Maintenance methods and usage precautions for chemical magnetic pumps

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Maintenance methods and usage precautions for chemical magnetic pumps 1. Broken pump shaft: The main reason for a broken pump shaft is that the shaft gets twisted as a result of the pump running without liquid, causing the bearings to grind against each other. Upon disassembling the pump for inspection, it can be seen that the bearings are severely worn. The main way to prevent the pump from breaking is to avoid running it without any load. 2. Bearing damage: If the pump runs out of water or contains impurities, it can cause damage to the bearings. If the coaxiality requirement between the inner and outer magnetic rotors of a cylindrical coupling is not ensured, it will also directly affect the lifespan of the bearings. 3. Magnetic pump fails to deliver liquid: The inability of a magnetic pump to pump out liquid is one of the most common faults it can experience, and there are various reasons for this. First, check whether there are any air leaks in the pump’s suction line, ensure that any air in the suction line has been removed, verify that the amount of liquid filled in the pump is sufficient, and check for any obstructions in the suction line. It is also necessary to determine whether the pump is running in reverse (especially after replacing the motor or after repairing the power supply circuit). Additionally, pay attention to whether the pump’s suction height is too high. If the problem remains unresolved after the above checks, the pump can be disassembled to inspect the centrifugal pump; it is necessary to check whether the pump shaft is broken, as well as whether the rotating and stationary rings of the pump are intact, and whether the entire rotor can move slightly in the axial direction. If axial movement is difficult, check whether the carbon bearing is too tightly fitted to the pump shaft. It is worth noting that the pump has been repaired several times with no problems found; attention should be paid to whether the magnetic coupling is functioning properly. Bearings, internal magnetic rotors, and spacers all generate heat during operation, which raises the working temperature. This not only reduces the power transmitted but also causes significant problems for pumps that are used to transport volatile liquids. The power transmitted by the magnet follows a continuously decreasing curve as the temperature rises. Generally, below the operating limit temperature of the magnet, the decrease in its transmission capacity is reversible, whereas above this limit temperature it becomes irreversible; that is, once the magnet is cooled, the lost transmission capacity cannot be restored. Under special circumstances, when slippage occurs in the magnetic coupling, the eddy current heat generated within the spacer increases sharply, causing a rapid rise in temperature. If this is not addressed promptly, it can lead to demagnetization of the magnets, resulting in the failure of the magnetic coupling. Therefore, magnetic pump should be equipped with a reliable cooling system. For media that are difficult to vaporize using chemical pumps, the cooling circulation system generally draws fluid from the impeller outlet or pump outlet, passes it through the bearings and magnetic drive components, and returns it to the suction inlet. For media that are prone to vaporization, heat exchangers should be added or the fluid should be directed to a storage tank outside the pump, in order to prevent heat from returning to the suction inlet. For media containing solid impurities or ferromagnetic contaminants, filtration should be considered. In the case of high-temperature media, cooling measures must be implemented to ensure that the magnetic coupling does not exceed its operating temperature limits. When considering whether the rotational speed is sufficient, it is first necessary to check whether the motor’s own rotational speed is normal; this can be done using a tachometer. Once the motor’s rotational speed is normal, then one can consider whether slippage of the magnetic coupling might occur. 4. Insufficient head: The causes of this fault include air in the medium being transported, damaged impellers, insufficient rotational speed, too high specific gravity of the liquid being transported, and excessive flow rate. 5. Insufficient flow: The main reasons for insufficient flow include damaged impellers, insufficient rotational speed, excessive head, and blockages caused by debris inside the pipes. Precautions for using magnetic pump: 1. After installation, manually rotate the coupling to check for any signs of rubbing. 2. To prevent debris from entering the pump, a filter must be installed at the pump inlet, with a filtering area that is 3 to 4 times larger than the cross-sectional area of the pipeline. 3. Idling is strictly prohibited. 4. A check valve should be installed on the outlet pipeline of magnetic pumps with high head to prevent damage caused by water hammer due to sudden shutdown. 5. Pump startup procedure: Before starting the pump, open the inlet valve to fill the pump with the liquid to be transported; close the outlet valve. Start the motor briefly to check whether the pump is rotating in the correct direction. Once the pump is running properly, slowly open the outlet valve, and adjust it to the desired opening degree after the pump has reached normal operating conditions. Run it for 5 to 10 seconds; if there are no abnormalities, it can be put into operation. 6. Shutdown procedure: Close the outlet valve, cut off the power supply, close the inlet; when the pump will not be used for an extended period, clean the flow channels inside the pump and cut off the power supply. (1) Since the cooling and lubrication of the magnetic pump bearings rely on the medium being transported, operating the pump without any medium is strictly prohibited. Additionally, it is necessary to avoid operation with no load after a power outage during operation and subsequent restart. (II) If the medium being pumped contains solid particles, a filter screen should be installed at the pump inlet; if ferromagnetic particles are present, a magnetic filter is required. (III) During operation, the ambient temperature around the pump should be below 40°C, and the temperature rise of the motor must not exceed 75°C. (IV) For media whose conveyed liquid tends to precipitate and crystallize, it should be cleaned promptly after use to drain all the accumulated fluid inside the pump. (5) After the magnetic pump has been operating normally for 1,000 hours, the wear of the bearings and the dynamic rings on the end faces should be inspected, and any worn-out components that can no longer be used should be replaced.