Electromagnetically controlled multistage centrifugal pump with axial force balance

Abstract

The invention discloses a multi-stage centrifugal pump with electromagnetically controlled axial force balance, comprising a pump body, a pump shaft, a balancing disk, an impeller, a guide vane, a water inlet section, a water outlet section, a high-pressure side bearing component, a high-pressure side mechanical seal, a low-pressure side bearing component, and a low-pressure side mechanical seal. The pump is characterized in that it also comprises a control device, an electromagnetic cavity, an electromagnet, a permanent magnet, a displacement sensor, and a pressure sensor. The axial movement clearance during the rotation of the pump shaft is monitored in real time by the displacement sensor and uploaded to the control device. The outlet water pressure is monitored in real time by the pressure sensor, and the pressure information is uploaded to the control device. The control device balances the fluctuation of the axial force of the multi-stage centrifugal pump by controlling the current of the electromagnet. The invention solves the technical problem of axial force imbalance of the multi-stage centrifugal pump during operation and when the multi-stage centrifugal pump is turned on and off, avoids wear or burning of the balancing disk of the multi-stage centrifugal pump, significantly improves the stability of operation, and prolongs the service life.

Description

Technical Field

[0001] The invention relates to the technical field of fluid machinery, in particular to a multi-stage centrifugal pump with electromagnetically controlled axial force balance. Background Art

[0002] At present, the existing multi-stage centrifugal pump shaft 2 force balancing mechanism is mainly a balancing disc 3. There are two sealing gaps in this balancing device, see the attached Figure 2 , one is that there is a radial gap b1 between the hub (or sleeve) and the pump body 1; the other is that there is an axial gap b2 between the end face of the balancing disc 3 and the pump body 1. The balancing chamber behind the balancing disc 3 is connected to the inlet of the pump body 1 by a connecting pipe. The pressure of the liquid before the radial gap is the pressure P3 under the rear cover plate of the last stage impeller 4, which drops to P4 through the radial gap b1, and then drops to P5 through the axial gap, while the liquid pressure at the lower back of the balancing disc 3 is P6, which is approximately different from the pump suction pressure by a connecting pipe loss. The pressure difference P4-P6 before and after the balancing disc 3 generates a backward thrust on the balancing disc 3, which is called the balancing force F1. The direction of F1 is opposite to the direction of the axial force F of the liquid on the rotor, so it can balance the axial force. The two gaps in this balancing device have their own functions and are interconnected. If the axial force F on the rotor is greater than the balancing force F1 on the balancing disc 3, the rotor will move to the left, thereby reducing the axial gap b2, increasing the gap resistance, and reducing the leakage. In this way, the speed of the liquid flowing through the radial gap b1 decreases, and the loss in the gap decreases, thereby increasing the pressure P4 in front of the balancing disk 3, and the rotor continues to move to the left. The balancing force continues to increase, and when it moves to a certain position, the balancing force F1 is equal to the axial force F, thus reaching a new balance. By the same token, when the axial force is less than the balancing force, the rotor moves to the right and can also reach a new balance. However, the inertial force during the left and right movement of the rotor causes the axial gap b2 to not stay at the position where the axial force is balanced, resulting in an imbalance of the axial force. If the balance is not established in time, it will cause wear and burning of the balancing disk 3. At the same time, this type of multi-stage centrifugal pump will also cause the axial force to be unable to establish balance due to the loss of pressure during the start-up and shutdown process, which will also cause wear and burning of the balancing disk 3.

[0003] In addition, for intermittent operation (such as the high-pressure hydraulic decoking pump in the delayed coking unit of the petrochemical industry, which is started 1-2 times a day and runs for 2-4 hours each time), frequent start-up and the medium contains particles, the balance disc 3 and the end face of the balance sleeve will be worn once the pump unit is started or shut down. When the wear amount of the balance disc 3 exceeds the amount of movement left by the balance disc 3 and the centrifugal pump body 1 to the suction end, the wear ring of the front cover plate of the centrifugal pump impeller 4 (rotating part) and the wear ring of the centrifugal pump body 1 (stationary part) will be worn. In severe cases, the impeller 4 and the wear ring in the centrifugal pump rotor component will bite, thereby threatening the safe and stable operation of the pump unit. In addition, with the balance disc 3 structure, the medium will heat up slightly in the pump, especially at a small flow rate, which will lead to lower pump efficiency. In this case, the balance leakage water is depressurized through a very small gap and may vaporize, resulting in pressure fluctuations. When it is directly introduced into the inlet of a multi-stage centrifugal pump through a balance return pipe, the pump will cavitate and cause unstable operation. Summary of the invention

[0004] The purpose of the present invention is to solve the above-mentioned deficiencies in the prior art and to provide an electromagnetically controlled axial force balanced multi-stage centrifugal pump with novel structure, high degree of automation, high operating stability, long service life and high working efficiency.

[0005] The technical solution adopted by the present invention to solve its technical problem is:

[0006] A multi-stage centrifugal pump with electromagnetically controlled axial force balance, comprising a pump body 1, a pump shaft 2, a balancing disc 3, an impeller 4, a guide vane 5, a water inlet section 6, a water outlet section 7, a high-pressure side bearing component 8, a high-pressure side mechanical seal 9, a low-pressure side bearing component 10, and a low-pressure side mechanical seal 11, characterized in that it also includes a control device, an electromagnetic cavity 12, an electromagnet 13, a permanent magnet 14, a first displacement sensor 15-1, a second displacement sensor 15-2, and a pressure sensor 16. The pump shaft 2 extends outwardly along the high-pressure side bearing component 8 into the electromagnetic cavity 12, a permanent magnet 14 is fixed on the pump shaft 2 in the electromagnetic cavity 12, an electromagnet 13 is fixed on the inner wall of the electromagnetic cavity 12 outside the permanent magnet 14, and the electromagnet 13 is electrically connected to the control device. The first displacement sensor 15-1 is installed on the balance The first displacement sensor 15-1 corresponds to the second displacement sensor 15-2, and the first displacement sensor 15-1 and the second displacement sensor 15-2 are electrically connected to the control device respectively. The pressure sensor 16 is installed on the side wall of the water outlet section 7, and the pressure sensor 16 is electrically connected to the control device. The axial movement clearance of the pump shaft 2 during the rotation process is monitored in real time by the first displacement sensor 15-1 and the second displacement sensor 15-2, and uploaded to the control device. The outlet water pressure is monitored in real time by the pressure sensor 16, and the pressure information is uploaded to the control device. The control device balances the fluctuation of the axial force of the multi-stage centrifugal pump by controlling the current of the electromagnet 13.

[0007] The control device of the present invention adopts a PLC control device, which is embedded with program steps for real-time monitoring of pressure and displacement during operation, program steps for controlling the current size of the electromagnet 13, and program steps for maintaining a minimum safety distance when starting and shutting down, so as to achieve the effect of automatically adjusting the balance.

[0008] By adopting the above structure, the present invention solves the technical problem of axial force imbalance caused by pressure fluctuation during the operation of the multi-stage centrifugal pump. At the same time, it also solves the technical problem of axial force imbalance caused by pressure loss when the multi-stage centrifugal pump is turned on and off, avoiding the wear or burning of the balance disk of the multi-stage centrifugal pump, significantly improving the operating stability and extending the service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a schematic structural diagram of an embodiment of the present invention.

[0010] Figure 2 It is a control principle block diagram of the present invention.

[0011] Figure 3 It is a schematic diagram of axial force balance in the prior art.

[0012] Figure numerals: pump body 1, pump shaft 2, balancing disc 3, impeller 4, guide vane 5, water inlet section 6, water outlet section 7, high-pressure side bearing component 8, high-pressure side mechanical seal 9, low-pressure side bearing component 10, low-pressure side mechanical seal 11, electromagnetic chamber 12, electromagnet 13, permanent magnet 14, displacement sensor 15, pressure sensor 16, pump motor 17, PLC control device 18. DETAILED DESCRIPTION

[0013] The present invention is described below in conjunction with the accompanying drawings and embodiments.

[0014] Embodiment, as attached Figure 1 As shown, an electromagnetically controlled axial force balanced multi-stage centrifugal pump comprises a pump body 1, a pump shaft 2, a balancing disc 3, an impeller 4, a guide vane 5, a water inlet section 6, a water outlet section 7, a high-pressure side bearing component 8, a high-pressure side mechanical seal 9, a low-pressure side bearing component 10, and a low-pressure side mechanical seal 11. The structures and connection relationships of the pump body 1, the pump shaft 2, the balancing disc 3, the impeller 4, the guide vane 5, the water inlet section 6, the water outlet section 7, the high-pressure side bearing component 8, the high-pressure side mechanical seal 9, the low-pressure side bearing component 10, and the low-pressure side mechanical seal 11 are the same as those in the prior art, which will not be described in detail. It is characterized in that The pump shaft 2 extends outwardly along the high-pressure side bearing component 8 into the electromagnetic cavity 12. A permanent magnet 14 is fixed to the pump shaft 2 in the electromagnetic cavity 12. An electromagnet 13 is fixed to the inner wall of the electromagnetic cavity 12 outside the permanent magnet 14. The electromagnet 13 is electrically connected to the control device. The first displacement sensor 15-1 is installed on the dynamic balancing plate of the balancing plate 3. The second displacement sensor 15-2 is installed on the inner wall of the electromagnetic cavity 12 outside the permanent magnet 14. The second displacement sensor 15-2 is installed on the inner wall of the electromagnetic cavity 12 outside the permanent magnet 14. The first displacement sensor 15-1 is installed on the dynamic balancing plate of the balancing plate 3. The first displacement sensor 15-1 is installed on the static balancing plate of the balancing plate, and the second displacement sensor 15-2 corresponds to the dynamic balancing plate. The dynamic balancing plate is fixed on the pump shaft, and the static balancing plate is fixed on the pump body. The first displacement sensor 15-1 and the second displacement sensor 15-2 are electrically connected to the control device respectively. The pressure sensor 16 is installed on the side wall of the water outlet section 7, and the pressure sensor 16 is electrically connected to the control device. The axial movement clearance of the pump shaft 2 during the rotation process is monitored in real time by the first displacement sensor 15-1 and the second displacement sensor 15-2, and uploaded to the control device. The outlet water pressure is monitored in real time by the pressure sensor 16, and the pressure information is uploaded to the control device. The control device balances the fluctuation of the axial force of the multi-stage centrifugal pump by controlling the current of the electromagnet 13. The present invention solves the technical problem of axial force imbalance caused by pressure fluctuation during the operation of the multi-stage centrifugal pump. At the same time, it also solves the technical problem of axial force imbalance caused by pressure loss when the multi-stage centrifugal pump is turned on and off, avoiding the wear or burning of the balancing plate 3 of the multi-stage centrifugal pump, significantly improving the operation stability and extending the service life.

[0015] The control device of the present invention adopts a PLC control device 18, which is embedded with program steps for real-time monitoring of pressure and displacement during operation, program steps for controlling the current size of the electromagnet 13, and program steps for maintaining a minimum safety distance when starting and shutting down, so as to achieve the effect of automatically adjusting the balance.

[0016] When the present invention is started up, the PLC control device 18 first supplies power to the electromagnet 13. When the displacement sensor 15 receives the displacement signal S of the balancing plate 3 on the pump shaft 2 and uploads it to the PLC control device, the PLC control device compares the received displacement signal S with the minimum safe axial distance b. When the displacement values ​​S monitored by the first displacement sensor 15-1 and the second displacement sensor 15-2 are greater than or equal to the minimum safe axial distance b, the PLC control device 18 directly instructs the pump motor 17 to supply power. If the displacement value S is less than the minimum safe axial distance b, the PLC control device 18 supplies power to the pump motor according to the current of the electromagnet 13 corresponding to the compared value, so as to balance the fluctuation of the axial force through the electromagnet 13 according to the corresponding current, so as to keep the pump shaft 2 running within the standard range.

[0017] During operation, when the operating conditions change, the pressure sensor 16 uploads the water pressure signal P5 of the water outlet section 7 to the PLC control device. The PLC control device 18 corresponds to the standard axial clearance b2 set in the program step according to the uploaded different pressure signals P5. The standard axial clearance b2 will ensure the axial force balance under the pressure of the pressure signal P5. At the same time, the first displacement sensor 15-1 and the second displacement sensor 15-2 receive the displacement signal value S of the balancing disk 3 on the pump shaft 2 and upload them to the PLC control device 18. The PLC control device 18 compares the uploaded displacement signal value S with the standard axial clearance b2, and controls the current of the electromagnet 13 by the difference between the displacement signal value S and the standard axial clearance b2, so that the electromagnet 13 changes the magnitude and direction of its own magnetic force through the current to control the permanent magnet 14 to generate an axial force, ensuring that the axial clearance between the pump shaft 2 and the pump body 1 can quickly reach the set standard axial clearance b2, effectively curbing the damage of the pump rotor inertia force to the axial force balance, avoiding wear and burning of the balancing disk 3, extending the service life, and significantly improving the work efficiency;

[0018] When the operation is to be stopped, the PLC control device 18 first cuts off the power to the pump motor, and the PLC control device 18 continues to supply power to the electromagnet 13 to ensure that the displacement signal value S monitored by the displacement sensor 15 is greater than or equal to the set value. When the pressure value monitored by the pressure sensor 16 is 0, it indicates that the pump shaft 2 does not rotate and the head reaches 0. The PLC system then cuts off the power to the electromagnetic system, so that the pump shaft 2 stops running within the standard range.

[0019] The minimum safe axial distance of the present invention is 0.1 mm, the standard axial clearance b2 is set to 0.1 mm-0.28 mm, and the displacement signal value S is set to 0.1 mm-0.28 mm.

[0020] By adopting the above structure, the present invention effectively solves the technical problem that the balancing disk may be worn or burned due to temporary imbalance of axial force caused by changes in working conditions during the operation of the multi-stage pump. At the same time, it also solves the technical problem that the axial force is unbalanced due to pressure loss when the multi-stage pump is turned on or off, thereby avoiding the wear and burning of the balancing disk of the multi-stage pump. The present invention has the advantages of novel structure, high stability, extended service life, and the ability to achieve rapid and automatic balancing of axial force.

Claims

1. An electromagnetically controlled axial force balanced multistage centrifugal pump, comprising a pump body, a pump shaft, a balancing disc, an impeller, a guide vane, a water inlet section, a water outlet section, a high-pressure side bearing component, a high-pressure side mechanical seal, a low-pressure side bearing component, and a low-pressure side mechanical seal, Features It also includes a control device, an electromagnetic cavity, an electromagnet, a permanent magnet, a first displacement sensor (15-1), a second displacement sensor (15-1), and a pressure sensor. The pump shaft extends outwardly along the high-pressure side bearing component into the electromagnetic cavity. A permanent magnet is fixed on the pump shaft in the electromagnetic cavity. An electromagnet is fixed on the inner wall of the electromagnetic cavity outside the permanent magnet. The electromagnet is electrically connected to the control device. The first displacement sensor (15-1) is installed on the dynamic balancing disk of the balancing disk. The second displacement sensor (15-1) is installed on the static balancing disk of the balancing disk. The first displacement sensor (15-1) corresponds to the second displacement sensor (15-1). The first displacement sensor (15-1) and the second displacement sensor (15-1) are electrically connected to the control device respectively. The pressure sensor is installed on the side wall of the water outlet section. The pressure sensor is electrically connected to the control device. The axial movement clearance during the rotation of the pump shaft is monitored in real time by the first displacement sensor (15-1) and the second displacement sensor (15-1), and the information is uploaded to the control device; the outlet water pressure is monitored in real time by the pressure sensor, and the pressure information is uploaded to the control device, and the control device balances the fluctuation of the axial force of the multi-stage centrifugal pump by controlling the current of the electromagnet; The control device adopts a PLC control device, and the PLC control device is embedded with program steps for real-time monitoring of pressure and displacement during operation, program steps for controlling the magnitude of the electromagnet current, and program steps for maintaining a minimum safety distance when starting and shutting down the machine; When the machine is started, the PLC control device first supplies power to the electromagnet. When the displacement sensor receives the displacement signal S of the balancing plate on the pump shaft and uploads it to the PLC control device, the PLC control device compares the received displacement signal S with the minimum safe axial distance b. When the displacement value S monitored by the first displacement sensor (15-1) and the second displacement sensor (15-1) is greater than or equal to the minimum safe axial distance b, the PLC control device directly instructs the pump motor to supply power. If the displacement value S is less than the minimum safe axial distance b, the PLC control device supplies power to the pump motor according to the magnitude of the electromagnet current corresponding to the compared value, so as to balance the fluctuation of the axial force through the electromagnet according to the corresponding current, so that the pump shaft can operate within the standard range. When the operation is to be stopped, the PLC control device first cuts off the power to the pump motor, and the PLC control device continues to power the electromagnet to ensure that the displacement signal value S monitored by the displacement sensor is greater than or equal to the set value. When the pressure value monitored by the pressure sensor is 0, it means that the pump shaft does not rotate and the head reaches 0. The PLC system then cuts off the power to the electromagnetic system, so that the pump shaft remains within the standard range and stops running.

Images