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Monitoring the effects of ice forces with the Sir David Attenborough
Karianne Pran, MSc.VP Engineering
13. November 2017
About Light Structures AS
• Norwegian company founded in 2001• Specializing on fibre optic instrumentation for ships and
offshore oil&gas installations• Technology originally developed for the Royal Norwegian
Navy at the Norwegian Defence Research Establishment• 180 systems sold
– Hull Stress Monitoring systems– Ice Load Monitoring systems– Sloshing Monitoring systems
• Fibre Bragg Grating (FBG) sensing technology• Recently acquired GME Korea (shaft torque monitoring)
Ice Load Monitoring
• Developed in collaboration with a number of Norwegian project partners in 2006/2007
• Motivated by the risks and challenges of sailing in ice infested waters
Reduta Ordona, 1996
ILM concept test system
• 9 frames instrumented with FBG optical strain sensors
• 54 strain gauges in 25 locations
• combination of – ±45° shear sensors – tri-axial rosette
sensors
Example results
Utilization
FEM: Load ensembles for instrumented locations
Commercial projects
• Experience: The shear in (intermediate) frames spanning the ice level provides the most quantitative results that are most easily interpreted
• Some later projects have supplemented with bending sensors on frames and longitudinals, and/or plate field rosette sensors
Image: sanap.ac.za
Image: SCF
Image: Havforskningsinstituttet
ILM on “Sir David Attenborough”
• Six side shell areas monitored
• 15 Pairs of shear sensors on 15 frames
• Denser instrumentation (10 consecutive frames) at one bow shoulder to allow tracking of ice forces over a “load patch”
• Global hull stress monitoring at main deck
• Vertical acceleration in bow
Parameters in system
• Raw data; measured strains– BWL to 100Hz before further
processing– Downsampled to 21Hz, 8.5Hz
bandwidth before saving to disk• ILM: Utilization of each
instrumented frame– Dynamic data, f > 0.01Hz– Calculated from measured
stress combined with stiffness & shear capacity from hull design (customer supply)
• HSM: Main deck stress – May be converted to bending
moment using section modulus– Fatigue calculations
• HSM: Vertical acceleration in the bow
– Dynamic data, f > 0.01Hz– Impact detection and peak
characterization• Data from interfaced systems
– Shaft torque monitoring (torque, power, RPM, thrust)
– GPS• Alarm thresholds can be set for
all parameters• Data values, alarm status and
validity information available for transfer to VDR and/or VMS
Statistics
• All parameters are subject to statistics processing at 5-minute intervals and 30-minute intervals
• 30-minute statistics often used for inspecting for events, and reporting– No. samples, no. mean
up-crossings– Max, min, average, max
peak-to-peak– Standard deviation,
skewness, kurtosis• Histograms
Objectives
1. Onboard Operator Guidance
Example of layout for detailed view
Objectives
2. Onshore status, maintenance planning, future design
Summary
• The Sir David Attenborough will be fitted with an Ice Load Monitoring System
• HMI onboard, possibility of exporting data to shore for post-processing and reporting
• Data and alarms are available for transfer to the centralized Vessel Monitoring System
• System measures the hull response in terms of bending shear in frames from ice forces acting on the side shell
• Key parameter is the utilization of the local shear stress capacity