Mechanical seal flushing adaptive compensation system for polyethylene axial flow pump
The mechanical seal flushing adaptive compensation system solved the problem of bearing lubrication and cooling interruption caused by high-speed pump failure, realizing continuous oil supply to the bearing and ensuring the safety and continuity of polyethylene production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HEFEI HUASHENG PUMPS & VALVES CO LTD
- Filing Date
- 2023-03-31
- Publication Date
- 2026-06-05
AI Technical Summary
The existing Plan32+52 flushing scheme relies on a high-speed pump for flushing fluid, which is susceptible to the effects of the high-speed gearbox and the lifespan of the seals. This can lead to interruptions in the lubrication and cooling of the bearings inside the pump chamber, affecting the safe operation of the equipment. Simple monitoring cannot prevent this.
An adaptive compensation system for mechanical seal flushing is adopted, including a compensating piston cylinder, an oil inlet compensation pipeline, a balance pipeline, and a differential pressure measurement pipeline, to achieve real-time online compensation of the flushing fluid and ensure continuous lubrication and cooling of the bearing.
In the event of a high-speed pump failure, seamless flushing fluid supply is achieved to ensure continuous lubrication and cooling of the bearings, thereby guaranteeing the safety and continuity of high-density polyethylene production and reducing the risk of equipment downtime.
Smart Images
Figure CN116464676B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of mechanical seal flushing technology for axial flow pumps, and specifically relates to an adaptive compensation system for mechanical seal flushing of polyethylene axial flow pumps. Background Technology
[0002] The circulating axial flow pump in the loop reactor is a core piece of equipment in the high-density polyethylene (HDPE) process, and its operation directly affects the safe production of the entire plant. The pump chamber and sealing chamber of the axial flow pump experience high pressure, and the medium is extremely hazardous; therefore, selecting a safe and reliable sealing and flushing scheme is crucial. Some HDPE axial flow pumps employ a Plan 32+52 flushing scheme; in this case, to ensure the safe and long-term operation of the axial flow pump, in addition to ensuring the safety of the mechanical seal, a continuous and stable supply of flushing fluid is also a key factor for the safe and reliable operation of the axial flow pump.
[0003] The HDPE axial flow pump features an end-inlet, top-outlet design. The pump body is constructed by welding a long-radius elbow to a flange, with the flange having a pressure rating of 600 lb. A rolling bearing, serving as the front-end bearing, is located within the pump chamber near the impeller. This rolling bearing is cooled and lubricated by an external flushing fluid. During operation, because the flushing fluid pressure is consistently higher than the internal pressure of the loop reactor, it effectively prevents media containing solid particles from entering the bearing. Furthermore, as... Figure 1 As shown, the external mechanical seal is a high-pressure tandem seal, with the intermediate cavity receiving heat and lubrication via a buffer tank. The inner and outer mechanical seal faces, along with the buffer tank, are all designed to withstand the highest pressure in a ring-pipe process. If the inner mechanical seal face leaks, high-pressure flushing fluid enters the buffer tank, causing the tank level to rise and triggering an alarm upon reaching the high level. When the pressure reaches a certain level, the safety overflow valve at the top of the buffer tank opens, allowing flushing fluid to overflow into the flare line, preventing the high-pressure, flammable, and explosive flushing fluid from leaking to the atmosphere. During this process, on-site operators will choose to promptly halt the process response based on the degree of mechanical seal leakage, such as performing an emergency shutdown of the axial flow pump.
[0004] Based on the existing solutions described above, the actual problem encountered is that the flushing fluid in the Plan32+52 flushing scheme is cyclohexane, and the consumption of a single pump is 1m³. 3 The total flushing volume of the two pumps is only 2m³ / h, which is approximately [amount missing]. 3 The flushing fluid operates at a rate of approximately [per unit speed], with a pressure exceeding 4.5 MPa and a head of about 900 m. This flushing fluid can only be propelled by a high-speed pump, which is susceptible to failure due to the limitations of the high-speed gearbox and seal lifespan. When the high-speed pump stops, the upstream flushing pipeline loses power and automatically shuts off, leaving the bearings within the pump chamber without lubrication and cooling. This can lead to rapid overheating, scratching, and even seizure of the bearings within a short period, severely impacting the safe operation of the unit. Furthermore, simple monitoring methods are insufficient to prevent these phenomena, necessitating a solution. Summary of the Invention
[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an adaptive compensation system for mechanical seal flushing of polyethylene axial flow pumps. This system realizes the function of real-time online compensation of flushing fluid after flushing interruption, thereby ensuring the continuous lubrication and cooling effect of the bearings in the pump chamber and ensuring the safety and continuity of high-density polyethylene production.
[0006] To achieve the above objectives, the present invention adopts the following technical solution:
[0007] An adaptive compensation system for mechanical seal flushing of a polyethylene axial flow pump includes a pump body with a pump chamber and a front-end bearing arranged inside the pump body. The system is characterized by: a compensation piston cylinder with its axis arranged vertically, wherein the return chamber of the compensation piston cylinder is located above the progress chamber; an oil inlet compensation pipeline is connected at one end to the return chamber and at the other end to the front-end flushing pipeline where the high-speed pump is located; and a balance pipeline is connected at one end to the progress chamber and at the other end to the lubrication chamber where the front-end bearing is located.
[0008] The bottom blade of the guide vane is provided with a sandwich-type first liquid inlet. The inlet of the first liquid inlet is connected to the front flushing pipeline, and the outlet of the first liquid inlet passes through the bottom wall of the lubrication cavity from bottom to top, thereby connecting to the lubrication cavity. The top blade of the guide vane is provided with a sandwich-type second liquid inlet. The inlet of the second liquid inlet is connected to the balance pipeline, and the outlet of the second liquid inlet passes through the top wall of the lubrication cavity, thereby connecting to the lubrication cavity.
[0009] The balancing pipeline is equipped with a dual filter that can be switched and used to clean solid particles inside the pipeline.
[0010] The system also includes an oil supply line, on which a replenishment pump is installed, and the two ends of the oil supply line are respectively connected to a buffer tank and the return chamber of a compensated piston cylinder.
[0011] A differential pressure measuring pipeline is bridged between the oil inlet compensation pipeline and the balancing pipeline, and a differential pressure transmitter is installed on the differential pressure measuring pipeline.
[0012] Switch valves are installed on the oil inlet compensation pipeline, the balancing pipeline, and the differential pressure measuring pipeline.
[0013] The pump body is arc-shaped, with the pump shaft penetrating the outer wall of the pump body and extending to the pump body inlet, forming a rotary fit with the guide vanes. The impeller is coaxially mounted on the shaft end located inside the pump cavity. With the direction of medium inflow as the front of the impeller, an inducer wheel is also coaxially fixed on the pump shaft in front of the impeller. Along the direction of medium travel, the number of blades of the inducer wheel, impeller, and guide vanes increases sequentially, and the outlet blade of the inducer wheel is staggered from the inlet blade of the impeller, and the outlet blade of the impeller is staggered from the inlet blade of the guide vane.
[0014] The inducer wheel and impeller are both connected to the pump shaft by a key. A locking nut is arranged at the front end of the pump shaft, so that the inducer wheel and impeller are clamped by the cooperation between the locking nut and the front end face of the guide vane.
[0015] The guide vane cavity extends horizontally along the guide vane axis to the outer wall of the pump body, thereby forming a passage cavity through which the pump shaft can pass; a sliding bearing constituting the front bearing is provided inside the guide vane cavity, and the section of the passage cavity where the sliding bearing is located constitutes the lubrication cavity; a rear bearing is provided at the frame on the outer wall of the pump body, thereby enabling the pump shaft to rotate in a simply supported beam manner at the pump body and the frame.
[0016] The passageway extends into the frame, and a mechanical seal is installed at the end of the passageway in front of the rear bearing. The flushing fluid from the front flushing pipeline enters the passageway through the inlet at the guide vane, passes through the sliding bearing, the gap between the pump shaft and the passageway, and the mechanical seal in sequence, and is then discharged to the buffer tank through the outlet. A branch pipeline is also provided at the front flushing pipeline, which directly connects to the gap between the pump shaft and the passageway.
[0017] The beneficial effects of this invention are as follows:
[0018] 1) Under the above scheme, during normal operation, the pressure in the front flushing pipeline and the lubrication chamber is consistent due to the normal start of the high-speed pump, and the pressure in the process chamber and return chamber of the compensating piston cylinder is balanced. When the high-speed pump suddenly stops due to malfunction or other reasons, the external flushing fluid stops entering the front flushing pipeline, causing the front flushing pipeline to lose pressure, which in turn causes the oil inlet compensation pipeline directly connected to the front flushing pipeline to lose pressure. At the same time, the lubrication chamber where the front bearing is located is temporarily still under high pressure, thus keeping the balance pipeline connected to the lubrication chamber under high pressure. At this time, the pressure balance between the process chamber and return chamber of the compensating piston cylinder is broken, and the piston is pushed upward by the high pressure in the lubrication chamber, squeezing the pre-stored white oil in the return chamber into the front flushing pipeline through the oil inlet compensation pipeline, thereby achieving a continuous supply effect to the lubrication chamber. Thus, this invention achieves seamless connection and real-time online compensation of flushing fluid after flushing interruption, ensuring continuous lubrication and cooling of the bearing in the pump chamber, and ensuring the safety and continuity of high-density polyethylene production.
[0019] 2) For the liquid inlet, the present invention adopts an upper and lower split structure, that is, the connection between the front flushing pipe and the balance pipe and the pump body is placed on the opposite side of the pump body to ensure working effect.
[0020] 3) In order to prevent solid particles in the pump chamber from being forcibly squeezed into the process chamber of the compensated piston cylinder due to the pressure in the pump chamber, thus affecting the operation of the compensated piston cylinder, a dual filter that can be switched and cleaned of solid particles in the balance pipeline is installed.
[0021] 4) The arrangement of the oil supply pipeline not only achieves a continuous white oil compensation effect for the compensating piston cylinder, greatly extending the supply time of the invention; it is also worth noting that the piston rod of the compensating piston cylinder used in this invention extends upwards, meaning that the pressure on the piston surface at the return chamber is lower than the pressure on the piston surface at the progress chamber. This is more conducive to pressure testing of the balance pipeline located in the progress chamber and squeezing the piston to produce a compensating oil delivery effect. Furthermore, since the return chamber is located above, the oil supply pipeline is also connected to the return chamber, avoiding the need to overcome the piston's own weight during oil supply. In fact, even with the piston's own weight, the oil supply efficiency can be further improved. At the same time, the oil supply pipeline connected to the return chamber is naturally isolated from the progress chamber and even the pump chamber, thus avoiding the influence of solid particles there, further improving the reliability and stability of the invention—a win-win situation.
[0022] 5) As a further preferred option of the above scheme, the presence of the inducer increases the pump inlet pressure and improves the cavitation performance of the centrifugal pump. This allows the inducer to operate under the aforementioned cavitation conditions and effectively reduces noise, vibration, corrosion damage to flow components, and performance instability caused by pump cavitation. Furthermore, the number of blades in the inducer, impeller, and guide vanes increases sequentially along the medium's direction of travel. The outlet blades of the inducer are staggered from the inlet blades of the impeller, and the outlet blades of the impeller are staggered from the inlet blades of the guide vanes. This effectively avoids the potential for resonance when the medium, after performing work through the inducer and impeller, enters the guide vanes and even the impeller, ultimately further improving the pump's operational stability and reliability, and ensuring its service life.
[0023] 6) Because the pump chamber uses sliding bearings, their service life is very long when lubrication is guaranteed. Furthermore, the cost of sliding bearings is less than one-third that of mechanical seals in similar devices compared to those using built-in rolling bearings, making them more cost-effective. In addition, sliding bearings are lightweight, easy to disassemble and maintain, exhibit better vibration control, and reduce the risk of leakage from the external mechanical seal. This allows for continuous, long-term operation, providing reliable and safe assurance for the long-term operation of the device. Attached Figure Description
[0024] Figure 1 Diagram showing the piping layout of an existing polyethylene axial flow pump;
[0025] Figure 2 This is a diagram showing the pipeline layout of the present invention;
[0026] Figure 3 This is a structural cross-sectional view of one embodiment of the polyethylene axial flow pump of the present invention.
[0027] The actual correspondence between the reference numerals and component names in this invention is as follows:
[0028] 10-Pump body; 11-Guide vane; 11a-First inlet; 11b-Second inlet; 12-Drain outlet;
[0029] 20 - Compensated piston cylinder; 21 - Return chamber; 22 - Progress chamber;
[0030] 31-Inlet compensation line; 32-Balancing line; 32a-Dual filter; 33-Inlet supply line; 33a-Make-up pump; 34-Differential pressure measurement line;
[0031] 40 - Sliding bearing;
[0032] 51-Front-end flushing line; 52-Buffer solution tank; 53-Branch line;
[0033] 61-Pump shaft; 62-Impeller; 63-Mechanical seal; 64-Locking nut; 65-Rear end bearing. Detailed Implementation
[0034] For ease of understanding, this section combines... Figure 2-3 The specific structure and operation of the present invention are further described below:
[0035] This invention, through Figure 1 Based on the structure shown, additional lines such as Plan 32 flushing lines are added. Figure 2 The adaptive compensation piping shown is illustrated. (Refer to...) Figure 2 As shown: In the compensated piston cylinder 20, the piston divides the cylinder body into an upper chamber and a lower chamber. Since the piston rod is located in the upper chamber, the upper chamber forms the return chamber 21, and the lower chamber forms the advancing chamber 22. Because the contact area between the piston and the lower chamber is large, approximately 1.1 times the contact area between the piston and the upper chamber, the upward thrust F1 on the piston is the product of the pressure P1 in the advancing chamber 22 and the circular area S1 of the piston's lower surface. The downward pressure F2 on the piston is the product of the piston's weight G, the pressure P2 in the return chamber 21, and the annular area S2 of the piston.
[0036] During normal operation, the return chamber 21 of the compensated piston cylinder 20 is connected to the front flushing pipe 51 of the high-speed pump via the oil inlet compensation pipe 31; simultaneously, the progress chamber 22 is connected to the lubrication chamber of the sliding bearing 40 in the pump chamber via the balance pipe 32. To prevent solid particles in the pump chamber from entering the progress chamber 22 of the compensated piston cylinder 20 and affecting its operation, a switchable dual filter 32a is added to the balance pipe 32 between the pump chamber and the progress chamber 22. Furthermore, a differential pressure measuring pipe 34 is bridged between the oil inlet compensation pipe 31 and the balance pipe 32, and a differential pressure transmitter is installed on the differential pressure measuring pipe 34.
[0037] Before operation, the pressure at the bottom of the compensated piston cylinder 20, i.e., the pressure in the process chamber 22, is the same as the pressure in the lubrication chamber. The return chamber 21 is connected to the buffer tank 52 via an oil supply line 33 with an oil replenishment pump 33a, so that white oil can be replenished as needed. During normal operation, the piston is at the bottom of the compensated piston cylinder 20, and the cylinder is filled with white oil. Of course, a support ring can be placed at the bottom of the piston to prevent damage to the piston due to impact with the cylinder when it reaches the bottom.
[0038] In actual operation, when the Plan32 flushing pump (i.e., the high-speed pump) malfunctions, the external flushing fluid supply stops, and the check valve at the front flushing line 51 prevents backflow of flushing fluid or even media from the pump chamber. The pressure at the bottom of the compensating piston cylinder 20 remains constant. At this time, the white oil stored in the return chamber 21 of the compensating piston cylinder 20 can seamlessly connect with the front flushing line 51, providing white oil to the sliding bearing 40 in the pump chamber. When the piston in the compensating piston cylinder 20 rises to a certain height along the cylinder body, the liquid level alarm of the compensating piston cylinder 20 is triggered, and the interlocked oil replenishment pump 33a starts to replenish oil to the return chamber 21 of the compensating piston cylinder 20. When the piston liquid level reaches the bottom, the interlocked oil replenishment pump 33a stops.
[0039] Thus, the compensating piston cylinder 20 of the present invention can continuously provide flushing fluid to the sliding bearing 40 of the pump chamber in emergency situations, ensuring the safe and continuous operation of the device.
[0040] For the polyethylene axial flow pump itself, such as Figure 3 As shown, it specifically includes a pump body 10 with a pump chamber, and a pump shaft 61 passing through the pump body 10. Along the axial direction of the pump shaft 61, a locking nut 64, an impeller 62, a guide vane 11, a front bearing, a connecting frame with a mechanical seal 63, a bearing housing with a shaft oil seal, and a rear bearing 65 are arranged sequentially. Of course, Figure 3 This is just one embodiment. In actual operation, additional functions can be achieved by adding an inducer wheel.
[0041] For the first inlet 11a and the second inlet 11b, the blades passing through the corresponding guide vanes 11 are arranged in an upper and lower split structure. That is, the connections between the front flushing pipe 51 and the balance pipe 32 and the pump body 10 are located on opposite sides of the pump body 10 to ensure optimal performance. The drain port 12 is directly connected to the buffer tank 52 to achieve a circulating flow effect. Furthermore, the front flushing pipe 51 also has a branch pipe 53, allowing direct access to... Figure 2 The connection shown leads to the middle section of the passageway, achieving a direct oil replenishment effect.
[0042] Taking the arrangement of the inducer as an example: In actual assembly, the guide vane 11 is welded inside the pump cavity, and the tube of the guide vane 11 extends horizontally and penetrates the pump body 10 to form a through cavity. The pump shaft 61 passes through the through cavity and extends from the pump body 10 into the pump cavity, with the inducer positioned at the front end of the pump shaft 61. The inducer can be driven to rotate with the pump shaft 61 via the front connecting key. The impeller 62 is positioned at the rear of the inducer. The number of blades in the inducer is less than that in the impeller 62, and the outlet blades of the inducer are offset from the inlet blades of the impeller 62 by a certain angle. In this way, when the impeller 62 and the inducer rotate together and drive the medium from the inlet through the inducer to do work before entering the impeller 62, the phenomenon of resonance of the medium at the same frequency can be avoided, thus affecting the performance of the device. The rear connecting key drives the impeller 62 to rotate with the pump shaft 61, and then the inducer and impeller 62 are locked by the threaded engagement of the locking nut 64 with the front end of the pump shaft 61. At this time, the guide vane 11 is positioned at the rear of the impeller 62 outlet. Similarly, the impeller 62 has fewer blades than the guide vane 11, and the outlet blades of the impeller 62 are offset from the inlet blades of the guide vane 11 by a certain angle. This way, when the impeller 62 and the inducer rotate together and drive the medium from the inlet through the impeller 62 to perform work before entering the guide vane 11, the phenomenon of resonance at the same frequency in the medium can be avoided, thus preventing any impact on the device's performance. In actual design, as mentioned above, the guide vane 11 is welded to the pump cavity, thus becoming an integral part of the pump body 10. Therefore, through the above improvements to the polyethylene axial flow pump, when inspection, maintenance, or pump disassembly is required, the impeller 62 and inducer can be removed by removing the locking nut 64, while the pump shaft 61 and bearing housing can be pulled out from the drive end for inspection and maintenance operations, making disassembly and assembly very convenient.
[0043] Furthermore, such as Figure 3 As shown, the front end of the through-cavity contains only the sliding bearing 40, which constitutes the front bearing. The front bearing and the rear bearing 65 form two-point contact, providing two-point support during pump operation for smoother operation. The mechanical seal 63 is installed in the frame at the rear of the pump body 10, primarily for sealing during pump operation. The frame includes a connecting frame and a bearing housing. In actual assembly, the connecting frame is installed outside the pump body 10, and the bearing housing is bolted to the rear of the connecting frame. The mechanical seal 63, which seals the end of the through-cavity, is placed inside the connecting frame, and the rear bearing 65 is installed inside the bearing housing.
[0044] Of course, those skilled in the art will recognize that the present invention is not limited to the details of the exemplary embodiments described above, but also includes the same or similar structures that can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.
[0045] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
[0046] The technologies, shapes, and structures not described in detail in this invention are all known technologies.
Claims
1. An adaptive compensation system for mechanical seal flushing of a polyethylene axial flow pump, comprising a pump body (10) with a pump chamber, wherein a front bearing is arranged within the pump body (10), characterized in that: The system includes a compensated piston cylinder (20) with its axis arranged vertically, the return chamber (21) of which is located above the process chamber (22); the oil inlet compensation pipeline (31) is connected at one end to the return chamber (21) and at the other end to the front flushing pipeline (51) where the high-speed pump is located; the balance pipeline (32) is connected at one end to the process chamber (22) and at the other end to the lubrication chamber where the front bearing is located; The bottom blade of the guide vane (11) is provided with a sandwich-type first liquid inlet (11a). The inlet of the first liquid inlet (11a) is connected to the front flushing pipeline (51), and the outlet of the first liquid inlet (11a) passes through the bottom wall of the lubrication cavity from bottom to top, thereby connecting to the lubrication cavity. The top blade of the guide vane (11) is provided with a sandwich-type second liquid inlet (11b). The inlet end of the second liquid inlet (11b) is connected to the balance pipeline (32), and the outlet end passes through the top wall of the lubrication cavity, thereby connecting to the lubrication cavity.
2. The adaptive compensation system for mechanical seal flushing of a polyethylene axial flow pump according to claim 1, characterized in that: The balancing pipeline (32) is equipped with a dual filter (32a) that can be switched and cleaned of solid particles in the balancing pipeline.
3. The adaptive compensation system for mechanical seal flushing of a polyethylene axial flow pump according to claim 1, characterized in that: The system also includes an oil supply line (33), on which a replenishment pump (33a) is arranged, and the two ends of the oil supply line (33) are respectively connected to the buffer tank (52) and the return chamber (21) of the compensated piston cylinder (20).
4. The adaptive compensation system for mechanical seal flushing of a polyethylene axial flow pump according to claim 3, characterized in that: A differential pressure measuring line (34) is connected between the oil inlet compensation line (31) and the balance line (32), and a differential pressure transmitter is arranged on the differential pressure measuring line (34).
5. The adaptive compensation system for mechanical seal flushing of a polyethylene axial flow pump according to claim 4, characterized in that: Switch valves are arranged on the oil inlet compensation pipeline (31), the balance pipeline (32), and the differential pressure measurement pipeline (34).
6. The adaptive compensation system for mechanical seal flushing of a polyethylene axial flow pump according to claim 5, characterized in that: The pump body (10) is in the shape of an arc tube. The pump shaft (61) passes through the outer wall of the pump body (10) and extends to the inlet of the pump body (10) to form a rotary fit with the guide vane (11). The impeller (62) is coaxially installed on the shaft end of the pump shaft (61) located in the pump cavity. With the direction of medium inflow as the front of the impeller (62), an inducer wheel is also coaxially fixed on the pump shaft (61) in front of the impeller (62). Along the direction of medium travel, the number of blades of the inducer wheel, impeller (62) and guide vane (11) increases sequentially. The outlet blade of the inducer wheel is staggered from the inlet blade of the impeller (62), and the outlet blade of the impeller (62) is staggered from the inlet blade of the guide vane (11).
7. The adaptive compensation system for mechanical seal flushing of a polyethylene axial flow pump according to claim 6, characterized in that: The inducer wheel and impeller (62) are both connected to the pump shaft (61) by a key. A locking nut (64) is arranged at the front end of the pump shaft (61), so that the inducer wheel and impeller (62) are clamped by the cooperation between the locking nut (64) and the front end face of the guide vane (11).
8. The adaptive compensation system for mechanical seal flushing of a polyethylene axial flow pump according to claim 7, characterized in that: The cavity of the guide vane (11) extends horizontally along the axial direction of the guide vane (11) to the outer wall of the pump body (10), thereby forming a passage cavity through which the pump shaft (61) can pass; a sliding bearing (40) constituting the front bearing is provided in the cavity of the guide vane (11), and the passage cavity where the sliding bearing (40) is located constitutes the lubrication cavity; a rear bearing (65) is provided at the frame on the outer wall of the pump body (10), thereby enabling the pump shaft (61) to rotate in a simply supported beam manner at the pump body (10) and the frame.
9. The adaptive compensation system for mechanical seal flushing of a polyethylene axial flow pump according to claim 8, characterized in that: The passageway extends into the frame, and a mechanical seal (63) is installed at the end of the passageway in front of the rear bearing (65). The flushing fluid of the front flushing pipe (51) enters the passageway through the inlet at the guide vane (11), passes through the sliding bearing (40), the gap between the pump shaft (61) and the passageway, and the mechanical seal (63) in sequence, and is then discharged to the buffer tank (52) through the drain port (12). A branch pipe (53) is also provided at the front flushing pipe (51), which is directly connected to the gap between the pump shaft (61) and the passageway.