First, the working principle of a centrifugal pump 1 centrifugal pump working principle Impeller installed in the pump housing 2, and fastened on the pump shaft 3, the pump shaft directly driven by the motor. The pump housing has a liquid suction 4 and suction pipe 5 connected. The liquid enters the pump through the bottom valve 6 and the suction tube. The liquid discharge port 8 in the pump housing is connected to the discharge pipe 9. Before the pump is started, the pump housing is filled with the liquid to be transported. After starting, the impeller is driven by the shaft to rotate at a high speed and the liquid between the blades must also rotate with it. Under the action of centrifugal force, liquid is thrown from the center of the impeller to the outer edge and gains energy, leaving the outer edge of the impeller to enter the scroll casing at a high speed. In the volute, the liquid due to the gradual expansion of the slowing down, but also part of the kinetic energy into static pressure, and finally to a higher pressure into the discharge pipe, to the required place. When the liquid flows from the impeller center to the outer edge, a certain vacuum is formed in the center of the impeller. Since the pressure above the liquid level in the sump is greater than the pressure at the inlet of the pump, the liquid is continuously pressed into the impeller. Visible, as long as the impeller constantly rotating, the liquid will be continuously inhaled and discharged. 2 gas binding phenomenon When there is air in the pump housing, due to the density of the air density is much smaller than the liquid generated less centrifugal force. Thus, the tank above the liquid level and the pump inlet pressure difference is not enough to liquid storage tank pressure into the pump, that is, centrifugal pump without self-suction capacity, so that the centrifugal pump can not deliver liquid, a phenomenon called "gas tied phenomenon". In order to fill the pump with liquid, a bottom valve with strainer is usually installed at the bottom of the suction pipe. The bottom valve is a check valve. The filter serves to prevent the solid matter from entering the pump and damaging the impeller or impeding the normal operation of the pump. Second, the main components of the centrifugal pump The main components are impeller, pump housing and shaft seal device. 1 Impeller The role of the impeller is the mechanical energy of the prime mover directly to the liquid to increase the hydrostatic pressure and kinetic energy (mainly to increase static pressure). Impellers generally have 6 to 12 blades after bending. Impeller has open, semi-closed and closed three. The open impeller has no cover plate on both sides of the blade, which is simple in manufacture and convenient in cleaning. It is suitable for conveying materials containing a large amount of suspended matter, which has low efficiency and low pressure of liquid to be transported. The semi-closed impeller has no cover on the suction inlet side Plate, and on the other side of the cover, suitable for conveying easily sediment or particles containing materials, the efficiency is lower; closed impeller impeller on both sides of the blade has a front and rear cover, high efficiency, suitable for the delivery of impurities Clean liquid. Most of the centrifugal pump impeller for such. Impeller has a single suction and double suction two suction method. 2 pump shell role is to seal the impeller in a certain space, so that the role of impeller suction and out of the liquid. Pump casing made of spiral shape, it is also known as the volute. Due to the gradual enlargement of the cross-sectional area of ​​the flow passage, the high-speed liquid thrown out from the impeller gradually reduces the flow velocity and effectively converts part of the kinetic energy into static pressure energy. Pump housing not only brings together the liquid thrown by the impeller, but also an energy conversion device. 3 shaft seal device is to prevent the liquid within the pump casing leakage along the shaft or outside air leakage into the pump casing. Common shaft seal packing seal and mechanical seal two. Fillers are generally impregnated with oil or asbestos rope coated with graphite. The main purpose of the mechanical seal is to achieve the purpose of sealing by the relative movement between the moving ring mounted on the shaft and the stationary ring fixed on the pump casing.
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