Pump head: how to determine the performance?

Choosing a pump of any design requires calculation of its performance. Conveniently, when the water pressure in the tap is adjusted in such a way that, at its greatest value, splashes do not scatter to the sides, and at the same time it does not take long to wait for the filling of a large container. On how to determine the performance of the pump, we'll talk further in the article.

Pump Selection Options

The optimum pump head can be obtained in two ways: artificial throttling or precise selection of the device parameters. If you choose it according to the principle "the one that is better with a neighbor", then the probability of a weak head of the jet is high, with the simultaneous inclusion of several flow points. Either it is necessary to restrain the flow of water by partial overlapping of the faucet, which reduces the efficiency of the device, and consequently, increases the cost of funds during its operation.

A professional approach to the issue of water supply requires consideration of many aspects:

• Power of the pump;
• Thickness of the supply pipe;
• Length of the main line;
• Number and shape of fittings;
• Number of cranes.

Of course, everything is very difficult to envisage, therefore, with a complex system of plumbing communications, several pumps are used for greater efficiency. Each performs its function: one fills the water intake from the well, another provides water to the house, the third watered the garden.

Pump characteristics, head

Pumps have many characteristics. In order for the consumer to determine what type of device he needs, there are several key indicators:

1. The volume of fluid supply, or the capacity of the pump. It shows how much water the unit can pump in a certain period of time. It means that the liquid flows directly to the output of the device. To determine the volume at the end of the line, it is necessary to subtract the pressure loss in the latter.
2. The amount of pressure, or pressure. Indicates how high the pump is capable of lifting water. It does not take into account the height from the device to the water level .
3. Height to water intake, or backwater. The distance from the water mirror to the outlet of the suction pipe is strictly defined - the excess leads to the appearance of the phenomenon of cavitation in the working space of the unit. This can change the important characteristics of the pump or simply will not allow it to pump water. The head can be increased by installing an auxiliary pump in front of the main pump, directly at the suction point. Exactly the same effect will result when creating artificial air pressure inside a tank with a liquid.
4. Power consumption .

Brief overview of pumps

Pumps can be classified according to the principle of operation, design features and purpose. There are also submersible and surface aggregates. All of them are designed for pumping liquids, but most provide for not only it, but also rising water from different depths:

• Pumps for wells. Basically they are submersible models. Characterized by the fact that they can lift water from great depths (they do not have limitations), depending on the power of the power unit. Create a powerful head in the pipeline.
• Drainers. They have higher productivity, but are not designed to create high pressure, high head does not give. Convenient in that they can pump dirty water with small physical particles.
• Centrifugal. Universal pumps. Can be used both in wells and for pumping liquid from reservoirs. The water does not fall and have a restriction on the distance from the surface of the water surface to the inlet of the suction pipe. The pump head depends on the number of impellers and engine power, but still they can not lift the water column higher than 120 meters.
• Vortex. They are similar to centrifugal, but here the impeller is organized in a different way. With less engine power, they provide high head and productivity. Raise the water column over 160 m. The disadvantage is the exacting to its purity.
• Circulating. Do not lift water from the depths, but also create a certain pressure and work at elevated temperatures.

Pumps: feed, head

Maybe not everyone knows, but the pumps work paired with the pressure of the atmosphere. They simply create a discharge and discharge area. Therefore, no matter what efforts we exerted from above, using the most powerful units, it will not be possible to raise water from a great depth. As soon as the force of air pressure is balanced by gravity, the water in the pipe will stop. To lift from the depths, powerful submersible devices are used that create pressure.

The main characteristics of the described units are the pump head, capacity. They have a certain dependence among themselves. Thus, under pressure is meant the ability to supply water at a certain height or to move horizontally by a given length. It is clear that the same pump will produce a different pressure at a height of 20 and 120 m.

The head must be known by selecting the pump type. Each model can create a strong or weak pressure, which is due to the design of the working mechanism. When the fluid comes into contact with the wheel blade either by a diaphragm or a piston, it receives a certain charge of kinetic energy, which raises it upward.

The most effective centrifugal systems with several successive impellers. They are pumps for increasing head and have very high efficiency.

How to adjust the head

In any complex water supply system, it is necessary to regulate the pressure created by the pump. There are four ways to influence the head:

1. Throttling. The essence of the method is that a special choke is installed at the outlet of the device or on the suction nozzle. In its role can act as a normal tap. At the installation site, depending on the diameter of the throttle opening, part of the head is extinguished. When the water flow limiter is in the pump outlet, the efficiency of the device is reduced, since the pump consumes the same amount when the head of the power system is weakened.
2. Electric control of the rotational speed of the impeller. This is the most effective method without losing the efficiency of the pump. The water supply decreases with a proportional decrease in the power consumption.
3. Mechanical decrease in speed. In this case, a reducing gear is used. The method is economically unprofitable - after all, the engine consumes the same power and requires an additional mechanism - a reducer.
4. Bypassing. Between the outlet and the suction pipe of the pump put a jumper. It turns out that part of the liquid just circulates in a circle, without doing useful work. As a result, the pressure drops in the pipes, and the efficiency decreases.

What will be the pressure of the pump pumping water from above

When the water intake capacity is located above the installation site of the pumping system, the energy for suction is practically not wasted. Then, to calculate the head of the pump, use the following formula:

Нтр = Нрео + Нпотерь + Нсвоб - The height of the tank.

Нтр here - the necessary value of pressure, due to the costs of the consumer.

Hreo - level difference between the pump installation platform and the highest point of water consumption.

Loss - loss of overcoming frictional force in the supply line with the exception of the vertical pipe section from the supply tank to the pump.

Nswob - the pressure from the points of consumption when they are fully opened.

Bottom height - the height between the tank and the pump.

Water injection from a depth

How to determine the pump head when pumping water from a well, a water storage pit or a well? The calculation formula takes the following form:

Нтр = Нрео + Нпотерь + Нсвоб + Source level.

In it, all the terms are the same, except for the last one, the source level , which is the difference between the suction point of the liquid and the pumping device.

What is a pumping station

The pump station represents a system of a pump and a hydraulic tank working in pairs. Plus, they have a special pressure control relay. The hydraulic accumulator serves as a smoothing head of the pump element, preventing the frequent activation of the electric motor and leveling possible water hammers in the plumbing communications.

Stations can be based on any type of pump, with the use of any amount of battery. The more the tank is bigger, the stronger the additional lifting force it creates.

Conclusion

When the water pressure in the pump is insufficient, you can exit the situation by installing two or more units in series. This scheme is often used for deep wells, where a submersible unit is installed at the bottom, which supplies water to the centrifugal suction pipe.