A centrifugal pump is used to transport fluids by converting rotational kinetic energy into hydrodynamic energy. It finds common applications across the food and beverage, dairy, and pharmaceutical processing industries. Reading a pump performance curve is important when choosing the pump that best fits your requirements.
A pump performance curve predicts the performance of a pump in terms of its flow and pressure head and being able to read it is imperative to a pump’s performance in the long term. Also, when selecting a centrifugal pump for a new application, you need to consider its composite curve so that its performance matches the one that is most suitable for the system. Generally, a composite curve consists of pump performance and horsepower curves, as well as the required NPSH (Net Positive Suction Head).
A centrifugal pump passes energy onto the fluid and possesses certain flow and head qualities. The pump needs to overcome a necessary level of pressure, and this is what determines where the performance point should be on the curve, and how much flow will be produced. The value of the pressure is inversely proportional to that of the flow. As pressure increases, flow decreases. This shifts the performance point to the left of the pump curve. Conversely, as pressure decreases, flow increases, and the point shifts to the right of the pump curve.
As a rule of thumb, when analyzing a pump curve for a new requirement, it is best to stay as close to the BEP (Best Efficiency Point) as possible. This is the operating point on the performance curve that shows the highest efficiency point for the pump’s impeller diameter.
There are 8 main pieces of information that you will need to be able to identify on a centrifugal pump curve. They are as follows:
1. Title Box
This contains the pump model, size, speed, and other characteristics of the pump.
2. Flow
The horizontal axis of the pump curve indicates the flow, so identify the amount needed from the pump.
3. Head
The vertical axis on the pump stands for the head.
4. Impeller Trim
In some cases, performance points cannot be met with the maximum impeller size alone. This is why centrifugal pumps accommodate trimmed impellers. On the pump curve, the impeller diameters are to the left and the performance for each trim is represented as a bold line across it.
5. Horsepower
The horsepower is displayed as a dotted line across the pump curve.
6. NPSHR
Net Positive Suction Head Required (NPSHR) is the minimum amount of pressure on the suction side of the pump to overcome losses in pump entrance. (This is not to be confused with Net Positive Suction Head Available or NPSHA.)
7. Efficiency
On the pump curve, the efficiency is the ratio of energy delivered by the pump to the energy supplied to the pump. The higher the efficiency, the less energy required to operate for a specific performance point. Pump efficiency numbers of 60-80% are normal.
8. Minimum Flow
A centrifugal pump needs a minimum flow moving through the pump to dissipate the heat that is generated. On the left side of the curve, the minimum flow is indicated by a vertical bold line. Operating to the left of the minimum flow line is detrimental to the shelf life of the pump and is not advisable.
For more information on industrial pumps, motors, and other equipment, contact us on +919819907445. As leading industrial water pumps dealers in Mumbai, we would be happy to assist you in finding the best match based on your requirements. VEMC is ISO 9001:2015 certified and a pioneer in the field of electromechanical engineering products, allied equipment, and services.