What Is an Air Lift Pump?
An air lift pumps are a device used to lift water from a well or a sump using compressed air. These pumps are also called mammoth pumps. Airlift pumps have been used since the early 20th century. The first airlift pump was invented in 1797 by German engineer Karl Emanuel Loscher. Air lift pumps are commonly found in agricultural land.
They are simple devices in which liquid enters from one end and a mixture of air and liquid discharge from the other end. Air is injected near the inlet. Almost without exceptions, the riser section of the airlift pumps has been a vertical pipe with a vertical cross-section.
Airlift pumps are typically used when maintenance needs to be kept to an absolute minimum. But this pump is not 100% maintenance-free because air is needed to deliver equipment to the pump that needs maintenance.
Different Symbols in the diagram:-
- h – the distance between the nozzle tip and static water level.
- H – the distance between the nozzle tip and a center point of the end of the delivery pipe where the water gets discharged.
- H – h (difference of H and h) – Useful Liftnull
Parts of Air Lift Pump:
#1. Air Compressor
The air compressor is used to compress the air and supply the compressed air to the pipeline of air. Compressed air is usually produced by engine-driven air compressors, but windmill-driven air compressors are also used.
#2. Delivery Pipe
These pipes are used to lift water from the well. Using this pipe, the mixture of water and air rises. Both ends of the delivery pipes are open. The lower end of this pipe is immersed in water through which water is raised.
#3. Air Pipeline
Compressed air is sent to the delivery pipes using this air pipeline. The upper end of this pipe is connected to the air compressor, while the bottom nozzle is fitted with an air nozzle.
Working Principle of Air Lift Pump:
In air lift pumps, compressed air is mixed with water. We know that the density of water is much higher than the density of air. By buoyancy, the air that has a lower density than liquid rises quickly. By fluid pressure, the liquid is taken into the flow of the ascending air and moves in the same direction as the air.
The air is fed into the bottom of the riser pump, and this air freezes in water and form. As air mixes in water, the density of water decreases because the density of air and the mixture of water is less than the density of water.
So the mixture of air and water, also called froth, is much lower in density than water. Hence the main principle of air lift pump is the density difference between air and water mixture and water.
The efficiency of air lift pumps depend on two things:
- Submerged length (HS) in relation to the geostationary head (Hgeo).
- The velocity of the fluid through the pump and the velocity through the medium. The greater the difference between the respective velocities of fluid and air, the lower the overall efficiency of the pump.
For these pumps, the air injector system is in the form of an air jacket in which several holes are radially drilled through the pipe, and the air is supplied to them from the surrounding manifold.
For best results,
H – h <h
The ratio h / H-h is always between 4 and 8.
Working of Air Lift Pump:
First, compressed air is transported from the air compressor to the air nozzle by the air compressor. The air duct is installed as required; it may be one or more. The air tip is located at the very bottom of the delivery pipe. The position of the delivery pipes is fixed in the well, and through this pipe, water is raised from the well.
When air enters the delivery pipes from the air nozzles, the air mixes with the water present in the delivery pipe. The density of the mixture of air and water will be very low if it is compared to the pure water present in the deep well.
The density of pure water is high, & the density of the air-water mixture is low, and due to this density difference, it would be possible that a small column of pure water would be able to balance the large column of air and water mixture and therefore From, the mixture of air & water will be discharged through the delivery pipe.
As soon as the pressure in the distribution pipe of height H decreases due to the height of the column H of water in the outlet of the delivery pipe, the water in the distribution pipe starts rising above the water level outside the distribution pipe.
Another reason for water to rise is that the water in the distribution pipe is lighter than the water outside the distribution pipe. This discharge lasts as long as the supplies of compressed air continue through the air compressor.
Advantages of Air Lift Pump:
- The air lift pumps do not have any moving part below the water level, & hence there are no chances of suspended solids particles damaging the pumps.
- This pump can raise water through a borehole of a given diameter than any other pump.
- Less maintenance is required.
- This pump can handle sand, mud, & gritty water too.
- The pump is very suitable when decompressed air is available.
Disadvantages of Air Lift Pump:
- Conventional airlift pumps have flow rates that are very limited.
- Efficiency is very nearly 20 to 30% when compared to the expenditures of energy in compressing air.
- It can not lift up water if the level of water goes down below the limit.
- The suction is limited.
Applications of Air Lift Pump:
- Air lift pumps are often used in deeps, dirty wells where conventional pump usage is difficult as sand would quickly abrade mechanical parts.
- These pumps are also used to collect faunas samples from sediment.
- They are sometimes used in wastewater treatment plants if a small head is required.
- It is also used in deep-sea mining.
- Also, it is used in the recovery of archaeological artifacts & many more.
- Sometimes used in an aquarium to pumps water to filter.