Before starting the centrifugal pump, it must first be filled with water to drain the air inside the pump casing. According to the working principle of the centrifugal pump, when the impeller rotates, the water is forced to the outer edge of the impeller by the centrifugal force, and a vacuum is formed at the center of the impeller, and the water is sucked to form a continuous working process of the water pump. If the pump body is not filled with water but full of air at start up, since the air density is much less than the density of water, when the impeller rotates at the same speed, the centrifugal force generated by the air will be much less than the centrifugal force of the water. This will accumulate in the center of the impeller, so that the impeller center can not form enough vacuum, hinder the inhalation of water, and affect the formation of the continuous working process of the pump. Therefore, before starting the centrifugal pump, it must first be filled with water to drain the air in the pump body to maintain the normal operation of the pump.
The centrifugal pump should fill the water pump and the inlet pipe with water before starting, otherwise the pump can’t lift the water. After the centrifugal pump is started, there is no water, which is often caused by the air in the pump being not drained and the water not being filled.
Before the pump starts, fill the water tank with water to seal it. After the pump is started, the water pump enters the water from the vacuum box. As the water level of the water tank drops, a certain vacuum is formed in the water tank. The water in the water pool will enter the water tank through the water inlet pipe under the action of atmospheric pressure, thereby forming a water circulation. The pump starts to run normally. The water filling method has the following advantages: small hydraulic loss, high pumping station efficiency, low labor intensity of the technician, simple starting, and favorable automation control of the pump unit.
There are two main methods of water filling before starting: one is to use the assembly bottom valve to fill the water, the bottom valve is the one-way valve, and is installed at the inlet of the inlet pipe. The disadvantage of this method is that the bottom valve head loss is large, which affects The pump efficiency of the pump; the other is the bottomless valve is filled with water. The biggest advantage of this method is energy saving, which can save 10%~15% compared with the pump station with bottom valve.