How to choose the right head of the pump

Update: 01-11-2019

Usually, when we choose the pump, we will ask the user […]

Usually, when we choose the pump, we will ask the user how much the flow head requirements are. If the flow head cannot be determined, it will not be correctly selected. Sometimes when asked about the customer's traffic head requirements, there are a few customers who don't care. Now we remind our customers of this statement. It is not possible, the flow can be no requirement, but the lift can not be without requirements. We must tell us the actual working conditions such as the vertical height, the horizontal distance, how the pipe is arranged, the number of elbows, the size of the pipe, what liquid to transport, etc. so that we can Choose the right pump.
Firstly, determine the specific model of the pump. After using the series of pumps, select the flow according to the actual working conditions. If the head is not determined, you can add the elbow and horizontal distance according to the vertical height of the conveyor. The pipeline loss can be calculated. The required head, amplifying 5% - the value after 10% of the margin is the required head, the two main parameters of the performance determine the specific model on the type spectrum or series of characteristic curves.
Using the pump characteristic curve, find the required flow value on the abscissa, find the required lift value on the ordinate, and draw the vertical or horizontal line from the two values ​​up and to the right respectively. The intersection of the two lines falls on the characteristic curve. This pump is the pump to be selected, but this ideal situation is generally not very small.
There are usually several situations:
A, one: the intersection point is above the characteristic curve, which means that the flow meets the requirements, but the lift is not enough. At this time, if the lift phase is similar, or the difference is about 5%, it can still be used. If the lift difference is much different, the lift is larger. Pump. Or try to reduce the loss of pipeline resistance.
B, two kinds: the intersection point is below the characteristic curve. In the fan-shaped trapezoidal range of the pump characteristic curve, the model is preliminarily determined, and then according to the difference of the head, the diameter of the impeller is determined. If the head difference is small, the cutting is not performed. If the head difference is very large, the impeller diameter is cut according to the required ns and cutting formula according to the required Q, H, and if the intersection point does not fall within the fan-shaped trapezoidal range, the pump with a smaller head should be selected. When selecting a water pump, it is sometimes necessary to consider the production process requirements and select Q-H characteristic curves of different shapes.
For example, the liquid level should be transported to a container that must maintain a certain liquid level. At this time, there is a large change in the desired amount, and the head change is small. The pump with a flat H-O curve should be selected.
Another example: the oil is sent to the tube heating furnace. If the flow changes during the operation are small, the coking phenomenon is likely to occur in the furnace tube. To avoid this situation, it is hoped that when the flow rate is slightly reduced, the pressure of the oil in the tube is greatly increased, so that the eschar which is just to be formed is washed away by the higher liquid flow pressure. In this case, the QH curve should be selected to be declining. Oil pump. Consider horizontal centrifugal pumps, vertical centrifugal pumps and other types (pipeline, right angle, variable angle, angle, parallel, vertical, submersible sewage pump, vertical sewage pump, disposable, submerged sewage) Pump, non-blocking type, self-priming pump, gear oil pump, oil-filled submersible pump, water-filled temperature, etc.). The horizontal pump is easy to disassemble and assemble, but it is easy to manage, but it is bulky, expensive, and requires a lot of floor space. Vertical pump, in many cases, the impeller is submerged in water, can be started at any time, easy to automate or remote control, and Compact, small installation area and cheaper price.
Therefore, the choice of the lift is very important. When purchasing the pump, you must first determine the required lift or outlet pressure to properly select the right pump!