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