0 Preface Submerged sewage pump with its excellent performance is widely used in urban water supply and drainage industry, construction site drainage, drainage of factories, mines, residential areas, sewage and wastewater discharge as well as farmland irrigation, water conservancy projects pouring water, aquaculture liquid fertilizer treatment. Its variety, installation methods are fixed wet installation, fixed dry installation and mobile installation. 1 Submersible pump usage and precautions 1.1 Selection During use, the submersible pump should be selected correctly according to the characteristics of its operating conditions. The flow, head, and installation methods should be considered when selecting the type of submersible pump. Only when the selected lift is close to the actual required head, the pump can operate efficiently and energy-saving. Improper selection will have a great impact on the operation of the pump. (High-temperature pump) will reduce the flow rate of the pump and it will not reach the high water pump. , Caused by increased mechanical friction, damage to the submersible pump, and the emergence of excessive flow of the motor overload, if long-term operation, the winding temperature increases, the insulation gradually aging, and even burned the motor. 1.2 Precautions before putting into operation and after maintenance When lifting, care should be taken to protect the cables from damage. Do not use cables to lift them directly. The lifting devices (such as tripods, hoists, or electric hoists) should be larger than the weight of the submersible pumps and have enough room. Before hanging, manually turn the impeller to check whether the rotation is flexible, whether the contact of the main contactor is in good contact, whether the cable and the cable joint have cracks or scratches, and whether the grounding of the motor housing is reliable (in order to ensure safety, the grounding line should generally be better than other lines. 5mm), and use a multimeter to check the three-phase line conduction. Conditional available digital low-resistance instrument (measurement accuracy up to 10 microohms) to check the balance of resistance of three-phase windings respectively. When measuring, generally select the appropriate measurement file depending on the power of submersible pump. For large and medium-sized submersible pumps above lOOkw The interphase resistance is generally several tens to hundreds of milliohms. The 0.2Q file can be selected. Note that the two pointers of the red and black test pens must be in contact with the detected part (ie conductor) at the same time to reduce the error. And interference as shown. (High-temperature pump) Note: Even if a partial phase or interturn short circuit occurs in the motor, the multimeter cannot accurately measure the balance of the three-phase winding resistance due to its own accuracy and the influence of the contact resistance. It is recommended that the motor be tens or hundreds of kilowatts. Digital DC low resistance meter. If you use a multimeter to measure the measured value of the winding is still the same as the display of the two pens, the displayed value is basically the same, according to the type of the multimeter used, the value is generally ranging from 0.5 to 112. During installation, it is not allowed to place the submerged pump horizontally or place it directly in the sewage population. Determine the minimum height of the submersible pump from the bottom according to the site conditions so as not to be buried in the mud sand or the pump inlet is blocked by the suspended matter, resulting in a reduced heat transfer speed. Winding temperature rises, insulation ages, shortens the service life of the stator or causes unprovoked tripping. Do not place the pump directly on mud or floating sand. If it is necessary to install it temporarily, it is recommended that the pump be placed on a large floor or on a solid floor to avoid sagging due to vibration. After the installation is completed, all the submersible pumps are immersed in water. Before connecting the power supply, check the relative insulation resistance of the motor three with a 500-volt megohmmeter. The minimum is not less than 1 megohm. 1.3 Precautions for Runtime Start submersible pump, should be smooth, no vibration and abnormal sound, observe the motor running current and line voltage before and after the start of any significant fluctuations. After the main circuit of the motor is energized, if it is found that the motor does not rotate, it should be stopped immediately to prevent the motor from being burned for a long time. Note that for submersible pumps that are put into operation after the first installation or overhaul, the submersible pump that is put into operation after the first installation or overhaul can only be started locally (heating oil pump) for observation. If the submersible pump is found to be abnormal, it should be shut down immediately to check if the rotation direction is correct and the installation is correct. The reason can be put into operation after troubleshooting. For submersible pumps that cause the windings to rewind due to motor burn, after a few hours of operation for the first time, the insulation resistance in the hot state to ground can be measured when the machine is turned off. It should not be less than 0.38M12 to continue to be used. The submersible pump must be submerged in water during operation, and the opening and stopping should not be too frequent; the number of starts per hour is generally not more than 6 times (the specific number is related to the power and submersible pump type), and the interval is required evenly. The restart should be carried out 3-5 minutes after the stop to prevent water hammer in the pipeline from damaging the submersible pump. 1.4 Power Supply, Environment and Other Precautions. Submersible pumps generally have certain requirements on the upper and lower deviation ranges of the power supply voltage and frequency, and areas where the power supply is unstable should be observed to prevent damage. For high-power submersible pumps, step-down or soft start must be used to reduce the impact on the power grid, nearby low-voltage electrical equipment, instrumentation, automatic control systems and submersible pumps themselves. Submersible pumps generally have solids content in the transported liquid and solid particle diameter, pH, water temperature, chloride ion The content, etc. have certain requirements, and attention must be paid in use so as to avoid unnecessary damage. When operating, the submersible pump should be completely submerged in the water, and the cooling water should be cooled to facilitate the heat dissipation of the submersible pump. The position of the input level gauge and float ball used for the control of the submersible pump must be properly installed to avoid muddy sand accumulation when the pump is too low. As a result, the level gauge cannot detect the water level or the accuracy is reduced. At the same time, the minimum water level at which the float stops should be considered. Ensure that the submersible pumps still submerge into the water, and always pay attention to clean up the sludge and debris at the bottom of the tank. If the submersible pump is deactivated for a long time, it should be lifted to clean the discharge port, and all the water in the cooling jacket should be drained cleanly and cleaned of mud and sand (especially in the cold winter to prevent freezing of the motor), and the motor water pump is scrubbed inside and outside. , conduct a comprehensive paint rust treatment, conditional can be painted in the key parts of the pump, bearing lubrication oil to prevent parts rust, after processing is stored in non-corrosive materials and dry and ventilated warehouse. If placed in water, run at least once every few days for no less than 30 minutes. 2 routine maintenance contents 2.1 Maintenance main content In order to ensure the reliable operation of the submersible pump and prolong its service life, the submersible pump and its control system must be regularly maintained. At least once a year, comprehensive preventive maintenance should be performed. The contents mainly include: whether there is abnormal vibration sound and voltage current at the time of starting. Whether the starting device is working properly, whether the over temperature leakage is alarmed, whether the multiple protections established by the metering control are frequently operated, whether the main cable and the control cable are aged and cracked, whether the main contactor has viscous oxidation or burr, whether the thermal relay is set correctly, and the winding Whether the insulation layer shows signs of aging, whether the insulation resistance to the ground is too low, whether the three-phase winding resistance is balanced, whether the stator rotor is wiped or scratched, whether the level gauge of the control system is accurate, and whether the upper and lower limit outputs are normal and reliable. Whether the operation is reliable, whether the temperature detection element is aged and malfunctions, whether the oil is emulsified, the mechanical seal is intact, the bearing has element wear, the impeller has no wear or cavitation, the shaft is rusted or deformed or worn, and the internal and external fastening screws of the motor have No looseness, presence of impurities in cooling jackets and circulating water pipes, and sediment deposits around and around the pump Blockage. During the preventive maintenance and operation of the submersible pump, the over-temperature alarm should be correctly distinguished, and whether the alarm is a true over-temperature or component aging malfunction. (Hot water pumps) In case of aging of components, only the signals must be connected to the alarm signal to prevent them from directly participating in the control, so as to reduce the frequent start of the submersible pump. 2.2 Common Problems and Precautions in Maintenance Work: Combined with our many years of maintenance experience, we have introduced common and difficult problems as follows: When the submersible pump is used for long-term soaking in water, the main cable skin is aged and cracked. The water passes through the crack directly into the submersible pump along the inside of the cable. Therefore, the cable must be inspected on a regular basis to reduce the local cracks and clean the surface of the cable. , Waterproof tape can be used for winding waterproof treatment, but pay attention to soak a few hours after the use of a watch to check the insulation, meet the requirements before they can be put into operation. Replace the main cable with inadequate insulation or no repair value. Because the main cable is a special cable with a watertight joint, it is expensive to replace, so it can be processed and bonded. Ways to save costs. For example, if one of our submersible pumps has bad ear contact due to vibration, it will cause about 40cm of heat from the ear to the watertight joint of the cable, but the rest is in good condition to save cost. It has been found through research that the watertight joint is mainly through the joint. The two ends were sealed, so it was decided to use PV rods with certain elasticity to process the seals and bond them to the cables with epoxy resin with high bonding strength. The results of the watertight test were good for more than a year. The operation is normal and the problem of waterproof seal is solved well. The material cost is only 20 yuan, and the temperature of the mold pump saves 6000 yuan. The oil that has been emulsified in the water must be replaced during maintenance, but it can be emulsified to save costs and reduce waste. The oil is recycled after being regenerated using a special oil filter. In the maintenance, sometimes the phenomenon occurs that the shaft of the pump shaft is rusted and the bearing cannot be removed. At this time, the bearing can be submerged into the oil and heated to 70-80°C. Then pull out the Ramara, and avoid directly using the Rama deadlift or gas cutting to avoid Damage to the bearing causes the spindle to deform. If the pump shaft is worn or bent, it can be repaired or corrected by spraying after derusting. After long-term use of the submersible pump, the impeller will be completely worn out due to wear and cavitation, or the impeller will completely penetrate, which will seriously affect the efficiency of the pump and the balance of the impeller. If the long-term operation will further damage the mechanical seal and the bearing, it will cause serious damage. Should be promptly replaced or repaired. In order to save costs, only impellers or localized wear may occur and the impeller may not be fully penetrated. Belzona 1311 or other repair material plus cast iron powder may be used for repair, but in practice, the surface finish of the repaired surface and the entire impeller should be noted. The curve and the dynamic balance test of the impeller are performed at the same time to ensure smooth rotation of the pump during operation. Generally, the restored impeller can continue to operate for 1-2 years. After replacing the bearing and mechanical seal of the submersible pump, pay attention to the lowering of the rotor and the pump shaft during the assembly process so as not to damage the stator winding and cause insulation damage or copper wire breakage. If you break a few, you can put it on the insulating sleeve, use low-melting solder (a similar situation occurred in our factory, using a solder melting point of 120 °C, before welding, pay attention to the two ends of the copper wire to be welded wet cloth , so as not to cause other parts of the insulation to be damaged during welding.) After welding and drying with insulating paint, move the insulating sleeve back to the welding place and then separate the repaired windings with insulating paper or insulating cloth. Reinforce the insulation, dry it with insulating paint, check the insulation with a rocker, and proceed to the next step after meeting the requirements. Also note that the fastening screws at the bottom of the rotor and the oil chamber must be tightened to prevent the stator coil from being damaged when the screws are loosened and then the rotor rotates. After installation, seals should be applied to the sealing surfaces of the submersible pumps to enhance sealing and prevent water ingress. After the submersible pump is repaired, it should be completely immersed in the pool or water tank, using a 0.2Mpa compressed air for a 20-minute watertight test to check that no part of the submersible pump can leak to the site for installation. 3 Case Studies Our factory has a total of eight WQ950-201 90-kilowatt submersible submersible sewage pumps produced by the Blue Deep Pump Group. The rated lift is 20m, the flow rate is 950m3/h, the rotation speed is 1470r/Min, the rated current is 178A, and the pump efficiency is 69%. The pump pump is coaxial, high efficiency, compact structure, superior over-current performance, water jacket-type circulating cooling and dual-rail automatic installation system, installation and maintenance is very convenient. The maximum medium temperature is 40°C, and the PH value is 5-9. The maximum solid particle diameter is ∮100 mm, and the maximum diving depth is 10 m. With double detection of leak detection alarm and winding temperature thermal element, when the mechanical seal of the submersible pump is damaged, the leakage protection device acts when the oil in the oil chamber enters the water and the motor enters into the water; and the winding is caused when the motor is single-phase operation or overloaded. When the heat is generated, the temperature switch of the winding is disconnected (normally closed in series), and the power supply is cut off or a fault signal is sent through the intermediate relay to ensure safe and reliable operation of the submersible pump. In order to ensure the safe and reliable operation of the submersible pump, our factory has set a low level of protection float below the level of the lower limit of the liquid level gauge. It adopts double protection of the float and digital level gauge, and simulates the float switch signal and liquid level. The signal is introduced into the PLC. The operator can set the upper and lower liquid levels directly on the field instrument or through the liquid level setting screen of the computer, so that the system can directly control the electrical automatic and remote control at the site according to the set upper and lower limit water levels. Start and stop the pump. Once the level gauge fails, the system can still be forced to stop by the float ball to ensure the safe and reliable operation of the system. At the same time, in our computer control system, in addition to collecting conventional signals such as water leakage and over-temperature alarms, the PLC also uses AI modules to collect submersible pump current signals. Combine many years of operation experience, give full play to the advantages of program control programming in program design, and adopt multiple protection measures: 1 When the submersible pump starts, use the delay to start the current shield, if the current after starting 1Min continues for 10S exceeds about normal current. When 15 times or the instantaneous value of the current is greater than 1.25 times the normal current, the metering control directly outputs the stop; 2 When the current drops to about 80% of the normal current, the metering control directly outputs the stop; 3 the use of the delayer, The output command of the boot is timed so that the boot output command is valid after the last boot output has issued lOMin and the stop 3Min, which effectively avoids the operator's misoperation and ensures that the number of boot times per hour does not exceed 6 times; 4 According to the past pump stop record automatic cycle switch, to ensure that the pump's regular switching and cyclic operation; 5 If more than one pump must be running at the same time, the system allows only one pump at a time, after the start and stop is completed, the delay 1Min , start and stop other pumps, reducing the impact on the grid. 4 Conclusion The system has been undergoing electrical transformation for more than eight years. 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