A pump is a device used to transfer fluid from one point to another. A pump is categorized as a hydraulic mechanical machine used to move fluid from a point of low pressure to point of high-pressure. A pump works adding pressure energy into the fluid. It is the pressure energy of the fluid that makes the fluid move from the interior of the pump to the required destination.
All pumps work by creating a vacuum. This vacuum is responsible for making the pump suck the fluid into the pump so that it can be moved to the required destination. There are various types of pumps used for different types of fluids. Some pumps are meant for use in gaseous applications while others are used for liquids and others for to transfer slurry media.
How does a pump work?
A pump can be a centrifugal or positive displacement pump. All pumps use similar principle of creating a vacuum in their working principle. The pump uses a prime mover which can be an electric motor or internal combustion (IC) engine. The work of the prime mover is to provide the power needed to run the pump. The prime mover is connected to the pump via the pump inlet shaft. This shaft is responsible for transmitting the power from the prime mover to the pump.
When the pump creates a vacuum (state of lower pressure than atmospheric pressure), it makes the high atmospheric pressure force the fluid into the pump at high speed. Inside the pump, the fluid’s kinetic energy is converted into pressure energy. This pressure energy is used to move the fluid from the pump to the required destination.
Types of pumps
1. Positive displacement pump
This is a type of pump that uses moving components such as pistons, plungers, lobes, rotors, and gears to drain fluid from the pump and increase fluid pressure simultaneously. This type of pump does not need to be primed since pump manufacturer design it to be self-priming.
There are various types of positive displacement pumps which include diaphragm pumps, gear pumps, progressive cavity pumps, screw pumps, piston pumps, and rotary lobe pumps among others.
Advantages of positive displacement pumps
- These pumps work at a very high pressure relative to centrifugal pumps.
- They have a high volumetric efficiency of around 98%.
- They have high power to their weight ratio.
- They have smooth and precise motion.
- They are flexible in performance.
- They work very well at high fluid head.
- They are very suitable for use in very viscous fluids.
- They do not have cavitation problems.
Disadvantages of positive displacement pumps
- They make high noise levels.
- They have low discharge capability.
- They cannot deliver fluid free from pulsation
2. Centrifugal pumps
This is a pump that works by increasing pressure as the fluid passes through the pump. As the name suggests, this pump works by using centrifugal force. This type of pump uses components known as impellers and diffusers. The impellers rotate at high speed which creates a vacuum in the pump. It is due to this vacuum that the fluid is sucked into the pump at high speed. The diffuser is used to convert the kinetic energy of the fluid into pressure energy.
There are several types of centrifugal pumps which include radial flow pumps, horizontal centrifugal pumps, vertical centrifugal pumps, submersible centrifugal pumps, axial flow pumps, and mixed flow pumps among others.
Advantages of centrifugal pumps
- These pumps are versatile since they can be used in different applications.
- These pumps are efficient in terms of energy usage.
- They need low maintenance.
- They are of different sizes from small, and medium to large sized pumps.
- They are resistant to corrosion.
- They have smooth fluid flow.
- Centrifugal pumps need smaller space for installation relative to displacement pumps.
Disadvantages of centrifugal pumps
- These pumps require priming.
- They do not work well at high fluid heads.
- They are not suitable for use in very viscous fluids.
- They are prone to cavitation.