A pump that delivers liquid by rotating a star-shaped impeller between covers with discontinuous channels is called a vortex pump. The working principle of the vortex pump is that when the star wheel rotates, a centrifugal force is generated. Under this centrifugal force, the liquid flows into the root of the blade from the side hole of the pump casing and is thrown to the outer circle to enter the channel of the cover on both sides. This part of the original blade with a circular motion of the original, with a certain speed, the speed in the cover channel can become pressure energy. After it was snapped by the leaves. During the passage of the liquid mass from the inlet to the outlet, this effect is repeated several times, increasing successively as the liquid is subjected to the action of a multistage impeller in centrifugal pumps. The liquid moves in the channel with the star-shaped impeller. At the cut-off point, the liquid flows out of the outlet hole due to the sudden blockage of the channel. The outlet opening is provided in the outlet cover, on the inlet cover, an inlet opening is provided which, in the event of sudden appearance of the channel behind the cut-off area, is here apparently a negative pressure in order to draw in the liquid. Vortex pump has a good self-priming function. Vortex pump pressure and flow were: H = φu2 / 2g Q = cF Where u - impeller circumferential speed; φ - coefficient, take 3.5 ~ 4.5; F - channel cross-sectional area; Flow velocity, approximately taken c = u / 2 or (0.55 ~ 0.65) u. Impeller leaves generally 24 to 60. The characteristic curve of a vortex pump is somewhat similar to that of a centrifugal pump, but it appears steeper. Its flow rate is small and the pressure head is large, but its efficiency is not high. Vortex pump side of the gap (that is, between the impeller and cover the gap) can not get too much, otherwise it will significantly reduce the efficiency, so this pump can only deliver relatively pure liquid. Vortex pump maintenance should be measured when the gap: 1, the axial clearance between the impeller and both sides of the cover. General 2a = 0.17 ~ 020 mm, measured by pressure lead wire method. 2, impeller and pump casing radial clearance. The general radial direction to take c = 0.15 ~ 0.20 mm, with feeler gauge. 3, bearing clearance, generally take b = 0.10 mm or so, with feeler or vernier caliper measurement. 4, Coupling assembly clearance. General i = 1 mm, d = 4 ± 0.5 mm, measured with vernier caliper and depth scale. 5, the impeller and the key with the impeller and the shaft are with the slide fit. The key top clearance should be not less than 0.20 mm, two test gap should be 0.01 ~ 0.04 mm.