A centrifugal pump is a mechanical pumping device designed to move fluids by using rotational energy from one or more electrically or motor driven rotors, called impellers. They are commonly used in industrial, agricultural and domestic applications. Common pumping fluids include water, solvents, sewage, petroleum and other petrochemicals, organics, oils, acids, bases and other low viscosity fluids.
Centrifugal pumps are often used because of their relatively simple engineering, as well as their high flow rates, ability to handle abrasive and other tough solutions and their mixing potential.
How do centrifugal pumps work?
Centrifugal pumps work by forcing the pumping fluid through one or more rapidly rotating impellers, thereby increasing the fluid’s velocity and pressure.
The fluid enters the impeller at its rotating axis, or at the eye of the impeller. The fluid is then accelerated by the rotation of the impellers and flows radially outward into the pump casing. From the casing (either a volute or diffuser casing), the fluid flow is translated to a controlled discharge at pressure.
Volute casings have an offset impeller, which creates a curved funnel with the area increasing towards the pump outlet or discharge. This helps to increase the fluid pressure towards the outlet.
In a diffuser casing, the same principle applies. However, the pressure is increased as the fluid is passed through a series of stationary vanes surrounding the rotating impeller. Diffuser casings can be custom designed to suit specific applications or fluids and can therefore be more efficient. However, diffuser casings may not be the best choice for applications involving entrained solids or high viscosity fluids, as the diffuser vanes can add unnecessary constrictions to the flow.
What types of centrifugal pumps are there?
There are many different types of centrifugal pumps with a range of different applications. For example, hot oil pumps are designed for the movement of heat-transfer oils and other liquids under high temperature conditions.
Cryogenic pumps, on the other hand, are designed to handle extremely low temperatures and are used for pumping liquid natural gas, coolants and other low-temperature fluids.
Magnetic drive pumps use a balanced magnetic field to create the rotation of the fluid impeller. These pumps replace a traditional direct drive mechanism with a magnetic field. This reduces the physical contact between moving parts and allows for a closed system that doesn’t rely on seals. These are particularly useful for pumping hydrocarbons and chemicals, where you want to avoid any leaks at all.
Chopper/grinder pumps include impellers fitted with grinding teeth to help chop up any solids in the fluids. These are mostly used for processing wastewater in industrial, chemical, food processing and sewerage applications.
Multistage pumps feature multiple impellers designed to maximise the output pressure and are used for high-pressure applications.
Trash pumps and slurry pumps are designed to handle fluids containing solid debris and highly abrasive slurries. These are used for heavy duty industrial applications like mining, mineral processing, industrial slurries and construction drainage.
The wide range of centrifugal pump designs and applications means that they supply simple and low-cost solutions to most low-pressure, high-capacity pumping applications.