Centrifugal Pumps
Centrifugal pumps use rotating impellors to move different types of fluids from
one location to another. Out of all the equipment used in the industrial economy, these pumps are considered by
many to be very simple and basic equipment.
How Centrifugal Pumps Work
The purpose of these centrifugal pumps is to transform the motor or engine’s energy
into kinetic energy and thereafter into pressurized fluid. This is achieved through the two main components within
the pump. The impeller, which is the rotating part, is responsible for converting the energy into kinetic energy.
The volute, which is the stationary part, works on transforming the energy into pressure.
The way these pumps function is that after fluid enters the pumps, the impellers spin the fluid
outward. The fluid’s pressure increases and gets pushed out of the pump and into a pipe to continue on its
journey.
3 Main Categories Of Centrifugal Pumps
Centrifugal pumps can be categorized according to the way in which fluid flows into and out of
the pumps. The manner of flow depends on the pump casing and also the impeller’s designs. Based on the flow type,
we can classify the pumps into 3 main categories.
- Radial Flow Centrifugal Pumps - In radial flow pumps, fluid enters
at the centre of impeller and flows out at right angles to the pump shaft. Pressure is developed totally through
centrifugal force.
- Axial Flow Centrifugal Pumps - Axial flow pumps are also known as
propeller pumps because the way it functions is the same as a boat’s propeller. Here, the fluid is pushed by the
impeller in a direction which is parallel to the pump shaft. Pressure is developed totally through the lifting
action of the impeller vanes.
- Mixed Flow Centrifugal Pumps - Mixed flow pumps contain the features
of both radial flow and axial flow pumps. Here, the impeller pushes the fluid away from the pump shaft at a more
than 90 degrees angle. Pressure is developed partially through centrifugal force, and partially through the lifting
action of the impeller vanes.
Things To Note When Operating Centrifugal Pumps
Many of the centrifugal pumps you find in the market are actually not self-priming. What this
means is that these pumps must be primed before you can use them. Before starting out the pump you will need to
make sure that the pump casing is filled with fluid, otherwise the pump will not work. Another thing to take note
is that the pump impeller will not be able to function if the pump casing is filled with gases.
Centrifugal pumps have the tendency to overheat if the fluid level inside gets too low, which other
pumps will shut themselves down when the fluid gets too low. Pump failure will occur if the fluid inside the
pump casing dries up. In addition, to prevent the fluid from overheating, the flow through the pump must be
maintained and monitored.
Just like any other equipment parts, the pump impellers are subject to wear and tear over time.
In centrifugal pumps, they often wear off much faster if the pump has to deal
with suspended solids. The other thing to note is the corrosion inside of the pump. Generally, the speed at
which corrosion develops depends a lot on what type of fluids the pumps are handling.
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