Starting and stopping of self-priming pumps

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The operations for starting and stopping a self-priming pump are described as follows: I. Preparations before starting the self-priming pump include inspection tasks. 1. Depending on the operating conditions of the pump, high-quality calcium-based grease or engine oil No. 10 should be used for lubrication. For pumps lubricated with grease, it is necessary to regularly add grease to the bearing housing; for pumps lubricated with oil, the oil level should be topped up if it is insufficient. 　　2. Check whether the liquid level inside the pump casing is above the upper edge of the impeller. If it is not sufficient, liquid can be directly added to the pump from the filling port on the casing. The pump should not be started when the liquid level is low, as this will prevent it from functioning properly and may also damage the mechanical seal. 　　3. Check whether there are any jamming or collisions in the rotating parts of the pump. 　　4. Check whether the footings of the pump body and the nuts at all connection points are loose. 　　5. Check the coaxiality and parallelism between the pump shaft and the motor shaft. 　　6. Check whether the inlet pipeline is leaking air; if there is a leak, it must be addressed. 　　7. Open the valve of the suction line, and slightly open the outlet control valve (do not open it fully). 　　II. Starting and Operation of the Self-priming Pump 　　1. Start the self-priming pump in jog mode, and pay attention to whether the rotation direction of the pump shaft is correct. 　　2. Pay attention to any abnormal noises and vibrations during rotation. 　　3. Pay attention to the readings on the pressure gauge and vacuum gauge. After startup, when the readings on these gauges become stable after fluctuating for a while, it indicates that liquid has entered the pump, and normal fluid pumping can now be carried out. 　　4. During the priming process, before the self-priming pump starts operating normally for liquid transfer, special attention should be paid to the increase in water temperature inside the pump. If this process takes too long and the water temperature inside the pump becomes too high, the pump should be stopped to investigate the cause. 　　5. If excessive liquid temperature inside the self-priming pump causes difficulty in priming, the pump can be stopped temporarily; the liquid in the discharge pipeline can be allowed to flow back into the pump, or liquid can be directly added to the pump at the liquid storage port, thereby cooling the liquid inside the pump, after which it can be started again. 　　6. If a self-priming pump experiences intense vibrations and noise during operation, it may be due to cavitation. There are two causes of cavitation: first, excessively high flow velocity in the inlet pipe; second, an overly long suction lift. When the flow rate is too high, the outlet control valve can be adjusted to increase the pressure gauge reading; in case of blockages in the inlet pipeline, they should be removed promptly ； When the suction lift is too high, the installation height of the pump can be appropriately reduced. 　　7. When the pump stops operating for some reason during operation and needs to be restarted, the outlet control valve should be left slightly open (not fully closed). This facilitates the expulsion of gas from the outlet during the self-priming process, while also ensuring that the pump can start under a lighter load. 　　8. For self-priming pumps, pay attention to checking whether there are any leaks in the piping system. 　　III. Shutting down a self-priming pump 　　1. First, the gate valve on the discharge pipeline must be closed. 　　2. Stop the pump from rotating. 　　3. During cold seasons, the liquid stored in the pump body and the water in the bearing chamber should be drained to prevent the components from cracking due to freezing.