# Pump affinity laws pdf

Horwitz project engineer affinity laws the performance of a given pump at various speeds and the performance of geometrically similar pumps is governed by a set of formulas known. The affinity laws relate the performance of a known pump along its. The affinity laws for centrifugal pumps state that the hq curves at various. The affinity laws for centrifugal pumps describe the impact. Hbhp hydraulic brake horsepower required by pump pump efficiency 1. Jun 02, 2014 what is the resulting change to the pump speed and horsepower needed. Hydraulically the major subjects consist of head, capacity, hydraulic efficiency, power, and speed.

The change in speed brings about a corresponding change in the head, flow, and power requirements of the pump according to the affinity laws. The good news affinity law theory helps us understand the principle of flow, head, and power dynamics. The laws will help you extrapolate and predict pump performance at different velocities. Boiler feed pump performance assessment method using pump affinity laws reduces uncertainty. This video screencast was created with doceri on an ipad. Now using the pump affinity laws, we can see there is a relation to the flow rate and the speed at which the impeller turns. In general, most manufacturers will place a lower limit on speed reduction to approximately 40 to 50 percent of full speed before considering speed reduction as extreme, and, beyond that, affinity laws may be used for predictive purposes. The affinity laws below are well known and used daily by pump people.

This method is referred to as the affinity laws or fan and pump laws. The mathematical relationships that exist between flow rate, head, power and speed and based on a known pump performance are referred to as the affinity laws. The affinity laws are a set of forumlas that predict the impact of a change in rotational speed or impeller diameter on the head and flow produced by a pump and power demanded by a pump. In this case, the prototype pump and the model are said to be homologous to each other. Often times a fans speed or impeller diameter will be changed.

Centrifugal pump affinity laws provide a method to determine a new pump operating point when a performance curve that indicates performance with different impeller diameters or operating speeds is not available. Note that there are two sets of affinity laws affinity laws for a specific centrifugal pump to. Note that the affinity laws for pumps are not identical with fans fan affinity laws. Pump curve speed calculator affinity law calculator. First affinity law flow is proportional to the shaft speed, i. Affinity laws are a set of equations or laws governing the operation. Another set of the affinity laws deal with changes to the diameter of the impeller. The affinity laws variable frequency drives theory the affinity laws can determine the system performance for centrifugal devices, including theoretical load requirements and potential energy savings. The affinity laws allow engineers to estimate the resulting changes to certain hydraulic parameters caused by the manipulation of a single centrifugal pump variable.

Cameron hydraulic data the cameron hydraulic data book is a flowserve corporation publication and, as in the previous nineteen editions, is published as an aid to engineers involved with the selection and application of pumping equipment. Or to put it another way, the affinity laws for a centrifugal pump do not and are not supposed to be dependent on duty. Pump efficiency is considered as a constant and variation in speed and impeller diameter is analyzed for the variation in above said parameters. Example pump affinity laws changing impeller diameter. The affinity laws of centrifugal pumps or fans indicates the influence on volume capacity, head pressure andor power consumption of a pump or fan due to. According to the affinity laws, the following relationships exist between the actual speed of the centrifugal pump and its most important performance. Capacity, head, npsh and horsepower change as a result of speed change. Head by the square cs current speed pumps brisbane pump. How to use affinity laws to calculate a new best efficiency point. The affinity laws see peerless technical information bulletin no. The relationships established between the physical quantity of the original and that of the model by means of the characteristic coefficients are called affinity laws. The pump speed needs to be reduced in order to achieve the required flow at the twl and the required speed can be calculated using the affinity laws.

White paper stop falling off the curve maintenance. The affinity laws or fan laws, as they are sometimes referred to play an important role in determining centrifugal pump performance when operating conditions change. All you need to know is the system head and flow requirements to determine the right pump for the job. Pump engineering calculations of brake horsepower, power, kilowatts, motor, motors, voltage drop, circular mills, transformers, turns ratio, ohms law, dc power. The affinity laws, also known as pump laws, for pumps are used to express the relationship between variables involved in pump performance such as head, flow rate, shaft speed and power. Using characteristic pump parameters such as the impeller diameter d, rotational speed n, acceleration due to gravity g and the density of the fluid handled. In the case of homologous pumps, the affinity laws state. Centrifugal pump fundamentals pumps are broadly classified as kinetic or positive displacement.

Q flow rate h head y specific energy n rotational speed if pq. The affinity laws also known as the fan laws or pump laws for pumps fans are used in hydraulics, hydronics andor hvac to express the relationship between variables involved in pump or fan performance such as head, volumetric flow rate, shaft speed and power. The maximum break horsepower bhp would then be determined using. These laws are mathematical expressions that define changes in pump brake horsepower bhp, head and capacity when a change is made to pump speed, impeller diameter, or both. A 25 horsepower and 3600 rpm b 15 horsepower and 1450 rpm c 60 horsepower and 2900 rpm d 15 horsepower and 2900 rpm.

Affinity laws and specific speed in centrifugal pumps. The affinity laws for centrifugal pumps state that the hq curves at various rotational speeds can be derived from the following relationship as conventionally represented q flow rate h head y specific energy n rotational speed. Affinity laws are also known as affinity equations. This would deliver less flow and conserve some power. Affinity laws the affinity laws are derived from a dimensionless analysis of three important parameters that describe pump performance. Several papers have investigated the use of the affinity laws for energy saving purposes, as the pump power required decreases when the flow rate decreases 6 11 12. When a fan operates in an unchanging system, the fan laws tell us that the airflow varies proportionally to fan rpm, static. Also using the pump law we can see that there is a relation to the flow rate of a pump and the power required for the pump.

If the fan is a centrifugal fan, then the change in performance of the fan can be. The affinity laws are useful as they allow prediction of the head discharge characteristic of a pump or fan from a known characteristic measured at a different speed or impeller diameter. Using the affinity laws, it is possible to determine approximate curves to estimate the centrifugal pumps new best efficiency point. The affinity laws for centrifugal pumps state that the hq curves at various rotational speeds can be derived from the following relationship as conventionally represented. A prototype pump is made from a model by multiplying all dimensions of the model by the same factor. Other pump formulas affinity laws changes in diameter changes in speed d diameter, in or mm q flow, gpm or m3h h head, ft or m p power, hp or kw. Affinity laws can be used to calculate volume capacity, head or power consumption when speed and wheel diameters are changed. To the affinity laws and beyond the affinity laws below are well known and used daily by pump people. The affinity laws govern the performance of your pumps. The affinity laws for centrifugal pumps and fans are used to express the influence on volume capacity, head pressure andor power consumption due to.

The flow gpm varies proportionally with the change in speed. The affinity laws are given below where q is the volumetric flow rate, is the pump speed, d s is the pump impeller diameter, g is the acceleration due to gravity, h is the pump head p g, and is the pump shaft torque. The affinity laws are derived from a dimensionless analysis of three important parameters that describe pump performance. Q1 q2 n1n2 x d1d2 h1 h2 n1n22 x d1d22 p1 p2 n1n23 x d1d23 npsh31 npsh32 n1n22 per standard nomenclature, q is flow rate, h is head, p is power, and npsh3 is net positive suction head for a 3% head drop. Centrifugal pump affinity laws calculation chemical. Peerless pump company indianapolis in, 462077026 technical. Pump affinity laws are equations of proportionality that indicate how a change in impeller diameter d, or rotative speed n, affects the capacity q, the differential head h, and the required brake horsepower hp of a centrifugal pump. This centrifugal pump curve calculator is meant to quickly calculate the different operating conditions when a centrifugal pump is sped up or slowed down. The affinity law for fans and dynamic pumps, 2692018 duration.

Variable speed photovoltaic water pumping using affinity laws. The analysis is based on the reduced impeller being geometrically similar and operated at dynamically similar conditions or equal. Enter information as instructed below and press calculate. May 07, 2016 this video screencast was created with doceri on an ipad. The pump affinity laws have been modified to include the effects of viscosity. The pool pump affinity law chlorine king pool service.

They are also useful to modify your pumps for new and different required duties. The results are simple 2d curves that represent the headflow rate and efficiencyflow rate relationships for a specific pump. Affinity laws the affinity laws can be used to predict pump performance if the impeller size or rotational speed is changed. If you know the shape of a pump performance curve at a certain speed or with a certain impeller diameter, you can use the affinity laws to predict the.

Using the affinity laws, it is possible to determine approximate curves to estimate the centrifugal pump s new best efficiency point. The new modified affinity laws were validated using experimental data from several different types of pumps and cfd simulations of a mixed. What is the resulting change to the pump speed and horsepower needed. Most of the savings is from the reduction of the speed of the motor rpms even though some of it is contributed to how efficient a permanent magnet motor is. In practical application, grundfos provides all the information you need to easily determine your energy savings with e pumps and boosterpaqs. If a centrifugal pump is driven by an ac driver, then it should operate at a fixed rate rpms dictated by the frequency of the supplied power. Care must be taken to correctly read the performance data from pump curves. The affinity laws are used to change the pump characteristics by changing the pump speed, and consequently, the pump flow rate, head, and power will be varied 10. Centrifugal pump affinity laws are set of mathematical equations correlating the flow rate, head, brake horse power, speed and impeller diameter of the pump. Hello everyone, i am sizing a pump and ran into a question of how to apply the affinity laws and interpret their results. Because most pumps are directly coupled to a standard industrial electric motor, the pump speed is most often the motor.

Aug 14, 2014 the affinity laws below are well known and used daily by pump people. The affinity laws state changes in the speed or diameter change capacity by direct proportion. If the fan is a centrifugal fan, then the change in performance of the fan can be predicted quickly through the affinity laws. Peerless pump company system analysis for pumping equipment selection peerless pump company 2005 dr. Inputting the data that was calculated form the earlier equations. The affinity laws for pumpsfans are used in hydraulics, hydronics andor hvac to express the. Pump affinity laws for centrifugal and positive displacement.

Nov 08, 2017 application of pump affinity laws peter rogers. The twentieth edition includes some new content additions. Hvac equipment and systems fan affinity laws for the. The only requirement is that the two pumps or fans are dynamically similar, that is the ratios of the fluid forced are the same. We finish with a discussion of suction conditions and liquid friction. The pump speed, head, and flow relationships are expressed by the affinity laws. Actual bhp should be calculat ed from empirical data rather than by using pump affinity laws. For a change in impeller diameter with the rotational speed held constant, the following performance. In practical application, grundfos provides all the information you need to easily determine your energy savings with epumps and boosterpaqs.

They are merely a way of predicting the charcteristic curve of the pump when you have a known characteristic curve and wish to make a variation in speed of the pump or diameter of the impeller. Todays eitpe exam question looks at the pump laws with with a constant diameter impeller. I told him to send me his pump curve and system curve with the next email to explore this option. With regard to total performance and efficient design, these two. Basic pump parameters and the affinity laws pdh online. The performance of a given pump at various speeds and the performance of geometrically similar pumps is. Download 707k power point download 177k pdf version download 92k pdf script.

Using affinity laws, we can accurately calculate the pressure, flow and required speed and power of a pump from a specific known set point. May 01, 2017 the affinity laws, also known as pump laws, for pumps are used to express the relationship between variables involved in pump performance such as head, flow rate, shaft speed and power. Turbo machines affinity laws can be used to calculate volume capacity, head or power consumption in centrifugal pumps with changing speed or wheel. Boiler feed pump performance assessment method using pump. The diameter of the pump impeller is reduced when the pump speed is constant. Note that there are two sets of affinity laws affinity laws for a specific centrifugal pump to approximate head, capacity. It is also required that the two impellers speed or diameter are running at the same efficiency. There are occasions when you might want to permanently change the amount of fluid youre pumping, or change the discharge head of a centrifugal pump. Engineers use a shorthand for estimating the effect of speed rpm on power. The pump affinity law for pool pumps shows how all of this is possible between the 3 main components.

How the affinity laws affect pump rerates turbomachinery. Q1 q2 n1n2 x d1d2 h1 h2 n1n22 x d1d22 p1 p2 n1n23 x d1d23 npsh31 npsh32 n1n22 per standard nomenclature, q is flow rate, h is head, p is power, and npsh3 is net positive suction head for a 3 percent head drop. Represented in figure 3 are the three affinity laws. If the speed should remain a constant, the affinity laws state. They are also used for scaleup purposes when performance parameters exceed that of existing pumps refer to figure 2. Affinity fan and pump laws what is the effect of a changing speed.

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