An operating method for a pump set capable of achieving self-regulating constant-flow water supply

Abstract

An operation method for a pump set capable of achieving self-regulating constant-flow water supply, configuring a pump set composed of a feed water pump, an MD pump, and a feed water pump outlet pipe, installing a flow regulating valve, a bypass pipeline, and a drain valve on the feed water pump outlet pipe; presetting the flow rate Q1 of the feed water pump, obtaining the actual operating point value of the MD pump, and taking Q1 as the flow rate value of the feed water pump corresponding to the lowest water level of the suction well; starting the feed water pump at low water level, starting the MD pump after detecting the pressure signal of the pipeline in front of the MD pump, using the flow regulating valve to adjust the flow rate to make the MD pump operate at 93%-98% of the rated current, and determining the flow rate value at this time as the constant flow rate value of the pump set; starting the pump set at high water level, increasing the pressure in the bypass pipeline to open the drain valve; when the water level of the suction well reaches the set low water level, closing the drain valve to achieve constant-flow drainage of the pump set. The present invention solves the problems of flow rate attenuation and cavitation of the MD pump, and achieves the purpose of cavitation-free constant-flow drainage of the pump set by the pump itself without relying on external forces.

Description

Technical Field

[0001] The present invention relates to an operation method for a pump set composed of a feed water pump and an MD pump, and particularly to an operation method for a pump set capable of realizing self-regulating constant flow water supply. Background Art

[0002] The water pump water supply and drainage system is widely used and is closely related to industrial and agricultural production and people's livelihood. It is an electromechanical product that covers all aspects of society with a large quantity and wide range. The total installed capacity of water pumps in the country exceeds tens of millions of units. There are hundreds of thousands of wear-resistant multi-stage water pumps used in coal mines alone. Although the total quantity is not high, its power consumption is very large. The power consumption of water pumps in one year accounts for about 20% of the national electricity consumption.

[0003] The efficiency of water pumps is generally not high, mainly for two reasons. One is that there are relatively serious cavitation problems in the negative pressure water supply (vacuum pumping method) of water pumps; the other is that even in positive pressure water supply (the method of installing a feed water pump at the front end of the main drainage pump), there is also a problem of flow attenuation during the water supply process. There are two reasons for the flow attenuation of water pumps. One is the head, and the other is the cavitation of the water pump.

[0004] It can be seen from the curve H-Q curve of the corresponding relationship between the flow and head of the water pump that during the operation of the water pump, its flow, head, power, and efficiency values are in dynamic changes. For a specific water pump, once it is designed and manufactured, its required net positive suction head (NPSH) is a fixed value. That is to say, once the flow, head, and motor speed of the water pump are determined, its required NPSH is already determined. Therefore, it can be said that the required NPSH of the water pump objectively exists and is something that the water pump itself cannot overcome. The cavitation phenomenon of the water pump is a harmful existence.

[0005] Generally speaking, most water pumps are for negative pressure water supply (the water pump is installed on the pump house floor near the suction well, and a vacuum pumping device is used to create a negative pressure in the pump body, and then under the action of the atmospheric pressure, the liquid enters the pump body, and the water pump starts to operate and transports the liquid to the set location or height), starting at high water level and stopping at low water level. Although there are clear parameters on the nameplate of the water pump, in fact, its flow, head, power, and efficiency values are in dynamic changes. The performance curve of the water pump can prove this. The efficiency at the design point of the water pump is the highest; at the large flow point, the flow increases, the head decreases, the shaft power increases, and the efficiency decreases; at the small flow point, the head increases, and the flow, power, and efficiency decrease. For the convenience of the pump house drivers of each enterprise, they often fully open the regulating valve at the water outlet end of the water pump, so that the water pump operates at a flow rate larger than the large flow point. As a result, the required NPSH of the water pump continues to increase, that is, the suction lift decreases. As a result, the cavitation phenomenon of the water pump is serious, the drainage speed slows down, and the pump efficiency decreases too much.

[0006] Through the above analysis, to improve the efficiency of the water pump, it is necessary to solve the problems of the suction lift and flow attenuation of the water pump. Once this problem is solved, the cavitation problem will be easily solved. To solve this problem, a feed water pump is mainly installed. If the negative pressure water supply of the water pump is changed to positive pressure water supply, the cavitation problem can be solved.

[0007] Although installing a feed water pump at the front end of the MD pump can solve the cavitation problem, it cannot solve the problem of constant flow. The hydraulic model of the feed water pump is a structure with a large flow rate and a low head. The structural feature of the feed water pump is that at a high water level (at this time, the head of the feed water pump is low), the flow rate is large, even exceeding the design point by a lot, which may cause the main drainage pump motor to have an overcurrent; as the liquid level drops, the flow rate of the main drainage pump begins to attenuate. If the drainage height is 9 meters, the attenuation amplitude of the flow rate may be 5%, or even more. Summary of the Invention

[0008] The object of the present invention is to solve the above technical problems existing in the background technology and provide an operation method for a pump group that can achieve self-regulating constant flow water supply.

[0009] The technical solution of the present invention is: an operation method for a pump group that can achieve self-regulating constant flow water supply, and its steps are:

[0010] S1. Pump group configuration: The pump group includes a feed water pump, an MD pump, and a feed water pump outlet pipe connected between the outlet of the feed water pump and the suction port of the MD pump. A flow regulating valve is installed at the corresponding position of the outlet of the feed water pump on the feed water pump outlet pipe. A bypass pipeline is installed at the rear end of the outlet of the flow regulating valve on the feed water pump outlet pipe, and a drain valve is installed on the bypass pipeline;

[0011] S2. Preset the flow rate of the feed water pump:

[0012] Q1 = (1 + a)Q0

[0013] In the formula: Q 1： The flow rate of the feed water pump, Q 0： The flow rate of the MD pump; a: coefficient, and the value of a is 0.15 - 0.25.

[0014] If the actual operating point of the MD pump operates near the design point, a takes the minimum value. If the actual operating point of the MD pump operates near the large flow point of the water pump, a takes the maximum value. When the actual operating point of the MD pump operates between the maximum value near the design point and the minimum value near the large flow point, the value is taken according to the proportional interpolation method;

[0015] Take the preset flow rate value Q1 of the feed water pump as the flow rate value of the feed water pump corresponding to the lowest water level of the suction well, select the feed water pump according to this flow rate value, and the minimum flow rate value of the feed water pump ≥ Q1;

[0016] S3. After the pump unit is installed, first start the feed water pump at the low water level of the set suction well. At this time, the drain valve is in the closed state. The MD pump starts after detecting the pressure signal in the pipeline in front of it. Adjust the flow rate using the flow regulating valve so that the MD pump motor operates at 93%-98% of the rated current. Determine the flow rate value at this time as the constant flow rate value of the pump unit. Stop the pump unit to complete the setting;

[0017] S4. Start the pump unit at the high water level of the set suction well. At this time, the flow rate of the feed water pump is greater than the set constant flow rate value, and the pressure in the bypass pipeline increases, causing the drain valve to open. The excess water in the outlet pipe of the feed water pump is drained through the bypass pipeline. As the water level in the suction well gradually drops, the switching value of the drain valve becomes smaller. When the water level in the suction well reaches the set low water level, the pressure in the bypass pipeline decreases, causing the drain valve to close and the bypass pipeline to stop draining, achieving constant flow rate drainage of the pump unit.

[0018] Further, the bypass pipeline is composed of a horizontal section and a vertical section. The drain valve is arranged in the horizontal section, and the outlet end of the bypass pipeline is located at the lower end of the vertical section.

[0019] Further, the vicinity of the design point refers to ±3% of the design point flow rate, and the vicinity of the large flow point refers to ±3% of the large flow point flow rate.

[0020] Further, install a pressure gauge on the outlet pipe of the feed water pump corresponding to the front end of the MD pump, and detect the pressure in the pipeline in front of the MD pump through the pressure gauge.

[0021] Further, the outlet end of the bypass pipeline communicates with the water well.

[0022] Further, the drain valve is a check valve and includes a valve body, a valve cover, a rocker hinged at the inlet of the valve body, and a valve flap installed on the rocker. The valve flap is inclined and arranged at the inlet of the valve body. When the pressure in the outlet pipe of the feed water pump is high, the valve flap is opened. When the pressure is low, the switching value of the valve flap is reduced, so as to achieve constant flow rate output.

[0023] Further, the horizontal inclination angle of the valve flap is 2-5°.

[0024] The beneficial effects of the present invention are:

[0025] 1. Eliminates the flow rate attenuation phenomenon of the MD pump, enables the MD pump to drain water at a constant flow rate, gives full play to the capabilities of the water pump and the motor, and achieves efficient and rapid drainage effects.

[0026] 2. Solves the problem of flow rate cavitation of the MD pump. The suction lift of the MD pump is not limited by cavitation, which can maximize the effective volume of the mine sump and improve the safety of mine drainage.

[0027] 3. Without relying on external forces, by utilizing the changes in the on-off quantities of the bypass pipeline and the drain valve, the flow rate of the pump group is automatically adjusted, and the pump itself achieves the purpose of cavitation-free constant-flow drainage of the pump group. Description of the Drawings

[0028] Figure 1 is a schematic structural diagram of the pump group of the present invention;

[0029] Figure 2 is Figure 1 a schematic connection structure diagram of the outlet pipe of the medium feed water pump and the bypass pipeline. Detailed Embodiments

[0030] To make the technical problems to be solved, the technical solutions adopted, and the technical effects achieved by the present invention clearer and easier to understand, the present invention will be further described below in conjunction with specific embodiments.

[0031] As shown in the figure, a method for operating a pump group capable of achieving self-regulating constant-flow water supply includes the following steps:

[0032] S1. Configuration of the pump group: The pump group includes a feed water pump 1, an MD pump 5, and a feed water pump outlet pipe 3 connected between the outlet of the feed water pump 1 and the suction port 501 of the MD pump. A flow regulating valve 2 is installed at the outlet of the feed water pump corresponding to the outlet of the feed water pump on the feed water pump outlet pipe 3. A bypass pipeline 6 is installed at the rear end of the outlet of the flow regulating valve 2 on the feed water pump outlet pipe 3. A drain valve 7 is installed on the bypass pipeline 6. A pressure gauge 4 is installed on the feed water pump outlet pipe 3 corresponding to the front end of the MD pump 5; the MD pump 5 is an MD450-60.

[0033] S2. Preset the flow rate of the feed water pump:

[0034] Q1 = (1 + a)Q0

[0035] In the formula: Q 1： The flow rate of the feed water pump 1, Q 0： The flow rate of the MD pump (main drainage pump) 5, a: coefficient, and the value of a is 0.15 - 0.25;

[0036] If the actual operating point of the MD pump is near the design point, a takes the minimum value. If the actual operating point of the MD pump is near the large flow rate point of the water pump, a takes the maximum value. When the actual operating point of the MD pump is between the maximum value near the design point and the minimum value near the large flow rate point, the value is taken according to the proportional interpolation method; the vicinity of the design point refers to ±3% of the design point flow rate value, the vicinity of the large flow rate point refers to ±3% of the large flow rate point flow rate value, the maximum value near the design point = design point flow rate × (1 + 3%), and the minimum value near the large flow rate point = large flow rate point flow rate × (1 - 3%).

[0037] The design point flow rate Q0 of the MD pump (MD450-60) = 450m3 / h, the flow rate Q at the large flow point 大 = 500 m 3 / h, the actual working condition point flow rate is 480 m 3 / h. Calculate the flow rate preset value Q1 of the feed water pump = (1 + a)Q0, and the value of a is determined by the proportional interpolation method:

[0038] a = 0.15 + (480 - 450) / (500 - 450)*(0.25 - 0.15) = 0.21

[0039] Q1 = (1 + a)Q0 = 450*(1 + 0.21) = 544.5 m 3 / h

[0040] Preset the flow rate Q1 of the feed water pump = 545 m 3 / h. Take the flow rate preset value Q1 of the feed water pump as the flow rate value of the feed water pump corresponding to the lowest water level of the suction well. Select the feed water pump according to this flow rate value, and the minimum flow rate value of the feed water pump ≥ Q1.

[0041] S3. After the pump unit is installed, first start the feed water pump 1 at the set low water level of the suction well. At this time, the drain valve 7 is in the closed state. The MD pump 5 starts after detecting the pressure signal of the pressure gauge 4 at its front end. Use the flow regulating valve 2 to adjust the flow rate so that the motor of the MD pump 5 operates at 93% - 98% (determined according to site requirements) of the rated current. If the site requires the motor of the MD pump 5 to operate at 98% of the rated current and the flow rate does not reach Q1 = 545 m 3 / h, such as 530 m 3 / h. To ensure the safety of the motor, determine the flow rate value of 530 m 3 / h at this time as the constant flow rate value of the pump unit. The pump unit stops, and the setting is completed.

[0042] S4. Start the pump unit at the set high water level of the suction well. At this time, the flow rate of the feed water pump 1 is greater than the set constant flow rate value, and the pressure in the bypass pipeline 6 increases, causing the drain valve 7 to open. The excess water in the outlet pipe 3 of the feed water pump is drained through the bypass pipeline 6; as the water level of the suction well gradually drops, the switching value of the drain valve 7 becomes smaller. When the water level of the suction well reaches the set low water level, the pressure in the bypass pipeline 6 decreases, causing the drain valve 7 to close, and the bypass pipeline 6 stops draining, achieving constant flow rate drainage of the pump unit.

[0043] Furthermore, the outlet end of the bypass pipeline 6 communicates with the water well.

[0044] Furthermore, the bypass pipeline 6 is composed of a horizontal section 601 and a vertical section 602. The drain valve 7 is arranged on the horizontal section 601, and the outlet end of the bypass pipeline 6 is located at the lower end of the vertical section 602.

[0045] Further, the flow discharge valve 7 is a one-way valve and includes a valve body 701, a valve cover 702, a rocker 703 hinged at the inlet of the valve body 701, and a valve flap 704 mounted on the rocker 703. The valve flap 704 is arranged obliquely at the inlet of the valve body 701. When the pressure in the outlet pipe 3 of the feed water pump is high, the valve flap 704 is opened. When the pressure decreases, the opening and closing amount of the valve flap 704 is reduced until it is closed, so as to achieve the purpose of constant flow output of the pump set.

[0046] Further, the horizontal inclination angle of the valve flap 704 is 2-5°.

[0047] Further, the start and stop of the pump set are controlled by a PLC, and the pressure signal detected by the pressure gauge is transmitted to the PLC.

[0048] The above are only specific embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An operating method for a pump set capable of achieving self-regulating constant flow water supply, characterized in that: S1. Pump set configuration: The pump set includes a feed water pump, an MD pump, and a feed water pump outlet pipe connected between the outlet of the feed water pump and the suction port of the MD pump. A flow regulating valve is installed at the outlet of the feed water pump corresponding to the outlet of the feed water pump on the feed water pump outlet pipe. A bypass pipeline is installed at the rear end of the outlet of the flow regulating valve on the feed water pump outlet pipe, and a drain valve is installed on the bypass pipeline. S2. Preset the flow rate of the feed water pump: Q1 = (1 + a)Q0, where: Q1: the flow rate of the feed water pump, Q0: the flow rate of the MD pump; a: coefficient, a ranges from 0.15 to 0.

25. If the actual operating point of the MD pump operates near the design point, a takes the minimum value. If the actual operating point of the MD pump operates near the large flow point of the water pump, a takes the maximum value. When the actual operating point of the MD pump operates between the maximum value near the design point and the minimum value near the large flow point, it takes values according to the proportional interpolation method; The preset flow rate value Q1 of the feed water pump is used as the flow rate value of the feed water pump corresponding to the lowest water level of the suction well. Select the feed water pump according to this flow rate value, and the minimum flow rate value of the feed water pump ≥ Q1. S3. After the pump set is installed, first start the feed water pump at the set low water level of the suction well. At this time, the drain valve is in the closed state. The MD pump starts after detecting the pressure signal of the pipeline in front of it. Use the flow regulating valve to adjust the flow rate so that the MD pump motor operates at 93% - 98% of the rated current. Determine the flow rate value at this time as the constant flow rate value of the pump set. The pump set stops, and the setting is completed. S4. Start the pump set at the set high water level of the suction well. At this time, the flow rate of the feed water pump is greater than the set constant flow rate value, and the pressure in the bypass pipeline increases, causing the drain valve to open. The excess water in the feed water pump outlet pipe is drained through the bypass pipeline; As the water level of the suction well gradually drops, the opening degree of the drain valve decreases accordingly. When the water level of the suction well reaches the set low water level, the pressure in the bypass pipeline decreases, causing the drain valve to close, and the bypass pipeline stops draining, achieving constant flow drainage of the pump set.

2. The operating method of the pump set capable of achieving self-regulating constant flow water supply according to claim 1, characterized in that: The bypass pipeline is composed of a horizontal section and a vertical section. The drain valve is arranged in the horizontal section, and the outlet end of the bypass pipeline is located at the lower end of the vertical section.

3. The operating method of the pump unit capable of achieving self-regulating constant flow water supply according to claim 1, characterized in that: Near the design point means ±3% of the design point flow rate, and near the large flow point means ±3% of the large flow point flow rate.

4. The operating method of the pump set capable of realizing self-adjusting constant flow water supply according to claim 1, characterized in that: A pressure gauge is installed on the feed water pump outlet pipe corresponding to the front end of the MD pump.

5. The operating method of the pump set capable of achieving self-adjusting constant flow water supply according to claim 1, characterized in that: The outlet end of the bypass pipeline communicates with the water well.

6. The operating method of the pump set capable of achieving self-adjusting constant flow water supply according to claim 1, characterized in that: The drain valve is a one-way valve and includes a valve body, a valve cover, a rocker hinged at the inlet of the valve body, and a valve flap installed on the rocker. The valve flap is inclined and arranged at the inlet of the valve body; When the pressure in the feed water pump outlet pipe is high, the valve flap is opened. When the pressure is low, the opening degree of the valve flap is reduced, so as to achieve constant flow output.

7. The operating method of the pump set capable of achieving self-adjusting constant flow water supply according to claim 6, characterized in that: The horizontal inclination angle of the valve flap is 2 - 5°.

Images