Who has information on self-priming pumps

Let me share one; see if it’s needed: The operations related to starting and stopping the suction pump are described as follows: I. Preparations before starting include inspection tasks. 1. Depending on the operating conditions of the pump, high-quality calcium-based grease or No. 10 engine oil should be used for lubrication. For pumps lubricated with grease, grease should be added to the bearing housing regularly; 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 added directly into the pump through 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 is any jamming or collision 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 repaired. 　　7. Open the valve of the suction line, and slightly open the outlet control valve (do not open it fully). 　　II. Starting and Operation 1. Start the self-priming pump manually, and pay attention to whether the rotation direction of the pump shaft is correct. 　　2. Pay attention to any abnormal noises or vibrations during rotation. 　　3. Pay attention to the readings on the pressure gauge and vacuum gauge. Once these readings stabilize after some fluctuation following startup, it indicates that liquid has filled the pump, and normal pumping operation can begin. 　　4. During the self-priming process before the pump starts normal pumping operation, 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 the temperature of the liquid inside the pump is too high, causing difficulties in self-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 reservoir port, in order to lower the temperature of the liquid inside the pump. Once that is done, the pump can be restarted. 　　6. If the pump experiences severe vibration and noise during operation, it may be due to cavitation. There are two reasons for cavitation: one is an excessive flow velocity in the inlet pipe, and the other is an excessively high suction head. When the flow rate is too high, the outlet control valve can be adjusted to increase the pressure gauge reading; if there is a blockage in the inlet pipeline, it 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 starts under lighter load. 　　8. Pay attention to checking for any leaks in the piping system. 　　III. Shutting down the pump 1. First, the gate valve on the discharge pipeline must be closed. 　　2. Stop the pump from rotating. 　　3. In cold seasons, the liquid stored inside the pump and the water in the bearing chamber should be drained to prevent the components from cracking due to freezing. The working principle of a self-priming pump is similar to that of a regular centrifugal pump; if the liquid level at the inlet is below the impeller, it is necessary to fill the pump with water beforehand before starting it, which is quite inconvenient. To hold water in the pump, a foot valve needs to be installed at the inlet of the suction pipe; when the pump is operating, this foot valve causes significant hydraulic losses. A self-priming pump is one that does not require priming before starting (although priming is still necessary for the first start after installation); after operating for a short period of time, it can draw water up by its own mechanism and begin to function normally. Suction pumps can be classified into the following categories based on their working principle: 1. Gas-liquid mixing type (including internal mixing and external mixing types) ； 2. Water ring type ； 3. Jet type (including liquid jets and gas jets). Working process of the gas-liquid mixed self-priming pump: Due to the special structure of the pump body, a certain amount of water remains inside the pump after it stops operating. When the pump starts again, the rotation of the impeller causes the air and water in the suction pipeline to mix thoroughly, and this mixture is sent to the gas-water separation chamber. The gas at the top of the chamber escapes, while the water at the bottom returns to the impeller, where it mixes again with any remaining air in the suction pipeline. This process continues until all the gas in the pump and suction pipeline has been removed, allowing the pump to achieve self-priming and start pumping water normally. The water ring pump is a self-priming pump that combines a water ring wheel with a pump impeller within a single housing; the water ring wheel is used to expel gas, thereby enabling self-priming. Once the pump is operating properly, the passage between the water ring wheel and the pump impeller can be blocked using a valve, allowing the liquid inside the water ring wheel to be drained. A jet self-priming pump is composed of a centrifugal pump and a jet pump (or ejector); it relies on a jetting mechanism to create a vacuum at the nozzle in order to achieve suction.

Reply to 2# feiyun2010: Thank you, I’d like to take a look at the internal structure

The working principle of a self-priming pump is as follows: before the pump starts operating, the pump casing is automatically filled with water (or there is already water inside the pump casing). After startup, the high-speed rotation of the impeller causes the water in the impeller channels to flow toward the volute; this creates a vacuum at the inlet, which opens the inlet check valve. Air from the suction pipe enters the pump and moves through the impeller channels to the outer edge. Generally, self-priming pumps are required for fire-fighting pumps, as they enable rapid water discharge and are thus useful for dealing with emergencies