Self-priming pump self-priming refers to the suction tube without filling the liquid (but the pump body must have enough liquid) to start the pump, the pump itself can automatically remove the suction tube gas, and then into normal work, the pump at the first start Must be filled with enough liquid, after start by the liquid stored in the pump body to ensure that the pump can start again.Self-priming pump self-priming time refers to the pumping pump to clean the liquid at room temperature, the installation height is to allow suction vacuum Going to 0.5, the minimum time it takes for the pump to start to stabilize the pressure, which is the time it takes for the pump to drain the tube of air, is the length of the suction line between the suction side of the centrifugal pump and the pump inlet Less than the installation height of the pump plus 20D (suction pipe hole diameter); the suction pipe length between the suction surface of the vortex self-priming pump and the inlet of the pump should be less than the installation height of the pump plus 2. The ordinary centrifugal pump in the suction pipe Bottom valve is installed at the bottom, more water needs to be filled into the entire suction pipe before starting, and the bottom valve often breaks down due to clutter or closing itself, and sometimes it takes a lot of labor to eliminate these faults, Do not be in the winter. Self-priming pump suction port is generally higher than the impeller suction port, as long as the pump body can be started in irrigation, without the above defects. Self-priming pumps are convenient for mobile irrigation and drainage, mobile work, frequent start-ups and difficult irrigation. Self-priming pumps are used in many places such as agriculture, construction, tank truck unloading, oil depots, fire fighting and shipbuilding. Self-priming pump works Centrifugal self-priming pump from the working principle can be divided into internal mix and external mix of two types. Mixed within the mixed type refers to the impeller near the gas-liquid mixing, the principle as shown. The pump body is filled with proper amount of liquid (flooded impeller) before the pump is started, the reflux valve is opened, the press-in chamber is communicated with the suction chamber, the impeller rotates, the liquid in the suction chamber and the impeller is delivered to the press-out chamber via the impeller, The negative pressure is formed at the inlet, the pressure in the suction pipe is higher than the pressure in the suction chamber, the suction valve is opened, the gas in the suction pipe is sucked into the impeller, the liquid in the pressure chamber is discharged through the backflow valve hole and the suction chamber, And was sucked into the impeller inlet gas-liquid mixture, the impeller and the gas-liquid mixture sent to the pressure chamber to go, due to gas-liquid separation chamber volume is large enough, making the flow rate decreases, depending on the liquid and gas specific gravity gas and liquid separation , The gas is discharged through the extrusion line, and the liquid is sucked into the impeller through the return valve hole to be mixed with the gas again, and then circulated until the gas in the suction pipe is drained, then the pump completes the self-priming process To work properly. External mixing External mixing refers to the outer edge of the impeller for gas, liquid mixture, and its working principle as shown. Before starting the pump, the pump body is filled with an appropriate amount of liquid. When the impeller rotates, the liquid in the suction chamber and the impeller is sent to the pressure chamber through the impeller, a negative pressure is formed at the inlet of the impeller, the suction valve is opened and the suction valve is opened Of the gas into the impeller through the suction chamber at the impeller exit with high speed rotation with the impeller mixing liquid due to the role of the impeller to make the gas-liquid mixture through the pressure chamber to a sufficiently large volume of the gas-liquid separation chamber to go, as the flow rate decreases , Depending on the specific gravity of liquid and gas separation, the gas is discharged through the pipeline, the liquid flows back through the outer runner and the outer edge of the impeller. Followed by cycle until the gas sucked into the pipeline was drained, then pump to complete the self-absorption process to achieve normal work. (1) to ensure that the pump is stopped, the pump body to store enough liquid, this need to have a one-way valve at the inlet of the pump body, and the pump body inlet above the centerline of the impeller to prevent the pump body of liquid in the pump after the stop Due to siphon effect was discharged to the suction pool. (2) Effective gas-liquid separation, for which a sufficient volume of gas-liquid separation chamber is required and the outlet of the pump body is sufficiently high to the impeller center line. (3) The separated liquid is continuously returned to the impeller. To this end, there should be a backflow hole for the internal mixed self-priming pump. There should be a large enough flow passage for the external mixed self-priming pump to return the separated liquid Impeller self-priming performance of the main factors 1. Liquid storage volume and the height of the liquid storage is the storage tank refers to the pump after the pump body can store the liquid part of the volume, which is the lowest point of the pump suction pump body Volume, this part of the volume is mainly the pressure chamber and gas-liquid separation chamber part. The volume of the reservoir should be not less than half of the pump design flow in seconds (for example, if the pump design flow is not less than the volume of the reservoir and the volume of the reservoir is too small (too little liquid is stored in the pump), self-priming Time increases, or even self-absorption; over, making the pump bulky. In addition to having a sufficient reservoir volume, there must also be a reservoir height, which is the height at which the pump sucks in to the center of the impeller, usually approximately equal to the impeller radius. 2. The volume of the gas-liquid separation chamber and the outlet of the pump The gas-liquid separation refers to the part outside the pressure chamber of the pump. The larger the volume is, the better the separation effect of gas and liquid is and the faster the separation is. Liquid separation chamber volume to a certain extent, and then increase the effect is not significant, the reverse will make the pump body bulky, so the gas-liquid separation chamber has an optimal volume value, according to the experience of its value is equal to or slightly larger than the liquid storage Volume, in ensuring the gas-liquid separation chamber capacity of the case, the pump outlet to the centerline of the impeller height can be based on liquid storage volume and gas-liquid separation chamber volume at the time of drawing to determine the height. 3 • Determination of liquid flow rate out of the chamber Centrifugal pump self-priming pump out of the chamber liquid flow rate than the average centrifugal pump is lower, about equal to the general centrifugal pump out of the chamber liquid flow rate of 80-90%. 4 • Determination of the clearance between the tongue and the impeller in the extrusion chamber For the centrifugal self-priming pump, the clearance between the separator and the impeller has a great influence on the self-priming performance. The clearance between the tongue and the impeller in the upper pressure chamber is smaller, Shorter, this gap is usually mixed outside; take mixed inside. If the design of the double cochlear chamber pressure chamber at the lower part of the gap between the tongue and the impeller, usually according to the general centrifugal pump pressure chamber to determine the gap between the tongue and the impeller to determine that the lower diaphragm located in the base of the volute chamber. 5 • Turning of the impeller rear cover For external mixing centrifugal self-priming pumps, when the impeller outer circle speed is less than the self-priming effect, the method of turning the impeller rear cover may be used to improve the self-priming capability because of the ease of self- Suction process of liquid and gas mixture. Turn the amount can not be too large, otherwise it will significantly reduce the pump head and efficiency. At that time, the impeller rear cover diameter after cutting; and in the upper septum at the stiffened, so as to avoid bubbles with liquid in the cut off the back cover at the cycle, affecting the self-priming effect. 6 • The area of ​​the return hole For the inner mixing centrifugal self-priming pump, the area of ​​the return hole has a great influence on the self-priming performance. The area is large so that more liquid is returned to the inlet of the impeller through the return hole, so the self-priming time is short. The maximum vacuum degree of self-priming decreases; self-priming time is longer when the backflow hole area is small, and the height of the maximum self-priming vacuum is high. In summary, to determine the area of ​​the backflow hole, we must consider the self-priming time and self-priming height requirements.
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