Structure of magnetic pump and methods for starting and stopping it

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Preparations before driving (1) Clean the area around the pump and remove any debris from the site. (2) Before starting the pump, test whether the motor insulation is satisfactory, and ensure that the motor’s rotation direction, current, power, etc. are all normal. (3) Check whether the coaxiality between the motor and the pump body meets the requirements. (4) The coupling guard is properly installed with no friction. (5) Check whether the bolts at all connections are tightened; any looseness is not allowed. (6) Check whether the quality of the lubricating oil has deteriorated, and maintain the oil level at 1/2 to 2/3. (7) Ensure that all connections and pipes of all imported pipelines are sealed tightly with no air leaks. (8) Ensure that the pipes connected to the pump are thoroughly cleaned; it is strictly prohibited for debris such as welding slag to enter the pump and damage the bearings. A temporary 40-mesh filter should be installed at the pump inlet. (9) Turn the crank 2–3 times to check whether all moving parts are functioning properly. (10) If the liquid temperature of the feed pump in the stripping tower is too high, the inlet valve should be opened slowly to preheat the pump, with a heating rate not exceeding 10°C/min. Testing (1) Close all drain valves, fully open the pump’s inlet valve and outlet vent valve to fill the pump with liquid. (2) Close the outlet valve to keep it at 1/4 open. (3) Start the motor and pay close attention to the reading on the outlet pressure gauge. If the pressure remains unstable and drops to lower levels, it indicates that the exhaust is not thorough; in such cases, the pump should be stopped immediately. (4) Stop the pump and wait for 10–15 seconds, then re-priming and vent the pump before starting it again until the outlet pressure reaches a high level and remains stable. (5) Check whether the pump operates with normal sound; if there is noise or the sound of metal scraping, it may indicate cavitation or friction within the pump components, and the pump should be stopped immediately for handling. Testing can resume only after the cause is identified and corrected. (6) Closely monitor the pressure drop before and after the temporary filter at the pump inlet; if the pressure drop is too high, immediately switch the pump to clean it out to prevent cavitation or dry running. Parking: (1) Gradually close the pump outlet valve to 1/4 open. (2) Cut off the power supply. (3) Close the inlet and outlet valves of the pump, open the drain port on the pump body as well as the inlet and outlet drain valves, and drain the material to prevent crystals from damaging the pump body. Operational precautions: (1) It is strictly prohibited to let the pump run dry. Once it idles, the bearing loses lubrication and wears down rapidly. (2) Reverse rotation of the pump for extended periods is prohibited. (3) It is prohibited to operate the pump continuously with the outlet valve closed. (4) It is prohibited to keep the pump running under cavitation conditions. (5) The pump’s flow rate should not be too high, otherwise it will cause overload in the bearings and the motor current. (6) A bypass line must be provided for the pump outlet pipeline, returning to the tank upstream of the pump inlet. When the pump is operating normally, adjust the opening of the bypass valve in a timely manner to ensure the minimum safe flow rate of the pump and prevent damage to the bearings. (7) The pump should not be subjected to thermal shock. When the temperature of the medium being transported is high, slow preheating should be carried out before starting the pump, and the heating or cooling rate should not exceed 10°C/min. (8) While the pump is in operation, especially during commissioning, the pressure drop before and after the temporary filter should be closely monitored to prevent cavitation or dry running of the pump due to excessive pressure differences.