What is the relationship between water pump head and water inlet and outlet has been a lot of pump user friends relationship problem, because the pump is one of the high general mechanical equipment, so a lot of knowledge of the pump will be interested in friends from all walks of life, next, the pump manufacturer "Changsha Zhonglian pump industry" to share a pump head and water inlet and outlet pipeline and What is the relationship between the pump head and the inlet and outlet piping and pipe diameter, to facilitate the user friends in the pump application scene to better make the pump play the proper performance.
1、High head pumps operating at low load.
Many people believe that the lower the pumping head, the lower the motor load. Misled by this misconception, when purchasing a pump, they often choose a very high pumping head. In fact, for centrifugal water pumps, when determining the pump model, the power consumption is proportional to the actual flow rate of the pump. The flow rate of the pump decreases as the head increases, so the higher the head, the lower the flow rate and the lower the power consumption. Conversely, the lower the head, the higher the flow rate and the higher the power consumption.
Therefore, to prevent motor overload, the actual pumping head of the pump is generally required to be no less than 60% of the calibrated head. When a high head is used for pumping water at too low a head, the motor is overloaded and heated, seriously burning out the motor. In an emergency, a gate valve must be installed on the discharge pipe to reduce the flow and prevent the motor from being overloaded.
Pay attention to the motor temperature rise. If the motor is found to be overheating, the outlet flow should be turned off or shut down promptly. This is also prone to misunderstanding. Some mechanics believe that blocking the outlet and forcing a reduction in flow will increase the load on the motor. In fact, quite the opposite is true; the gate valve is installed on the outlet pipe of a regular high power centrifugal pump discharge unit. To reduce the load on the motor when the unit is started, the gate valve should be closed first and gradually opened after the motor has started.
2、Large diameter pump with small hose to pump water.
Many users believe that this increases the actual head. In fact, the actual head of the pump = total head - lost head. After determining the pump type, the total head is certain; the lost head mainly comes from the pipe resistance. The smaller the diameter of the pipe, the greater the resistance and the greater the loss of head. Therefore, after reducing the pipe diameter, the actual head of the pump will not increase, but will decrease, resulting in a lower efficiency of the pump.
Similarly, when a small diameter pump is pumped with a large water pipe, the actual head of the pump will not be reduced, but the loss of head will be reduced due to the reduction in pipe resistance, thus increasing the actual head. Some users also think that when a small diameter pump uses a large pipe to pump water, the motor load is bound to increase greatly. They believe that when the pipe diameter increases, the pressure of the water in the outlet pipe on the impeller of the pump will be great, thus greatly increasing the motor load.
It is well known that the size of the hydraulic pressure is only related to the head and has nothing to do with the cross-sectional area of the water pipe. As long as the head is determined and the impeller size of the pump remains unchanged, the pressure acting on the impeller is certain, no matter how large the pipe diameter is. However, when the pipe diameter increases, the resistance to water flow decreases, the flow rate increases and the power consumption increases appropriately. But as long as in the rated head range, no matter how the pipe diameter increases, the pump can work normally, but also reduce the pipeline loss, improve the efficiency of the pump.
3、The horizontal section of the inlet pipe is too flat or upturned.
This will cause air to collect in the inlet pipe, reducing the vacuum in the pipe and pump, lowering the pump's suction head and reducing the amount of water discharged. The correct method is to tilt the flat section slightly to the direction of the water source, not horizontally, let alone upwards.
4、Too many elbows in the inlet pipe.
If more elbows are used in the inlet pipe, this will increase the local resistance to water flow. Elbows should be turned vertically, no horizontal turns are allowed to avoid air build-up.
5、The pump inlet is connected directly to the elbow.
This will cause an uneven distribution of water flow through the elbow into the impeller. When the inlet pipe diameter is larger than the pump inlet, an eccentric reducer should be installed. The flat part of the eccentric reducer should be installed on top and the bevelled part on the bottom. Otherwise, air gathers, water output is reduced or the pump cannot deliver water and there is an impact sound. If the inlet pipe is equal in diameter to the water pump inlet, 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 2~3 times the diameter of the pipe.
6、The bottom of the bottom valve inlet pipe is not vertical.
This prevents the valve from closing on its own and leads to leaks. Correct installation method: The inlet pipe of the bottom valve is extremely well vertical. If it cannot be installed vertically due to topographical conditions, the angle between the shaft of the water pipe and the horizontal surface should be at least 60°.
7、The water inlet of the inlet pipe is in the wrong position.
The distance between the inlet of the inlet pipe and the bottom of the inlet pool and the pool wall is less than the diameter of the inlet. If there is dirt such as sediment at the bottom of the pool, the distance between the inlet and the bottom of the pool is less than 1.5 times the diameter, which can lead to poor water intake when pumping or the inhalation of sediment, which can block the inlet.
When the water inlet depth of the water inlet pipe is not enough, it will cause swirling of the water surface around the water inlet pipe, affecting the water inlet and reducing the water output. The correct installation method is: the water inlet depth of small and medium-sized pumps is not less than 300~600mm, and that of large pumps is not less than 600~1000mm.
8、The outlet is above the normal water level of the outlet pool.
If the outlet is higher than the normal level of the outlet pond, it increases the head of the pump but reduces the flow rate. If, due to topographical conditions, the outlet must be higher than the water level of the outlet pond, an elbow and short pipe should be installed at the outlet to make the water pipe a siphon and reduce the height of the outlet.