Engineering measurements from subsea laser scanningData gathering and analysis

Presented by Brett Lestrange, Regional Director Europe

Introduction

• There is a growing number of aging subsea assets in use today

• Repairs and modifications are required to prolong lifespan

• Engineering data for assets may be limited, or not available

• Ability to produce accurate “as is” engineering models is hugely beneficial

• Historically photogrammetry, sonar and physicalmeasurements have been employed subsea tocollect engineering data

Laser scanning applications

• Modelling of subsea components

• Spool Metrology

• Pipeline damage inspection

• Inspection of wear on subsea components

• Structural corrosion monitoring

Subsea lasers

• An increasing number of laser systems are available for subsea use

• The two most common types of subsea laser scanners Triangulation Time of Flight (TOF)

• All subsea lasers face similar challenges Mobilisation Subsea Data collection Data processing Report generation

• Laser scanning creates an almost instant3D point cloud representation of an objects surface features

Benefits of subsea laser scanning

• Non contact measurement

• Scanned area data available in seconds

• Diver or ROV deployed

• Ultra High Resolution data

• Sub millimetre measurement capability

• Data can be converted to CAD models for measurement and analysis

Image of surface corrosion

Meshed scanned data

Subsea laser scanning constraints

• Good visibility is essential

• Poor visibility will result in increased noise within the data

• High reflectivity within the scan creates noise within the data

• Maximum range for triangulation laser systems is typically 10m

• Ambient light causes reduced laser line detection

• Overall accuracy of the data decreases with range

Example laser scanning project

• Wellhead laser inspection

• Well-bay laser inspection

• Diver deployment

• 110m water depth

• Less than 24hr inspection time

• Sub millimetre data analysis

Project planning and deliverable requirements

• Clearly defined measurement requirements

• A “Scan Plan” is essential to ensure coverage

• Agreed reporting format

• Project specific system integration

Typical diver deployment configurationSubsea equipment including laser scanner,

pan & tilt multiplexer

Subsea laser scanner

Surface equipment including control software and multiplexer console

Control laptop

Multiplexer topside

150m power and fibre communications umbilical

Multiplexer subsea bottle

Final Acceptance Test (FAT)

Subsea deployment mock up Computer suite

Data processing (noise)

• Noisy data requires filtering

• Noise from turbidity

• Noise from reflections

• Initial noise is filtered through software

• Final filtering performed manually

• Differing processing requirements from topside laser scanning

Processed data (noise)

Before noise filtering After noise filtering

Data processing (scan registration)

• Multiple scans stitched together

• Co-locating features between scans (REGISTRATION)

• Registration targets may be employed

• Initial manual feature selection

• Software automatically aligns selected features

Processed data set

• Registration targets removed during processing

• CAD models can be created from the processed data

Meshed data set CAD model

Example measurements

Unrolled heat map

Deformation analysis

• Comparison between the scanned data and the CAD model• Measurements in millimetres

Example measurements

• Horizontal deformation

• Vertical deformation

• Ovality analysis

Horizontal section Vertical section

Summary

• An emerging subsea technology • Specialised personnel are required

to deliver results• Subsea laser scanning requires a

different skillset to that for topside scanning

• Deliverables must be clearly defined from the outset

• Detailed project preparation and FAT minimise offshore risks

• Scan data can provide critical sub millimetre measurements of subsea infrastructure

Questions

Engineering measurements from subsea laser scanningData gathering and analysis