Techniques and innovation in

NDT of wind turbines

Manfred Johannes

CSIR

Overview of the presentation

1. Introduction

2. Failures – an overview

3. What information is required for performing effective NDT

4. NDT methods – an overview w.r.t. different components

5. Condition monitoring

6. Innovation

7. Conclusions

• All the components of a wind turbine are highly stressed.

• Foundations

• Bolting as part of the tower structure

• Welding seams in the tower

• Gearboxes

• Bearings

• Rotor blades

• Current design data is based on experience pertaining to smaller

turbines

• Wind turbine technology is again coming up against its limitations

• Concern to:

• Plant owner

• Insurance companies

• Public – indirect consequence for the image of the technology

• Need exists to limit these “negative effects”

1. Introduction

Failures – an overview

Failures - an overview

Failures - an overview

Failures – an overview

Failures – an overview

Failures – an overview

Failures an overview

Failures an overview

Failures an overview

Failures an overview

What information is required

• Baseline NDT results

• Welding

• Bolting

• Manufacturing of gears and gearboxes

• Manufacturing of bearings

• Blades

• Baseline NDT data is in the hands of the OEM

• Assure that the contract demands inclusion of NDT results in

the Quality Packages for every component

• Who should do this?

• Technology partners such as MotMacDonald etc.

• QC personnel of the main contractor or owner

• Data is available and should be at hand for planning in-service

inspections

• Without the baseline data ISI becomes a nightmare!

NDT Methods - an overview

• NDT Process

• Define target flaw – what is acceptable and what can not

be tolerated (Fracture toughness plays a role)

• Perform a technical justification (could also be the

selection of a code)

• Select the NDT technique and equipment

• Develop procedures

• Perform open trials – validate / demonstrate that the

procedure and equipment do find the flaws

• Perform blind trials – qualify the NDT technician

• NDT System

• Procedure

• Equipment

• Technician

• A part of procedures are the reporting requirements

NDT Methods - an overview • Foundations

• Plan Ultrasonic Testing (UT) into the design

• Perform UT at regular intervals

• Adapt technology from seismology

• NDT of concrete – google search 1,6 million hits

• Welding

• Most welding specifications pertain to pressure vessels

• Need to involve a welding engineer

• Plan NDT into the design

• Approve / validate the procedures

• Design the ISI and validate the techniques in the workshop

• Perform ISI at regular intervals (depending on design

stresses and finite element results)

• Bolting

• Approve / validate procedures

• Assure adequate access for ISI

• Perform ISI at regular intervals (depending on design

stresses and finite element results)

NDT Methods - an overview

• Gearboxes , gears and bearings

• Most problems arise due to lack of NDT during

manufacture

• Assure the NDT system is validated

• Blades

• Plan NDT into the design

• Approve / validate the procedures

• Design the ISI and validate the techniques in the workshop

• Perform ISI at regular intervals (depending on design

stresses and finite element results)

Condition monitoring

• Many technologies available

• Vibration monitoring

• Oil analyses

• Acoustic emission monitoring

• Infrared thermography

• Strain gauges

• Must be designed into the plant and monitored

• Plan all maintenance work from

• Baseline NDT

• Condition monitoring results

• Operation parameters

• Do not cut corners

• Develop check lists for every turbine

Innovation

• Where is innovation required?

• Online monitoring

• Access for ISI

• Reduction in outage time

• Reliability of NDT results

• Almost all problems initiate at the rotor blades

• Damage

• Water ingress

• Balance problems

• Consequential damage

• Gear boxes

• Bearings

• Towers

Innovation – remote monitoring by IRT

• Turbine blades are continually stressed

• Heat generated in areas where

• Cracking has occurred (rubbing)

• Delaminations are present

• Water ingresses (temperature differences)

• Bird strikes damage

• Lightning strikes

• Need to monitor the blades online – in operation

• New IRT lens technology – 3-degree telelens

• Already used for flame monitoring in chemical industry

• Need to adapt for online blade monitoring

• Log-in thermography

• Transient thermography – difference between day (sun

shine) and night

• Think of “new” data capturing modes

Innovation for access

• Crawlers

Conclusions

• Even though the NDT Techniques and procedures are “old tacky”

the wind energy industry is a young industry – needs to take note

of what should and can be done

• Paper read at WESSA – spend 10% more initially and add easily

10 to 20 years to the life of the plant.

• If you fail to plan, you are planning to fail – also in NDT

• NDT is already being performed by the OEM, insist on the

information

• The owner has a right to the data – make it part of the

contract

• The O&M company can not operate effectively without the

data

• At the latest the data will be needed at the end of contract

negotiation or when a due diligence is being performed when

plant changes hands

1. Cracks in onshore wind power foundations - Causes and consequences, Elforsk rapport 11:56

2. On the analysis of the causes of cracking in a wind tower; R. Lacalle et al Centro de Desarrollo Tecnológico de la Universidad de Cantabria (CDTUC), Cantabria, Spain

3. Analysis and design of the prototype of a steel 1-MW wind turbine tower Lavassas et al. Department of Civil Engineering, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece

4. Failure analysis and risk management of a collapsed large wind turbine tower Jui-Sheng Chou ⇑, Wan-Ting Tu, Department of Construction Engineering, National Taiwan University of Science and Technology (Taiwan Tech), 43 Sec. 4, Keelung Rd., Taipei 106, Taiwan

5. Wind Turbine Gearbox Failures, Robert Errichello, GEARTECH 6. Blade monitoring, Steve Baines, TWI, Cambridge, UK 7. Flame monitoring, Automation Technologies, Bad Oldersloe, Germany 8. Wind Turbine Inspection – a strategic service, C. Hilario, DEWI, France

Sources for pictures and data

Thank you