Positive displacement pumps are those in which energy is imparted to the liquid in a fixed displacement volume, such as a casing or a cylinder, by the rotary motion of gears. The wrong pump will not only operate inefficiently, but can fail prematurely because it is not ideally suited to the applications conditions. Centrifugal pump pump curves pumps can generate high volume flow rates when pumping against low pressure. The pump curve also displays the pump model, the pump size and number of stages for multistage pumps. To do that, an engineer would refer to a pumps composite curve. 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. The characteristic curve s shape is primarily determined by the pump type i. Identifying the best pump for your application starts with examining the pump curve, which.
By reducing impeller size, the pump can be limited to your specific performance requirement. To read pump system curve and operating points click here. Before we start first we will understand the basics of centrifugal pump performance curve. Manufacturers will put several different trim curves on a pump performance curve to make pump specification easier, although this sometimes makes the pump performance curve more difficult to read. Pump performance curves generally show performance for various impeller diameters or trims.
The centrifugal pump characteristic curves show the law and. Pdf centrifugal pump performance characteristics for domestic. Reading centrifugal pump curves national environmental. The characteristic curves of centrifugal pumps plot the course of the following parameters against flow rate q. A centrifugal pump converts driver energy to kinetic energy in a liquid by accelerating the fluid to the outer rim of an impeller.
A curve is defined for a specific operating speed rpm and. In centrifugal pumps, the fluid enters along the centerline of the pump, is pushed outward by the rotation of the impeller blades, and exits along the outside of the pump. The efficiency of centrifugal pumps varies over the individual curve. Reading centrifugal pump curves environmental finance center. The centrifugal pump performance curve consists of four set of curves. Positive displacement pumps have a constant torque characteristic, whereas centrifugal pumps demonstrate variable torque characteristics. Pump performance charts with multiple pump curves are shown below.
The possible combinations of total pressure and volume flow rate for a specific pump can be plotted to create a pump curve. Understanding centrifugal pump curves when selecting a centrifugal pump, one should match the performance of the pump to that needed by the system. Centrifugal pump pump curves pumps can generate high volume flow rates when pumping against low pressure or low volume flow rates when pumping against high pressure. A pump performance curve indicates how a pump will perform in regards to pressure head and flow. The specific speed can be used to classify the optimum impeller design see.
Pumps can generate high volume flow rates when pumping against lowpressure head or low volume flow rates when pumping against highpressure head. Understanding of centrifugal pump performance curve is very important for select a proper pump for the required application. The flow rate q and the developed head h are both determined by the intersection. Pump performance curve a centrifugal pump performance curve is a tool that shows how a pump will perform in terms of head and flow. A typical composite curve includes the pump performance curves, horsepower curves and npsh required. Flow, head, impeller trim diameter, efficiency, power, npshr, mcsf minimum continuous stable flow and rpm. Pdf water pressure problems at home can be quite frustrating in daily life. To change the operating point either the system curve or the pump curve must be changed. Typical performance curves for a single impeller speed and diameter appear as. Choosing the correct centrifugal pump for your application is critical for maximizing longterm performance. To accommodate different performance points, centrifugal pumps have the capability of trimming impellers. Centrifugal pump curves show 8 important factors that are critical in selecting the right pump for your application.