Centrifugal pump is the most commonly used industrial pump used in any industry hence understanding centrifugal pump is essential. A term which is associate with centrifugal pumps are centrifugal pump curves. Pump curve help engineers to evaluate the performance of the curve and help to choose the right pump for the process. it also helps engineers to evaluate conditions and helps them to solve problems related to the performance of the pump. There are different type of pump available in the market like positive displacement pumps, centrifugal pump AOD pumps, and many more. Today we are going to look and learn about centrifugal pump curves, components, and how to read pump curves?. We had posted various articles also like cooling tower efficiency formula and many more, make sure you do check it.
Centrifugal Pump curves are also called centrifugal pump performance curves or sometimes simply as performance curves are important tools. As the name suggests, how a pump will perform in terms of head and flow and it helps the engineer to select the proper pump for the particular system. Generally, the pump performance curve is provided by the manufacturer. Now lets us start with the introduction.
What is Pump Performance Curve?
The pump performance curve is a chart plotted as the flow on the x-axis and Pressure head on the y-axis. The graph begins with zero flow i.e maximum pressure, also know as shutoff head which decreases gradually to the maximum flow rated.
Pump performance chart – Pump Curve
As you can see in the above pump curve chart, pump characteristic curve consists of total 4 curves. All the components and curves are discussed in details
Pump Curve components
- Q-H Curve
- Efficiency Curve
- Net Positive Suction Head (NPSH) Curve
- Energy Curve
Don’t forget to check unit operation and unit process which will help you to get knowledge about unit operations with examples. Let us discuss all the curves of pump in detail and understand the concept.
1. Q-H Curve | Head vs Flow curve
The graph is plotted in the figure consists of Flow on X-axis and Head on Y-axis. Head and flow are inversely proportional to each other. higher the pressure less will be the flow rate and this relation between the volume flow rate and the pressure head is shown into the pump performance curve diagram. At zero flowrate, pressure will be the highest and this pressure is known as shutoff pressure.
Efficiency Curve gives the relation between pump efficiency with the volumetric flow rate. The efficiency of the pump is directly proportional to the operating cost. The lower efficiency of a pump results in higher power consumption and leads to an increase in operating cost to run pump. Pump selection is to be based on the BEP known as Best Efficiency Point as at BEP, one can get maximum flow rate with highest efficiency.
3. Net Positive Suction Head (NPSH) Curve
NPSH is an important factor that needed to be considered while selecting pump for the process. NPSH stands for net positive suctions head and it is of two forms, net positive suctions head available and net positive suctions head required. net positive suctions head required should always be greater than the net positive suctions head available (NPSHA) to avoid cavitation. As you can see in the figure, NPSHR curve is flat till BEP point and rises sharply beyond that point
4. Energy Curve | BHP Curve
Enery is required to operate a pump. At minimum flow of pump, there is some amount of energy is required which is shown in the fig i.e. Brake horse power vs flow graph is a straight line ploted in the fig. as flow increases, energy required will also get increase. At shutoff pressure, flow is zero but minimum amount of energy to operate pump is consumed by the pump.
This was the detailed article on the centrifugal pump curve or in other words pump performance curve. How now you can understand the components of curve charts. If you have any problem while reading the performance curve then do share your doubt in the comment section. We will help you with your questions. If you are a chemical engineering student or a chemical engineer then this site is for you. We had posted a detailed tutorial on Types of Distillation do read.