How to read a pump curve ?

1. Title Box :
The title box provides information about the pump model, size, speed, and other identifying criteria specific to the pump. If checking the performance of an existing pump, confirm that you are matching the pump to the associated curve.


2. Flow :
To start your selection, identify the amount of flow you require from the pump. For this example, we have chosen 300 gpm. Flow is indicated across the bottom horizontal axis of the curve.


3. Head :
You will also need to know the total head the pump is required to overcome at the specified flow. For this example, we will use 100 ft. Head is indicated in increments along the vertical axis. Follow 100ft across the curve intersects your flow line which indicates your performance point.


4. Impeller Trim :
To accommodate different performance points, centrifugal pumps have the capability of trimming impellers. By reducing impeller size, the pump can be limited to your specific performance requirement. The impeller diameters are listed on the left side of the curve and the performance for each trim is shown across as a bold line. Our selection is between 10” and 11” so a trim of 10.5” is appropriate.


5. Horsepower :
Now that you have your performance point, we can determine the amount of horsepower required. Horsepower is indicated across the curve as a dotted line in this case at a downward angle. Our performance point is between the 10hp and 15 hp lines, we estimate this selection to require 12 hp.


6. NPSHR :
Net positive suction head required is important for proper pump operation. This is the minimum amount of pressure on the suction side of the pump to overcome pump entrance losses. If sufficient NPSH is not met the pump will cavitate which will affect performance and pump life.


7. Efficiency : 
When selecting the best pump for an application, efficiency many times is an important factor. The higher the efficiency, the less energy required to operate for a specific performance point.


8. Minimum Flow
A centrifugal pump requires a minimum amount flow to be moving through the pump to dissipate heat created. On the left side of the curve, minimum flow is indicated by a vertical bold line; operation to the left of this line is not recommended and can significantly decrease the life of the pump.

Source : https://blog.craneengineering.net/how-to-read-a-centrifugal-pump-curve