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s part of the push to betterprotect the environment byestablishing alternative energysources for the future, off-shore wind farms havebecome an increasingly popu-lar approach for producingcleaner energy – particularly inEurope. These wind farms con-

sist of a series of wind towers mounted on topof steel foundations that are driven into theseabed. Like offshore oil and gas platforms,these wind farms are exposed to harsh, corro-sive conditions including seawater exposure,wet-dry cycles and temperature variations; andprotective coatings are an effective way ofshielding these structures from the conditionsthey face.

Topsides, jackets and other accompanyingcomponents for offshore wind farms havelarge dimensions and weights that cannot beaccommodated within most paintwork facili-ties. Accessibility in terms of height and widthis also a huge challenge with respect to safe-ty. The design of scaffolding or the applicationof special cherry pickers has become a spe-cialty in order to keep the production processunder control.

This article describes shop coating thelarge steel jacket foundation membersemployed at the Thornton Bank Wind Farmproject, recipient of the E. Crone Knoy Awardat the SSPC 2014 Structure Awards.

About Thornton BankThe Thornton Bank Wind Farm, owned andoperated by C-Power N.V., is an offshore windfarm located 19 miles from the Belgian coast-line on a sand bank in the North Sea. It con-sists of 54 wind turbines, which produce atotal of 325 megawatts of power – enough for

300,000 families, according to the C-Powerwebsite.

Construction of the wind farm took place inthree phases, beginning in 2007. The firstphase included just six turbines, while the addi-tional 48 were installed during the second andthird phases. The third phase wrapped up inJuly of 2013, making the wind farm fully opera-tional.

The wind towers are placed on top of steeljackets, which are driven into seawater thatranges from 12 to 27 meters (40 to 90 feet)in depth. The turbines stand 157 meters (515feet) tall, and their rotors have a diameter of126 meters (413 feet).

Jacket ConfigurationDuring the second and third phases of the pro-ject, the contractor was responsible for fabri-cating and coating 48 steel jacket foundationsfor the wind turbine towers and one additionalsteel jacket foundation for an offshore trans-former station. This fabrication required theuse of large, modern blast and paint facilitiesbefore the parts could be loaded onto a bargeand sent out for installation at the wind farm.

The jacket foundations consist of a steeljacket with four legs that is assembled in sev-eral different pieces including:• The midsection (or transition piece) betweenthe main jacket and the wind turbine towersection, upon which the rotors are mounted;• The main jacket part;• The pile stoppers (four per jacket), whichconnect the main jacket and the pinpiles; and• Secondary steel elements such as anodes,boat landings and ladders.

In total, the contractor produced the 48jackets over a two-year period. The steel jack-ets weighed a total of 27,840 tons and werepainted using 96,000 liters (25,360 gallons) of

epoxy and polyurethane coatings. In the end,the contractor logged a total of 32,000 man-hours for blasting and 144,000 man-hours forstripe coating, masking and painting.

Blast and Coat FacilitiesThe jackets for the Thornton Bank project wereblasted and coated in the contractor’s threelarge blasting and painting facilities in Belgium:Iemants in Arendonk, Willems in Balen andSmulders Projects Belgium in Hoboken.

Secondary steel was coated at Iemants inArendonk and the midsections were painted inBalen at the Willems facility. The jacket legsand bracings were welded together accordingto a 3-D model and painted in the new paintshop at Smulders Projects Belgium in Hobokenafter the midsections were secured to the restof the jacket. These facilities have special fea-tures which are described as follows.

Arendonk FacilityIemants in Arendonk has a workshop area cov-ering over 50,000 square meters (538,200square feet). In addition to components for off-shore platforms and towers, Iemants producesparts for bridges and buildings. The blastingcabin is 40 meters (131 feet) long, 10 meters(33 feet) wide and 8 meters (26 feet) tall. Thecabin is located next to the production hall sothat transport carts can be driven directly intothe blasting cabin. After blasting, these cartsgo to the paint shop through the back of theblasting cabin.

Balen FacilityThe midsections for the Thornton Bank jack-ets were assembled, blasted and painted atWillems facility in Balen. This facility’s recent-ly built paint shop covers 2,430 squaremeters (26,147 square feet). Inside, there is

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suction device was also constructed, with acapacity of 85,000 cubic meters(3,001,775 cubic feet) per hour.

Hoboken FacilityThe third and largest production facility isSmulders Projects Belgium, located inHoboken. This facility is divided into threesections, including two production halls and a

dry dock and storage yard. The first production hall is 12,000 square

meters (129,168 square feet). This hall con-tains blasting and paint workshops, with a roofthat opens in eight sections so that parts canbe lowered in using overhead cranes.

The blasting cabin is 44 meters (144 feet)long, 15 meters (49 feet) wide, and 15 metershigh. Four blasters can blast manually, butthere is also a robot that can take over theblasting work. The robot is used for items thathave common dimensions and is controlledentirely by computer. The dust suction capacityamounts to 24,000 cubic meters (847,560cubic feet) per hour.

This facility is mainly used to coat transitionpieces for offshore wind farms. These transi-tion pieces are placed on top of a monopile,which is drilled into the seabed. The transitionpieces have an upper flange upon which thewind tower is mounted, as well as working plat-forms inside and boat landing areas on the out-side. They are also equipped with J-tubes forelectrical cables.

A typical transition piece weighs approxi-mately 240 tons, has a 6-meter (20-foot) diameter and is 30 meters (98 feet) long. Atransition piece such as this undergoes a NOR-SOK standard system treatment, which meansthat three coats are applied to the outside andtwo to the inside. (NORSOK is a Norwegianacronym for the Norwegian shelf competitiveposition, a project conceived in order to reduceimplementation time and costs for constructionand operation of offshore installations on theNorwegian continental shelf.)

a blasting cabin of 352 square meters(3,788 square feet) with a height of justover 7.6 meters (25 feet). The roof of theblasting cabin can be opened completely sothat larger pieces can be placed insideusing the overhead crane. The blastinginstallation was constructed in 2011 andfour to six blasters can work simultaneously.In order to facilitate this, an adapted dust

By Ronny Van Poppel, Project Staff, Smulders Group

Shop Coating Steel for the Thornton Bank Wind Farm

In-Shop to Offshore:

After fabrication and coating, steel jacketswere placed offshore at the Thornton Bank.All photos courtesy of Ronny Van Poppel,Smulders Group

largest of items. Inside, there is a blastingcabin with removable doors so that the heavypieces can be transported from the blastingcabin to the paint shop. The roof opens pro-viding access to the gantry crane allowingcomponents weighing up to 500 tons to belifted in.

The blasting cabin is 56 meters (184 feet)long, 26 meters (84 feet) wide and 23 meters(74 feet) high allowing four to six blast to workat the same time. The dust suction systemoperates at high efficiency affording blastersincreased visibility. Cherry pickers are used toblast at heights and are placed between theitems by the overhead crane.

The paint shop has the same dimensions asthe blasting cabin and contains moveablescaffolding on each side which can be adjust-ed to fit the shape of the construction. Cherry

54 JPCL August 2014 / paintsquare.com

The components are coated as soon aspossible after the blasting check, which is con-ducted according to ISO 8501-1, “Preparationof steel substrates before application of paintsand related products.” Dusting, taping and pro-viding the necessary stripe coat are time-con-suming processes that can only be done man-ually. The transition piece and its correspond-ing attachments must be coated properly; nosingle spot can remain insufficiently coveredwith paint. The tubular section, with attach-ments, is lifted into the blasting area and com-pletely cleaned. It is then transported to thededicated and conditioned paint area.

The 48 main jacket parts for the ThorntonBank project were primarily painted in the sec-ond production hall. At 14,720 square meters(158,387 square feet) and 35 meters (115feet) high, this facility accommodates the

in- shop to offshore

(Top of page and above): Individual steel mem-bers are brought to one of the contractor's largeblast and paint facilities, where they are weldedtogether, blasted and coated.

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pickers can be used to access the insides ofthe jackets.

Outside the paint shop, the site has accessto the harbor basin, which can accommodate

coasters and barges. Once the jackets for theThornton Bank were finished and coated, theywere transported to this area, loaded ontobarges and shipped offshore for placement.

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in- shop to offshore

The Paint SpecThe paint specification, developed by the con-tractor and the coating manufacturer, calledfor two coats of a two-component, low-VOC,high-solids modified epoxy barrier coat,designed to give long-term protection, appliedat dry film thickness of 375 microns per coat;and a topcoat of a two-pack, acrylicpolyurethane finish, providing excellent durabil-ity and long-term “recoatability” with a dry filmthickness of 80 microns.

SSPC Structure AwardIn 2014, this project was awarded SSPC’s E.Crone Knoy Award at the annual StructureAwards ceremony. This award, named afterthe late founder of Tank Industry Consultants,recognizes coatings work that demonstratesinnovation, durability or utility. It is given foroutstanding achievement that may include

The contractor's facilities had enough space toaccommodate the largest items for blastingand coating, including the main jacket sections.

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excellence in craftsmanship, execution of work or the use of state-of-the-art techniques and products to creatively solve a problem or pro-vide long-term service.

The complexity of the project, along with the challenges the con-tractor and subcontractors faced regarding production, worker safetyand meeting deadlines, are among the reasons this project was cho-sen as the award recipient.

About the AuthorRonny Van Poppel is a project staff mem-ber for Smulders Group, a steel construc-tion contracting company based in Belgiumthat specializes in wind turbine construc-tion. He has almost 40 years of experiencein the industry and is an SSPC ProtectiveCoatings Specialist, an SSPC BridgeCoating Inspector and a NACE Level 3-cer-tified Coating Inspector. JPCL

(Above and below): Finished jackets were loaded from the facility ontobarges and then shipped out for placement at the Thornton Bank.

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