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    Gas Line Velocity

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    putrude
    This document discusses gas and multiphase line sizing. It provides equations to calculate gas velocity and erosional velocity in pipes based on factors like flow rate, temperature, pressure, and pipe diameter. For gas lines, the recommended maximum velocity is 60-80 ft/sec to minimize noise and allow corrosion inhibition. For multiphase lines, the minimum velocity is 10-15 ft/sec to prevent slugging, while the maximum is 60 ft/sec or lower if corrosives are present. Guidelines are given for selecting design velocities and installing protections based on whether solids may be present.

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    Gas Line Velocity

    Uploaded by

    putrude
    194 views3 pages
    This document discusses gas and multiphase line sizing. It provides equations to calculate gas velocity and erosional velocity in pipes based on factors like flow rate, temperature, pressure, and pipe diameter. For gas lines, the recommended maximum velocity is 60-80 ft/sec to minimize noise and allow corrosion inhibition. For multiphase lines, the minimum velocity is 10-15 ft/sec to prevent slugging, while the maximum is 60 ft/sec or lower if corrosives are present. Guidelines are given for selecting design velocities and installing protections based on whether solids may be present.

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    This document discusses gas and multiphase line sizing. It provides equations to calculate gas velocity and erosional velocity in pipes based on factors like flow rate, temperature, pressure, and pipe diameter. For gas lines, the recommended maximum velocity is 60-80 ft/sec to minimize noise and allow corrosion inhibition. For multiphase lines, the minimum velocity is 10-15 ft/sec to prevent slugging, while the maximum is 60 ft/sec or lower if corrosives are present. Guidelines are given for selecting design velocities and installing protections based on whether solids may be present.

    Copyright:

    © All Rights Reserved
    Download as DOCX, PDF, TXT or read online from Scribd
    Download as docx, pdf, or txt
    194 views3 pages

    Gas Line Velocity

    Uploaded by

    putrude
    This document discusses gas and multiphase line sizing. It provides equations to calculate gas velocity and erosional velocity in pipes based on factors like flow rate, temperature, pressure, and pipe diameter. For gas lines, the recommended maximum velocity is 60-80 ft/sec to minimize noise and allow corrosion inhibition. For multiphase lines, the minimum velocity is 10-15 ft/sec to prevent slugging, while the maximum is 60 ft/sec or lower if corrosives are present. Guidelines are given for selecting design velocities and installing protections based on whether solids may be present.

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    Gas line sizing

    The pressure drop in gas lines is typically low in gas-producing facilities because the piping
    segment lengths are short. The pressure drop has a more significant impact upon longer segments
    such as gas-gathering pipelines, transmission pipelines, or relief or vent piping.
    The velocity in gas lines should be less than 60 to 80 ft/sec (18 to 24m/s) to minimize noise and
    allow for corrosion inhibition. A lower velocity of 50 ft/sec should be used in the presence of
    known corrosives such as CO2. The minimum gas velocity should be between 10 and 15 ft/sec,
    which minimizes liquid fallout.
    Gas velocity is expressed in Eq. 6 as
    (Eq. 6)
    where
    Vg
    Qg
    T
    P
    Z
    and
    d

    =
    =
    =
    =
    =

    gas velocity, ft/sec,


    gas-flow rate, MMscf/D,
    gas flowing temperature, R,
    flowing pressure, psia,
    compressibility factor, dimensionless,

    pipe ID in.

    Multiphase line sizing


    The minimum fluid velocity in multiphase systems must be relatively high to keep the liquids
    moving and prevent or minimize slugging. The recommended minimum velocity is 10 to 15
    ft/sec. The maximum recommended velocity is 60 ft/sec to inhibit noise and 50 ft/sec for CO2
    corrosion inhibition.
    In two-phase flow, it is possible that liquid droplets in the flow stream will impact on the wall of
    the pipe causing erosion of the products of corrosion. This is called erosion/corrosion. Erosion of
    the pipe wall itself could occur if solid particles, particularly sand, are entrained in the flow
    stream. The following guidelines from API RP14E[5] should be used to protect against
    erosion/corrosion.
    Calculate the erosional velocity of the mixture with Eq. 7.

    (Eq. 7)
    where C = empirical constant. M is the average density of the mixture at flowing conditions. It

    can be calculated from


    (Eq. 8)
    where
    SG
    and
    S

    = specific gravity of the liquid (relative to water),


    = specific gravity of the gas relative to air.

    Industry experience to date indicates that for solids-free fluids, values of C = 100 for continuous
    service and C = 125 for intermittent service are conservative. For solids-free fluids where
    corrosion is not anticipated or when corrosion is controlled by inhibition or by employing
    corrosion-resistant alloys, values of C = 150 to 200 may be used for continuous service; values
    up to 250 have been used successfully for intermittent service. If solids production is anticipated,
    fluid velocities should be significantly reduced. Different values of C may be used where specific
    application studies have shown them to be appropriate.
    Where solids and/or corrosive contaminants are present or where c values higher than 100 for
    continuous service are used, periodic surveys to assess pipe wall thickness should be considered.
    The design of any piping system where solids are anticipated should consider the installation of
    sand probes, cushion flow tees, and a minimum of 3 ft of straight piping downstream of choke
    outlets.
    Once a design velocity is chosen, to determine the pipe size, Eq. 9 can be used.

    (Eq. 9)
    where
    d
    Z
    R
    P
    T
    V
    and
    QL

    =
    =
    =
    =
    =
    =

    pipe ID, in.,


    compressibility factor, dimensionless,
    gas/liquid ratio, ft3/bbl,
    flowing pressure, psia,
    gas/liquid flowing temperature, R,
    maximum allowable velocity, ft/sec,

    liquid-flow rate, B/D.

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