When using a multistage centrifugal pump, it is inevitable that there will be some mistakes in use, but I can’t find it in time, sometimes even because of this mistake, the pump is damaged, then what are the misusages of the general horizontal multistage centrifugal pump? What?
1. Large diameter pump with small water pumping
Many operators think that this can improve the actual lift, in fact, the actual lift of the pump = total lift – loss head. When the pump model is determined, the total lift is certain; the loss head is mainly from the pipeline resistance. The smaller the diameter, the greater the resistance, so the larger the lift head is. Therefore, after the diameter is reduced, the actual lift cannot be increased but instead will decrease, resulting in a drop in pump efficiency. In the same way, when the small pipe diameter is horizontally pumped with a large water pipe, the actual lift of the water pump will not be lowered, but the loss head will be reduced due to the decrease of the resistance of the pipeline so that the actual lift is improved. It is also believed that the small-diameter horizontal multistage centrifugal pump will greatly increase the motor load when pumping water with a large water pipe. It is considered that the pressure of the water pair in the outlet pipe is large after the pipe diameter is increased, thus greatly increasing the motor load… As everyone knows, the magnitude of the liquid pressure is only related to the height of the lift and has nothing to do with the cross-sectional area of the water pipe. As long as the head is certain, the impeller size of the pump is constant. Regardless of the diameter of the pipe, the pressure acting on the impeller is constant. Only after the pipe diameter increases, the water flow resistance will decrease, and the flow rate will increase, and the power consumption will be appropriate. increase. However, as long as it is within the rated head range, the pump can work normally regardless of the pipe diameter and can also reduce the pipeline loss and improve the pump efficiency.
2. Use for low lift pumping
Many operators believe that the lower the pumping lift, the smaller the motor load. Under the misunderstanding, when the pump is purchased, the lift of the pump is often selected very high. In fact, for horizontal high pressure multistage centrifugal pumps, when the pump model is determined, the power consumption is proportional to the actual flow of the pump, and the pump flow will decrease with the increase of the lift, so the higher the lift, the flow the smaller, the smaller the power consumption. Conversely, the lower the lift, the greater the flow and the greater the power consumed. Therefore, in order to prevent the motor from overloading, it is generally required that the actual pumping stroke of the pump should not be lower than 60% of the nominal head. Therefore, when used for pumping with low lift, the motor is easily overloaded and heated, and the motor can be burnt when it is severe. If it is used in an emergency, a gate valve for adjusting the amount of water must be installed on the outlet pipe to reduce the flow and prevent the motor from being overloaded. Pay attention to the temperature rise of the motor. If the motor is overheated, turn off the flow of the small outlet or shut down. This is also easy to misunderstand. Some operators think that blocking the water outlet and forcibly reducing the flow will increase the motor load. In fact, on the contrary, the gate valve of the regular high-power horizontal multi-stage centrifugal pump drainage and irrigation unit is equipped with a gate valve. In order to reduce the motor load when the unit starts, the gate valve should be closed first, and then the gate valve is gradually opened after the motor starts. reason.
3. The inlet pipe is not in the right position.
- a. The inlet pipe is smaller than the inlet diameter from the bottom of the pool and the wall of the pool. If there is dirt such as sediment at the bottom of the pool, the distance from the bottom of the pool to the bottom of the pool is less than 1.5 times the diameter, which may result in poor water intake during pumping or inhalation of debris and blockage of the water inlet.
- b. When the water inlet of the inlet pipe is not deep enough, this will cause a vortex on the water surface around the inlet pipe, affecting the inflow and reducing the amount of water. The correct device method is that the water depth of the small and medium-sized water pump should not be less than 300-600mm. The large water pump should not be less than 600-1000mm.
4. The outlet is above the normal water level of the outlet. If the outlet is above the normal water level of the outlet, the horizontal multistage centrifugal pump head is increased, but the flow is reduced. If the water outlet must be higher than the water level of the pool due to terrain conditions, the elbow and short pipe should be installed at the nozzle to make the water pipe siphon type and reduce the height of the water outlet.