing end face in an embodiment of the present invention;

[0023] Figure 3 This is a friction curve diagram of specimen 1 in an embodiment of the present invention;

[0024] Figure 4 This is a friction curve diagram of specimen 2 in an embodiment of the present invention;

[0025] Figure 5 This is a friction curve diagram of specimen 3 in an embodiment of the present invention. Appendix Figure 1 illustrate:

[0027] 1-Upper shaft seal, 2-Upper shaft, 3-Stationary ring clamp, 4-Stationary ring, 5-Rotating ring, 6-Rotating ring clamp, 7-Rotating shaft seal, 8-Rotating shaft. Detailed Implementation

[0028] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter range described in the present invention. Reasonable variations derived therefrom are still within the protection scope of the claims of the present invention.

[0029] It should be noted that the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0030] Embodiments of the present invention provide a method for achieving super-lubricity in mechanical seals, requiring the use of a testing apparatus comprising a sealing cavity, a sealing water station, and a control console. The sealing cavity structure is as follows: Figure 1 As shown, the system includes components such as an upper shaft seal 1, an upper shaft 2, a stationary ring clamp 3, a stationary ring 4, a rotating ring 5, a rotating ring clamp 6, a rotating shaft seal 7, and a rotating shaft 8. The upper shaft 2 connects to a loading force mechanism, a torque sensor, and a force sensor outside the sealing cavity. The rotating shaft 8 connects to a drive motor. The loading force mechanism can vary the loading force, and the drive motor's speed is varied via a frequency converter. The sealing cavity has a volume of 14 liters and is open at the front. After removing the cover, the stationary ring 4 and the rotating ring 5 can be installed and replaced. Leaks are ejected through a leak hole, and the leakage rate is generally controlled to 10 ml / h. A sealing water station is installed outside the sealing cavity. The sealing water station automatically controls the temperature and is connected to the sealing cavity via pipelines, enabling pressure-maintaining circulation. The sealing chamber is also equipped with a control console. The console inputs parameters such as the inner and outer diameters of the test ring and the rotational speed. After operation, it automatically displays parameters such as torque, loading force, friction coefficient, end face specific pressure, rotational speed, linear velocity, PcV value, and sealing fluid temperature. It can also automatically load and change speed according to requirements, and display the relevant parameter change curves. The above-mentioned test device is actually a complete vertical mechanical seal device, equivalent to a mechanical seal with an externally mounted spring, internal flow type (referring to the leakage direction at the sealing end face; leakage from the outer radial direction to the inner diameter is called internal flow), and a single end face (composed of a set of sealing end faces). The end face specific pressure is adjustable, the rotational speed is adjustable, and the friction pair can be replaced.

[0031] The method for achieving super-lubricity in mechanical seals includes the following steps:

[0032] (1) Measure the limit PcV values of different paired materials, and select the paired materials for the stationary ring and the rotating ring

[0033] Install the stationary ring and the rotating ring of the paired materials on the stationary ring fixture and the rotating ring fixture of the sealing chamber respectively, control the upper shaft to move down to make the sealing end faces of the friction pair fit, load to Pc=0.1MPa, install the sealing chamber cover plate, and then conduct air tightness inspection. In accordance with the requirements of API 682, the national standard general mechanical seal standard, pass compressed air at a pressure of 0.17MPa into the sealing chamber, close all inlet and outlet valves, and a pressure drop ΔP ≤ 0.028MPa after 5 minutes is qualified.

[0034] Pass circulating water into the sealing chamber at a water pressure of 0.3MPa. When the temperature of the water in the sealing chamber reaches 70±3°C, reset the displayed loading force to zero, then reload to Pc=0.1MPa and increase it gradually, with the rotational speed kept constant at 3000rpm, and observe the changes of parameters such as sealing torque and friction coefficient; the loading is adjusted by automatic loading. As Pc increases, if any of the phenomena such as sudden sharp rise in torque, sudden increase in friction coefficient, increased leakage, squeal, and vibration occurs during the loading adjustment process, it indicates that the seal fails, and the PcV value at this time is the limit PcV value.

[0035] For each paired material, at least 3 groups of test pieces shall be used for testing, then the average limit PcV value shall be calculated, and the calculated standard deviation shall satisfy S≤8. If the value exceeds the standard, add 2 more groups of test pieces for test each time, then reselect 3 groups of data for calculation. The test results are shown in Table 1 below.

[0036] Table 1 Limit PcV values obtained by testing different paired materials

[0037]

[0038] According to the test results, the paired material of reaction sintered silicon carbide and pressureless sintered silicon carbide (S / SS) has the maximum limit PcV value, so this embodiment selects this paired material as the material for the stationary ring and the rotating ring.

[0039] (2) Perform surface texturing treatment on the sealing end faces of the stationary ring and the rotating ring

[0040] The stationary ring is made of pressureless sintered silicon carbide, which is processed according to structural requirements through steps such as inner diameter machining, outer diameter machining, axial dimension machining, and chamfering, and then the sealing end face is processed into a bright finish through processes such as rough grinding, fine lapping, superfine lapping, and polishing.

[0041] The moving ring material is reaction-sintered silicon carbide. According to structural requirements, it undergoes machining steps including inner diameter, outer diameter, axial dimensions, and chamfering. Then, densely arranged grooves are machined on the sealing end face to form a satin finish. Diamond grinding wheels are used for end face machining, followed by rinsing with clean coolant to create fine grooves on the sealing end face. Careful operation is crucial during machining to ensure uniform, clear grooves free from misalignments, random patterns, or deep grooves. After ultrasonic cleaning, ultra-precision grinding and polishing are performed. The groove depth Ry is 0.50–1.0 μm, the width Rz is 10.0–20.0 μm, and the average roughness Ra is 0.20–0.32 μm, forming a satin finish with the following morphology: Figure 2 As shown.

[0042] (3) Apply a certain end-face pressure to the sealed end face and test the friction coefficient of the friction pair.

[0043] Three sets of friction pairs were tested according to the above steps, namely specimen 1, specimen 2, and specimen 3. The test conditions were as follows: the relative rotational speed between the stationary ring and the rotating ring was maintained at 3000–9000 rpm; water was used as the sealing lubricating medium, and the water circulated to form a stable, continuous fluid lubricating film on the sealing end face; the water temperature was 70±3℃, and the pressure was 0.3 MPa. The friction curve of specimen 1 is shown below. Figure 3 As shown, the friction curve of specimen 2 is as follows: Figure 4 As shown, the friction curve of specimen 3 is as follows: Figure 5 As shown in Table 2, the friction coefficients of the three groups of specimens are as follows.

[0044] Table 2 Data on end-face pressure and friction coefficient of three groups of specimens

[0045]

[0046] After combined calculations, the average friction coefficient of the three groups of specimens was 0.0068, and the standard deviation S was 0.0015. It can be seen that the above method can make the mechanical seal super-lubricated.

[0047] In other embodiments, selecting pair materials with a limiting PcV value greater than 50 MPa·m / s as the materials for the stationary and dynamic rings, controlling the end-face specific pressure applied to the sealing end face to be 6.5–8.5 MPa, and maintaining the temperature of the sealing lubricating medium water at 67–73°C and the pressure at 0.25–0.35 MPa can also achieve a super-lubricated state.

[0048] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for achieving super-lubricity on the sealing end face of a mechanical seal, characterized in that, Includes the following steps: S1. Determine the limiting PcV value of different material pairs, and select material pairs with a limiting PcV value greater than 50 MPa·m / s as the materials for the stationary ring and the dynamic ring. The selected material pairs are reaction-bonded silicon carbide and pressureless sintered silicon carbide. The method for determining the limiting PcV value includes: installing the stationary and dynamic rings of the assembled materials in the sealing cavity and performing an airtightness check; circulating water into the sealing cavity, gradually increasing the end face specific pressure, and observing the changes in sealing torque and friction coefficient; when any of the following phenomena occur, such as a sudden and rapid increase in torque, a sudden increase in friction coefficient, an increase in leakage, a whistling sound, or vibration, the seal is deemed to have failed, and the PcV value at this time is the limiting PcV value; for each assembled material, at least three sets of specimens are used for testing, and the average limiting PcV value and standard deviation are calculated, with the standard deviation S≤8; S2. Perform surface texturing on the sealing end faces of the stationary ring and the rotating ring. Process the sealing end face of the stationary ring into a bright surface, and process densely arranged grooves on the sealing end face of the rotating ring to form a satin surface. The groove depth Ry on the sealing end face of the rotating ring is 0.50~1.0μm, the width Rz is 10.0~20.0μm, and the average roughness Ra is 0.20~0.32μm. S3. The stationary ring and the moving ring rotate relative to each other. The end face pressure Pc applied to the sealing end face is 6.5 to 8.5 MPa. Water is used as the sealing lubricating medium to form a stable and continuous fluid lubricating film on the sealing end face.

2. The method for achieving super-slippery sealing end face of a mechanical seal according to claim 1, characterized in that, In step S3, the sealing lubricating medium water is kept circulating.

3. The method for achieving super-slippery sealing end face of a mechanical seal according to claim 1, characterized in that, In step S3, the temperature of the sealing lubricating medium water is maintained at 67-73°C and the pressure is maintained at 0.25-0.35 MPa.

4. The method for achieving super-slippery sealing end face of a mechanical seal according to claim 1, characterized in that, In step S3, the relative rotational speed between the stationary ring and the moving ring is maintained at 3000-9000 rpm.

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