Monitoring the effects of ice forces with the Sir David Attenborough Karianne Pran, MSc. VP Engineering 13. November 2017
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