Measures to prevent air ingress in self-priming pumps, understood in seconds

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This post was last edited by shiwendong on 2016-6-14 21:52. A self-priming pump draws water by relying on the high-speed rotation of the impeller, which creates a low-pressure area inside the pump; therefore, it is essential that the inlet pipe of such a pump does not leak, so as to prevent outside air from entering the inlet pipe. Otherwise, it will not only affect the water pumping efficiency but also cause severe vibration and noise during pump operation. In operation, if the water pump does not deliver sufficient water or no water at all, the first thing to consider is whether air has entered the inlet pipe due to sand holes, cracks, or loose connections; such areas should be inspected to locate the source of air intrusion. Some defects are very subtle and difficult to detect with the naked eye; often, much effort is spent with no result. Here are several simple and easy methods for checking for air leaks in the pump inlet pipeline. (1): Lol duck feather method: Use a duck feather and, while the water pump is running, bring it close to the suspected air intake point to observe how the feather moves. Similarly, a lit cigarette can be used: lol follow these steps. Use the direction in which the duck down and smoke drift to help locate it:victory:. 　　 (2) Oil method: For intake points that are difficult to identify, apply a small amount of oil at the approximate location where the intake is presumed to be; the spot where the oil is quickly absorbed is the intake point. Methods to check for air leakage in the pump inlet pipeline: (1) The installation location of the self-priming pump should be as close to the water surface as possible, to ensure that no air is drawn in when the water level drops. 　　 (2) When installing the suction pipeline, the inlet horizontal pipe should be tilted slightly downward or installed horizontally in the direction of water flow; no point on the inlet pipe shall be higher than the water pump’s inlet, otherwise the air inside the pipe cannot be completely removed. 　　 (3) Prevent air leakage from the packing box. The tightness of the packing gland should be appropriate; if it is too loose, the packing gland cover should be tightened ； If the filler is damaged or no longer functional, it should be replaced promptly ； If the water seal tube at the packing cover becomes blocked and heats up, it will cause air leakage from the packing cover; the water seal tube should be cleaned. 　　 (4) Before installing the water inlet pipe connected by flanges, clean the surfaces where the two flanges meet, place a gasket 3–5 mm thick between them, and tighten the bolts symmetrically in several stages. 　　 (5) The bottom valve of the self-priming pump must have an adequate submersion depth; measured from the plane of the valve, this depth should be 1.5 to 2 times the outer diameter of the bottom valve, and in any case it must be at least 0.5 m. If the flooding is too shallow, vortices are likely to form, which draw in air and cause cavitation, thereby damaging the impeller and pump casing. If it is observed that the water level drops rapidly while the pump is running, several pieces of wood can be placed on the water surface to reduce turbulence and prevent air from entering the pump casing. 　　 (6) The self-priming pump body is equipped with a vent plug; to facilitate venting, a faucet with the same thread size can be used as a substitute for the vent plug – simply open the faucet during venting. 　　 (7) The vacuum level at the water intake of a self-priming pump is limited; an excessive vacuum can cause the water inside the pump to vaporize, which is detrimental to the operation of the self-priming pump. Therefore, each suction pump has its maximum allowable suction lift, which is generally between 3 and 8.5 meters; the installation should be carried out within this range. 　　 (8) Pay attention to exhaust gas. Before starting the self-priming pump, sufficient water should be supplied to remove the air inside the pump ； Normally, the vent plug on the pump cover should be opened regularly to remove the air accumulated inside.