A centrifugal pump is essentially a mechanical device made to move fluid by adopting the transfer of rotational energy from single or several driven motors, known as impellers. Fluid passes the quickly rotating impeller across its axis and is expelled by centrifugal force across its circumference all through the vane tips of the impeller. The impeller’s action increases the fluid’s pressure and velocity and directs it to the pump outlet as well. The pump casing is specifically made to constrict the fluid passing through the pump inlet, then direct it into the impeller. Later, it will slow and regulate the fluid before discharging it.
How Does A Centrifugal Pump Work?
On a centrifugal drum pump, the impeller is usually the key component. It generally comprises a series of curved vanes. In most cases, these are sandwiched between two discs, called an enclosed impeller. An open or semi-open impeller would be a preferable option for fluids that have entrained solids.
Volute and diffuser are the two basic designs when it comes to pump casing. The main goal in both designs is to shift the fluid flow into a regulated discharge at pressure.
The Casing Design Of A Centrifugal Volute
Diffuser designs apply the same principle. In this case, typically, the fluid pressure increases when fluid is cast out between a group of stationary vanes surrounding that impeller. Since diffuser designs can be customized for specific applications, they can be more efficient. Mostly, volute cases are a preferable option to applications involving high viscosity fluids or entrained solids when it is beneficial to avoid the extra constrictions of diffuser vanes. Also, the volute design’s asymmetry can lead to greater wear on the driveshaft and impeller.
Centrifugal Diffuser Case Design
The main components of a centrifugal pump
Positive and centrifugal displacement pumps are the two major families of pumps. In contrast to the former, centrifugal pumps are often specified for higher flows and also for pumping down lower viscosity liquids, to 0.2 cP. In certain chemical plants, you will find that 90% of the pumps in operation will be centrifugal pumps. But, there are a few applications where positive displacement pumps become a preferable option.
What Are The Drawbacks Of A Centrifugal Pump?
A centrifugal pump’s efficient operation depends on the steady, high-speed rotation of its particular impeller. Centrifugal pumps become very inefficient due to high viscosity feeds; therefore, higher pressure and greater resistance is required to maintain a particular flow rate. Generally speaking, centrifugal pumps are thus suited to high capacity, low pressure, pumping applications of liquids that have viscosities ranging from 0.1 and 200 cP.
Besides, slurries like mud, or perhaps high viscosity oils can lead to excessive wear and overheating, which leads to more damage and premature failures. Typically, positive displacement pumps operate at relatively lower speeds and are also less prone to these issues.
Any pumped medium that is quite sensitive to shearing, which is the separation of biological liquids, slurries, or emulsions, can also be destroyed due to the high speed that comes with a centrifugal pump’s impeller. In these cases, a positive displacement pump’s lower speed is preferred.