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    Centrifugal Vs PD Pumps

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    JHONY TEODORO ALBORNOZ DIONICIO
    This document compares centrifugal and positive displacement pumps. Centrifugal pumps are best for high flow, low pressure applications like water transfer, while positive displacement pumps can handle high pressures and viscosities. Centrifugal pumps have simpler designs but are less efficient over a range of pressures and flows. Positive displacement pumps maintain a constant flow rate regardless of pressure changes and are better for shear-sensitive or high solids content liquids. Both pump types have different applications depending on the fluid properties and system requirements.

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    © All Rights Reserved
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    Centrifugal Vs PD Pumps

    Uploaded by

    JHONY TEODORO ALBORNOZ DIONICIO
    31 views10 pages
    This document compares centrifugal and positive displacement pumps. Centrifugal pumps are best for high flow, low pressure applications like water transfer, while positive displacement pumps can handle high pressures and viscosities. Centrifugal pumps have simpler designs but are less efficient over a range of pressures and flows. Positive displacement pumps maintain a constant flow rate regardless of pressure changes and are better for shear-sensitive or high solids content liquids. Both pump types have different applications depending on the fluid properties and system requirements.

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    PD pumps

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    Centrifugal vs PD Pumps

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    This document compares centrifugal and positive displacement pumps. Centrifugal pumps are best for high flow, low pressure applications like water transfer, while positive displacement pumps can handle high pressures and viscosities. Centrifugal pumps have simpler designs but are less efficient over a range of pressures and flows. Positive displacement pumps maintain a constant flow rate regardless of pressure changes and are better for shear-sensitive or high solids content liquids. Both pump types have different applications depending on the fluid properties and system requirements.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    31 views10 pages

    Centrifugal Vs PD Pumps

    Uploaded by

    JHONY TEODORO ALBORNOZ DIONICIO
    This document compares centrifugal and positive displacement pumps. Centrifugal pumps are best for high flow, low pressure applications like water transfer, while positive displacement pumps can handle high pressures and viscosities. Centrifugal pumps have simpler designs but are less efficient over a range of pressures and flows. Positive displacement pumps maintain a constant flow rate regardless of pressure changes and are better for shear-sensitive or high solids content liquids. Both pump types have different applications depending on the fluid properties and system requirements.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 10

    Centrifugal vs.

    PD Pumps

    January 26, 2021

    White Paper - Volume 16

    Headquarters Address: E-mail:


    300 E-Business Way, Suite 300 info@bsiengr.com
    Cincinnati OH 45241
    Phone: 513-201-3100 Website:
    Fax: 513-201-3190 www.bsiengr.com
    CONTENT

    2 Abstract

    3 Performance Curves Comparison

    4 General Applications Selections

    5 Main Differences

    6 Comparison

    7 Illustrations of Pump Types

    8 Summary

    Centrifugal vs PD Pumps 1
    ABSTRACT

    There are two principal groups of pumps: positive displacement and


    centrifugal (rotodynamic). Both have their uses and best areas of
    application. It is important to be able to identify where each pump type
    is best suited for the application and be selected, which ultimately comes
    down to their working principle and the intended application.
    Positive displacement pumps are characterized by an operation that
    moves fluid by trapping a fixed volume and then forces that trapped fluid
    into the discharge pipe. A centrifugal pump transfers the kinetic energy
    of the motor to the liquid by a spinning impeller; as the impeller rotates
    it draws in fluid causing increased velocity that moves the fluid to the
    discharge point.
    The intent of this White Paper is to allow a user a quick evaluation and
    decision to be able to focus on other aspects of the pump selection.
    2 Centrifugal vs PD Pumps
    PERFORMANCE CURVES COMPARISON

    3 Centrifugal vs PD Pumps
    GENERAL APPLICATIONS SELECTIONS
    Centrifugal Pumps are the most common pump type for the transfer of low viscosity fluids in
    high flow rate, low pressure installations, which makes them ideal for applications that require the
    pump to deal with large volumes. The centrifugal pump design is often associated with the transfer
    of water but is also a popular solution for handling thin fuels and chemicals. Generally, centrifugal
    pumps are used with clean liquids, but if a correct impeller is selected, they can handle some solids
    slurries.

    Centrifugal pumps are suited to applications where the pump is used often or is even continuously
    run. The simplicity of the construction also makes centrifugal pumps easy to produce in many
    different materials including plastics and cast iron for lighter duties, and bronze and stainless steels
    for more corrosive or hygienic application. Hence the multiple fluids that centrifugal pumps are
    suitable for use with.

    The centrifugal pump design is also very compact in comparison to other pump types that produce
    the same output levels, making them a good option when space saving is an issue. Basic centrifugal
    pumps, unless specially designed to maintain a flooded impeller at all times, are not capable of self-
    priming.

    Centrifugal pumps – operate via rotation of the impeller


    • Open impeller
    • Closed and semi-closed impeller
    • Multi-stage

    Positive Displacement Pumps are usually selected for their ability to handle high viscosity fluids
    at high pressures and relatively low flows as their efficiency isn’t affected by pressure. Unlike
    centrifugal pumps, which are commonly installed due to their simplicity, positive displacement
    pumps provide capability of handling more difficult conditions where centrifugal pumps may fail,
    thanks to their ability to be run at any point on their curve. Most of the positive displacement
    pumps are capable of self-priming.

    There are two classifications of positive displacement pump; rotary and reciprocating.

    Rotary positive displacement pumps – operate via rotation of the pumping element
    • Progressive cavity pumps
    • Vane pumps
    • Screw pumps
    • Peristaltic pumps
    • Gear pumps
    • Lobe pumps

    Reciprocating positive displacement pumps – operate via a constant back and forth motion
    • Diaphragm pumps
    • Piston pumps Centrifugal vs PD Pumps 4
    MAIN DIFFERENCES
    COMPARISON
    Factor Centrifugal Positive Displacement

    Mechanics Impellers pass on velocity from Traps confined amounts of


    the motor to the liquid which liquid and forces it from the
    helps move the fluid to the suction to the discharge
    discharge port (produces flow port (produces pressure by
    by creating pressure). creating flow).

    Performance Flow rate varies with a change Flow rate remains constant
    in pressure. with a change in pressure.

    Viscocity Flow rate rapidly decreases Due to the internal clearances


    with increasing viscosity, even high viscosities are handled
    any moderate thickness, due to easily and flow rate increases
    frictional losses inside the pump. with increasing viscosity.

    Efficiency Efficiency peaks at a specific Efficiency is less affected


    pressure and flow; any variations by pressure, but if anything
    decrease efficiency, sometimes tends to increase as pressure
    significantly. Does not operate increases. Can be run at any
    well when run off the middle of point on their curve without
    the curve; can cause damage damage or efficiency loss.
    and cavitation.

    Suction Lift Standard models cannot create Create a vacuum on the inlet
    suction lift, although self- side, making them capable of
    priming designs are available creating suction lift.
    and manometric suction lift is
    possible through a non-return
    valve on the suction line.

    Shearing High speed motor leads to Low internal velocity means


    shearing of liquids. Not good for little shear is applied to the
    shear sensitive mediums. pumped medium. Ideal for
    shear sensitive fluids.

    Centrifugal vs PD Pumps 6
    ILLUSTRATIONS OF PUMP TYPES
    Open Impeller Closed & Semi-Closed Impeller Multi-stage

    Progressive Cavity Pumps Vane Pumps Screw Pumps

    Peristaltic Pumps Gear Pumps Lobe Pumps

    Diaphragm Pumps Piston Pumps

    Centrifugal vs PD Pumps 7
    SUMMARY
    Both centrifugal and positive displacement pumps have their place in
    industrial and commercial applications.

    Centrifugal pumps benefit from a simple design with few moving parts,
    resulting in lower maintenance requirements and costs. Multistage
    centrifugal pumps are capable of increased pressure delivery, however not
    as high as the positive displacement pumps.

    Positive displacement pumps are designed for the transfer of high viscosity
    fluids such as thick oils, slurries, sewage and pastes. Thanks to their internal
    clearances, some types such as progressive cavity pumps and peristaltic
    pumps, are also excellent at applications handling mediums containing high
    levels of solids. Screw and vane pumps on the other hand and are ideal for
    pumping relatively clean fluids.

    Being lower speed pumps than the centrifugal design, rotary positive
    displacement pumps with larger pumping chambers such as progressive
    cavity, lobe and peristaltic pumps are typically low shear pumps that provide
    a smooth flow. This allows them to pump shear sensitive products that need
    their structure to remain intact and cannot lose their stickiness and retain
    their properties.

    Positive displacement pumps are able to handle variations in pressure, flow


    and viscosity and remain efficient, unlike centrifugal pumps which do not
    operate well off the center of their curve. As their flow rate remains constant
    (proportional to the speed of operation), smooth and low pulsating despite
    changes in the pressure, positive displacement pumps such as peristaltic,
    piston and diaphragm pumps are ideal solutions for dosing applications as
    it allows accurate metering to be carried out.

    Centrifugal vs PD Pumps 8
    THANK YOU
    FOR CHOOSING US!
    BSI Engineering is a full-service provider of
    engineering and design services for a very broad
    range of industry sectors.

    The majority of our 200+ employees have over 300 E-Business Way, Suite 300
    twenty years of technical experience and are ready Cincinnati OH 45241
    to add their expertise to your project from any of our Phone: 513-201-3100
    Fax: 513-201-3190
    midwestern office locations. We deliver exceptional E-mail: info@bsiengr.com
    value for our clients wanting a fully integrated, Website: www.bsiengr.com
    engineering-led EPCM model.

    Centrifugal vs PD Pumps 9

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