A regulating and balancing system for a segmental multistage pump

Abstract

The present invention discloses a regulating and balancing system for a segmented multistage pump. The segmented multistage pump of the present invention comprises a suction section, a middle section, and a discharge section penetrated by a pump shaft, wherein the pump shaft is sleeved with a first-stage impeller in the suction section, the pump shaft is sleeved with a middle-section impeller in the middle section, and the pump shaft is sleeved with a final-stage impeller in the discharge section, and the balance drum is provided with a balance drum high-pressure end and a balance drum low-pressure end; a high-pressure pressure sensor is installed on the high-pressure end of the balance drum, and a low-pressure pressure sensor is installed on the low-pressure end of the balance drum. The segmented multistage pump of the present invention has a simple structure and a reasonable design; the PLC control system is installed on the outside of the pump body, so that the pump user can observe the axial force change of the multistage pump and the axial force balancing capacity of the balance drum in real time during the operation of the pump; the reverse compensation work of the balance drum mechanism is automatically adjusted by the PLC; the balance drum gap is prevented from being blocked, and the service life of the balance drum is increased; the anti-cavitation performance of the first-stage impeller is improved, and the cover plate force of the front cover plate of the first-stage impeller is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of segmented multistage pumps, and in particular to a method for automatically regulating the axial force of a segmented multistage centrifugal pump when the axial force changes during operation, specifically a regulating and balancing system of the segmented multistage pump. Background Art

[0002] Segmental multistage pumps are widely used in many fields such as petroleum, chemical industry, machinery, mining, light industry, medicine and food. The axial force is the key factor that causes the failure of multistage centrifugal pumps and affects their life. The balance drum is the simplest and most commonly used axial force balancing device for segmental multistage pumps. Due to its compact structure and stable operation, the balance drum is widely used in multistage pumps.

[0003] The balance drum is installed after the last-stage impeller, with one end connected to the pump cavity behind the last-stage impeller and the other end connected to the low-pressure fluid in the suction chamber through a balance pipe, forming a pressure difference between the front and rear surfaces of the balance drum, thereby balancing the axial force generated during the operation of the multi-stage pump. However, during the operation of the pump, due to the presence of impurities in the conveying medium, the gap between the front and rear seals of the impeller and the gap between the balance drum increase, and the operating conditions deviate from the design conditions, etc., causing the axial force to change significantly, and the ability of the balance drum to balance the axial force is affected; if the axial force of the balance drum cannot change with the operation of the multi-stage pump, the following two situations will occur:

[0004] When the balancing axial force of the balance drum is too large, an "excessive axial force" opposite to the impeller inlet direction is generated;

[0005] On the contrary, when the balancing axial force of the balance drum is too small, it will cause a "residual axial force" in the same direction as the impeller inlet; the residual axial force is the main cause of bearing damage, but the continuous change in the direction of the axial force on the bearing will also accelerate the deformation of the bearing and shorten the service life of the bearing, thereby affecting the safe and long-term operation of the multi-stage pump. Summary of the invention

[0006] The purpose of the present invention is to provide a regulating and balancing system for a segmented multi-stage pump.

[0007] To achieve the above-mentioned purpose, the present invention discloses a segmented multi-stage pump, comprising a suction section, a middle section and a discharge section, which are fastened by flanges, the suction section, the middle section and the discharge section are penetrated by a pump shaft, the pump shaft is sleeved with a first-stage impeller in the suction section, the pump shaft is sleeved with a middle-section impeller in the middle section, and the pump shaft is sleeved with a last-stage impeller in the discharge section, the middle section is composed of an annular channel tightly attached to the middle-section impeller, a balance drum is provided on the pump shaft near the discharge section, and is characterized in that: a balance drum high-pressure end and a balance drum low-pressure end are provided on the balance drum; a high-pressure pressure sensor is installed on the high-pressure end of the balance drum, and a low-pressure pressure sensor is installed on the low-pressure end of the balance drum.

[0008] The suction section includes a first-stage impeller, a suction chamber, and a pump chamber in front of the first-stage impeller; the suction chamber is connected to the pump chamber in front of the first-stage impeller and the first-stage impeller in sequence.

[0009] The last-stage impeller is connected to a thrust bearing, an upper cover plate is installed on the thrust bearing, and a gap between the thrust bearing and the upper cover plate is a thrust bearing gap.

[0010] The first-stage impeller is provided with a front cover plate, the front cover plate is connected to a decompression and de-rotation pipe, the decompression and de-rotation pipe is connected to the low-pressure end of the balance drum through a connecting balance pipe, and a proportional flow valve is provided on the balance pipe.

[0011] A temperature sensor is installed on the upper cover plate of the thrust bearing.

[0012] The high-pressure sensor, the low-pressure sensor, the temperature sensor and the proportional flow valve are respectively connected to the PLC control system; a balance drum gap is provided between the balance drum and the high-pressure end of the balance drum.

[0013] The balancing method of a segmented multistage pump described in the present invention is implemented by the following steps:

[0014] 1) Measure the pressure difference between the high-pressure sensor on the high-pressure end of the balance drum and the low-pressure sensor on the low-pressure end of the balance drum at the initial time (design flow, when the balance drum is initially used); the pressure measured by the high-pressure sensor is p1, and the pressure measured by the low-pressure sensor is p2; the pressure difference Δp = p1-p2; measure the initial thrust bearing clearance oil temperature, i.e. T;

[0015] 2) Measure the pressure difference between the high-pressure sensor on the high-pressure end of the balance drum and the low-pressure sensor on the low-pressure end of the balance drum in the working state; the pressure measured by the high-pressure sensor is p'2, and the pressure measured by the low-pressure sensor is p'1; the pressure difference is Δp'=p'2-p1'; measure the temperature of the thrust bearing clearance oil temperature in the working state, that is, T';

[0016] 3) When the pressure difference signal Δp'>Δp received by the PLC control system, ΔT is the temperature rise, and T'>T+ΔT, it means that the balancing axial force of the balance drum is greater than the axial force generated by the multi-stage pump, and "excessive axial force" occurs. The PLC control system sends an electrical signal to reduce the proportional flow valve, so that the pressure at the low-pressure end of the balance drum rises until T'=T, and the valve stops changing;

[0017] 4) When the pressure difference signal Δp'<Δp, T'>T+ΔT received by the PLC control system, ΔT is the temperature rise, indicating that the axial balancing ability of the balance drum is weakened, but the axial force generated by the multi-stage pump increases accordingly. At this time, the PLC control system sends a signal to increase the proportional flow valve to reduce the pressure at the low-pressure end of the balance drum until T'=T, and the valve stops changing;

[0018] 5) When the pressure difference signal Δp'>Δp received by the PLC control system, ΔT is the temperature rise, set to ΔT=5°, when T'>T+ΔT, and the temperature cannot be changed by adjusting the proportional flow valve, it means that the balance drum gap is blocked and the machine should be stopped immediately for inspection.

[0019] The ΔT=5°.

[0020] The ΔT can be adjusted according to requirements.

[0021] The regulating and balancing system of a segmented multi-stage pump described in the present invention has the following beneficial effects:

[0022] 1. Simple structure and reasonable design;

[0023] 2. The actuator and monitoring device of the control device are installed in a very obvious and convenient position outside the pump body, which is convenient for the pump user to observe the changes in the axial force of the multi-stage pump and the axial force balancing capacity of the balance drum in real time during the operation of the pump;

[0024] 3. Automatically adjust the reverse compensation work of the balance drum mechanism through PLC;

[0025] 4. Prevent the balance drum gap from being blocked and increase the service life of the balance drum;

[0026] 5. Improve the anti-cavitation performance of the first-stage impeller and reduce the cover force of the front cover of the first-stage impeller. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a front view of the present invention;

[0028] Figure 2 It is a schematic diagram of the position of the balance drum and its pressure difference monitoring mechanism of the present invention;

[0029] Figure 3 It is a schematic diagram of the position of the thrust bearing and the temperature monitoring mechanism of the present invention;

[0030] Figure 4 This is a schematic diagram of the position of the pressure reducing and de-spinning tube on the front cover of the first-stage impeller;

[0031] In the figure: 1-water absorption chamber, 2-first stage impeller, 3-middle stage impeller, 4-final stage impeller, 5-balance drum, 6-balance drum high pressure end, 7-high pressure sensor, 8-balance drum low pressure end, 9-low pressure sensor, 10-thrust bearing, 11-upper cover, 12-thrust bearing clearance, 13-temperature sensor, 14-balance pipe, 15-proportional flow valve, 16-pressure reduction and de-racing pipe, 17-front cover, 18-PLC control system, 19-balance drum clearance. DETAILED DESCRIPTION

[0032] Example 1

[0033] like Figure 1 , 2 As shown in Figures 3 and 4, a segmented multi-stage pump according to the present invention comprises a suction section, a middle section and a discharge section, which are fastened by flanges, the suction section, the middle section and the discharge section are penetrated by a pump shaft, the pump shaft is sleeved with a first-stage impeller 2 in the suction section, the pump shaft is sleeved with a middle-section impeller 3 in the middle section, and the pump shaft is sleeved with a last-stage impeller 4 in the discharge section, the middle section is composed of an annular channel tightly attached to the middle-section impeller 3, a balance drum 5 is provided near the discharge section of the pump shaft, and is characterized in that: a balance drum high-pressure end 6 and a balance drum low-pressure end 8 are provided on the balance drum 5; a high-pressure pressure sensor 7 is installed on the balance drum high-pressure end 6, and a low-pressure pressure sensor 9 is installed on the balance drum low-pressure end 8.

[0034] The suction section includes a first-stage impeller 2, a suction chamber 1, and a first-stage impeller front pump chamber; the suction chamber 1 is connected to the first-stage impeller front pump chamber and the first-stage impeller 2 in sequence.

[0035] The final impeller 4 is connected to a thrust bearing 10 , an upper cover plate 11 is mounted on the thrust bearing 10 , and a gap between the thrust bearing 10 and the upper cover plate 11 is a thrust bearing gap 12 .

[0036] The first-stage impeller 2 is provided with a front cover plate 17 , which is connected to a decompression and de-racing pipe 16 . The decompression and de-racing pipe 16 is connected to the low-pressure end 8 of the balance drum via a connecting balance pipe 14 , and a proportional flow valve 15 is provided on the balance pipe 14 .

[0037] A temperature sensor 13 is installed on the upper cover plate 11 of the thrust bearing 10 .

[0038] The high-pressure sensor 7 , the low-pressure sensor 9 , the temperature sensor 13 , and the proportional flow valve 15 are respectively connected to the PLC control system 18 ; a balance drum gap 19 is provided between the balance drum 5 and the balance drum high-pressure end 6 .

[0039] The balancing method for a segmented multi-stage pump is characterized in that the implementation steps are as follows:

[0040] 1) Measure the initial pressure difference between the high pressure sensor 7 on the high pressure end 6 of the balance drum and the low pressure sensor 9 on the low pressure end 8 of the balance drum; the pressure measured by the high pressure sensor 7 is p1, and the pressure measured by the low pressure sensor 9 is p2; the pressure difference Δp = p1-p2; measure the initial oil temperature of the thrust bearing gap 12, i.e. T;

[0041] 2) Measure the pressure difference between the high pressure sensor 7 on the high pressure end 6 of the balance drum and the low pressure sensor 9 on the low pressure end 8 of the balance drum in the working state; the pressure measured by the high pressure sensor 7 is p'2, and the pressure measured by the low pressure sensor 9 is p'1; the pressure difference is Δp'=p'2-p1'; measure the temperature of the oil temperature of the thrust bearing clearance 12 in the working state, that is, T';

[0042] 3) When the pressure difference signal Δp' received by the PLC control system 18 is greater than Δp, ΔT is the temperature rise, and T' is greater than T+ΔT, it means that the balancing axial force of the balance drum 5 is greater than the axial force generated by the multi-stage pump, and "excessive axial force" occurs. The PLC control system 18 sends an electrical signal to reduce the proportional flow valve 15, so that the pressure at the low-pressure end 8 of the balance drum rises until T'=T, and the valve stops changing;

[0043] 4) When the pressure difference signal Δp'<Δp, T'>T+ΔT received by the PLC control system 18, ΔT is the temperature rise, ΔT=5°, indicating that the axial balancing ability of the balance drum 5 is weakened, but the axial force generated by the multi-stage pump increases accordingly. At this time, the PLC control system 18 sends a signal to increase the proportional flow valve 15, so that the pressure at the low-pressure end 8 of the balance drum is reduced until T'=T, and the valve stops changing;

[0044] 5) When the pressure difference signal Δp' received by the PLC control system 18 is greater than Δp, ΔT is the temperature rise, set to ΔT = 5°, T'>T+ΔT, and the temperature cannot be changed by adjusting the proportional flow valve 15, it means that the balance drum gap 19 is blocked and the machine should be stopped immediately for inspection.

[0045] When the liquid passes through the suction chamber and enters the first-stage impeller, the energy of the liquid increases continuously through the middle section of the impeller and finally reaches the last-stage impeller. Since a certain axial force is generated when passing through each stage of the impeller, the more stages there are, the greater the axial force is. The axial force must be balanced by a balance drum, and as the working conditions and operating cycle become longer, the axial force generated by the impeller is constantly changing.

[0046] The following situations may occur:

[0047] First: The axial force generated by the impeller is greater than the axial force balanced by the balance drum, and the direction of the axial force is along the direction of the suction chamber;

[0048] Second: The axial force generated by the impeller is smaller than the balancing axial force of the balance drum, and the direction of the axial force is along the direction of the thrust bearing. This constantly changing force is the main reason for the deformation and fracture of the bearing.

[0049] Monitoring method: First, the axial force is monitored by the pressure difference (Δp=p1-p2) between the high-pressure pressure sensor 7 (the measured pressure is p1) installed at the high-pressure end 6 of the balancing drum 5 and the low-pressure pressure sensor 9 (the measured pressure is p2) installed at the low-pressure end 8 of the balancing drum. When Δp becomes smaller, it means that the balancing drum gap 19 becomes larger and the axial capacity of the balancing drum 5 is weakened; on the contrary, when Δp is larger, it means that the axial capacity of the balancing drum 5 is good, or abnormal factors occur and the balancing drum gap 19 is blocked. Therefore, it is unreasonable to monitor the axial force capacity of the balancing drum 5 only from the pressure difference.

[0050] When the balance drum 5 cannot balance the axial force generated by the impeller, the excess axial force is borne by the thrust bearing 10. When the roller of the thrust bearing 10 moves, it rubs against the surrounding solids, causing the surrounding liquid oil temperature in the thrust bearing gap 12 to rise.

[0051] When the oil temperature at the thrust bearing clearance 12 rises, there are two possibilities:

[0052] First, the thrust bearing force is in the direction of the thrust bearing, which means that the balancing axial force of the balance drum is smaller than the axial force generated by the impeller. At this time, the pressure at the low-pressure end 8 of the balance drum needs to be reduced to increase the pressure difference at both ends of the balance drum.

[0053] Second: The thrust bearing 10 is stressed in the direction of the water absorption chamber 1, indicating that the balancing axial force of the balance drum is greater than the axial force generated by the impeller. At this time, the pressure at the low-pressure end 8 of the balance drum needs to be increased to reduce the pressure at both ends of the balance drum. In addition, when the oil temperature at the thrust bearing gap 12 remains unchanged, but the pressure difference at the balance drum gap increases, and the pressure difference cannot be changed by increasing the pressure at the low-pressure end 8 of the balance drum, it means that the balance drum gap 19 is blocked and the machine needs to be stopped for inspection immediately.

[0054] Method for adjusting the low pressure end 8 of the balance drum:

[0055] Since the balancing pipe 14 connects the balancing drum low-pressure pipe 8, the anti-rotation pipe 16 and the front cover plate 17 of the first-stage impeller 2, a proportional flow valve 15 is installed on the balancing pipe 14. When the proportional flow valve is opened wide, the pressure at the low-pressure end 8 of the balancing drum decreases, the pressure difference Δp at both ends of the balancing drum increases, and the axial force balancing ability is enhanced; when the proportional flow valve is opened small, the pressure at the low-pressure end of the balancing drum increases, the pressure difference Δp at both ends of the balancing drum decreases, and the axial force balancing ability is weakened.

[0056] The high-pressure fluid in the balance pipe 14 of the present invention is connected to the low-pressure fluid in the front cover plate gap 17 of the first-stage impeller 2 through the pressure reducing de-cyclone pipe 16. This design not only effectively prevents cavitation caused by the connection with the suction chamber 1, but also helps to weaken the swirl in the gap of the front cover plate 17 of the first-stage impeller 2, thereby reducing the cover plate force of the front cover plate 17.

[0057] Example 2

[0058] like Figure 1 , 2 As shown in , 3 and 4, a segmented multi-stage pump according to the present invention has the same structure as that of Example 1; the axial force of the balance drum is automatically adjusted, and the pressure difference signal (Δp) at both ends of the balance drum 5 and the oil temperature signal T of the thrust bearing 10 are input to the PLC control system 18, and the PLC control system 18 determines the size of the opening of the proportional flow valve 15.

[0059] The PLC control system 18 of the present invention controls the proportional flow valve 15 through dual control of temperature and pressure. The specific control method is as follows:

[0060] 1. Under the design flow rate, record the pressure difference between the high pressure sensor 7 at the high pressure end 6 of the balance drum and the low pressure sensor 9 at the low pressure end 8 of the balance drum on both sides of the newly designed balance drum 5 (at this time, the balance drum gap has not been worn), and the pressure difference value is Δp=p2-p1 (where p2 is the pressure difference measured by the high pressure sensor 7 at the high pressure end 6 of the balance drum; p1 is the pressure difference measured by the low pressure sensor 9 at the low pressure end 8 of the balance drum); and record the oil temperature at the gap of the upper cover plate 11 of the thrust bearing 10, that is, T;

[0061] 2. When the pressure difference signal received by the PLC control system 18 is Δp'=p'2-p1' (where p'2 is the pressure difference measured by the high-pressure pressure sensor 7 at the high-pressure end 6 of the balance drum; p'1 is the pressure difference measured by the low-pressure pressure sensor 9 at the low-pressure end 8 of the balance drum), Δp'>Δp and the temperature signal received by the PLC (where T' is the oil temperature at the gap between the upper cover plate 11 of the thrust bearing 10 under the condition change or long-term state; T is the oil temperature at the gap between the upper cover plate 11 of the thrust bearing 10 under the design condition; ΔT is the temperature rise, set to ΔT=5°, in addition, it can also be adjusted according to demand. When T'>T+ΔT, it means that the balancing axial force of the balance drum 5 is greater than the axial force generated by the multi-stage pump, and "excessive axial force" occurs. At this time, the PLC control system 18 sends an electrical signal to reduce the proportional flow valve 15, so that the pressure in the pump chamber in front of the first-stage impeller rises until T'=T, and the valve stops changing;

[0062] 3. When the pressure difference signal Δp'<Δp received by the PLC control system 18 and the temperature signal T'>T+ΔT received by the PLC, it indicates that the axial balancing ability of the balance drum 5 is weakened, but the axial force generated by the multi-stage pump increases accordingly. At this time, the PLC control system 18 sends a signal to increase the proportional flow valve 15 to reduce the pressure in the pump chamber in front of the first-stage impeller until T'=T, when the valve stops changing;

[0063] 4. When the pressure difference signal Δp'>Δp received by the PLC and the temperature signal T'>T+ΔT received by the PLC, and the temperature cannot be changed by adjusting the proportional flow valve 15, it means that the balance drum gap 19 is blocked and the machine should be stopped immediately for inspection.

[0064] The outer surface of the balance drum 5 of the present invention is provided with sawtooth grooves along the axial direction. This design not only offsets the swirl generated in the outer edge gap but also can draw impurities in the gap into the sawtooth grooves to reduce the risk of blockage of the balance drum gap 19.

Claims

1. A balancing method for a segmented multistage pump, characterized in that: A segmented multistage pump comprises a suction section, a middle section and a discharge section, which are fastened by flanges. The suction section, the middle section and the discharge section are penetrated by a pump shaft. The pump shaft is sleeved with a first-stage impeller (2) in the suction section, the pump shaft is sleeved with a middle-section impeller (3) in the middle section, and the pump shaft is sleeved with a last-stage impeller (4) in the discharge section. The middle section is composed of an annular channel tightly attached to the middle-section impeller (3). A balance drum (5) is provided on the pump shaft near the discharge section, and is characterized in that: a balance drum high-pressure end (6) and a balance drum low-pressure end (8) are provided on the balance drum (5); a high-pressure pressure sensor (7) is installed on the balance drum high-pressure end (6), and a low-pressure pressure sensor (9) is installed on the balance drum low-pressure end (8); the suction section comprises a first-stage impeller (2), a suction chamber (1), and a pump chamber in front of the first-stage impeller; the suction chamber (1) is connected to the pump chamber in front of the first-stage impeller and the first-stage impeller (2) in sequence; The last-stage impeller (4) is connected to a thrust bearing (10), an upper cover plate (11) is mounted on the thrust bearing (10), and a gap between the thrust bearing (10) and the upper cover plate (11) is a thrust bearing gap (12); A front cover plate (17) is installed above the first-stage impeller (2) component, the front cover plate (17) is connected to a decompression and de-raculation pipe (16), the decompression and de-raculation pipe (16) is connected to a low-pressure end (8) of a balance drum via a connecting balance pipe (14), and a proportional flow valve (15) is installed on the balance pipe (14); The high-pressure sensor (7), the low-pressure sensor (9), the temperature sensor (13), and the proportional flow valve (15) are respectively connected to the PLC control system (18); a balance drum gap (19) is provided between the balance drum (5) and the balance drum high-pressure end (6); A temperature sensor (13) is installed on the upper cover plate (11) of the thrust bearing (10); The implementation steps are as follows: 1) measuring the initial design flow rate, the pressure difference between the high pressure sensor (7) on the high pressure end (6) of the balance drum and the low pressure sensor (9) on the low pressure end (8) of the balance drum when the balance drum is in the initial use state; the pressure measured by the high pressure sensor (7) is p1, and the pressure measured by the low pressure sensor (9) is p2; the pressure difference Δp = p1-p2; measuring the initial oil temperature of the thrust bearing clearance (12), i.e. T; 2) measuring the pressure difference between the high pressure sensor (7) on the high pressure end (6) of the balance drum and the low pressure sensor (9) on the low pressure end (8) of the balance drum in the working state; the pressure measured by the high pressure sensor (7) is p'2, and the pressure measured by the low pressure sensor (9) is p'1; the pressure difference value is Δp'=p'2-p1'; measuring the temperature of the oil temperature of the thrust bearing clearance (12) in the working state, that is, T'; 3) When the pressure difference signal Δp' received by the PLC control system (18) is greater than Δp, ΔT is the temperature rise, and when T' is greater than T+ΔT, it means that the balancing axial force of the balance drum (5) is greater than the axial force generated by the multi-stage pump, and "excessive axial force" occurs. The PLC control system (18) sends an electrical signal to reduce the proportional flow valve (15), so that the pressure at the low-pressure end (8) of the balance drum increases until T'=T, and the valve stops changing; 4) When the pressure difference signal Δp'<Δp, T'>T+ΔT received by the PLC control system (18), ΔT is the temperature rise, indicating that the axial balancing ability of the balance drum (5) is weakened, but the axial force generated by the multi-stage pump increases accordingly. At this time, the PLC control system (18) sends a signal to increase the proportional flow valve (15), so that the pressure at the low-pressure end (8) of the balance drum is reduced until T'=T, and the valve stops changing; 5) When the pressure difference signal Δp' received by the PLC control system (18) is greater than Δp, ΔT is the temperature rise, which is set to ΔT=5°. When T'>T+ΔT, and the temperature cannot be changed by adjusting the proportional flow valve (15), it means that the balance drum gap (19) is blocked and the machine should be stopped immediately for inspection.

2. A balancing method for a segmented multistage pump as claimed in claim 1, characterized in that: The ΔT=5°.

3. A balancing method for a segmented multistage pump as claimed in claim 2, characterized in that: The ΔT can be adjusted according to requirements.

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