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Pumps are used to supply water to the house or water the garden. There are different types and designs, and each of them finds its own scope. If you need an inexpensive and reliable device for pumping water from a well, a deck or some kind of container, pay attention to a self-priming pump. These are relatively inexpensive devices that are installed on the surface, they can pump water from a fairly decent depth – 8-9 m. If necessary, the models are supplemented with ejectors, then the suction depth increases to 20-35 m.
Self-priming pumps: device and types
Self-priming pumps pump water from a depth of 8-9 meters, while they themselves are on the surface. Water rises due to the fact that in the central part of the body, due to the movement of wheels with blades, a low pressure area is created. In an effort to fill it, the water rises. So it turns out that the pump sucks water.
Like any other pump, a self-priming one consists of an engine and a working chamber in which the discharge mechanism is located. The shafts of the pump and motor are connected through a coupling, the reliability of the connection and tightness is determined by the type of seal. There are two types of seals:
- stuffing box – cheaper and less reliable;
- end seal – more reliable, but expensive.
There are models of self-priming pumps with magnetic couplings. They do not require sealing, since they do not have through connections. This is by far the most reliable design, but also the most expensive too.
The structure and principle of action
According to the mode of action, a self-priming pump can be vortex and centrifugal. In both, the key link is the impeller, only it has a different structure and is installed in a housing of a different handicap. This changes the principle of operation.
Centrifugal
Centrifugal self-priming pumps have an interesting structure of the working chamber – in the form of a snail. Impellers are fixed in the center of the body. There can be one wheel, then the pump is called single-stage, there can be several – a multi-stage design. Single-stage always operate at the same power, multi-stage can change performance depending on the conditions, respectively, they are more economical (less energy consumption).
The main working element in this design is a wheel with blades. The blades are bent in the opposite direction with respect to the movement of the wheel. When moving, they seem to push the water, squeezing it to the walls of the case. This phenomenon is called centrifugal force, and the area between the blades and the wall is called the “diffuser”. So, the impeller moves, creating an area of increased pressure on the periphery and pushing water towards the outlet pipe.
At the same time, a zone of reduced pressure is formed in the center of the impeller. Water is sucked into it from the supply pipeline (suction line). In the figure above, incoming water is indicated by yellow arrows. Then it is pushed by the impeller to the walls and rises up due to centrifugal force. This process is constant and endless, repeating as long as the shaft is spinning.
Their disadvantage is connected with the principle of operation of centrifugal pumps: the impeller cannot create centrifugal force from the air, therefore, the housing is filled with water before operation. Since pumps often operate in intermittent mode, so that water does not flow out of the housing when stopped, a check valve is installed on the suction pipe. These are the features of the operation of centrifugal self-priming pumps. If the check valve (it must be mandatory) is at the bottom of the supply pipeline, the entire pipeline has to be filled, and this will require more than one liter.
| Name | Power | Head | Maximum suction depth | Performance | Housing material | Connecting dimensions | Price |
|---|---|---|---|---|---|---|---|
| Caliber NBC-380 | 380 W | 25 m | 9 m | 28 l / min | cast iron | 1 in. | $32 |
| Metabo P 3300 G | 900 W | 45 m | 8 m | 55 l / min | cast iron (stainless steel drive shaft) | 1 in. | $87 |
| ZUBR ZNS-600 | 600 W | 35 m | 8 m | 50 l / min | plastic | 1 in. | $71 |
| Elitech HC 400V | 400Vt | 35 m | 8 m | 40 l / min | cast iron | 25 mm | $42 |
| PATRIOT QB70 | 750 W | 65 m | 8 m | 60 l / min | plastic | 1 in. | $58 |
| Jilex Jumbo 70/50 Ch 3700 | 1100 W | 50 m | 9 m (integrated ejector) | 70 l / min | cast iron | 1 in. | $122 |
| BELAMOSS XI 13 | 1200 W | 50 m | 8 m | 65 l / min | stainless steel | 1 in. | $125 |
| BELAMOS XA 06 | 600 W | 33 m | 8 m | 47 l / min | cast iron | 1 in. | $75 |
Vortex
The vortex self-priming pump differs in the structure of the casing and the impeller. The impeller is a disk with short radial baffles located at the edges. It’s called an impeller.
The housing is made in such a way that it quite tightly covers the “flat” part of the impeller, and a significant lateral clearance remains in the baffle area. When the impeller rotates, the water is carried away by the bridges. Due to the action of centrifugal force, it is pressed against the walls, but after some distance it again falls into the zone of action of the partitions, receiving an additional portion of energy. Thus, in the gaps, it also twists into vortices. It turns out a double vortex flow, which gave the name to the equipment.
Due to the peculiarities of work, vortex pumps can create pressure 3-7 times more than centrifugal ones (with the same wheel sizes and rotation speed). They are ideal when low flow and high pressure are required. Another plus is that they can pump a mixture of water and air, sometimes they even create a vacuum if they are filled only with air. This makes it easier to start it up – no need to fill the chamber with water or a small amount is enough. The disadvantage of vortex pumps is low efficiency. It cannot be higher than 45-50%.
| Name | Power | Head (lifting height) | Performance | Suction depth | Housing material | Price |
|---|---|---|---|---|---|---|
| TODAY XKSm 60-1 | 370 W | 40 m | 40 l / min | 9 m | cast iron | $24 |
| TODAY XKSm 80-1 | 750 W | 70 m | 60 l / min | 9 m | cast iron | $89 |
| I AM QB 60 | 370 W | 30 m | 28 l / min | 8 m | cast iron | $47 |
| I AM QB 70 | 550 W | 45 m | 40 l / min | 8 m | cast iron | $ 68 |
| Pedrollo RKm 60 | 370 W | 40 m | 40 l / min | 8 m | cast iron | $77 |
| Pedrollo RK 65 | 500 W | 55 m | 50 l / min | 8 m | cast iron | $124 |
Ejector
The greatest depth from which surface vortex and centrifugal pumps can lift water is 8-9 meters, often it is located deeper. To “get” it from there, an ejector is installed on the pumps. This is a tube of a special shape, which, when water moves through it, creates a vacuum at the inlet. So such devices also belong to the category of self-priming. The ejector self-priming pump can lift water from a depth of 20-35 m, and this is already more than enough for most sources.
The disadvantage is that in order to ensure operation, part of the understood water must be returned back, therefore, productivity is significantly reduced – such a pump can provide not very large water consumption, but no less electricity is spent on ensuring performance. When the injector is installed in a well or well of sufficient width, two pipelines are lowered into the source – one supply of a larger diameter, the second, a return one, of a smaller one. An ejector is connected to their outlets, and a filter and a check valve are installed at the end. In this case, the disadvantage is also obvious – double consumption of pipes, which means a more expensive installation.
In small diameter wells, one pipeline is used – the supply pipeline, and the well casing is used instead of the return one. Thus, a rarefaction zone is also formed.
Vortex and centrifugal – comparison and scope
First the generalities:
- maximum suction depth – 8-9 meters;
- installation method – surface;
- there must be a pipe or a reinforced hose on the suction pipeline (do not install the usual one, it will be flattened by negative pressure).
Now about what are the differences between vortex and centrifugal models. Peripheral pumps are more compact, cost less, but produce more noise during operation. Centrifugal – quieter, at the exit they create a small pressure. Vortex with the same dimensions of the impeller and the speed of its rotation can create a pressure of 3-7 times more. But it cannot be said that this is their advantage – far from always a large output pressure is required. For example, it is not needed when watering the garden and vegetable garden. Water supplied with high pressure will simply wash away the soil, exposing the roots. Therefore, it is better to take a self-priming pump of a centrifugal type as a pump for irrigation.
High outlet pressure may be required when organizing a home water supply system. This is where the characteristics of vortex pumps will be required. They only have one drawback: they cannot provide a large flow. So more often for these purposes they use the same centrifugal, but paired with a hydraulic accumulator. True, then it turns out to be a pumping station.
The main disadvantage of surface centrifugal self-priming pumps is the need to fill them with water before starting. Not the most pleasant activity, which adds to the hassle when using such a pump for irrigation.