A mechanical seal friction coefficient testing device with adjustable closing force and simulated real-world conditions

Abstract

The present invention discloses a simulated working condition mechanical seal friction coefficient test device with adjustable closing force, including a mechanical seal pair, a drive shaft, a main seal cavity, a secondary seal cavity, an air bearing, a seal torque transmission component, a seal torque test component and an axial force loading test component; the main seal cavity is fixedly connected to the secondary seal cavity, the drive shaft is arranged in the main seal cavity, the mechanical seal pair is arranged at the connection between the main seal cavity and the secondary seal cavity, the air bearing is arranged in the secondary seal cavity, the seal torque transmission component is arranged in the secondary seal cavity and cooperates with the air bearing, the axial force loading test component is arranged in the secondary seal cavity, and the seal torque test component is arranged at one end of the secondary seal cavity away from the main seal cavity. The present invention can realize the convenient regulation of the closing force of the mechanical seal end face under the conditions of speed and pressure and the online and in-situ precise test of the end face friction coefficient.

Description

Technical Field

[0001] The invention relates to the technical field of mechanical seal performance testing devices, and in particular to a mechanical seal end face friction coefficient testing device. Background Art

[0002] Mechanical seals are widely used in rotating machinery such as centrifugal pumps, compressors and stirred tanks because of their advantages such as low leakage and good self-compensation performance. The friction coefficient is one of the important parameters in the design of mechanical seals. It can reflect the lubrication state of the seal end face and is closely related to other sealing properties such as seal friction power consumption, wear, and end face temperature rise. The mechanical seal end face friction coefficient is the ratio of the end face friction force to the axial load. The friction force can be obtained indirectly by testing the sealing torque, while the axial load can be directly obtained by the loading force or measured by a force sensor.

[0003] At present, there are three main methods for testing the friction coefficient of the mechanical seal end face: the first method is to connect a torque sensor in series between the motor output shaft and the seal shaft, measure the total torque of the input seal shaft through the torque sensor, and then subtract the additional torque generated by the stirring of the seal shaft support bearing and the rotating parts in the seal chamber, and sometimes subtract the additional torque of the auxiliary seal on the same shaft; because there are too many factors affecting the test mechanical seal end face torque in this method, its test results are often inaccurate. The second method is the support reaction method, which fixes the seal static ring on the floating seal cavity supported by the bearing, installs a force arm on the seal cavity, and indirectly obtains the friction torque transmitted from the dynamic ring to the static ring end face through the length of the force arm and the value of the force sensor at the end of the force arm. Although this method is direct for the test of the mechanical seal end face torque, the setting of the floating seal cavity changes the structure of the original fixed seal cavity, reducing its pressure bearing capacity. At the same time, the inlet and outlet pipelines installed on the seal cavity will also affect the torque test accuracy. The third method is to directly use a specially made cylindrical torque sensor as the stationary ring seat. The torque transmitted from the dynamic ring to the stationary ring will drive the torque sensor to rotate slightly to achieve torque testing. However, in order to obtain high test accuracy in this method, the wall thickness of the cylindrical torque sensor is often thin, which makes it adaptable to a narrow range of medium pressure. On the other hand, in the second and third methods, since the stationary ring seat structure needs to be specially designed, the in-situ online adjustment of the sealing closing force is also very difficult.

[0004] It can be seen that the existing mechanical seal end face friction coefficient testing device still has shortcomings such as insufficient testing accuracy, narrow operating range, and difficulty in online adjustment of the sealing closing force. Summary of the invention

[0005] In view of the problems existing in existing mechanical seal friction coefficient measuring devices, such as insufficient testing accuracy, narrow applicable working condition range, and difficulty in online adjustment of sealing closing force, the present invention provides a simulated working condition mechanical seal friction coefficient testing device with high testing accuracy and convenient closing force adjustment.

[0006] The technical solution of the present invention is as follows:

[0007] A device for testing the friction coefficient of a mechanical seal under simulated working conditions with adjustable closing force, comprising a mechanical seal pair, a drive shaft, a main seal cavity, a secondary seal cavity, an air bearing, a seal torque transmission assembly, a seal torque test assembly and an axial force loading test assembly; the main seal cavity is fixedly connected to the secondary seal cavity, the drive shaft is arranged in the main seal cavity, the mechanical seal pair is arranged at the connection between the main seal cavity and the secondary seal cavity, the air bearing is arranged in the secondary seal cavity, the seal torque transmission assembly is arranged in the secondary seal cavity and cooperates with the air bearing, the axial force loading test assembly is arranged in the secondary seal cavity, and the seal torque test assembly is arranged at one end of the secondary seal cavity away from the main seal cavity.

[0008] Furthermore, the mechanical seal pair includes a dynamic ring and a static ring, the dynamic ring is located in a main sealing cavity, and a first air inlet is provided on the main sealing cavity, and the static ring is arranged in the auxiliary sealing cavity.

[0009] Furthermore, the secondary sealing cavity includes a first sealing cavity, a second sealing cavity and a third sealing cavity, the second sealing cavity is arranged between the first sealing cavity and the third sealing cavity, and the first sealing cavity and the third sealing cavity are axially fastened by bolts.

[0010] Furthermore, the air bearing is located in the first sealed cavity, and a throttling air inlet is provided on the first sealed cavity. The throttling air inlet is connected to the throttling hole on the air bearing. There is a radial gap between the inner surface of the air bearing and the outer surface of the supporting sleeve. The air bearing floats the supporting sleeve through a layer of air film, and a first auxiliary sealing ring is provided radially between the air bearing and the first sealed cavity.

[0011] Furthermore, the sealing torque transmission assembly includes a supporting sleeve and an auxiliary sleeve, the supporting sleeve and the auxiliary sleeve are connected by a pin, a second auxiliary sealing ring is provided radially between the supporting sleeve and the auxiliary sleeve, and the static ring is fastened to the supporting sleeve by a set screw.

[0012] Furthermore, the sealing torque test assembly includes a force arm, a force sensor and a force sensor seat, the force sensor seat is arranged on the third sealing cavity, the force sensor is fixed on the force sensor seat, the force arm is fixed on the auxiliary sleeve, and the force arm is in contact with the force sensor.

[0013] Furthermore, the axial force loading test assembly includes a flexible diaphragm and an axial force sensor; the flexible diaphragm is fixed on the third sealing cavity and forms a closed pressure cavity therewith, the third sealing cavity is provided with a second air inlet connected to the closed pressure cavity, and the axial force sensor is arranged between the supporting sleeve and the auxiliary sleeve.

[0014] Furthermore, the flexible diaphragm is a circular ring structure, including a flexible diaphragm outer diameter section, a flexible diaphragm middle section and a flexible diaphragm inner diameter section, the flexible diaphragm outer diameter section is clamped between the second sealing cavity and the third sealing cavity, the flexible diaphragm middle section is pressed onto the auxiliary sleeve through a first pressing plate, and the flexible diaphragm inner diameter section is pressed onto the third sealing cavity through a second pressing plate.

[0015] The beneficial effects of the present invention are as follows:

[0016] 1) The torque test assembly is installed on the static ring end to test the seal end face torque directly. The static ring assembly is supported by an air bearing and a softer flexible diaphragm is used to reduce the additional torque as much as possible, so that the device has high test accuracy for the mechanical seal end face torque.

[0017] 2) A pressure regulating chamber is added to the back of the stationary ring assembly to regulate the axial load acting on the stationary ring. By changing the gas pressure in the pressure regulating chamber, the axial load on the stationary ring of the mechanical seal can be steplessly regulated under speed and pressure conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a cross-sectional view of the present invention;

[0019] Figure 2 It is a right side view of the present invention;

[0020] Figure 3 is a schematic diagram of the structure of the flexible diaphragm of the present invention;

[0021] Figure 4 It is a schematic diagram of the structure of the air bearing of the present invention;

[0022] Figure 5 It is a schematic diagram of the transmission of the internal sealing end face axial force and sealing torque of the present invention;

[0023] In the figure: 1, mechanical seal pair; 11, dynamic ring; 12, static ring; 121, set screw; 2, driving shaft; 3, main sealing cavity; 31, first air inlet; 4, auxiliary sealing cavity; 41, first sealing cavity; 411, throttle air inlet; 42, second sealing cavity; 43, third sealing cavity; 431, closed pressure cavity; 432, second air inlet; 44, bolt; 5, air bearing; 51, throttle hole; 52, inner surface; 53, first auxiliary sealing ring; 6, sealing torque Torque transmission assembly; 61, supporting sleeve; 611, outer surface; 612, pin; 62, auxiliary sleeve; 621, second auxiliary sealing ring; 7, sealing torque test assembly; 71, lever arm; 72, force sensor; 73, force sensor seat; 8, axial force loading test assembly; 81, flexible diaphragm; 811, flexible diaphragm outer diameter section; 812, flexible diaphragm middle section; 813, flexible diaphragm inner diameter section; 814, first clamping plate; 815, second clamping plate; 82, axial force sensor. DETAILED DESCRIPTION

[0024] The implementation of the present invention is further described in detail below in conjunction with the accompanying drawings.

[0025] like Figure 1-4 A mechanical seal friction coefficient test device with adjustable closing force and simulated working conditions, comprising a mechanical seal pair 1, a drive shaft 2, a main seal cavity 3, a secondary seal cavity 4, an air bearing 5, a seal torque transmission assembly 6, a seal torque test assembly 7 and an axial force loading test assembly 8. The mechanical seal pair 1 comprises a dynamic ring 11 and a static ring 12, wherein the dynamic ring 11 is a fixed mounting ring, and the static ring 12 is a floating mounting ring. The dynamic ring 11 is driven to rotate by the drive shaft 2, and the static ring 12 is fastened to the support sleeve 61 by a set screw 121, and the dynamic ring 11 and the static ring 12 form a pair of mechanical seal pairs. The drive shaft 2 and the dynamic ring 11 are located in the main seal cavity 3.

[0026] The secondary sealing cavity 4 includes a first sealing cavity 41, a second sealing cavity 42, and a third sealing cavity 43. The first sealing cavity 41 and the third sealing cavity 43 are axially fastened by bolts 44. The first sealing cavity 41 is connected to the main sealing cavity 3. The main sealing cavity 3 is provided with a first air inlet 31.

[0027] The air bearing 5 is located in the first sealed cavity 41 and is axially pressed and fixed by the first sealed cavity 41 and the second sealed cavity 42. A throttle air inlet 411 is provided on the first sealed cavity 41. The throttle air inlet 411 is connected to the throttle hole 51 on the air bearing 5. A first auxiliary sealing ring 53 is provided radially between the air bearing 5 and the first sealed cavity 41. The air bearing 5 floats the support sleeve 61 through a layer of air film 54. There is a radial gap between the inner surface 52 of the air bearing 5 and the outer surface 611 of the support sleeve 61, which avoids direct contact between the support sleeve 61 and the air bearing 5, thereby minimizing the influence of the additional torque generated at the support of the support sleeve 61 on the sealing torque test value.

[0028] The sealing torque transmission assembly 6 includes a supporting sleeve 61 and an auxiliary sleeve 62. The supporting sleeve 61 and the auxiliary sleeve 62 are connected by a pin. A second auxiliary sealing ring 621 is provided between the supporting sleeve 61 and the auxiliary sleeve 62. The axial force sensor 82 is located between the supporting bearing 61 and the auxiliary sleeve 62 in the axial direction and is used to test the axial load on the stationary ring 12. The sealing torque transmitted to the stationary ring 12 by the end face friction and the viscous shear of the medium during the rotation of the dynamic ring 11 is transmitted to the auxiliary sleeve 62 through the screw connection between the stationary ring 12 and the supporting sleeve 61 and the pin connection between the supporting sleeve 61 and the auxiliary sleeve 62.

[0029] The sealing torque test assembly 7 includes a lever arm 71, a force sensor 72, and a force sensor seat 73. Two force sensor seats 73 arranged symmetrically in the center are fixed on the third sealing cavity 43. The lever arm 71 is fixed on the auxiliary sleeve 62, and the force sensor 72 is fixed on the force sensor seat 73. The lever arm 71 is in contact with the force sensor 72. The sealing torque is transmitted to the lever arm 71 through the auxiliary sleeve 62 and pressed against the force sensor 72. The sealing torque can be obtained according to the reading of the force sensor 72 and its distance from the central axis of the static ring 12.

[0030] The axial force loading test assembly 8 includes a flexible diaphragm 81 and an axial force sensor 82. The flexible diaphragm 81 is a circular ring structure, and a closed pressure chamber 431 is formed between the flexible diaphragm 81 and the third sealing chamber 43. A second air inlet 432 connected to the closed pressure chamber 431 is provided on the third sealing chamber 43, and the air pressure in the closed pressure chamber 431 can be adjusted to adjust the axial load loaded on the stationary ring 12. The outer diameter section 811 of the flexible diaphragm is clamped between the second sealing chamber 42 and the third sealing chamber 43, the middle section 812 of the flexible diaphragm is pressed against the auxiliary shaft sleeve 62 through the first pressing plate 813, and the inner diameter section 814 of the flexible diaphragm is pressed against the third sealing chamber 43 through the second pressing plate 815.

[0031] Working principle:

[0032] The friction coefficient of the mechanical seal end face is the ratio of the friction force of the seal compensation ring end face to the axial load, so the test problem of the friction coefficient is converted into the test problem of the two parameters of end face friction force / end face torque and axial load. In order to obtain the state of the friction coefficient of the mechanical seal end face under different axial load conditions, it is very necessary to regulate the closing force of the mechanical seal compensation ring in place.

[0033] Combination Figure 5 The mechanical seal axial load adjustment test and seal torque transmission test method in the present invention are analyzed. A closed pressure chamber is formed between the flexible diaphragm and the third sealing cavity, and the closed pressure chamber is connected to the external gas pipeline through the air inlet. The outer diameter section and the inner diameter section of the flexible diaphragm are pressed tightly against the third sealing cavity, and the gas pressure F in the closed pressure chamber is 3 Acting on the auxiliary sleeve, and then transmitted to the axial force sensor between the auxiliary sleeve and the supporting sleeve, the reading of the axial force sensor is F 2 , force F 2 Further loading onto the stationary ring through the support sleeve, F 2 With F 3 The difference in the value is the friction force F between the auxiliary sleeve and the supporting sleeve. f Since there is an air film support between the support sleeve and the air bearing, there is no direct contact between the two, so there is no axial force between the two, and the additional torque of the air bearing on the support sleeve can also be ignored. Therefore, the reading measured by the axial force sensor is F 2 Friction force F with auxiliary seal ring f The difference is the axial load on the static ring as the compensation ring. The axial load of the mechanical seal compensation ring can be adjusted by changing the gas pressure in the closed pressure chamber, and this regulation can be carried out under the conditions of mechanical seal pressure and speed.

[0034] The sealing torque M is transmitted from the dynamic ring to the static ring end face through end face friction and medium viscous shear. 1 , which is transmitted to the auxiliary sleeve through the screw connection between the stationary ring and the supporting sleeve, and the pin connection between the supporting sleeve and the auxiliary sleeve. At this time, the stationary ring, the supporting sleeve and the auxiliary sleeve can be regarded as a fixed part. The flexible diaphragm fixed on the auxiliary sleeve will generate an additional torque M due to the micro-torsion deformation. 2 The additional torque can be obtained by calibration before the test; in order to minimize the additional torque M 2 , requiring the flexible diaphragm to be softer and thinner. Sealing torque M 1 Minus additional torque M 2 The remaining torque M 3 The torque M is further transmitted to the force sensor fixed on the third sealing cavity through the auxiliary sleeve and the force arm rod installed on the auxiliary sleeve. The torque M can be obtained by the force sensor reading and its distance from the compensation ring axis.3 In order to improve the torque test accuracy, two force sensors are symmetrically arranged on the third sealed cavity. The torque M measured by the force sensor 3 The additional torque M obtained by pre-calibration with the flexible diaphragm 2 The sealing torque M can be calculated 1 .

[0035] Force analysis:

[0036] The axial load on the end face of the stationary ring 12 is F 1 , the test value of axial force sensor 82 is F 2 The force exerted by the air pressure in the closed pressure chamber 431 on the static ring 12 through the flexible diaphragm 81 is F 3 The friction force of the second auxiliary seal ring 621 between the supporting sleeve 61 and the auxiliary sleeve 62 is F f When the air pressure in the closed pressure chamber 431 is continuously increased to make the auxiliary sleeve 62 slightly move to the left, the axial force on the auxiliary sleeve 62 is first analyzed. The auxiliary sleeve 62 is subjected to the friction force F of the second auxiliary seal ring 621 in the right direction. f The right side of the auxiliary sleeve 62 is subjected to a leftward gas pressure force F 3 The left end face is subjected to the rightward axial force sensor 82 reaction force F 2 , at this time, the force balance formula F 3 =F 2 +F f The axial force of the support sleeve 61 and the stationary ring 12 assembly is analyzed. The support sleeve 61 is subjected to the friction force F of the second auxiliary seal ring 621 in the left direction. f The right end face of the support sleeve 61 receives the leftward axial force sensor 82 reaction force F 2 , the end face of the stationary ring 12 has a force F acting to the right 1 , at this time, the force balance formula F 1 =F 2 +F f It can be seen that the axial load F on the end face of the stationary ring 12 is 1 The air pressure force F applied by the closed pressure chamber 431 3 The force value can be calculated based on the axial force sensor reading F 2 With the pre-calibrated friction force F f Obtained by calculation.

[0037] The sealing torque between the dynamic ring 11 and the static ring 12 is M 1 , the additional torque of the flexible diaphragm 81 is M 2 The torque measured by the lever arm 71 and the force sensor 72 is M 3Since the additional torque of the air bearing 5 on the support sleeve 61 can be ignored, the sealing torque M 1 The torque M can be measured by the force sensor 72 3 The additional torque M of the pre-calibrated flexible diaphragm 81 2 Obtain the sealing torque M by performing a difference operation. 1 The axial load F on the stationary ring 12 1 On this basis, the friction coefficient of the mechanical seal end face can be calculated.

[0038] The contents described in the embodiments of this specification are merely an enumeration of implementation forms of the inventive concept. The protection scope of the present invention should not be deemed to be limited to the specific forms described in the embodiments. The protection scope of the present invention also extends to equivalent technical means that can be conceived by those skilled in the art based on the inventive concept.

Claims

1. A mechanical seal friction coefficient testing device with adjustable closing force and simulated real-world conditions, characterized in that: The invention comprises a mechanical seal pair (1), a driving shaft (2), a main sealing cavity (3), a secondary sealing cavity (4), an air bearing (5), a sealing torque transmission assembly (6), a sealing torque test assembly (7) and an axial force loading test assembly (8); the main sealing cavity (3) is fixedly connected to the secondary sealing cavity (4); the driving shaft (2) is arranged in the main sealing cavity (3); the mechanical seal pair (1) is arranged at the connection between the main sealing cavity (3) and the secondary sealing cavity (4); the air bearing (5) is arranged in the secondary sealing cavity (4); the sealing torque transmission assembly (6) is arranged in the secondary sealing cavity (4) and cooperates with the air bearing (5); the axial force loading test assembly (8) is arranged in the secondary sealing cavity (4); and the sealing torque test assembly (7) is arranged at one end of the secondary sealing cavity (4) away from the main sealing cavity (3); The mechanical seal pair (1) comprises a dynamic ring (11) and a static ring (12), wherein the dynamic ring (11) is located in a main sealing cavity (3), and a first air inlet (31) is provided on the main sealing cavity (3), and the static ring (12) is arranged in a secondary sealing cavity (4); The secondary sealing cavity (4) comprises a first sealing cavity (41), a second sealing cavity (42) and a third sealing cavity (43); the second sealing cavity (42) is arranged between the first sealing cavity (41) and the third sealing cavity (43); the first sealing cavity (41) and the third sealing cavity (43) are axially fastened by bolts (44); The sealing torque transmission assembly (6) comprises a supporting sleeve (61) and an auxiliary sleeve (62), the supporting sleeve (61) and the auxiliary sleeve (62) being connected by a pin (612), a second auxiliary sealing ring (621) being provided radially between the supporting sleeve (61) and the auxiliary sleeve (62), and the stationary ring (12) being fastened to the supporting sleeve (61) by a set screw (121); The axial force loading test assembly (8) comprises a flexible diaphragm (81) and an axial force sensor (82); the flexible diaphragm (81) is fixed on the third sealed cavity (43) and forms a closed pressure cavity (431) therewith; the third sealed cavity (43) is provided with a second air inlet (432) connected to the closed pressure cavity (431); and the axial force sensor (82) is arranged between the supporting shaft sleeve (61) and the auxiliary shaft sleeve (62).

2. The device for testing the friction coefficient of mechanical seals under simulated working conditions with adjustable closing force according to claim 1, characterized in that: The air bearing (5) is located in a first sealed cavity (41), and a throttling air inlet (411) is provided on the first sealed cavity (41). The throttling air inlet (411) is connected to a throttling hole (51) on the air bearing (5). A radial gap is provided between an inner surface (52) of the air bearing (5) and an outer surface (611) of the supporting sleeve (61), and a first auxiliary sealing ring (53) is provided radially between the air bearing (5) and the first sealed cavity (41).

3. The device for testing the friction coefficient of mechanical seals under simulated working conditions with adjustable closing force according to claim 1, characterized in that: The sealing torque test assembly (7) comprises a force arm (71), a force sensor (72) and a force sensor seat (73); the force sensor seat (73) is arranged on the third sealing cavity (43); the force sensor (72) is fixed on the force sensor seat (73); the force arm (71) is fixed on the auxiliary shaft sleeve (62); and the force arm (71) is in contact with the force sensor (72).

4. The device for testing the friction coefficient of mechanical seals under simulated working conditions with adjustable closing force according to claim 1, characterized in that: The flexible diaphragm (81) is a circular ring structure, comprising a flexible diaphragm outer diameter section (811), a flexible diaphragm middle section (812) and a flexible diaphragm inner diameter section (813); the flexible diaphragm outer diameter section (811) is sandwiched between the second sealing cavity (42) and the third sealing cavity (43); the flexible diaphragm middle section (812) is pressed onto the auxiliary shaft sleeve (62) via a first pressing sheet (814); and the flexible diaphragm inner diameter section (813) is pressed onto the third sealing cavity (43) via a second pressing sheet (815).

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