Words: Morgan Troedsson, Product Manager, FORCE Technology
A familiar commentator in the pages of PES, Morgan Troedsson of FORCE Technology is one of the world’s foremost experts when it comes to blade inspection (and a lot more besides)…
Every manufacturer of rotor blades for contemporary wind turbines is concerned with efficient and safe Quality Assurance (QA) of blade integrity. The manufacture of blades is a rather manual layup and assembly process, where variability in quality is a key issue for the ultimate blade performance.
Automated ultrasonic inspection systems have been successfully applied for a number of years. They follow a continuous evolution, from uncomplicated manual inspection systems, to more advanced track scanner and crawling scanner concept. A regular meander scan pattern is currently the state of the art. It provides high resolution 3D data on the inherent composite structure.
In recent years the fatal issues with fibre misalignments, UD fibre waviness (wrinkles) in spar caps and girders, was commonly recognised. Span-wise line scanning was established as the most suitable method to capture UD fibre contour data on waviness properly. Multiple line scanning is today setting a new standard for high performance ultrasonic blade inspection.
The concept with autonomous scanner systems has also been exploited recently. They are based on a mobile self-propelled fork lift chassis, carrying all the scanner mechanics, cranes, ultrasonic probes and required control units for safe data handling and physical manipulation.
Vertically oriented blades
Non-Destructive Testing (NDT) on vertically oriented rotor blades has been a request for some of years. The evolution has also brought a couple of scanner systems of this nature to the market. In 2013, FORCE Technology introduced a novel autonomous Mobile Blade Scanner concept [AMS-60]. A regular meander scanner manipulator in vertical orientation is attached to a customised fork lift truck base structure, equipped with an added crane handling device.
Perfect coupling of the ultrasonic contact probes to vertical surfaces has been a major challenge. Efforts were granted with a unique and successful coupling solution. Then high performance ultrasonic blade inspection became feasible, even when blades were available in vertical orientation only – the normal storage position for blades. Added to that, continuous NDT on very long blades became feasible, managed by only a single operator. A complete blade survey is accomplished in short inspection time (two hours).
The ultrasonic array
In 2014 FORCE Technology proudly announced a revolutionary inspection concept, based on the Mobile Blade Array Scanner [AMS-71]. It is equipped with a unique full size 24 channel probe array (Fig 3), collecting NDT data in a multiple line-scan mode. P-scan multi-channel electronics and software may record, collect and analyze scanning data from the load-bearing spar caps (girders) and bonding to internal shear webs.
Inspection speed
The greatest revolution comes from the inherent performance of the Mobile Blade Array Scanner. Simultaneous multi-channel line scan data handling allows for an unbeaten high inspection speed, reaching 5-7 metres per minute (Fig 4).
All is obtained with a pre-determined resolution for detection of hidden flaws. Anything invisible in the vital blade structure may be disclosed for proper QA of any OEM rotor blade.
The capacity for full spar cap inspection on 60-80 meter long rotor blades is within 60 minutes, both blade sides covered. Another advantage is that only one single UT inspector is required to operate this revolutionary mobile blade array scanner. Keeping the line scan principle in mind, the accuracy for monitoring and sizing of any UD fibre waviness (wrinkles) is excellent.
This is not compromising the ability for full and accurate girder bond-line assessment. Data on the embedded spar cap (girder) structure will be included without extra work.
Future prospects
Today there is a fortunate trend in the OEM blade industry to consider and invest in smart automation in various steps during blade manufacture:
Fibre layup, for the basic FRP composite shell, spar and web components.
Infusion and moulding of the basic FRP composite blade shell and shear web components.
Adhesive bonding of the assembled integer rotor blade.
Finishing, with flash milling, surface grinding and protective painting.
The demonstrated Blade Array Scanner concept may quite easily be adapted to contemporary automated robot systems, to accommodate the full capacity for an integrated system approach. The multiple probe array may be conveniently attached to autonomous robot systems. When the OEM industry is ready for this expansion in automated technology, the required advanced NDT inspection technology is available.
These innovative blade scanner solutions will be shown and displayed at the September WindEnergy Hamburg 2014 event, hall B7, booth B7-427.
Watch the videos
Want to see more? Head to the links below for exclusive content from Force Technology.
Video link: http://www.youtube.com/watch?v=xUoRFQ0LfcY
Video link: https://www.youtube.com/watch?v=_zqWag2E-hM
About the company
FORCE Technology is an independent leading technological consulting and service provider internationally. The company’s target is to offer highly specialised engineering know-how that delivers useful and efficient testing solutions to the wind energy industry.
Solutions we provide enhance customer’s competitiveness and are based on both customer and industrial insight, that we have acquired over 25 years in wind energy business. That alone makes FORCE Technology the market leader in integrated systems for automated quality inspection on rotor blades.
We are currently around 1,300 employees, located at the headquarters in Brondby and with subsidiary companies and multiple local offices in Sweden, Norway, Russia, China, Singapore and the USA.
