Deformation effects on vessels The effects of flexibility on calibrations

HSB Workshop Vessel Geometry and Calibrations15 January 2014

Erich Gaikhorst

The effects of flexibility on calibrations

Index

• Two examples • Fallpipe vessels– Flexibility– Temperature

The effects of flexibility on calibrations

Remaining error after calibration

The effects of flexibility on calibrations

Remaining error

Offset Survey Noise (Quality offset survey) Sensor Noise (Quality sensor) Sensor Drift (Quality sensor)

Calibration Noise (Quality calibration survey)

Vessel Deformations(Load/Sea state/temperature/design)

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Example 1: Flexibility

• High accurate sensors• Offsets with mm accuracy• Angles with 0.01° accuracy• Correct calibrations

• Position jumps (xy) of the ROV• Why

The effects of flexibility on calibrations

The effects of flexibility on calibrations

The effects of flexibility on calibrations

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The effects of flexibility on calibrations

-15.000 -10.000 -5.000 0.000 5.000 10.000 15.000

-40.000

-20.000

0.000

20.000

40.000

60.000

80.000

Top view

PS DockSB DockPS floatingSB floating

Fwd

Aft

Surveyed

• Points SB and PS

The effects of flexibility on calibrations

-40.000 -20.000 0.000 20.000 40.000 60.000 80.0000.000

0.020

0.040

0.060

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0.100

0.120

0.000

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SBSeries3Best fit circle SBBest fit circle PS

Average angle (pitch err) between Sb and Ps: 0.13°

Difference between docked and floating

The effects of flexibility on calibrations

Example 2: Temperature

• High accurate sensors• Offsets with mm accuracy• Angles with 0.01° accuracy

• Placing tolerance gravel +/-35mm• Temperature a significant part of the error

budget.• Height influenced by temperature

The effects of flexibility on calibrations

65m

The effects of flexibility on calibrations

• Geometry December +5°C– Steel +5°C

The effects of flexibility on calibrations

• First calibration May +23°CSteel +30°C;Water +25°C

• Last calibration August +35°CSteel +60°C ;Water +27°C

The effects of flexibility on calibrations

35m

Steel Lenght [m]

temp [°]

0 5 10 15 20 25 30 35 40 45 50 55 60 65 705 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3.0 3.3 3.6 3.9 4.2

10 0.6 1.2 1.8 2.4 3.0 3.6 4.2 4.8 5.4 6.0 6.6 7.2 7.8 8.415 0.9 1.8 2.7 3.6 4.5 5.4 6.3 7.2 8.1 9.0 9.9 10.8 11.7 12.620 1.2 2.4 3.6 4.8 6.0 7.2 8.4 9.6 10.8 12.0 13.2 14.4 15.6 16.825 1.5 3.0 4.5 6.0 7.5 9.0 10.5 12.0 13.5 15.0 16.5 18.0 19.5 21.030 1.8 3.6 5.4 7.2 9.0 10.8 12.6 14.4 16.2 18.0 19.8 21.6 23.4 25.235 2.1 4.2 6.3 8.4 10.5 12.6 14.7 16.8 18.9 21.0 23.1 25.2 27.3 29.440 2.4 4.8 7.2 9.6 12.0 14.4 16.8 19.2 21.6 24.0 26.4 28.8 31.2 33.645 2.7 5.4 8.1 10.8 13.5 16.2 18.9 21.6 24.3 27.0 29.7 32.4 35.1 37.850 3.0 6.0 9.0 12.0 15.0 18.0 21.0 24.0 27.0 30.0 33.0 36.0 39.0 42.055 3.3 6.6 9.9 13.2 16.5 19.8 23.1 26.4 29.7 33.0 36.3 39.6 42.9 46.260 3.6 7.2 10.8 14.4 18.0 21.6 25.2 28.8 32.4 36.0 39.6 43.2 46.8 50.465 3.9 7.8 11.7 15.6 19.5 23.4 27.3 31.2 35.1 39.0 42.9 46.8 50.7 54.6

coefficient of linear expansionSteel 1.20E-02 mm/°CAluminium 2.30E-02 mm/°C

The effects of flexibility on calibrations

65 m5 3.9

10 7.815 11.720 15.625 19.530 23.435 27.340 31.245 35.150 39.055 42.960 46.865 50.7

The effects of flexibility on calibrations

Thank you for your attention

Questions?