Application of the most popular delaire variable f

2022-10-18
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Application of delaire variable frequency speed regulation in water pump system

1. Preface

the annual power consumption cost of the water supply company of Daqing Petroleum Administration Bureau accounts for about 30% of the total cost of water supply, and the power cost of water transmission and distribution accounts for about 70% of the total power cost. Therefore, how to adjust the daily operation of the export pump to maintain the power consumption per ton of water transmission and distribution within a more economical and reasonable range is the focus of energy conservation. We have always actively explored, carefully studied and taken effective measures to solve this problem

2. Raising problems

the Longhupao water intake plant of the company is located on the North Bank of Longhupao, with a daily water intake capacity of 500000 cubic meters/day. In the original design, considering the medium and long-term planning and the most unfavorable water volume and water level, two pump types were selected, one is the motor 1400kw/10kv, the water intake pump 900hr (H62 meters, q6360 cubic meters/hour), and the other is the motor 900kw/10kw, the water intake pump 700hr (H62 meters, q3900 cubic meters/hour). The design water supply of the first and second phases of the water diversion plant, the secondary pump station of the water intake plant, is 500000 cubic meters/day. Due to the limited production of the oil field, the external water consumption has decreased year by year. At present, the actual water delivery volume of the water intake plant is only 10000 cubic meters, which improves the attraction of personnel, funds and projects/day. The total flow Q of the pump is only 10000 cubic meters/hour, the head loss of the water delivery pipeline is 18-20 meters, and the nameplate lift of the pump is 62 meters. If the pressure drop of the pump is equal to the pipe resistance, the pump will run overload. Therefore, the water intake plant can only control the pump pressure by adjusting the outlet gate, so that the pump can operate in the high-efficiency area. Such operation not only increases the head loss of the gate and wastes a lot of electric energy, but also if the throttle adjustment of the gate is not appropriate, the pump is easy to deviate from the high-efficiency section or overload operation, resulting in an increase in the failure rate of the pump and shortening the service life of the unit. In the past two years, the pump has been repaired more than 10 times, consuming more than 1 million yuan of maintenance cost. As a major producer of the company, Zhongshui water diversion plant plays a decisive role in ensuring the use of water in the oil field. Therefore, the technical transformation of the water delivery pump of Longhupao water plant is inevitable

3. Preliminary calculation and demonstration of frequency conversion transformation scheme

generally, the pump is designed and operated according to the best working conditions under the rated working conditions. As shown in Figure 1, the typical working curve of the pump is shown. AB is the performance curve of the pump, which matches the rated system pressure curve ob. At point B, the rated flow under the rated pressure can be obtained. At this point, the pump has the highest efficiency, and the flow can be controlled by closing the valve. When the flow decreases, the pump works at points P, Q, R and s respectively. At this time, the pump needs to work under a very high differential pressure, so the energy output of the pump is much more than that of the actual system, The excess energy is shown as heat loss on the valve and is taken away by the liquid flow. The total input energy to the pump can be obtained by dividing the output energy of the pump by the efficiency of the pump. Generally, the opening of the outlet valve of the pump is adjusted by the digital display box to display the experimental results to reduce the flow, and the energy loss is quite large

by using frequency converter speed regulation, the motor-driven pump can run at variable speed. The characteristic curve of the pump matches the needs of the system under any flow. The flow is proportional to the motor speed, and the resulting differential pressure is proportional to the square of the rotational speed. As shown in Figure 2, after stepless frequency regulation, countless ab-cd pump characteristic curves can be obtained, and any intersection of the pipeline characteristic curve and the shadow zone formed by abdc, It can be used as a working point to adapt to the change of external water volume, reach the flow corresponding to points P, Q, R and s at a small head, and only lose a little energy, so its energy-saving effect is quite considerable

for the same vane pump, there are the following rules:

q1/q2=n1/n2 h1/h2= (n1/n2) 2 n1/n2= (n1/n2) 3

the 1#, 3#, 6# pumps of Longhupao water intake plant are imported large pumps, and their motor speeds are 748 r/m, 745 r/m, 750 r/m respectively

if the speed of 3 # pump is adjusted to 500 r/m, its flow, head and power parameters are as follows:

q original/q change =n original/n change =748/500=1.496

q change =4251.3 vertical foaming ratio 10-30 times square meters/hour

h original/h change = (N original/n change) 2=1.496 2

h change =28.59 meters

n original/n change = (N original/n change) 3=1.496 3

n transformer =412.2 kW

if the speed is adjusted to 550r/m, then q=4663 m3/h, h=34 m, n=547 kW, After speed regulation, the pump parameters are basically suitable for the current working conditions. Of course, the above calculation is carried out on the assumption that the pipeline characteristic curve of the system remains unchanged. After installing the frequency conversion and speed regulation equipment, the pump outlet valves can be fully opened, and the pipeline characteristic curve of the system will shift outward, so the pump operating parameters after speed regulation are more likely to meet the requirements of actual working conditions. Therefore, this scheme can be determined to be desirable

4. Energy saving estimation of variable frequency speed regulation scheme

the energy consumption calculation formula of water pump is: p= (k × H × Q)/ η K: Is margin coefficient η: Efficiency

assuming that the actual pressure of the water pump is reduced from the current 5.8kg speed regulation to 2.5kg, and the flow remains unchanged, p25/p58=25/58 = 43%, that is, the power consumption is theoretically reduced by 1-43% = 57%. If the electricity charge is 0.41 yuan/kWh, the motor efficiency is 0.95, and the operation is 330 days/year, the original annual electricity consumption is (1400kW × twenty-four × three hundred and thirty × 0.41)/0.95 = 4.78 million yuan

after the variable frequency speed regulation is reduced to 2.5kg, the annual electricity consumption is 478 × 43% = 2.0554 million yuan, and the annual electricity saving is 4.78-2.0554 million yuan = 2.725 million yuan. Initially, the energy-saving effect is considerable

5. Scheme determination

considering the actual conditions of the middle lead pump, after careful introduction of the test function calculation, demonstration, multi-faceted investigation and comparison of many manufacturers of the lower spring fatigue testing machine, we decided to install the high-voltage high-power frequency converter produced by Beijing Lide Huafu company. All performance indexes of the frequency converter meet the process requirements of the water pump, with high reliability, short transformation time and quick effect

the specific scheme is to close the connecting valve between phase I and phase II, and the phase II pipe operates independently. The frequency converter uses the belt and one method to drive the 6 pump. When the 6 pump fails, it can be put into power frequency operation. The power frequency/frequency conversion is switched manually through the bypass cabinet. Moreover, power frequency and frequency conversion switching have electrical interlocking and

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