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About the technological innovation of small and medium pumping stations

06 Nov 2020Email

About the technological innovation of small and medium pumping stations

 


1 Drainage station unit performance test
In order to further check the accuracy of the investigation content, especially the accuracy of the performance of the drainage station unit and the technical status of the existing electromechanical equipment, the drainage station energy-saving technical transformation plan is proposed, and the drainage station unit must be comprehensively tested. Based on the results of the test, it is judged whether and how to reform and how much technical and economic indicators can be improved after the reform, especially how much guarantee can be provided for agricultural production after the reform.

1.1 Test items and methods of use
(1) Test items: According to the test purpose and drainage station conditions, four project parameters such as flow, head (working head, net head), power (motor input power, water pump shaft power), and speed are mainly tested.
(2) Measuring method. Flow measurement method: This test uses the salt concentration method for single unit flow measurement. The main method is to inject a salt solution with a constant flow rate Q into the forepool of the water pump. After the turbulent water particles mix and collide with each other, as well as the stirring action of the pump impeller, the water sample is taken out after the pump is fully mixed with the raw water. , Use a potentiometric titrator to measure the concentration of chloride ions in the raw water and mixed water samples and compare them with the standard mixture prepared from the injection solution and the raw water to calculate the dilution factor, and then calculate the pump water flow.

Method of measuring head:
①The working head H of the centrifugal pump is measured mainly by setting a pressure gauge at the outlet of the pump impeller. The head is converted according to the measured pressure value, and then the difference between the center elevation of the pressure gauge and the water surface elevation of the inlet is added to obtain the working head of the water pump.
②The net head HST measurement mainly uses a level to measure the water surface elevation at the water outlet and the water surface elevation at the water inlet, and the difference between the two elevations is the net head of the pumping station. The method of measuring the input power of the motor: the input power of the motor is measured by the two-wattmeter method, and then checked by the electricity method. The measurement method of the shaft power of the water pump: the output power of the asynchronous motor is equal to the input power of the motor minus the various losses inside the motor. The main internal losses of the motor include five losses including stator iron loss PFE, mechanical loss PMECH, stator copper loss PCU, rotor copper loss PCU2 and stray loss PS. Among them, the stator iron loss and mechanical loss are called constant loss, which can be calculated by measuring the no-load phase current and the motor no-load DC resistance through the no-load test. The copper loss of the rotor can be obtained by measuring the no-load and load speeds, based on the speed difference. The stray loss can be calculated according to the national standard, and the eight-level motor can be calculated at 1% to 1.5% PN (PN is the rated power of the motor). Because the motor and water pump in our region are directly driven, the calculated motor input power is equal to the pump shaft power. Rotation speed measurement method: Directly measured with Shanghai HT-441 non-contact handheld digital tachometer.


1.2 Arrangement of test results
Whether the test is successful, in addition to making accurate records, it is also necessary to organize the test results in detail. Mainly organized as: pump station single unit flow rate results, pump station net head and working head calculation results, motor input power calculation results, motor loss calculations and shaft power results. Various results are used to calculate the efficiency of the drainage station of the statistics office. Pump efficiency np, motor efficiency nmot, unit efficiency ngr, pipeline efficiency npi, and energy unit consumption e, which together constitute the comprehensive economic and technical indicators of the drainage station. 3 Evaluation of technical status of drainage station The evaluation of technical status of drainage station is mainly to compare the measured data with the industry standards publicly promulgated by the state. Those who fail to meet the technical requirements must be reformed, and those that meet the technical requirements must also pass comprehensive economic indicators. Calculate, comprehensively evaluate the economic rationality of the continued use of the drainage station, and finally determine whether it needs to be reconstructed. Generally, the ministerial standard η installed = 54.4% is used as a measure of whether the drainage station needs to be updated.

 


2 Analysis of the problems existing in the drainage station
Through technical achievements and status assessment, the main reasons for generally failing to meet the requirements of the ministerial standards are as follows: (1) The service life of the pumping station equipment has exceeded and approached the 20-year life specified by the Ministry of Water Resources.
(2) Poor management has aggravated engineering and equipment damage. If the silt in the pool in front of the station is heavy and cannot be removed in time, the sediment will be carried into the pump body and severely eroded the impeller and pump body. Lack of funds directly affects the normal maintenance of projects and equipment. my country has always had the problem of rebuilding light pipes, and this defect also exists in drainage stations.
(3) The aging and disrepair of the project (development direction of construction machinery coating) aggravated and shortened the project life. For example, most of the inlet and outlet wing walls and the trash racks in the front pool collapsed and shattered, affecting the normal operation of the project. This is also mainly due to the underestimation of management and insufficient investment after the construction.
(4) The water pump has serious wear and corrosion due to long-term work under water, causing mechanical problems such as vibration, shaft swing, temperature rise, and loud noise during the operation of the equipment. Most of the farmland drainage discharges are not clean water, but rather corrosive sewage containing a lot of pesticides, fertilizers and other chemical substances, especially the illegal discharge of some aquaculture and small factories, which intensifies the corrosive strength of water, water supply pumps and pipelines. Waiting for the equipment to cause considerable damage.

 


3 Determine the technical transformation plan
According to the requirements of the "General Rules for Technical Transformation of Pumping Stations" (SD141-85) issued by the Ministry of Water Resources, the transformation plan is proposed based on the following principles:
(1) For the electromechanical equipment that has exceeded the service life and the equipment of the obsolete model, the technical status of the equipment has been significantly reduced and cannot be modified or repaired, and it is proposed to update.
(2) For equipment that has deteriorated performance and can be used after repair, according to the principle of maximizing the cost-effectiveness ratio, it is necessary to adopt changes during repairs or to update individual components.
(3) For the updated equipment, all new products that are popularized by the country and the existing or potential technical strength of the drainage station can be used for later maintenance are used. It is strictly forbidden to replace the old equipment with old models.
(4) Reinforce or rebuild the entrance and exit wing walls or entrance trash racks.
(5) Reinforce or rebuild the pumping station workshop.

 


4 Conclusion
The renewal and reconstruction of the drainage station is a project of people’s livelihood. We should operate and execute in a realistic and responsible spirit. As long as we pass normal procedures, detailed investigations and studies, accurate test calculations, and comprehensive evaluation and analysis, we will be able to find The most scientific and reasonable transformation plan is put forward to provide guarantee for agricultural production safety.

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