Pump pipeline

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Pump-Pipeline SystemsInstructor: Parjang Monajemi

Water Supply and Wastewater Removal

Introduction Simply stated, a pump is a machine used to move liquid through a piping system and to raise the pressure of the liquid. A pump can be further defined as a machine that uses several energy transformations to increase the pressure of a liquid. There are actually three distinct reasons for raising the pressure of a liquid with a pump:Static elevation A liquids pressure must be increased to raise the liquid from one elevation to a higher elevation. This might be necessary, for example, to move liquid from one floor of a building to a higher floor.Water Supply and Wastewater Removal2Spring 1390

Friction. It is necessary to increase the pressure of a liquid to move the liquid through a piping system and overcome frictional losses. Liquid moving through a system of pipes, valves, and fittings experiences frictional losses along the way. Pressure. In some systems it is necessary to increase the pressure of the liquid for process reasons. In addition to moving the liquid over changes in elevation and through a piping system, the pressure of a liquid must often be increased to move the liquid into a pressurized vessel, such as a boiler or fractionating tower, or into a pressurized pipeline. Water Supply and Wastewater Removal3Spring 1390

Pressure and HeadIt is important to understand the relationship between pressure and head. Pressure is measured in psi (pounds per square inch) or kilopascal (kPa), bar, or kilograms per square centimeter (kg/cm2), while the equivalent units for head are meters (m) or feet(ft).

Water Supply and Wastewater Removal4Spring 1390

Classification of PumpsThere are many ways to classify pumps: according to their function, their conditions of service, materials of construction, etc. The pump industry trade association, the Hydraulic Institute, has classified pumps as follows:Kinetic: In a kinetic pump, energy is continuously added to the liquid to increase its velocity. When the liquid velocity is subsequently reduced, this produces a pressure increase. Although there are several special types of pumps that fall into this classification, for the most part this classification consists of centrifugal pumps.Water Supply and Wastewater Removal5Spring 1390

Centrifugal pumps, involve a collection of blades, buckets, flow channels, or passages arranged around an axis of rotation to form a rotor. Rotation of the rotor produces dynamic effects that either add energy to the fluid or remove energy from the fluid. centrifugal pumps are classified as axial-flow, mixed-flow, or radial-flow machines depending on the predominant direction of the fluid motion relative to the rotors axis as the fluid passes the blades


Positive Displacement In a positive displacement pump, energy is periodically added to the liquid by the direct application of a force to one or more movable volumes of liquid. This causes an increase in pressure up to the value required to move the liquid through ports in the discharge line. The important points here are that the energy addition is periodic (i.e., not continuous) and that there is a direct application of force to the liquid. Typical examples shown include the common tire pump used to fill bicycle tires, the human heart, and the gear pump. Water Supply and Wastewater Removal7Spring 1390

The following are some key application criteria that would lead to the selection of a P.D. pump over a centrifugal pump:High viscositySelf-primingHigh pressureLow flowHigh efficiencyLow velocityLow shearFragile solids handling capabilityAccurate, repeatable flow measurementConstant flow/variable system pressureTwo-phase flow


(Volk, 2005)Water Supply and Wastewater Removal9Spring 1390

Cavitation in TurbomachinesCavitation refers to conditions at certain locations within the turbomachine where the local pressure drops to the vapor pressure of the liquid, and as a result, vapor filled cavities are formed. As the cavities are transported through the turbomachine into regions of greater pressure,

they will collapse rapidly, generating extremely high localized pressures. Signs of cavitation in turbopumps include noise, vibration, and lowering of the head-discharge and efficiency curves.Water Supply and Wastewater Removal10Spring 1390

On the suction side of a pump, low pressures are commonly encountered, with the possibility of cavitation occurring within the pump. The requiered head at the pump inlet to keep the liquid from cavitating or boiling is called Net Possitive Suction Head (NPSH).Consider the shown operating pump. Location 1 is on the liquid surface on the suction side, and location 2 is the point of minimum pressure within the pump.


The design requirement for a pump is thus established as follows


A centrifugal pump is to be placed above a large, open water tank, as shown, and is to pump water at a rate of 0.5 cfs. At this flowrate the required net positive suction head, is 15 ft, as specified by the pump manufacturer. If the water temperature is and atmospheric pressure is 14.7 psi, determine the maximum height, that the pump can be located above the water surface without cavitation. Assume that the major head loss between the tank and the pump inlet is due to filter at the pipe inlet having a minor loss coefficient k=20. Other losses can be neglected. The pipe on the suction side of the pump has a diameter of 4 in. (Munson, 2009)Water Supply and Wastewater Removal13Spring 1390


Calculate NPSHa for this system and verify the adequacy of the selected pump. (Volk, 2005)

Suction lift=12ftDesign capacity Q=2000 gpmDesign pump total head=175 ftLiquid=water at 80F (s.g.=1.0)Hf=3ft P=14.2psiaWater Supply and Wastewater Removal15Spring 1390

Solve the previous problem, except using water at 160F (Volk, 2005).

From previous figure, at 2000 gpm, NPSH = 11.2 ft,


Performance CharacteristicsThe flow system used to test a centrifugal pump at a nominal speed of 1750 rpm is shown. Data measured during the test are given in the table. Calculate the net head delivered and the pump efficiency at a volume flow rate of 1000 gpm. Plot the pump head, power input, and efficiency as functions of volume flow rate. (Pritchard, 2011)



Basic Output ParametersUsually V2 and V1 are about the same, z2 z1 is no more than a meter or so, and the net pump head is essentially equal to the change in pressure head

The power delivered to the fluid simply equals the specific weight times the discharge times the net head change This is traditionally called the water horsepower. The power required to drive the pump is the brake horsepower where is the shaft angular velocity and T the shaft torque.


Water at 10 C (nu=1.3x10-6m2/s) is to flow from reservoir A to reservoir B through a cast-iron pipe of length 20 m at a rate of Q=0.015 m3/s as is shown. The system contains a sharp-edged entrance and six regular threaded 90 elbows. Determine the the required head of the pump that must be used if the pipe diameter is 5 cm. (Munson, 2009)



The given pump adds 25 kW to the water and causes a flowrate of 0.04 m3/s. Determine the flowrate expected if the pump is removed from the system. Assume f=0.016 for either case and neglect minor losses. (Munson, 2009)



The efficiency is basically composed of three parts: volumetric, hydraulic, and mechanical. The volumetric efficiency is where QL is the loss of fluid due to leakage in the impeller-casing clearances The hydraulic efficiency where hf has three parts: (1) shock loss at the eye due to imperfect match between inlet flow and the blade entrances, (2) friction losses in the blade passages, and (3) circulation loss due to imperfect match at the exit side of the blades.the mechanical efficiency is


where Pf is the power loss due to mechanical friction in the bearings, packing glands, and other contact points in the machine. By definition, the total efficiency is simply the product of its three parts

Performance characteristics for a given pump gometry and operating speed are usually given in the form of plots of and bhp versus Q commonly referred to as capacity as is llustratedWater Supply and Wastewater Removal25Spring 1390

Water is to be pumped from one large, open tank to a second large, open tank as shown. The pipe diameter throughout is 6 in. and the total length of the pipe between the pipe entrance and exit is 200 ft. Minor loss coefficients for the entrance, exit, and the elbow are shown on the figure, and the friction factor for the pipe can be assumed constant and equal to 0.02. A certain centrifugal pump having the given performance characteristics is suggested as a good pump for this flow system. With this pump, what would be the flowrate between the tanks? Do you think this pump would be a good choice?(Munson, 2009)Water Supply and Wastewater Removal26Spring 1390

QH08904008630800815312007573160065862000538824002860


As can be seen, although the operating efficiency is not the peak efficiency, which is about 86%, it is close (about 84%). Thus, this pump would be a satisfactory choiceWater Supply and Wastewater Removal28Spring 1390

Solve the previous problem if two pumps were used (a) in series, (b) in parallelQH08904008630800815312007573160065862000538824002860

QH0178400172800162120015016001302000106240056

QH08980086160081240075360065400053480028

Single pumpTwo pumps in parallelTwo pumps in seriesWater Supply and Wastewater Removal29Spring 1390


Dimensionless Parameters and Similarity LawsAs we studied earlier, we know that the principal, dependent pump variables are the actual head rise ha, shaft power shaft, and efficiency . We expect that these variables will depend on the geometrical configuration, which can be represented by some characteristic diameter D, other pertinent lengths L, and surface roughness , In addition, the other important variables are flowrate Q, the pump shaft rotational speed , fluid viscosity , and fluid density .


When the pump flow involves high Reynolds numbers experience has shown that the effect of the Reynolds number can be neglected. For simplicity, the relative roughness, can also be neglected in pumps since the highly irregular shape of the pump chamber is usually the dominant geometric factor rather than the surface roughness. Thus, with these


simplification and for geometrically similar pumps (all pertinent dimensions, scaled by a common length scale), the dependent pi terms are functions of only Q/D3 so that:


An 8-in diameter centrifugal pump operating at 1200 rpm is geometrically similar to the 12-in diameter pump having the shown performance characteristics while operating at 1000 rpm. For peak efficiency, predict the discharge, actual head rise, and shaft horsepower for this smaller pump. The working fluid is water at 60 F (Munson, 2009).Water Supply and Wastewater Removal34Spring 1390

For a given efficiency the flow coefficient has the same value for a given family of pumps.


A centrifugal pump provides a flowrate of 500 gpm when operating at 1750 rpm against a 200-ft head. Determine the pumps flowrate and developed head if the pump speed is increased to 3500 rpm. (Munson, 2009)


Specific Speed, Suction Specific SpeedA useful pi term named specific speed can be obtained by eliminating diameter D between the flow coefficient and the head rise coefficient.

With an analysis similar to that used to obtain the specific speed pi term, the suction specific Speed Ss, can be expressed as


Select a pump to deliver 500 gal/min of water with a pressure rise of 65 psi. Assume a rotational speed not to exceed 3600 rpm. (Potter, 2012)

(Munson, 2009)


References:Munson B.R., Young D. F., Okishi T. H., and Huebsch W. W., Fundamentals of Fluid Mechanics, John Wiley and Sons inc, Sixth Edition, 2009. Potter M. C., Wiggert D. C., and Ramadan B. H., Mechanics of Fluids, Cengage Learning, Fourth Edition, 2012. Pritchard P. J., Fox and McDonalds Introduction to Fluid Mechanics, John Wiley and Sons inc, Eighth Edition, 2011.Volk M., Pump Characteristics and Applications, Taylor & Francis Group, Second Edition, 2005. Water Supply and Wastewater Removal39Spring 1390

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Pump pipeline