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    Selection of Test Parameters: Ashley Jolley

    Uploaded by

    Asish desai
    Based on the information provided in the document, for a 8" pipe with 8.18mm wall thickness, I would recommend using a 30mm ring spacing for L(0,2) longitudinal wave testing. The 46mm spacing would likely result in lower test frequencies and less optimal signal output due to the increased ring separation.

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    Selection of Test Parameters: Ashley Jolley

    Uploaded by

    Asish desai
    101 views19 pages
    Based on the information provided in the document, for a 8" pipe with 8.18mm wall thickness, I would recommend using a 30mm ring spacing for L(0,2) longitudinal wave testing. The 46mm spacing would likely result in lower test frequencies and less optimal signal output due to the increased ring separation.

    Original Description:

    Lrut study

    Original Title

    Lrut study

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    Based on the information provided in the document, for a 8" pipe with 8.18mm wall thickness, I would recommend using a 30mm ring spacing for L(0,2) longitudinal wave testing. The 46mm spacing would likely result in lower test frequencies and less optimal signal output due to the increased ring separation.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    101 views19 pages

    Selection of Test Parameters: Ashley Jolley

    Uploaded by

    Asish desai
    Based on the information provided in the document, for a 8" pipe with 8.18mm wall thickness, I would recommend using a 30mm ring spacing for L(0,2) longitudinal wave testing. The 46mm spacing would likely result in lower test frequencies and less optimal signal output due to the increased ring separation.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 19

    SELECTION OF TEST PARAMETERS

    ASHLEY JOLLEY
    Ideal Test Conditions

    SINGLE WAVE MODE GENERATED

    NO DISPERSION

    SINGLE TEST DIRECTION


    General Dispersion Curves – Phase Velocity (Vp)

    Phase Velocity dispersion curves can be easily recognised as at their frequency cut off the (Vp) tends toward infinity. This graph
    displays the variation of phase velocity (Vp) over frequency (f). Phase velocity (Vp) is the apparent speed of any point of constant
    phase inside the pulse

    12” – 9.53mm WT
    General Dispersion Curves – Group Velocity (Vg)

    Group Velocity dispersion curves can be easily recognised as at their frequency cut off the (Vg) tends toward zero. This
    graph displays the variation of group velocity (Vg) over frequency (f). Group velocity (Vg) is the apparent speed of the pulse

    12” – 9.53mm WT
    Effect of Diameter
    Lower frequency limit for L(0,2)
    50

    45

    3 inch OD
    40

    Cut off frequency, kHz 35

    30

    20 inch OD
    25

    20

    15

    10

    0
    0 10 20 30 40 50 60
    Pipe Diameter, inches
    Effect of thickness
    Upper frequency limit for L(0,2)
    Upper cut-off frequency for L(0,2) Testing

    180

    160

    140

    120
    Frequency, kHz

    100

    80

    60

    40

    20

    0
    0 5 10 15 20 25 30 35 40 45 50
    Pipe thickness, mm
    Upper cut of frequency for T(0,1)

    Upper cut off frequency for T(0,1) mode

    180.0
    160.0
    140.0
    Frequency kHz 120.0
    100.0
    80.0
    60.0
    40.0
    20.0
    0.0
    10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
    Thickness mm
    Effect of frequency and ring spacing on L(0,2) output

    - 3 Ring, 46mm
    30mm

    Frequency Selections: Frequency Regime:


    Peak PO = 40
    61 kHz 51 kHz (Peak –
    31
    10 kHz)
    3dB)
    -3dB points = 31
    47 & 48
    74 kHz 61 kHz (L(0,1))
    33 (Peak PO)
    L(0,1) cancellation = 33
    65 kHz 65 kHz (Peak
    40 (L(0,1))
    PO) 71 kHz (Peak + 10 kHz)
    48 kHz (Peak + 3dB)
    Effect of frequency and ring spacing on L(0,2) output

    - 3 Ring, 46mm

    Frequency Selections: Frequency Regime:


    Peak PO = 40 kHz 31 kHz (Peak – 3dB)
    -3dB points = 31 & 48 kHz 33 kHz (L(0,1))
    L(0,1) cancellation = 33 kHz 40 kHz (Peak PO)
    48 kHz (Peak + 3dB)
    Effect of frequency and ring spacing on L(0,2) output –
    Both Ring Spacings
    Effect of frequency and ring spacing on T(0,1) output

    2 Ring, 45mm
    -3 30mm

    Frequency Selections: Frequency Regime:


    36 72
    27 & 48
    Peak PO = 24 81 kHz 36 kHz
    20 & 72(Lowest
    kHz (Peak PO)
    Usable)
    -3dB points = 28,
    19, 44,
    14, 29, 64
    43&&95
    41,68 81 kHz
    54kHz 28
    24 & 48
    27 64 – 3dB)
    81 kHz (Peak PO)
    44 & 81(Peak
    71 kHz
    43 -– 3dB)
    kHz (Peak + 3dB)
    10 kHz)
    37 & 54
    29 91 kHz (Peak + 10 kHz)
    3dB)
    Output conditions on pulse shape
    1. In the process of
    ‘controlling’ the
    direction of mode
    propagation and
    selecting a single
    mode, the actual signal
    is distorted at sub-
    optimum frequencies
    2. The middle ring is the
    inverted sum of the outer
    two rings – under some
    circumstances this adds up
    to not a lot
    Effect of thickness on L(0,1) suppression

    120
    Frequency, kHz 100 30mm spacing

    80

    60 46mm
    spacing
    40

    20

    0
    0 10 20 30 40 50
    Pipe thickness, mm
    Combined effects on L(0,2) test conditions selection

    120

    100 30mm spacing


    Frequency, kHz

    80
    46mm spacing
    60
    Upper cut off frequency
    40
    Upper Optimum Frequency

    20
    Lower Optimum Frequency

    0
    0 10 20 30 40 50
    Pipe thickness, mm
    Selection criteria for L(0,2) testing
    Example - 1

    We are inspecting a 12” pipe with a wall thickness of 14.27mm. What would you consider the most
    appropriate ring spacing for this pipe when using the Longitudinal wave mode?

    30mm

    46mm
    Example - 2

    We are inspecting a 6” pipe with a wall thickness of 7.11mm. What would you consider the most
    appropriate ring spacing for this pipe when using the Longitudinal wave mode?

    30mm

    46mm
    Example - 3

    We are inspecting a 8” pipe with a wall thickness of 8.18mm. What would you consider the most
    appropriate ring spacing for this pipe when using the Longitudinal wave mode?

    30mm

    46mm

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