1. pipeline centrifugal pump pipeline matching
Some pipeline centrifugal pump users think that this can improve the actual head, in fact, the actual head of the pump = total head ~ loss head. When the pump model is determined, the total head is certain; the loss of head mainly comes from the pipeline resistance, the smaller the pipe diameter obviously the greater the resistance, and thus the greater the loss of head, so after reducing the pipe diameter, the actual head of the pump not only can not increase, but will be reduced, resulting in a decline in pump efficiency. Similarly, when the small diameter water pump with large water pipe pumping, it will not reduce the actual head of the pump, but will reduce the loss of the head due to the reduction of the resistance of the pipeline, so that the actual head has been improved. It is also believed that when a small-diameter pump uses a large water pipe to pump water, it will inevitably increase the motor load. They believe that after the pipe diameter increases, the water in the outlet pipe will have a large pressure on the pump impeller, thus greatly increasing the motor load. As everyone knows, the size of the liquid pressure is only related to the height of the lift, and has nothing to do with the size of the cross-sectional area of the water pipe. As long as the lift is certain, the impeller size of the pump is unchanged, no matter how big the pipe diameter is, the pressure acting on the impeller is certain. Only when the pipe diameter increases, the water flow resistance will decrease, and the flow rate will increase, and the power consumption will also increase appropriately. However, as long as the rated lift range, no matter how the pipe diameter increases, the pump can work normally, and it can also reduce the pipeline loss and improve the efficiency of the pump.
2. high-lift pump for low-lift pumping
Some pipeline centrifugal pump users believe that the lower the pumping head, the smaller the motor load. Under the misguidance of this misunderstanding, when purchasing a pump, the head of the pump is often selected to be very high. In fact, for centrifugal pumps, when the pump model is determined, the size of its power consumption is proportional to the actual flow of the pump. The flow of the pump will decrease with the increase of the head, so the higher the head, the smaller the flow and the smaller the power consumption. Conversely, the lower the head, the greater the flow, the greater the power consumption.
Therefore, in order to prevent the motor overload, the actual pumping head of the pump is generally required not to be less than 60% of the calibrated head. Therefore, when the high lift is used for pumping water with low lift, the motor is easy to overload and generate heat, and the motor can be burned in severe cases. In case of emergency use, a gate valve (or a small outlet with wood and other objects) must be installed on the outlet pipe to adjust the water output to reduce the flow and prevent the motor from overloading.
Pay attention to the temperature rise of the motor. If the motor is overheated, turn off the water outlet flow or shut down in time. This is also prone to misunderstandings, some machine hands think that blocking the outlet, forced to reduce the flow, will increase the motor load. In fact, on the contrary, the regular high-power centrifugal pump irrigation and drainage unit of the outlet pipe 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 gradually open the gate valve after the motor starts.
3. pipe centrifugal pump inlet pipe elbow
If more elbows are used on the inlet pipe, local water flow resistance will be increased. And the elbow should turn in the vertical direction, not allowed to turn in the horizontal direction, so as not to gather air.
When the 4. is installed with the water inlet pipe, the horizontal section is horizontal or upward.
This will cause the water inlet pipe to gather air, reduce the vacuum of the water pipe and the water pump, so that the water pump suction head is reduced, the amount of water is reduced. The correct approach is: the horizontal section should be slightly inclined to the direction of the water source, should not be horizontal, and should not be tilted upward.
The 5. pipeline centrifugal pump inlet is directly connected with the elbow
This results in an uneven distribution of the flow through the elbow and into the impeller. When the diameter of the water inlet pipe is larger than the water inlet of the water pump, an eccentric reducer pipe should be installed. The planar part of the eccentric reducer pipe shall be installed on the top, and the inclined part shall be installed on the bottom. Otherwise, air will be gathered, the water output will be reduced or water cannot be pumped, and there will be impact sound, etc. If the diameter of the water inlet pipe and the water pump inlet are equal, a straight pipe should be added between the water pump inlet and the elbow, and the length of the straight pipe should not be less than 2 to 3 times the diameter of the water pipe.
The outlet of the 6. pipe centrifugal pump is above the normal water level of the outlet pool.
If the outlet is above the normal water level of the outlet pool, the pump head is increased, but the flow is reduced. If the water outlet must be higher than the water level of the water outlet due to the limitation of terrain conditions, elbow and short pipe shall be installed at the pipe orifice to make the water pipe become siphon type and reduce the height of the water outlet.
Inlet position of 7. inlet pipe is wrong
① The distance between the inlet of the inlet pipe and the bottom and the wall of the inlet is less than the diameter of the inlet. If there is sediment and other dirt at the bottom of the pool, the distance between the water inlet and the bottom of the pool is less than 1.5 times of the diameter, which will cause poor water flow during pumping or suck in sediment and debris, blocking the water inlet.
When the water depth of the water inlet of the water inlet pipe is not enough, it will cause the water surface around the water inlet pipe to produce a vortex, which will affect the water inflow and reduce the water output. The correct installation method is: small and medium-sized water pump into the water depth shall not be less than 300~600mm, large water pump shall not be less than 600~1000mm.
When the bottom valve is set in the 8., the bottom section of the inlet pipe is not vertical
If so installed, the valve will not close on its own, causing water leakage. The correct installation method is: the inlet pipe with the bottom valve, the bottom section is vertical. If the vertical installation is not possible due to terrain conditions, the angle between the axis of the water pipe and the horizontal plane should be above 60 °.