How to Select a Centrifugal Pump?

A centrifugal pump is the most common type of pump widely used across different industries all around the world. With its simple design, the centrifugal pump delivers smooth flow, offers high efficiency and is easy to maintain and operate. However, all these benefits are possible only if the right centrifugal pump meets the right operative conditions.

Right Centrifugal Pump Machinery
Right Centrifugal Pump Machinery

What is a centrifugal pump?

A pump is a hydraulic machine that converts mechanical energy into hydraulic energy. A pump that achieves this energy conversion by means of centrifugal force is called a centrifugal pump.

Though simple in design with limited moving parts, there are countless types of centrifugal pumps each catering to different applications. For an ideal centrifugal pump, the right suction conditions, flow rates, head pressure must thoroughly go hand-in-hand with ideal cost, efficiency maintenance & longevity requirements.

Without expert assistance, finding the right centrifugal pump can be daunting, to say the least, and C-Way exports are here to help.

Selecting a Centrifugal Pump:

As one of the leading global industrial equipment suppliers, C-Way exports regularly work with industrial facilities and help them choose a right centrifugal pump for their application. And with the inputs from our experts, today we aim to provide a simplified account of choosing the right centrifugal machinery.

Here we deep dive into key graphical curves that represent the performance of the centrifugal pump, help you identify the ideal operating point and assist you choose the right centrifugal pump for your application. Read on:

Pump Performance Curves: When operating at a constant speed centrifugal pumps can deliver variable flow rate (Q) which is inversely proportional to the Head pressure or Head.  Keeping the diameter of the impeller and the operating speed constant, a graph is plotted with Total head (H) at y-axis and Flow rate (Q) at Y-axis to help understand the performance of the specific pump. This graphical representation is called as Pump Performance Curve.

The graphical plot starts at the 0 flow rate where the Total head is at its peak ‘A’. The curve descends and reaches 0 Total Head at maximum flow rate point B. The operating region of this pump at a specific impeller diameter and speed is now can be said as A to B.

Efficiency Curves: Radial forces and vibrational forces do interfere in the operation efficiency of the pump. The efficiency of the pump varies throughout its operation area and the best efficiency point (BEP) for a specific pump is the point where these forces are at a minimum. Efficiency curves are plotted with flow rates on the x-axis and efficiency percentages on the y-axis.

System Curve:  A graphical plot of head and capacity required in the operating condition, System Curve plays a critical role in selecting the right centrifugal pump for your specific application.

While the performance curve mentioned represents how the pump operates in the isolation, system curves represent the flow rate and head requirements of the piping subsystem. In short performance curve is what a centrifugal pump can give (at the specific size & specific speed) and the system curve is a representation of what is needed in the operative conditions.

The desired flow rate and head needed are plotted in the x and y-axis respectively in the System Curve. System head is calculated for each flow rate by taking upstream & downstream pressures, static head, and piping losses are other key variables. Different system curves are generated for different conditions and given to the pump manufacturers to help in choosing the right centrifugal pump machinery.

Finding the Operating Point:

The given system curves are graphically superimposed over the various performance curves (head-capacity curves) to help understand the interaction of the pump and system curves. The intersection of the system and performance curves is usually the operating point of the system with specific centrifugal pump machinery. In case multiple performance curves give multiple operating points, a centrifugal pump that offers better efficiency is easy to maintain and suits the needs of your current application is chosen.

Right Centrifugal Pump Selection:

Every centrifugal pump has its own Best Efficiency Point (BEP) on its pump curve. This BEP is where the pump operates with the best efficiency which translates to lower maintenance and higher efficiency in operative conditions. It is recommended to choose a centrifugal pump with an operating point within the vicinity of the pump’s BEP (+10% or -10% is acceptable).

Right centrifugal machinery selection is all about closing-in to this BEP. The operating point happening too far left to the BEP will lower the flowrate leading to overheating and failure. If the pump’s operating point is too far right of BEF results in cavitation resulting in wear and tear of the impeller and pump cases.

That said, as we have mentioned before, this is only a simplified version of selecting the right centrifugal pump for industrial applications. If you are looking for more information on centrifugal pumps our engineering experts at C-way Exports will be happy to help.

If you have already zeroed in on your centrifugal machinery requirements and are looking for quality centrifugal pump suppliers in India we can also source and supply the high-quality centrifugal pumps as per your requirements. You can contact us here: https://www.cwayexports.com/

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