08 Aug Centrifugal Pumps | Impeller Pumps
The Working Principle of Centrifugal Pumps
Centrifugal pumps are mechanical devices designed to transfer fluids by utilising rotational energy applied to one or more impellers. The impellers are driven to rotate rapidly. The fluid to be moved enters the chamber, or casing, in which they rotate along their axis. Once in chamber, the fluid is propelled outward by centrifugal force, flowing through the impeller’s vane tips along its circumference. This action boosts the fluid’s velocity and pressure while guiding it towards the casing outlet.
To optimise the process, the pump casing is engineered with a specific design. Its purpose is to restrict the fluid flow from the pump inlet, channel it into the impeller, and subsequently regulate and control the fluid before it is discharged from the pump outlet.
The Shortcomings of Centrifugal Pumps
While centrifugal pumps are widely used in several industries to transport fluids, they can also present a number of challenges.
- Centrifugal pumps are prone to cavitation. Cavitation occurs when the pressure in the pump drops below the vapor pressure of the fluid. This leads to the formation of vapor bubbles. When these bubbles collapse in higher-pressure regions, it may cause damage to the pump components.
- The high-velocity flow of fluids in the centrifugal pumps may lead to erosion of the impeller and wear rings, which reduces pump efficiency and shortens its lifespan.
- Centrifugal pumps also have specific temperature and pressure limitations based on their design and the materials used in their construction.
- They can consume a significant amount of energy, especially if they are not optimised for the fluid and application they are employed for.
Meeting the Challenges
Cavitation can be eliminated or substantially reduced by proper pump selection based on the required flow rate and head. The objective is to operate the pump as close as possible to its best efficiency point (BEP). Use system designs that reduce excessive pipe friction by, for example, specifying larger pipe sizes. The utilisation of cavitation-resistant materials for the impeller and pump casing will minimise the damage caused by cavitation. The installation of variable frequency drives (VFD) allows pump speed to be controlled and prevents the pump from being operated at speeds that cause cavitation.
Choose erosion-resistant materials for component manufacture, such as hardened stainless steel or ceramic coatings. Adjust pump-operating conditions to reduce the flow velocity in critical areas and choose pumps with materials capable of handling the fluid’s temperature and pressure requirements.
In high temperature applications, implement a cooling system for pumps. Consider the use of multistage pumps for applications with very high discharge pressures.
Select pumps that are appropriately sized for the specific application to operate near their BEP. At the BEP, flow enters and leaves the pump with a minimum amount of flow separation, turbulence, and other losses. Follow a proactive pump-maintenance regime and regularly monitor pump performance and efficiency to identify areas for improvement.
You Don’t Need to Be a Pump Expert
The short outline above is aimed at making the reader aware of some of the nuances of using centrifugal pumps. Fortunately, the guidance and help of the real experts is on hand. At Prochem Chemical Pump Manufacturers, we have been designing, manufacturing, and supplying pumps and pumping equipment for over 30 years.
We will assess your requirement and provide the optimum pump solution for your specific requirement. Trust the industry leaders with decades of experience to get it right first time. For professional advice on centrifugal pumps or any other pumps or pump-related equipment, contact us.