Static head is the difference in height between the starting elevation. How to select a centrifugal pump examples of total head calculations sizing a pump for a home owner application 14. On the pump curve, the intersection of 120 feet of total head and 55 gpm shows the need for a new impeller trim of nine inches, a brake horse power of about four hp, and a npsh of 3. Pump runout is the maximum flow that can be developed by a centrifugal pump without. Npshr curve the 3rd part of the pump curve is the net positive suction head required npshr curve. Pump performance curve a centrifugal pump performance curve is a tool that shows how a pump will perform in terms of head and flow. In general, pump curves are designed according to iso 9906 annex a, which specifies the tolerances of the curves. Components of centrifugal pump performance curve 1. These curves are necessary to predict the behaviour and performance of the pump when the pump is working under different flow rate head and speed. A centrifugal pump requires a minimum amount flow to be moving through the pump to dissipate heat created.
However, as piping systems are quite complicated with lots of branch points, control features, and dynamic interactions, creating a useful system curve can quickly. Flow characteristics of globe valves, such as the mark one and two, can be determined by the shape of the plug head. For the choice of the right pump, the system characteristic curve or data must be known about it. The curve defines the range of possible operating conditions for the pump. This paper addresses the influence of airwater twophase mixture on the characteristic curve of a centrifugal pump. Jun 23, 2016 lets first go through the characteristic curves of centrifugal and reciprocating pump so that the ones referring it for the first time also get the idea of it. Affinity laws applied to centrifugal pump applications. Centrifugal pump curves show 8 important factors that are critical in selecting the right pump for your application.
Typical performance curves for a single impeller speed and diameter appear as. From there you can adjust operating speeds, viewsave electronic curves and data sheet reports in a pdf format, generate system curves, simulate multiple pumps speeds, request quotes and much more. System curve and pump performance curve engineering toolbox. Experimental and numerical investigations have been carried out to study the behaviour of a centrifugal pump operating in direct mode or turbine mode. On the left side of the curve, minimum flow is indicated by a vertical bold line. Reading and understanding centrifugal pump curves is key to proper pump selection, and to their reliable and efficient operation. The possible combinations of total pressure and volume flow rate for a specific pump can be plotted to create a pump curve. Other important information for a proper pump selection is also included like efficiency curves, npsh r curve, pump curves for. That is, analyze the system to determine the pump head required as a function of flow rate through the pump this will form the system line.
The fastest way to access pump efficiency curves and other pump information. The curves for power consumption and efficiency will normally only cover the pump part of the unit i. Characteristic curves for a centrifugal pump examining figure 3, the general performance of the pump can be determined. Centrifugal pump characteristic curve engineers edge. The single most energy efficient discharge versus head point on the pump curve is termed as the best efficiency point bep. A centrifugal pump performance curve is a tool that shows how a pump will perform in terms of head and flow. The characteristic curves of centrifugal pumps plot the course of the following parameters against flow rate q. The choice of pump for a given application depends largely on how the pump headflow characteristics match the requirement of the system downstream of the pump.
Characteristics of centrifugal pumps working in direct or. Pump characteristic curves manufacturer of a pump supplies a curve that shows head obtained by the pump for different discharge values. Jan 08, 20 by ron astall, united pumps australia some pump curves look different. Our selection is between 10 and 11 so a trim of 10. Sep 21, 2017 how to read the pump and system characteristic curve theoretical explanation of the pump characteristics curve, you may read the previous article. Centrifugal pump characteristic curve components of. The h tq curve shows the relationship between head and flow rate. This pressure is expressed in units of measure called pounds per square inch psi or feet of headft. Pump system curve and pump operating point mechanical. Do not depend on the size of the pump flanges, in most cases larger pipes and valves are required. The main advantage of this approach is the fact that only one characteristic curve is used for all possible operating. This type of curve is referred to as a rising characteristic curve. A pump curve is a graphical representation of the performance characteristics of a pump. Centrifugal pump performance curves and technical information 0 20 40 60 80 100 120 140 0 10 20 30 40 50 60 70 80 0 100 110 capacity ead ft nps in feet 10 20 30 40 50 10,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000 160 npsh req u i r e d 2 5 0 m i mp e l r dia t r 9 16 45 h e a d c a p a c i t y 0 5 10 15 20 25 30 35 40 gpm lbs.
Shutoff head is the maximum head that can be developed by a centrifugal pump operating at a set speed. Combined curve for pumps a and 8 shows a headdischarge characteristic curve for two operating in series pumps operating in parallel. Characteristic curves for a singlestage centrifugal and other components. First of all, the complete characteristics head, power, and efficiency were measured experimentally using a specific test loop. It is often parabolashaped and does not generally pass through the origin of the hq coordinate system. Search by design point flow rate and head, set limits, correct for viscosity and analyze pump performance. To change the operating point either the system curve or the pump curve must be changed. Pump characteristic an overview sciencedirect topics. The pump curve shows the flowrate range on the horizontal scale. The npshr curve provides information about the suction characteristics of the pump at different flows. The starting point for the curve at no flow, will be the same. The key thing to remember when reading a pump curve is all curves are based upon the principle of plotting data using the x and y axis. Different pumps that operate with different pump curves will all operate along the system curves but at different fixed points.
Whats the significance of pump characteristic curves. The figure below shows the pump curve of a single pump a, two pumps operat ing in parallel b, and the system curve c. In this case it is the p1value that has to be taken into account. Explain the performance and characterstic of centrifugal pumps. How to read the pump and system characteristic curve.
Grundfos product center makes accessing and reading pump curves easier than ever, providing a simple display of system characteristics to help you understand your pump s efficiency and verify your pump choice. The operating point of a centrifugal pump, also called its duty point, is given by the intersection of the pump characteristic curve with the system curve. But for a specific operation there exists a head vs discharge equation depending on the system characteristics. Pump headflow curves are typically given for clear water. Pumping system curves michigan technological university. Versatility is one of the main characteristics of neptuno pumps vtp. Experimental study of characteristic curves of centrifugal. Calculate the pump discharge pressure from the pump total head. In fluids dynamics the term pump head is used to measure the kinetic energy which a pump creates.
The pump characteristic curve is influenced by the size and design of the pump, the size of the impeller diameter, as well as the magnitude of the operating rotation. Pump efficiency and power pump efficiency, epump pump water horsepower whp e brake horsepower bhp 221 n by the pump manufacturer calculate required bhp, knowing epump water horsepower is defined as. A typical composite curve includes the pump performance curves, horsepower curves and npsh required. Pumps operating in series pumps operating in parallel. Reading centrifugal pump curves national environmental. The h in the curve is the difference in energy level between the suction and the pressure side of the pump. In the example shown, even though 2 hp is required for a flow of 140 gpm with 40 ft head, the end of curve horsepower requires a 2. Pdf centrifugal pump monitoring and determination of pump.
Reading centrifugal pump curves environmental finance center. Do the calculations and insure that the pipe losses and velocities are at acceptable levels. Pdf dimensionless characteristics of centrifugal pump. Pump connections the right pipe size is a compromise between pipe cost and excessive friction loss.
The pump curve directly above the duty point is the 722. A stable curve has maximum head at zero flow and a negative gradient constantly falling as flow increases. Pumps and pumping system bureau of energy efficiency 116 figure 6. A drooping pump curve is a characteristic headflow pump performance curve that does not continually rise when moving from the best efficiency point bep back to shutoff.
Unlike positive displacement pumps such as piston pumps, centrifugal pumps deliver a var iable flow rate q increasing. Centrifugal pump monitoring and determination of pump. The characteristic curves shape is primarily determined by the pump type i. How to read a centrifugal pump curve crane engineering. If the head and flow operating point of your system is on or below a given pump curve, then that pump will be sufficient. Pumps can generate high volume flow rates when pumping against lowpressure head or low volume flow rates when pumping against highpressure head. The three most common types of flow characteristics are quick opening, equal percentage and linear. A typical centrifugal pump characteristic curve is shown below. The pump performance curve describes the relation between the flowrate and the head for the actual pump. 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. Centrifugal pump characteristic curve components of centrifugal. Creating a pump and system curve for a simple system with a single flow path and no control features is an easy and typically wellunderstood process. To do that, an engineer would refer to a pumps composite curve.
The performance or characteristic curve of the pump. Flow, head, impeller trim diameter, efficiency, power, npshr, mcsf minimum continuous stable flow and rpm. Pump manufacturers use the terminology called head and pump users use pressure to measure the performance. Therefore the constant between each curve is the capacity or xaxis. Two equations were presented to estimate the complete characteristic curves of centrifugal pumps as turbines based on their best efficiency point. Figure 91 shows the ideal characteristic curve for each. 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. Pump cavitation is caused by the reduction in system heads. By reducing impeller size, the pump can be limited to your specific performance requirement. Pump system curve represents the resistance offered by the system ie. In english engineering units used in the united states, at 6. There are several terms associated with the pump characteristic curve that must be defined.
Theory one way of illustrating pump characteristics is to construct contour lines of. This set of four curves is known as the pump characteristic curves or pump performance curves. Centrifugal pump exercise b objective to create head, power and efficiency characteristic curves for a centrifugal pump. Qh curves will be given by the manufacturer of the pump and can normally be considered as a simple quadratic. At 2 m of head, the pump will have a flow rate of 8 lpm or 8. These are graphed for fixed pump speed for each impeller diameter in a given family of pumps. Manufacturers data for this pump is contained in figures 7.
Positive displacement pumps deliver a definite volume of liquid for each cycle of pump operation. The possible combinations of total pressure and volume flow rate for. In some pump types with integrated motor and perhaps also an integrated frequency converter, e. It is evident from this figure that for a typical radial flow pump, npshr gradually increases as the pump discharge increases. Curves relating total head, efficiency, power, and net positive suction head required npshr to discharge or pump capacity q are utilized to describe the operating properties characteristics of a pump. The fourth characteristic curve typically published by pump manufactures is the net positive suction head required npshr versus pump discharge q curve as shown in fig. Positive displacement pump characteristic curve engineers edge. When a pump curve has a hump in it or a high point away from zero flow it is said to be unstable. The pump develop maximum head at zero flow it is called shutoff point or shutoff head and the corresponding pressure is called shutoff pressure. Introduction to pump curves the pump develops energy called discharge pressure or total dynamic head tdh. Centrifugal pump performance curves and technical information. Know your pump and system curves part 1 aft product tips.
In the composite shown bottom of the graph and 5 feet on the side. The numerical data obtained from a cfd study performed with the ansys cfx software and based on steady state and. The curve becomes progressively steeper as throttling increases. For systems pump manufacturers normally publish a set of with a high total head this component is very small characteristic curves for each pump model they compared with other components of the total sys make. Aft fathom can easily generate a pump and system curve for your piping system. The curve immediately above this point will be most suitable. As standard the flowrate is from zero flow to 20% past the best efficiency flow. Dimensionless characteristics of centrifugal pump p. On monitoring of systems or pump characteristic, in principle it has to be decided, which effort for it is adequate altogether. Fundamentals of fluid mechanics chapter 12 pumps and turbines jyhcherng shieh department of bioindustrial mechatronics engineering national taiwan university.
Data for these curves are developed by testtem head. Pump curves pumps can generate high volume flow rates when pumping against low pressure or low volume flow rates when pumping against high pressure. After a pump is installed in a system, it is usually tested to ensure that the flow rate and head of the pump. Head is a measurement of the height of the incompressible fluid column the pump could create from the kinetic energy, that the pump gives to the liquid. Figure 4 shows a typical head, h ft, versus capacity discharge, q gpm, curve for a singlestage. At each pump curve intersection, the flow and tdh is fixed. Qh curves will be given by the manufac turer of the. The pump characteristic is normally described graphically by the manufacturer as the pump performance curve. Complete pump performance data and product information. Certrifugal pump reciprocating pump schematic diagram characteristic curve is essential. Information is plotted on an xy graph where the xaxis is measured in units of flow and the yaxis is measured in units of head, power, and npshr. The characteristic curve s shape is primarily determined by the pump type i. Centrifugal pump characteristic curve for an operations engineer who is working in a chemical process industry or a process engineer who is involved in hydraulic calculations understanding the centrifugal pump performance curve is an important aspect.
Velocity head is calculated using the ing several pumps of a specific model. Pump and system curves the pump curve is solely a function of the physical characteristics of the pump. The first point on the curve at zero flow is referred to as shut off and the last point at maximum flow is run out. Lets first go through the characteristic curves of centrifugal and reciprocating pump so that the ones referring it for the first time also get the idea of it. Nm 05 bar p b mbar pa atmospheric pressure barometric. A pump curve provides a wealth of information regarding the performance capabilities of a pump. These curves are observed to have the following characteristics. A performance curve is used to determine which pump best. The pump curve also displays the pump model, the pump size and number of stages for multistage pumps. Finally, a procedure was presented for selecting a suitable pump to work as a turbine in a small hydrosite. This tech brief examines how pump curves can provide data about a pump s ability to produce flow against certain head, shows how to read a typical centrifugal pump curve, and provides.
Choose from over 6,000 sizes in goulds extensive offering. The head and flow rate determine the performance of a pump, which is graphically shown in the figure as the. Therefore, the only factor that effects flow rate in an ideal positive displacement pump is the speed at which it operates. Each of the characteristics is explained in the next sections for propeller pumps.
Characteristic curves of centrifugal pumps are defined as those curves which are plotted from the results of a number of tests on the centrifugal pump. What follows is a brief presentation of the different pump performance curves. The flow rate q and the developed head h are both determined by the intersection. The figure below shows a typical pump curve as furnished by a manufacturer. With an increase in pump flow rate, the head developed by the pump start decreases. Pumping head characteristic curves are plots of what an existing pump can do under various loads duties we measure the pump characteristic curve by determining.
A typical characteristic curve shows the total dynamic head, constant horsepower, efficiency, and net positive suction head all plotted over the capacity range of the pump. A vendor manual for a specific pump usually contains a curve of pump flow rate versus pump head called a pump characteristic curve. The system curve is completely dependent on the size of pipe, the length of pipe, the number and location of elbows, and other factors. It is a composite curve which tells at a glance what the pump. Pumps doehdbk1018193 positive displacement pumps figure 20 diaphragm pump positive displacement pump characteristic curves positive displacement pumps deliver a definite volume of figure 21 positive displacement pump characteristic curve liquid for each cycle of pump operation. In this curve, the head is on the vertical axis and flow rate on the horizontal axis. Whether permanent, or with a mobile measuring system only from time to time, whether measuring is cyclically or daily or one carried out only weekly is sufficient. With this in mind, the curves typically plotted are head vs. The size information indicates a 112 inch outlet pipe and a 2 inch inlet pipe with a nominal maximum impeller diameter of 6 inches.
To account for future expansion and pump at a higher rate, such as 55 gpm, the total head would stay the same. It exhibits a falling headcapacity characteristic in which the head diminishes continuously as the. Deviation of suggested method from experimental data were considered and discussed. Efficiency considerations e during the pump selection process, only pumps pump b having high efficiencies above 70% for the design pump a discharge should be considered for a system. In some cases an additional pressure behind the impellers to the point that the. Understanding centrifugal pump curves when selecting a centrifugal pump, one should match the performance of the pump to that needed by the system.
Aug 22, 2017 learn about pump characteristic curve in this excerpt from the pumps and motors lecture from our distribution exam prep course. For the sake of example, today were going to look at a selection made for the following design. A step by step guide example as an example, size a pump to pump 50 gallons per minute and generate 5 feet of head. This lecture is all about centrifugal pump characteristic curves, npsh available and npsh required. The same goes for the efficiency value, which only covers the pump part. The system characteristic curve see characteristic curve represents the relationship between the system head hsys and the flow rate q. The operating point adapts itself to the intersection point of these two lines in dependence of pump characteristic curve and system characteristic curve automatically see diagram 5 24. Lower efficiency curves at other discharges and head, at the same speed and the same size impeller, when plotted. Lesson 28 characteristic curves of centrifugal pumps. Operating line system curve this is dependent on the system you are putting the pump into. Pump characteristics curves can be classified into four groups.