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    Api 674

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    Francesca Coatti
    1) Reciprocating pumps can generate high head but also generate pulsations that can cause cavitation, pipe fatigue, reduced efficiency, and capacity limitations. 2) TNO Science and Industry uses simulation software to analyze the acoustic behavior of liquid in pipe systems to optimize pump systems and avoid problems. 3) Their three-step API 674 analysis approach includes a prestudy to size pulsation dampers, a pulsation study of the full pipe system to evaluate pulsations, and a mechanical response study to evaluate stresses and prevent fatigue failures.

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    Api 674

    Uploaded by

    Francesca Coatti
    103 views2 pages
    1) Reciprocating pumps can generate high head but also generate pulsations that can cause cavitation, pipe fatigue, reduced efficiency, and capacity limitations. 2) TNO Science and Industry uses simulation software to analyze the acoustic behavior of liquid in pipe systems to optimize pump systems and avoid problems. 3) Their three-step API 674 analysis approach includes a prestudy to size pulsation dampers, a pulsation study of the full pipe system to evaluate pulsations, and a mechanical response study to evaluate stresses and prevent fatigue failures.

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    API 674

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    1) Reciprocating pumps can generate high head but also generate pulsations that can cause cavitation, pipe fatigue, reduced efficiency, and capacity limitations. 2) TNO Science and Industry uses simulation software to analyze the acoustic behavior of liquid in pipe systems to optimize pump systems and avoid problems. 3) Their three-step API 674 analysis approach includes a prestudy to size pulsation dampers, a pulsation study of the full pipe system to evaluate pulsations, and a mechanical response study to evaluate stresses and prevent fatigue failures.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    103 views2 pages

    Api 674

    Uploaded by

    Francesca Coatti
    1) Reciprocating pumps can generate high head but also generate pulsations that can cause cavitation, pipe fatigue, reduced efficiency, and capacity limitations. 2) TNO Science and Industry uses simulation software to analyze the acoustic behavior of liquid in pipe systems to optimize pump systems and avoid problems. 3) Their three-step API 674 analysis approach includes a prestudy to size pulsation dampers, a pulsation study of the full pipe system to evaluate pulsations, and a mechanical response study to evaluate stresses and prevent fatigue failures.

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    API 674 05 2005 23-05-2005 14:58 Pagina 1

    TNO Science and Industry

    API 674 Analysis for


    Reciprocating Pumps
    Reciprocating pumps are frequently used in many applications, because
    they can generate high head, independent of density. However, a recipro-
    cating pump system also generates pulsations, which can lead to cavita-
    tion, fatigue pipe failures, reduction of efficiency and capacity limitations.
    TNO Science and Industry uses the digital simulation program PULSIM
    (PULsation SIMulation) to calculate the acoustical behaviour of the liquid in
    the pipe system.
    Using these tools the system can be opti-
    mised from the dynamic point of view in
    such a way that cavitation, fatigue problems
    and inefficiently operating pump systems
    can be avoided. The importance of such an
    analysis is also reflected in the API Standard
    674, 2nd edition of June 1995. TNO Science
    and Industry uses a three-step approach in
    the API 674 analysis.

    Step 1: Prestudy or dampercheck


    Projects can be delayed considerably when
    pulsation dampers are not designed well in
    an early stage of the project. To size bottles
    more accurately, and to prevent costly, time-
    consuming changes in a later stage of the
    project, an acoustic prestudy (also called
    dampercheck) of the damper is carried out.
    © URACA

    Even when pulsation levels are within Pulsation and mechanical response studies
    Discharge damper
    allowable levels, high vibration and cyclic have demonstrated to be effective tools to Endless line
    stress levels can occur. Especially for very meet such objectives.
    Vessel
    flexible pipe systems and variable speed
    pump systems, it can be difficult to achieve Importance of analysis Pump
    an optimum design from the dynamic point The PULSIM program has been developed by
    of view. Cavitation and vibration problems TNO Science and Industry. PULSIM solves the
    can be avoided, and consequently life cycle one dimensional flow equations with the
    costs can be reduced when they are solved method of characteristics in the time Suction damper

    during the design stage of the project. domain. The general purpose finite element
    program ANSYS is used to calculate the
    mechanical behaviour of the system.
    052005/250
    API 674 05 2005 23-05-2005 14:58 Pagina 2

    TNO Science and Industry


    API 674 Analysis for Reciprocating Pumps

    Process Industry

    During this study the minimum volume and Step 3: Mechanical response study The team of the ‘Flow and Structural
    most-effective damper layout (in-line, off- One of the objectives of the pulsation study Dynamics’ department: your partner in
    line, with or without gas volume) is is to reduce the pulsation-induced shaking solving questions about the dynamics of
    your installation. Modelling, measuring and
    designed. To avoid cavitation caused by pres- forces to a minimum. However, unallowable
    optimising of dynamic flow and vibration
    sure pulsations the dampercheck is therefore vibration and cyclic stress levels can occur in phenomena is our specialty.
    carried out with the interaction of the pipe case a mechanical natural frequency is close We use modelling techniques like PULSIM
    system, which includes acceleration, hydro- to, or coincides with a frequency component to enhance the reliability and safety of your
    static and friction effects. of the pulsation-induced shaking forces, even process installation.
    in case the pulsation levels itself are within
    Step 2: Pulsation study the allowable levels. To prevent fatigue fail- TNO Science and Industry
    This step in the analysis is the pulsation ure of the pipe system, cyclic stresses in the P.O. Box 155
    2600 AD Delft
    study of the complete pipe system. The simu- system must not exceed the endurance limits
    The Netherlands
    lation model, as used by TNO Science and of the material.
    Industry, comprises the connected and inter- Therefore, TNO Science and Industry calcu-
    acting subsystems such as driving piston, lates the cyclic stresses in the pipe system www.tno.nl
    cylinder volume, pump valves, internal pas- with a full mechanical response analysis.
    sages, orifices, pulsation dampers, straight This is in addition to the analysis as required André Eijk
    and curved pipe elements, etc. following the API 674, because for pumps Tel. +31 15 269 21 33
    Fax +31 15 269 21 11
    The pulsations and pulsation-induced with variable speed, mismatch of acoustical
    E-mail: andre.eijk@tno.nl
    shaking forces are calculated and compared and mechanical natural frequencies is diffi-
    with allowable levels. In case of exceedings cult to achieve, especially for a wide speed www.pulsim.com
    of these levels, modifications are investi- range.
    gated. Frequently advised modifications are:
    the installation of orifice plates, increasing
    the diameter of pipe parts, relocating closed
    valves, installation of additional volume etc.
    The final aim of the pulsation study is the
    prevention of:
    • cavitation
    • high pressure losses
    • unacceptable pulsations, vibrations
    an cyclic pipe stresses causing fatigue
    failure
    • opening of relief valves due to pulsations © URACA
    • inaccuracies of flow measuring devices
    The mechanical model is built up with beam
    type elements and includes all important
    16
    Pressure pulsations
    components, which influence the mechanical
    14 natural frequencies and cyclic stresses such
    12
    P suction as nozzle and flange flexibilities, pipe racks,
    Pressure [bar]

    10
    stress intensification factors of T-joints and
    8

    6
    nozzles.
    4
    Pmin
    2
    P vapor
    In case the vibration and/or cyclic stress lev-
    0 els exceed the allowable levels, modifications
    0 90 180 270 360
    Crank angle [degrees] are investigated to achieve acceptable levels.
    This can be accomplished by the installation
    of additional pipe supports and/or by
    increasing the stiffness of the structures on
    which the system is mounted.

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