1. Cause analysis The working principle of the centrifugal water pump: before the pump starts, the pump first fills the water with the water injection funnel, starts the motor, drives the shaft to rotate the impeller, and the water in the impeller is pressed by the center of the impeller to the periphery of the impeller under the action of centrifugal force. , discharged through the drain line. At the same time, at the inlet of the impeller center, the water is pumped to the rim to form a vacuum. Under the action of the atmospheric pressure on the liquid level of the suction well, the water enters the water pump through the water filter and the bottom valve and the suction pipe, and immediately fills the center of the impeller. The impeller rotates continuously, and the water continuously flows into the pump and is discharged to the outlet pipe. The structure of a centrifugal water pump is generally divided into two parts: a fixed part and a rotating part. The fixed part is mainly composed of a water inlet section, a middle section, a water outlet section, a bearing body, a stuffing box and a guide. The inlet section, the intermediate section and the outlet section are connected by a tensioning screw. The rotating part is mainly composed of an impeller, a balance disc, a shaft, a coupling and the like. We carefully analyzed the cause of the pump according to its working principle: 1.1 The gap between the seal ring and the impeller is too large. 1.2 The impeller is blocked by debris. 1.3 Mechanical disc friction loss increases. The mechanical disc friction loss refers to the pressure of the liquid under the action of the adhesion force and the viscous force when the centrifugal pump impeller rotates at high speed in the pump casing filled with liquid. As the impeller radius increases, the pressure increases and the inertial centrifugal force increases. An annular vortex is formed on both sides of the impeller. The energy of the eddy current is transmitted to the fluid by the impeller, which causes the impeller to consume a portion of the power. When the axial spacing increases, the disc friction loss is increased. △N=Kyn3D3 (K fluid constant y fluid gravity n speed D impeller radius) 2. Disintegration test results The water pump is an imported pump (see the table below for specific parameters). Since the overhaul in 2003, various parameters are normal. With the increase of running time, the output of the pump is gradually decreasing, and the current is gradually increasing. The reasons for the specific analysis are as follows: 2.1 Check the water pump inlet filter The output of the water pump is insufficient, and the pressure is low. Firstly, the inlet filter is blocked and the flow area is insufficient. The disassembly check is taken to the inlet filter of the water pump. It is found that the inlet filter is blocked by soft dirt, and the inlet filter is cleaned. The current is reduced, but it is still too high, and it is decided to overhaul the pump. 2.2 Disintegration overhaul found the following problems 2.2.1 There is no blockage at the impeller and no cavitation. 2.2.2 After measurement, it is found that the sealing ring of the pump is seriously worn. According to the technical requirements, the gap between the sealing ring and the inlet and outlet of the impeller should be 0.15mm. Now the gap is 0.4-0.5mm, which is seriously exceeded and the leakage is increased. The main reason for insufficient output and large current. 2.2.3 The balance plate of the water pump and the balance seat have wear phenomenon. After comparison with the standard parts, the total friction amount is 3.5-4mm; the axial and dynamic friction phenomenon at the inlet of the impeller makes the dynamic and static gap of the front part of the impeller become larger, the mechanical disc The friction loss increases, which is another cause of the increase in current. 3. Processing method 3.1 Clean the soft dirt of the flow passage part of the pump impeller, so that the flow passage part meets the design requirements. Cleaned by mechanical means. 3.2 Take the water pump impeller inlet and outlet sealing ring because the wear gap exceeds the standard, according to the conventional maintenance method, the impeller and the sealing ring must be replaced to meet the technical requirements. However, because the pump used in our factory is an imported pump, the price of the parts is relatively high. The price of an impeller should be 200,000, and the sealing ring should be 80,000. The five units must replace five impellers and ten sealed rings. The cost is quite high. Because repairing old and waste, saving energy and reducing consumption is our consistent maintenance principle. After research, it is decided not to replace the pump impeller. Instead, the minimum diameter of the pump inlet and outlet seal ring is Φ294.5±0.02mm (the original design is 4.7294.7±0.02mm), and the material is designed according to the manufacturer. Bronze) processing and manufacturing of the impeller inlet and outlet sealing ring Φ294.8mm (original design is Φ295mm), the data after installation meet the design requirements. The material cost and processing fee of each sealing ring are 5,000 yuan, which saves the maintenance cost by 1.75 million. 3.3 After the pump is disassembled, it is found that the balance disc and the balance seat are worn. Compared with the standard parts, the wear amount reaches 3.5-4mm; the axial and dynamic friction phenomenon at the inlet of the impeller makes the axial gap become larger, and the friction loss of the mechanical disc increases. If it takes 100,000 to replace the balance plate and the balance seat, in order to save money, we will process the balance plate of the water pump according to the original design size and subject the friction surface to nitriding treatment. Calculate the sum of the thickness reduction of the balance plate and the standard part after processing plus the increase of the depth of the balance seat and the standard part, and then add a steel pad of the same thickness a at the axial joint surface of the balance seat and the pump body. The balance tail is welded with stainless steel welding rod to increase the thickness by a to ensure the clearance between the balance seat and the mounting sleeve is 0.6-0.8mm. After reinstallation, the dynamic clearance of the outlet side of the impeller is reduced to reach the design value and the mechanical disc is reduced. Friction losses increase efficiency. The gap between the various departments has reached the design requirements, and the trial operation effect is better. 4. Maintenance effect 4.1 The pump water current is reduced, the output is obviously increased, and the design requirements can be met. 4.2 This overhaul is clearly diagnosed due to the cause, and a reasonable maintenance method is applied, which significantly reduces the maintenance cost. 5. Conclusion Summing up the experience, we deeply understand that the maintenance and repair of mechanical equipment is the foundation of an enterprise development. It requires the full participation and active cooperation of all aspects of personnel. Secondly, a good maintenance process can save raw materials and reduce the maintenance cost of enterprises. In the future, we should continue to carry out technical transformation in accordance with the maintenance principle of “repair first, then replace†and “first attachment, rear main part, and no further machine†under the premise of ensuring quality, and strive to reduce the cost of water supply and ensure the unit. Safety. Commercial Auto Spares,Commercial Auto Parts,Heavy Commercial Vehicle,Auto commercial spares CTT TECHNOLOGY (UK) LIMITED , https://www.cttechx.com