Uisge Gorm, courtesy BES
General information
Monitoring of motions is nowadays common on board most floaters and offshore vessels and even ships. Compact sensor units based on three accelerometers and three solid state rate gyros or Fiber Optic Gyros (FOGs) provide continuous and accurate records of motions in 6 degrees of freedom. The value of motion recording is increased significantly by utilizing the information to derive the operational critical data such as the motions, accelerations or velocities at specific locations, relative motions between floaters or the fatigue loads in e.g. a jacket transport on tow barges.
Typical 6 .d.o.f. sensors can measure vessel motions up to 20 or 30 seconds. For longer periods either high end sensors must be used. Instruments like DGPS etc. can be used to measure low frequency motions, but only in 2 or 3 degrees of freedom.
If full scale monitoring of motions is not a viable option, than dedicated model tests can provide a good alternative.
Monitoring of motions is nowadays common on board most floaters and offshore vessels and even ships. Compact sensor units based on three accelerometers and three solid state rate gyros or Fiber Optic Gyros (FOGs) provide continuous and accurate records of motions in 6 degrees of freedom. The value of motion recording is increased significantly by utilizing the information to derive the operational critical data such as the motions, accelerations or velocities at specific locations, relative motions between floaters or the fatigue loads in e.g. a jacket transport on tow barges.
Typical 6 .d.o.f. sensors can measure vessel motions up to 20 or 30 seconds. For longer periods either high end sensors must be used. Instruments like DGPS etc. can be used to measure low frequency motions, but only in 2 or 3 degrees of freedom.
If full scale monitoring of motions is not a viable option, than dedicated model tests can provide a good alternative.
Service & Activities
Full scale motion monitoring is performed by the Trials & Monitoring department.
Motion monitoring by means of model tests is performed by the following departments:
Full scale motion monitoring is performed by the Trials & Monitoring department.
Motion monitoring by means of model tests is performed by the following departments:
- Offshore department for offshore structures in waves, wind and current
- Seakeeping department for ships in waves
- Manoeuvring department for manoeuvring characteristics of ships
Facilities & Tools
To measure motions on full scale ships and offshore structures a range of motion sensors is available:
To measure motions on full scale ships and offshore structures a range of motion sensors is available:
- High end motion sensors
- Marine Quality Kit (MQK)
- Low end motion sensors
- DGPS
MARIN has developed its own 6 degree of freedom motion sensor MQK, which has a proven track record in the offshore environment for more than 10 years. The MQK measures real-time and fully automatically the accelerations and motions in six degrees of freedom by means of accelero meters and angular rate gyros. The sensor unit measures 0.25 x 0.17 x 0.12 [m] and can be placed at any location on the ship. It can be connected to a laptop PC to store and dispay the measured motions. Sample rate can be adjusted upto 50 Hz, but for normal ship motions a 5 Hz sample rate is sufficient.
DGPS is widely available and low cost receivers allow accurate position measurement for surge, sway and yaw. Comparison with conventional 6 d.o.f. sensors shows that accuracies up to a few cm's are achievable, provided the right instrument and correction method is chosen.
For specific applications, either low budget - low resolution projects or higher budget - high resolution projects, we make use of 3rd party instruments. Depending on the type of project a suitable sensor is selected. For most types of sensors an interface with the data logging system is available. If a suitable interface is not available, MARINs software department is capable of generating such an interface on short notice.
DGPS is widely available and low cost receivers allow accurate position measurement for surge, sway and yaw. Comparison with conventional 6 d.o.f. sensors shows that accuracies up to a few cm's are achievable, provided the right instrument and correction method is chosen.
For specific applications, either low budget - low resolution projects or higher budget - high resolution projects, we make use of 3rd party instruments. Depending on the type of project a suitable sensor is selected. For most types of sensors an interface with the data logging system is available. If a suitable interface is not available, MARINs software department is capable of generating such an interface on short notice.
The following MARIN facilities are used to measure motions using model tests:
- Offshore basin for model tests on offshore structures in waves, wind and current
- Seakeeping and Manoeuvring basin, for model tests in deep water
- Shallow Water basin, for model tests in shallow water
Software Sales
Some software tools are available for commercial use outside MARIN. A complete overview of these software tools for sale can be found under Software Sales.
Some software tools are available for commercial use outside MARIN. A complete overview of these software tools for sale can be found under Software Sales.
Experience record
The list below gives a review of motion monitoring projects carried out at MARIN:
The list below gives a review of motion monitoring projects carried out at MARIN:
- TotalFinaElf, Analysis of motions FPSO Girassol, 2002
- Petrobras, Motion Monitoring P-35, 2002
- FPSO Roll JIP (22 companies), Roll Motions of FPSO’s, 2002
Most recent papers on motion measurements presented by MARIN
(complete overview of papers can be found under Publications)
(complete overview of papers can be found under Publications)
Full Scale Monitoring Marco Polo Tension Leg Platform
van Dijk R.R.T. & van den Boom H.J.J. , OMAE, 2007
Offshore Monitoring; Real World Data for Design, Engineering and Operation
van den Boom, H., Koning, J. & Aalberts, P., Offshore Technology Conference (OTC), Houston, 2005
van Dijk R.R.T. & van den Boom H.J.J. , OMAE, 2007
Offshore Monitoring; Real World Data for Design, Engineering and Operation
van den Boom, H., Koning, J. & Aalberts, P., Offshore Technology Conference (OTC), Houston, 2005
Most recent articles on motion monitoring written for MARIN Report
(complete overview of articles can be found under Publications)
(complete overview of articles can be found under Publications)
Safetrans celebrates 10th anniversary!
MARIN Report, 2010
Is cargo securing in need of shoring up?
MARIN Report, 2010
Fatigue Lifetime Assurance with Monitas
Mirek Kaminski, MARIN report, 2010
DCV Balder instrumented for lifetime extension
Pieter Aalberts, MARIN report, 2010
OWME project makes technological breakthrough
Henk van den Boom, MARIN Report, 2009
MARIN Report, 2010
Is cargo securing in need of shoring up?
MARIN Report, 2010
Fatigue Lifetime Assurance with Monitas
Mirek Kaminski, MARIN report, 2010
DCV Balder instrumented for lifetime extension
Pieter Aalberts, MARIN report, 2010
OWME project makes technological breakthrough
Henk van den Boom, MARIN Report, 2009
Contact
For more information on how MARIN can assist your organisation with full scale motion measurements, please contact MARIN's Trials & Monitoring department.
For more information regarding motion measurements using model tests, please contact the Offshore department, the Seakeeping department or the Manoeuvring department.
For more information on how MARIN can assist your organisation with full scale motion measurements, please contact MARIN's Trials & Monitoring department.
For more information regarding motion measurements using model tests, please contact the Offshore department, the Seakeeping department or the Manoeuvring department.