With the development of urban water supply, water supply enterprises pay more and more attention to energy conservation and consumption reduction under the premise of high quality and quantity water supply. In the water supply enterprises, the pump as a transmission and distribution equipment, which consume 85% -90% of the electricity consumption of the water plant, therefore, to explore and apply energy-saving pump technology for water conservation is of great significance.

First, through a reasonable choice of pump energy

1. Pump reasonable selection

The new water plant should be based on the daily water supply to determine the pump parameters. In principle, the pump flow and lift of the water intake pump room should be selected according to the maximum average daily water supply and lift, and at the same time, the pump efficiency should be taken into consideration when the flow changes and the water level changes, in order to achieve economic operation. The pumps of the second-level pumping station should be selected according to the total lift calculated from the highest daily maximum water supply and pipe network. In addition, the pump efficiency during flow conversion should also be considered. The shape of the pump should make the pump head and flow close to the rated head and rated flow so that the mining point in operation often remain in the university area. Pump selection is often based on the speed than ns to choose, it is an important indicator of the type of pump, the formula is:

Where Q, H for the highest efficiency of the flow and head, but in the actual calculation, because the pump model to be elected, unable to check the value of the highest efficiency point, the general value of the production requirements to replace or use the following approximate Get:

Pump speed n should be consistent with the motor speed, in order to facilitate direct connection. With Q, H and n can find ns, by ns to check the pump "type Pu" to determine the type of pump, select the most suitable type in this type of type Pu, the last in the pump sample fine Check the performance curve of the pump, and then by the pipeline performance curve to determine the pump operating point, such as efficiency in the high-efficiency zone, then meet the requirements, you can choose.

2. Pump performance options

For the process flow stability of the pump, the performance of its choice of focus is to ensure efficient pump operation. In the process of average head lift, if the process flow is large and complicated, pay special attention to whether the adjustment range of Q-H curve and Q-Y curve is relatively flat and whether the pump can operate in the area with higher efficiency.

Second, through a reasonable combination of pumps and energy-saving operation

A reasonable pump matching

Generally, there are at least 2-3 working pumps in the pumping station. From the perspective of energy conservation and economic operation, pumps with similar heads and different flow rates should be used in order to realize the rational configuration of large and small pumps. When the water load changes larger and more frequent, it is best to configure a speed control pump to adapt to changes in water consumption. When the amount of water is large, the operation of large pumps, water consumption hours, stop the pump to run a small pump. This configuration not only reduces the number of pumps running, but also make all the pumps are running in the high-efficiency zone, the pump power consumption decreased significantly, while the deployment of water is also more flexible.

2. Pumps combined parallel operation

In the process of large flow or flow requires dramatic changes in the occasion, depending on the specific circumstances to take different combinations of pumps to run in order to improve the pump efficiency (maximum number of parallel pumps not more than four).

Third, the use of pump speed control technology

1. Pump speed energy saving principle

The principle of energy-saving pump speed can be deduced according to the similar law of fluid dynamics, the relationship between performance and speed is: flow is proportional to speed, lift is proportional to the square of the speed, the power is proportional to the speed of the cubic. The function is as follows:

2. Pump speed conditions and speed pump selection

(1) select the pump speed conditions

Water supply with the seasons, diurnal changes significantly change or when the coefficient of variation is large, the pump often in the high lift or deviate from the high-flow area, low-lift operating conditions point in the pump can not be replaced when the election should be considered Speed ​​pump.

(2) speed pump selection

In the case of multiple pumps, the pump with the largest flow rate and the regular operation should be selected as the variable speed pump. The operating point of the variable speed pump should be located in the middle of the high efficiency pump section. That is, the operating point at rated speed is located at the right end of the high efficiency section , Can even go beyond the high-efficiency section to the right. In addition, the pump is too small or too large than the number of revolutions as a pump, medium and high than the number of revolutions centrifugal pump (ns = 80-300) as the best pump.

3. Pump speed control methods and features

(1) SCR cascade speed control is characterized by high efficiency, mature technology, suitable for 70-95% speed control, but the governor low power factor, and the power grid pollution.

(2) Electromagnetic slip speed control is characterized by simple control, stable and reliable operation, easy remote control and automatic control, high power factor, the disadvantage is that with slip loss.

(3) Liquid viscosity governor (also known as oil film clutch) is characterized by large capacity adjustment, small size, speed control in the range of 30% -100% of the rated speed, low cost, but the film clutch on the mechanical oil requirements are very high , And there is a certain slip loss.

(4) VVVF is the most advanced way in speed regulation technology. It has great potential for energy saving, low noise, stable pressure in water supply network, convenient maintenance and management, less failure, but expensive. The second pump house of our company uses ABB ACS-600 high-power frequency conversion speed control device, the pump power is 560KW. In the current water supply capacity of less than the design load, running the device can maintain a constant water supply network pressure and ease of scheduling, running well.

With the further development of power electronics technology, variable frequency speed regulation will become the mainstream of the pump speed, set a significant profit for energy saving.

4 pump determine the best speed ratio

From the pump theory shows that the speed range is not very wide, the pump speed change will lead to changes in the characteristic curve, resulting in changes in operating conditions, the pump in the high-efficiency zone operation.

The best pump speed ratio should be

Fourth, to strengthen the pump balance test, and timely updates and improvements to improve pump efficiency, to save energy

1. Regular measurement of pump characteristics, mainly Q-H characteristics and Q-y characteristics, such as measuring the pump efficiency is very low, you should promptly replace the pump or impeller.

2. Improper selection or head, the flow is too large, the single-stage pump can be used to cut the outer diameter of the impeller to reduce head and flow, to run in the high-efficiency zone. The amount of impeller cutting and the specific rotation, as shown in Table 1, such as turning over the assembly caused by the pump efficiency is too low but not worth the candle, the general step-by-step turning method to obtain the best amount of impeller turning.

Fifth, to strengthen the maintenance and management of pumps, and actively adopt new technologies and new materials to improve pump efficiency

1. Improve the pump processing, assembly quality, ensure safe and reliable pump operation, minimize the gap between the mouth ring.

2. To enhance maintenance, timely repair of a reasonable leakage gap, when the mouth ring rupture or wear after the leakage gap to exceed the specified value, should be repaired or replaced, based on experience and measured data to determine the mouth ring radius gap outside the impeller mouth ring 2.5-3.5% of the diameter.

3. Actively adopt the new type of packing. Packing in the shaft seal device plays the role of water or gas barrier seal, select a good sealing performance of the filler, not only can solve the leakage, reduce consumption, but also to some extent, improve pump efficiency. In 2000, our company first tried BPT20 liquid new type sealing filler in the centrifugal pump of two pump houses in the waterworks, which did not need cooling and washing, did not wear the shaft and the bearing, improved the pump efficiency and used the good effect.

The prospect of energy-saving pump is very broad, as long as we explore new ideas, continue to explore, according to local conditions to implement the pump energy-saving technologies, water supply enterprises will achieve remarkable results in energy saving.

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June 18, 2024