Operating characteristic curves of a centrifugal pump. Characteristic curves for a singlestage centrifugal and other components. Centrifugal pump behavior in steady and transient two. Suitable for application pump speeds up toapi674 1995andhydraulicinstitutespeedlimitations. The pump curve also displays the pump model, the pump size and number of stages for multistage pumps. This type of curve is referred to as a rising characteristic curve. Cat pumps configures a number of pumps for special applications and certifications such as atex, co 2, teg, flushed, hightemp and others. In practice the combined head and volume flow moves along the system curve as indicated from 1 to 3.
Gear pumps are often used in pumping relatively viscous liquids, such as some viscous liquid hydrocarbons, liquid fuels, lubrication oil pumping in machinery packages, hydraulic units and fluid power transfer units. 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. For an existing pump, the diameter of the impeller is known. 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.
Study on flow characteristic of gear pumps by gear tooth. Follow the pressure line, down and to the right, until it intersects 3 the product viscosity 2. How to read a centrifugal pump curve crane engineering. In the composite shown bottom of the graph and 5 feet on the side. In the gear pump, the meshing points of the driving. Examples of these pumps are shown in figure 2 figure 2 gear pump and screw pump most pipelines transporting water and petroleum products today use centrifugal pumps due to their flexibility in flow rates and pressures. This pumping principle produces a pulsating flow, rather than a smooth flow.
As a result of this study, it was shown that the characteristics of any pump with specific. 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. Products combination of extruder and gear pump for your. 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. The h in the curve is the difference in energy level between the suction and the pressure side of the pump. Also, in the present study, the measured pump characteristics. Pdf flow characteristics of external gear pumps considering. Therefore, it can be frustrating to get the data required from a positive displacement curve. Combination of several pumps possible contents note.
Centrifugal pump characteristic curve engineers edge. The numerical coordinates of three kinds of tooth profiles were calculated based on the concept of generation by rack type of a tool as shown in fig. The characteristic curves of centrifugal pumps plot the course of the following parameters against flow rate q. They are mainly used in the plastic and sheetmetal processing sectors, presses as well as conveying and lifting equipment. Operating line system curve this is dependent on the system you are putting the pump into. This tech brief examines how pump curves can provide data about a pumps ability to produce flow against certain head, shows how to read a typical centrifugal pump curve, and provides. Polymers, chemical processing, bulk transfer, asphalt, chocolate, adhesives. Please contact cat pumps directly at 763 7805440 for more. Manufacturers data for this pump is contained in figures 7. The characteristic curves shape is primarily determined by the pump type i. Usually one of the gears is capable of driving the others.
Flow, head, impeller trim diameter, efficiency, power, npshr, mcsf minimum continuous stable flow and rpm. Centrifugal pump behavior in steady and transient twophase flow. Knowing how to read a centrifugal pump curve is essential to the health. To do that, an engineer would refer to a pumps composite curve. The curve immediately above this point will be most suitable. 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. Selecting a positive displacement pump using performance. The system characteristic curve see characteristic curve represents the relationship between the system head hsys and the flow rate q. Products combination of extruder and gear pump for your success. Qh curves will be given by the manufac turer of the. Pump speed as discussed earlier, positive displacement pumps are dependent on the speed that the pump is operating at.
For any of the flii pumps, use the curve on page 32 and for the fkl pump use the curve on page 11. Selecting a positive displacement pump using performance curves. After a pump is installed in a system, it is usually tested to ensure that the flow rate and head of the pump are within the required specifications. Typical reciprocating pump performance is shown in capacity against speed curve as figure 7 at constant discharge pressure, and capacity against stroke length as shown in figure 8. Whats the significance of pump characteristic curves. Diagram of a cooling tower system and system curves at variable water levels in the river the intersection of the pump specific hq curve with the systemspecific curve hsysq determines the operating point. Locate the calculated differential pressure on the vertical axis 1. Guide to reading a positive displacement pump curve. Centrifugal pumps sample pump curve 3500 is the rpm impeller size 6. 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. Calculation of theoretical torque and displacement in an internal gear pump 1. The headdischarge curve hq curve relates the head produced by a pump to the volume of water pumped per unit time i.
Product photo deviates from delivery condition product description 2 type codes 4 technical data 8 diagrams characteristic curves 18 dimensions 23 project planning information 69 information 70 accessories 71 re 1008920190717, bosch rexroth ag external gear pump high performance azpf. The simplest form of this type of rotary pump is the gerotor pump. Pumps can be arranged and connected in serial or parallel to provide additional head or flow rate capacity. Pump complete characteristics and homologous curves as the method for expressing pump twophase flow characteristics, pump data are in normal put by using homologous curves, when a trac, are utilized. To change the operating point either the system curve or the pump curve must be changed. The pump curve directly above the duty point is the 722. The curve becomes progressively steeper as throttling increases. The size information indicates a 112 inch outlet pipe and a 2 inch inlet pipe with a nominal maximum impeller diameter of 6 inches. The flow rate q and the developed head h are both determined by the intersection. They are one of the most common types of pumps for hydraulic fluid power applications. A gear pump uses the meshing of gears to pump fluid by displacement. Positive displacement pumps deliver a definite volume of liquid for each cycle of pump operation. Sep 24, 2018 centrifugal pump curves show 8 important factors that are critical in selecting the right pump for your application. With pd pump you can operate the pump on any point of the curve.
Positive displacement pd pump technologies vary, as do the curves for these pumps. Qh curves will be given by the manufacturer of the pump and can normally be considered as a simple quadratic curve. Study on flow characteristic of gear pumps by gear tooth shapes wen wang1, yanmei yin1, shanghong he1 and guangming liu2 1hunan province key laboratory of safety design and reliability technology for engineering vehicle, changsha university of science and technology, changsha 410114, p. Gear pumps are rotary pumps in which two or more gears mesh to provide the pumping action. Crosssectional views of external gear pump demonstrating operating principle. Figure 4 shows a typical head, h ft, versus capacity discharge, q gpm, curve for a singlestage. In a positivedisplacement pd pump, a discrete amount of fluid is trapped, forced through the pump, and discharged. Please use the curves to select the pump specific to your application. 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. Positive displacement pump characteristic curve engineers edge.
Positive displacement pumps can handle many difficult applications. Another application advantage is the speedproportional feeding characteristic curve. Viking pump a unit of idex corporation cedar falls, ia 2006 section 141 page 141. Static head is the difference in height between the starting elevation. Explain the performance and characterstic of centrifugal pumps. A person without significant exposure to pump selection is often experienced only with centrifugal pump curves. Understanding how to read a positive displacement pump curve can help troubleshoot a currently installed system, or help to size equipment for the next project down the road.
Gear pumps superior engineering and low cost of ownership designed to reliably handle viscous fluids across a broad range of flows and pressures, flowserve gear pumps feature double helical, herringbone type gears. A centrifugal pump imparts energy on a liquid, and based on the system it is installed on, has flow and head characteristics. Many positive displacement pumps use gear reducers, vbelt. Back to basics a characteristic resistance coefficient, or value, which k can be found in perrys handbook 1 and other sources table 1 2. For a pd pump, if the system resistance increases, the pump will increase its discharge pressure. A typical composite curve includes the pump performance curves, horsepower curves and npsh required. Reading centrifugal pump curves environmental finance center. Gear pumps are also widely used in chemical installations to pump high viscosity fluids. Centrifugal pump characteristic curve components of. The h tq curve shows the relationship between head and flow rate. Please note that this speed would be the pump speed, not the motor speed. Gear pumps are the most popular type of positive displacement pump. Iph catalog highpressure internal gear pumps machines that run rarely seen, but hard at work in countless machines, voith turbo internal gear pumps reliably provide high pressures. Gear pump engineering documents are available for download in pdf format.
Provides information about which pump this curve refers to ie. The investment costs for the pump may be partially offset as the extruder required in this combination may be of smaller size. 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 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. A vendor manual for a specific pump usually contains a curve of pump flow rate versus pump head called a pump characteristic curve. The gear pump was invented around 1600 by johannes kepler. Maximum normal capacity line should not operate in the region to the right of the line because pump can be unstable.
Therefore the constant between each curve is the capacity or xaxis. Calculation of theoretical torque and displacement in an. Characteristic curve pumps, valves and service ksb. When two or more pumps are arranged in serial their resulting pump performance curve is obtained by adding their heads at the same flow rate as indicated in the figure below centrifugal pumps in series are used to overcome larger system head loss than. Reading and understanding centrifugal pump curves is key to proper pump selection, and to their reliable and efficient operation. 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. Centrifugal pump problems 5 overview of pump problems typically found on centrifugal pumps. Study on flow characteristic of gear pumps by gear tooth shapes.
As you move either to the right, additional considerations come into play. Rotary pumps include gear pumps and screw pumps used with high viscosity liquids. 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. The twophase flow characteristics data for the pump were plotted with use of homologous curves method and the twophase degradation multiplier in order to examine the effect of specific speed and void fraction. System characteristic curve pumps, valves and service ksb. Contact the sales department for engineering information. Guide to reading a positive displacement pump curve pumps. Pump system curve and pump operating point mechanical. It is often parabolashaped and does not generally pass through the origin of the hq coordinate system. The results show that the curve of trapped volume is.
If you move far enough to the left or right, pump life is reduced due to either shaft deflection or increased cavitation. Its output flow tends to vary little with respect to the pressure at the pump outlet, because the moving. Therefore, the only factor that effects flow rate in an ideal positive displacement pump is the speed at which it operates. The operating point will always be where the two curves intersect. 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. Centrifugal pump curves show 8 important factors that are critical in selecting the right pump for your application. Lesson 28 characteristic curves of centrifugal pumps. Figure 8 shows three kinds of transverse tooth profiles of pump gear, namely, involute curve, trochoid curve, and circular arc. Understanding centrifugal pump curves when selecting a centrifugal pump, one should match the performance of the pump to that needed by the system. With this in mind, the curves typically plotted are head vs.
Each of the characteristics is explained in the next sections for propeller pumps. The results show that the curve of trapped volume is similar to a parabola and the pump designed with a large number of teeth, module, and pressure angle easily. These pumps are often used for smallvolume capacity applications where space is quite limited 4. Characteristic curves for a centrifugal pump examining figure 3, the general performance of the pump can be determined. And other calculation examples jacques chaurette p. Centrifugal pumps in parallel are used to overcome larger volume flows than one pump can handle alone. The gear pump was invented around 1600 by johannes kepler gear pumps are also widely used in chemical installations to pump. Combination of extruder and gear pump troester extruder gear pump combi nation type zp with vacuum extruder vak. The figure below shows the pump curve of a single pump a, two pumps operat ing in parallel b, and the system curve c. The amount of pressure the pump is required to overcome dictates where the performance point will be on the curve and how much flow is produced. Ratio of power output of the pump to power input to the pump or shaft. 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. Small gear pumps usually operate at a speed between 1,700 rpm and 4,500 rpm, and larger models most often.
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