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    Full Scale Measurements - Sea Trials

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    erudite_0206
    Dedicated sea trials are conducted for new vessels to test contractual performance requirements as well as to investigate special problems. Key tests conducted include speed-power tests, bollard pull tests for tugs, maneuvering tests, and seakeeping tests for high-speed craft. Trials are organized by the shipbuilder and measurements are taken to characterize vessel performance and environmental conditions like waves, wind and current. A variety of instrumentation is used to measure vessel speed, shaft power, ship motions, wave conditions and more to evaluate contractual compliance and vessel behavior. Standard procedures exist for conducting trials and analyzing results.

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    Full Scale Measurements - Sea Trials

    Uploaded by

    erudite_0206
    548 views47 pages
    Dedicated sea trials are conducted for new vessels to test contractual performance requirements as well as to investigate special problems. Key tests conducted include speed-power tests, bollard pull tests for tugs, maneuvering tests, and seakeeping tests for high-speed craft. Trials are organized by the shipbuilder and measurements are taken to characterize vessel performance and environmental conditions like waves, wind and current. A variety of instrumentation is used to measure vessel speed, shaft power, ship motions, wave conditions and more to evaluate contractual compliance and vessel behavior. Standard procedures exist for conducting trials and analyzing results.

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    Sea Trials

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    Full Scale Measurements- Sea Trials

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    Dedicated sea trials are conducted for new vessels to test contractual performance requirements as well as to investigate special problems. Key tests conducted include speed-power tests, bollard pull tests for tugs, maneuvering tests, and seakeeping tests for high-speed craft. Trials are organized by the shipbuilder and measurements are taken to characterize vessel performance and environmental conditions like waves, wind and current. A variety of instrumentation is used to measure vessel speed, shaft power, ship motions, wave conditions and more to evaluate contractual compliance and vessel behavior. Standard procedures exist for conducting trials and analyzing results.

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    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    548 views47 pages

    Full Scale Measurements - Sea Trials

    Uploaded by

    erudite_0206
    Dedicated sea trials are conducted for new vessels to test contractual performance requirements as well as to investigate special problems. Key tests conducted include speed-power tests, bollard pull tests for tugs, maneuvering tests, and seakeeping tests for high-speed craft. Trials are organized by the shipbuilder and measurements are taken to characterize vessel performance and environmental conditions like waves, wind and current. A variety of instrumentation is used to measure vessel speed, shaft power, ship motions, wave conditions and more to evaluate contractual compliance and vessel behavior. Standard procedures exist for conducting trials and analyzing results.

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    of 47

    Full Scale Measurements Sea trials

    Experimental Methods in Marine Hydrodynamics


    Lecture in week 45
    Contents:
    Types of tests
    How to perform and correct speed trials
    Wave monitoring
    Measurement
    Observations
    Motion measurement
    Hull monitoring
    Propeller cavitation observations
    Performance monitoring
    1

    Covers Chapter 11 in the Lecture Notes

    Dedicated sea trials are conducted under the


    following circumstances:
    Delivery of newbuildings (Contractual Trials)
    Speed-power (compliance with contracted performance)
    Bollard Pull test (tugs and offshore vessels compliance with
    contracted performance)
    Maneuvering (compliance with IMO criteria)
    Sea keeping (only high speed craft)

    If a special problem has arisen, for instance:


    Propeller noise and/or erosion
    Steering problems
    Excessive fuel consumption

    For research purposes (quite rare due to high costs)


    3

    Delivery Sea trials (Contractual trials)


    Ship building contracts contain specific requirements for
    speed-power performance
    Failure to meet requirements means fees to be paid and ultimately
    that the ship owner has the right to refuse to accept the ship

    For tugs and offshore vessels, there will be requirements


    for bollard pull as well
    There might be requirements also for maneuvering trials :
    Emergency stop test
    Turning circles
    Zig-zag tests

    High speed craft requirements also for seakeeping tests


    4

    IMO: 2000 HSC Code (IMO 185E)

    Applicable standards
    ISO 19019:2005 Sea-going vessels and marine technology -Instructions for planning, carrying out and reporting sea
    trials
    ISO 15016:2015(E) Guidelines for the assessment of speed
    and power performance by analysis of speed trial data
    Replaced previous version in 2015. Significant differences!

    ITTC Recommended procedure 7.5-04-01-01.1 Preparation


    and Conduct of Speed/Power Trials
    IMO: 2000 HSC Code (IMO 185E) Requirements for
    testing of high speed craft
    5

    IMO HSC testing requirements


    Stopping
    Normal stop from max speed to zero
    Emergency stop
    Crash stop

    Cruise performance in two sea states


    Normal conditions
    Worst intended conditions
    Measurements of accelerations, speed, relative wave heading

    Failure tests
    Check that the ship, crew and passengers are not at risk if for
    instance the steering fails
    6

    Organization of Delivery Trials


    The Shipbuilder is responsible
    Trial Leader
    From the shipbuilder
    Responsible for the execution of all phases of the trial

    Ship masters
    There is one ship master hired by the shipbuilder who is in charge
    of handling the ship
    There is usually one or more ship masters hired by the shipowner
    who is going to take over the ship

    Measurements are performed by shipbuilder or by third


    party (like Marintek or Maskindynamikk)
    7

    Execution of speed trials

    Always run back and forth at same engine setting


    Run back and forth at the same track
    Perform runs at different speeds (at least three)
    If possible, orient the track with and against the wind
    direction
    > 5 min and 1 mile
    Steady Approach

    Steady Approach
    > 5 min and 1 mile

    Wind, current
    8

    Measured mile

    Trial Conditions max acceptable


    Sea state
    Preferably sea state 3
    Ultimately sea state 5 (or up to sea state 6 for ships with L>100 m)

    Wind
    Beufort 6 (20 knots) (for ships with L>100 m)
    Beufort 5 (for ships with L 100 m)

    Water depth h
    h>6.0*Am2 and h>V2
    Smaller depths require corrections for shallow water

    Current
    Current of more than a few knots is unacceptable
    10

    Trial Conditions Contractual


    Sea state
    No waves
    In practice: Beufort 1 (Wave height 0.1 m)

    Wind
    No wind
    In practice: Beufort 2 (Wind speed 6 knots)

    Water depth h
    Deep,
    In practice: h>6.0*(Am) and h>V2

    Current
    No current
    No practical limit for when corrections are made. Use of double runs
    means that corrections are always included
    11

    Correction of trial results


    When trial conditions are not fulfilled corrections must be
    made
    Typical corrections:
    Draught interpolation in model test results on two draughts
    Wind calculation of wind resistance using empirical drag coef. or
    results from wind tunnel tests
    Shallow water empirical formulas
    Waves calculation of added wave resistance and speed loss

    Standards for how corrections shall be performed:


    ISO 15016 Guidelines for the assessment of speed and power
    ITTC Procedure for the Analysis of Speed/Power Trial Data
    STAWAVE by Marin
    12

    Comes with a free software package for performing the analysis

    IMO Energy Efficiency Design Index EEDI


    Increases the need for standardized trial and correction
    procedures
    The speed at 75% MCR in calm water must be accurately
    determined
    Now longer just a matter for yard and ship owner
    Shall be approved by classification society

    13

    Recent developments
    The ISO 15016 is about to be discarded
    Too complicated to use
    Too much freedom to manipulate results
    Outdated correction methods

    IMO has tasked ITTC to develop a new standard


    ITTC works with Marin, and the new guideline is based on
    the STAWAVE methods

    14

    Speed measurement
    Speed over ground and Speed through water
    Timing a measured mile
    the old-fashioned way, only applicable to dedicated speed trials
    Gives speed over ground

    GPS
    The obvious choice, always used
    Gives speed over ground

    Speed log
    Device to measure speed through water
    Always installed on ships
    Doppler log is most common on large ships
    Measures speed at about 10 m below bottom, close to bow
    15

    The accuracy is questionable!

    Measurement of shaft power


    Strain gauges glued directly to the shaft
    Calibration factor must be calculated, so shaft dimensions and
    material properties must be known exactly
    Tachometer to measure shaft speed

    Commercial power meters


    Made for permanent installation
    The best, but most expensive alternative

    Poor, but cheap alternatives are

    16

    fuel rack measurements (measurement of fuel consumption,


    combined with supplier data for fuel quality)
    measurement of cylinder pressure (used on large, slow speed
    engines)
    For diesel-electric drive-trains, the frequency converter (drive)
    will usually be able to output information about power supplied to
    the electric motor

    Shaft measurements

    Torque measurement
    17

    Thrust measurem.

    Optical torque sensor

    18

    Optical thrust and torque measurement

    Required accuracy for thrust measurement is


    25 naonometers!
    Challenging, but possible, according to
    supplier VAF Instruments
    19

    Bollard Pull
    Tests

    Good location
    20

    Poor location

    Bollard pull test

    21

    Bollard pull test


    2x460 kW

    22

    Maneuvering trials
    Trial types and execution same as in model scale
    Measurements:

    23

    (D)GPS position measurement


    Gyro compass course
    Rate of turn (if possible)
    Rudder angle
    Propeller revs

    Types of Ship Maneuvers


    IMO standard maneuvers:
    Zig-zag tests
    10/ 10 to both sides
    20/ 20 to both sides

    Turning circle test


    35 rudder angle

    Full astern stopping test

    Additional maneuvers:
    Spiral test
    Reverse spiral test
    Pull-out maneuver
    normally added at the end of a turning test
    24

    Zig-zag test

    25

    Test 2011: 20-20 zig zag

    26

    Turning circle

    27

    Testing of position-keeping ability and


    thruster performance at zero speed
    Important for vessels that have requirements to Dynamic
    Positioning performance
    No standard tests or commonly recognised procedures
    There is a need for development of standardized tests and analysis
    procedures for this purpose

    A way to characterise thruster performance at zero speed:


    Run the thrusters in different combinations (one by one, and in
    specific combination) for a short time
    Measure the acceleration of the ship in the horisontal plane
    Compute the impulse required to create the acceleration
    Compare the effective impulse with the impulse provided by the
    thruster(s) to arrive at a kind of efficiency
    28

    Measurements environmental conditions


    Water depth
    Echo sounder (ship instrument) or nautical charts

    Water quality
    Temperature: Cooling water intake temperature can be used
    Density: From nautical charts or density measurements

    Wind
    Velocity and direction from anemometer
    A separate, calibrated instrument is preferable
    Watch out for influence of superstructure on the measurement

    Current

    Nautical charts and tables


    the difference in speed between double runs
    a 360 turning test at low speed
    The difference between log speed and GPS speed
    often, one doesnt trust the speed log sufficiently for this purpose

    29

    Wave measurements
    Visual observation and estimation
    Estimates by yard representative, ship-owner representative, and
    possibly a neutral third party are compared and averaged

    Mobile wave buoy


    Accurate (but only at a single point)
    Recovery of the buoy is difficult (risk of loosing it)

    Fixed weather station


    Good solution if one is nearby

    Wave radar (Wavex)


    Bow-mounted altimeter
    Wave information without measurement: Hindcast data
    30

    Wave buoys
    Fugro Oceanor Wavescan

    Directional wave spectrum


    Wind
    Current
    Water temperature and salinity
    Must be moored; large, heavy, costly

    Smaller, spherical buoys

    31

    Drifting or moored
    Simple buoys measure wave height only by use
    of an accelerometer
    Advanced buoys can measure the directional
    wave spectrum through use of the Doppler shift
    of the GPS signals
    Usually measures position for a drifting buoy
    this can be used as an estimate of current
    Can be brought along for a full scale test

    Wavex by Miros AS

    32

    Bow-mounted altimeter

    SM - 094

    Measures relative wave motion


    Ship motions must also be measured
    in order to calculate absolute wave
    height

    SM - 055

    33

    Using the ship as wave buoy


    Measurement of ship motions and accelerations
    Knowledge of ship motion transfer functions can be used
    to find the wave spectrum from the measured ship motion
    power spectrum
    Current research topic
    Can hardly work for short waves, since then the ship
    doesnt move

    34

    Beufort wind scale with related sea conditions

    36

    Sea Description term


    Beufort state Wind
    0
    0 Calm
    1
    0 Light air
    2
    1 Light breeze
    3
    2 Gentle breeze
    4
    3 Moderate breeze
    5
    4 Fresh breeze
    6
    5 Strong breeze
    7
    6 Near gale
    8
    7 Gale
    9
    8 Strong gale
    10
    9 Storm
    11
    9 Violent storm
    12
    9 Hurricane
    13
    9 Hurricane
    14
    9 Hurricane
    15
    9 Hurricane

    Wave
    Calm
    Ripples
    Small wavelets
    Large wavelets
    Small waves
    Moderate waves
    Large waves
    Large waves
    Moderately high waves
    High waves
    Very high waves
    Exceptionally high waves
    Exceptionally high waves
    Exceptionally high waves
    Exceptionally high waves
    Exceptionally high waves

    Wind sp. [knots] Wave height [m] S


    min
    max
    Probable Max
    D
    0
    1
    0
    0c
    1
    3
    0.1
    0.1 R
    3
    6
    0.2
    0.3 S
    6
    10
    0.6
    1L
    10
    16
    1
    1.5 S
    16
    21
    2
    2.5 M
    21
    27
    3
    4L
    27
    33
    4
    5.5 S
    33
    40
    6
    7.5 M
    40
    47
    7
    10 H
    47
    55
    9 12.5 V
    55
    63
    11.5
    16 E
    63
    71
    14
    16 A

    71
    80
    89

    80 >14
    89 >14
    99 >14

    >16
    >16
    >16

    37

    Illustrations of Beufort wind (and wave) scale


    From: http://en.wikipedia.org/wiki/Beaufort_scale

    38

    Hindcast data
    Information about wave and wind condition in the past
    Data collected by meteorological institutes
    From wave buoys, weather stations, satellites, observations

    Many different sources


    Might be hard to find the right source for your test
    National Oceanic and Athospheric Administration www.noaa.gov
    is the main source
    Many different applications are using their open data

    From hindcast data you can get information about sea state
    and wind in your area
    You can of course not get wave elevation time series!

    Generally only available for open ocean areas


    39

    Measurement of motions

    Accelerations: Conventional accelerometers


    Angles: Gyros, compass, accelerometers
    Rate gyro to measure rate of change of angles
    Inertial Measurement Units (IMU)
    Consists of a number of accelerometers built into one compact unit
    Gives out accelerations, velocities and motions at any point
    Konsberg Seatex MRU is a good example of a commercial IMU

    Kongsberg Seapath
    Combination of DGPS and IMU for accurate position
    measurement

    41

    Kongsberg Seatex MRU 5+

    42

    Kongsberg Seapath 330

    43

    Measurement of forces:
    Hull Monitoring
    Hull Monitoring System:

    Strain gauges most


    common sensor
    Short and long gauges
    Cabling exposed to
    damage, gauges work
    loose
    Sensors based on fiberoptics - polarimetric and
    bragg-grating suggested as
    alternative

    Strain gauge in protective casing:

    44

    Rolls-Royce Health and Monitoring


    System - HEMOS

    45

    Example: Monitoring of loads


    on an azimuthing thruster of a
    seismic vessel
    Measurement of ship motions and
    position with Seapath
    Measurements on the port
    azimuthing thruster
    Automatic triggering of data storage
    Data acquisition system remotely
    monitored from land

    46

    Performance monitoring
    Typical merchant ship application:
    To monitor the development of speed and fuel consumption
    over time, in order to detect need for maintenance
    Challenges:
    Monitoring and correcting for environmental conditions
    Waves, wind, water temperature

    47

    Accurate measurement of shaft power and speed through water


    Measuring and correcting for loading condition
    Data processing
    Setting-up and running automatic data transmission

    Propeller Cavitation
    Observations

    Seen from below


    48

    Seen from the side

    Cavitation observation techniques

    2. generation borescope

    49

    Source: marin.nl

    1. generation borescope

    Sample picture from full scale propeller cavitation observation

    Summary:

    50

    Types of tests
    How to perform and correct speed trials
    Wave monitoring
    Measurement
    Observations
    Motion measurement
    Hull monitoring
    Propeller cavitation observations

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