If you are trying to buy a pump then you will come across a pump performance curve. This graph is a very important form of visual data pertaining to the performance of your pump. Being able to understand and read a pump performance curve will help you select a pump that will suit your needs. The article below will help explain how to read a pumps performance curve and help you select the right pump.
What is a pump performance curve?
A pump curve is a visual graph of performance data collected from testing. Every pump will have slightly different performance based on the size, horsepower, shape of the impellers and pump body.
Why is a pump performance curve so important?
Selecting a pump too large will put added pressure on your system while selecting a pump too small with put stress on a pump leading to failure. By understanding the performance of your pump, you are able to understand the limitations of that pump and thus match a pump to your needs.
How to read a pump performance curve
Two vital bits of information are read in a pump curve, Flow and Head.
Flow is the rate at which liquid moves throughout a system. Typically it’s measured in litre per minute (lpm) or metre per hour (m3/h) but can sometimes be measured in gallon per minute (gpm).
Head loss is the amount of friction accumulated from friction fluid passing though pipes, fittings or the lifting of fluid vertically. Pressure is measured in PSI, pound per square inch but in hydronic, pressure is calculated in term of head pressure or head loss as measured in head.
In order for a pump to work, it needs to produce a certain amount of pressure to overcome the head loss in a system.
Reading the curve
Below is a pump performance curve. The unit of Head is displayed on the verticle axis while the flow is displayed on the horizontal. If we look at the left-hand side arriving to 12 meters of head, and follow the line until it hits the blue curve, It shows we will be supplied slightly over 250 litres per minute.
Finding a pumps best efficiency point
All pumps have a recommended best efficiency point to make sure damage is not done to the unit. Typically this is around 85% of the shutoff head. It is important to note that pumps should be operated as close to the best efficiency point at all times.
- Pump curves have two units displayed, Flow and Head.
- Both help to select a pump suitable for your needs.
- Always use a pump at its best efficiency point.