Five Things Centrifugal Pump Operators Need to Understand About Reading a Pump Curve

If you use a centrifugal pump, you need to be able to read a pump curve. This will help you to ensure you are not over straining the pump, and in some cases, it can also help you troubleshoot certain issues. Here is a look at the basics of reading pump curves:

Understanding The Layout

Generally, at the top of the graph, there is information on the pump -- always check that the curve you are using matches the model number of the centrifugal pump you are using. The horizontal axis of the graph has numbers related to flow, and head measurements appear along the vertical axis. Curved lines related to impeller trimming run across the center of the graph, and finally, dashed vertical lines represent horsepower.

Finding Your Point on the Pump Curve

To find your point on a curve for a centrifugal pump, figure out what flow you need. This is measured in litres per minute. Then, figure out your head requirements, measured in metres. Find the point on the graph that corresponds with those two axis points.

Interpreting Impeller Recommendations.

Once you have found your point on the graph, it should fall on one or between two of the impeller lines. Use the measurements corresponding to those impeller lines to determine which measurement your trim needs to be. Then, reduce the size of your pump's impeller by that number of millimetres. Centrifugal pumps are unique in the fact that you can trim the impellers to help them run more efficiently at certain head and flow rates. With most other pumps you have to make speed adjustments.

Ensuring Safety

If the flow rate and head you need do not fall on a point that is represented on the pump curve, you need a different pump. Trying to operate a pump past its capabilities can cause it to malfunction. Additionally, if you use a centrifugal pump at a rate below its minimum flow rate, there won't be enough liquid going through the system. This can cause the pump to overheat, reducing its lifespan.

Troubleshooting With a Pump Curve

If you have troubles with your pumping system, you can do a preliminary check using the pump curve to help pinpoint the source of the issue. Figure out the head measurement and the flow rate of the pump. Then, find this point on the graph. If the point falls inside the standard operating range for that pump, the pump is likely not the source of the problem. Instead, you should start looking at the rest of the system or the pumpage. However, if the point is outside of the normal operating range, the issue is with the pump, and you may want to call a professional to help you check things like suction pressure, discharge and horsepower.