Wind Turbines - Metal Spray Protection
Descon Quimica of Spain has supplied a metal spraying system for wind turbine components to Granallados Molinero S.L. Molinero approached Descon because of its expertise in supplying automated metal spraying equipment and their industry specific expertise in relation to wind turbines. Molinero was new to the industry of thermal spraying wind turbine components and wanted to utilise the benefits of automating the process. This is in contrast to a lot of wind turbine thermal spraying which is carried out manually.
The issue surrounding atmospheric corrosion of wind turbines is significant, particularly considering that many turbines are situated in coastal/saltwater environments. It is for this reason that many manufacturers of wind turbines specify thermal sprayed zinc or zinc/aluminium alloys as a method of corrosion protection, to all or part of the steel wind turbine structure. The joint areas of the columns and the components being assembled are thermal sprayed to offer corrosion resistance in areas where paints may be damaged during assembly of these large items. Thermal sprayed coatings offer a very resilient finish, which is less susceptible to damage than many paint coatings.
For many years, Descon Quimica has been supplying metal spraying equipment and materials for the protection of wind turbine parts throughout Spain, as well as other anti-corrosion and engineering applications. Descon provides anti-corrosion protection for diverse industries including, liquid gas bottles, tube manufacturers, beer tanks, silos, parts of railroad bridges and aqueducts.
The spray equipment is being used by Molinero to spray components within the assembly that support the turbine blades. The actual coating with pure zinc is only one part of the process. To ensure optimum adhesion of the coating, the surface of the turbine part is first grit blasted to a profile of around 75 microns and a cleanliness of SA3. A robot mounted arc spray system then applies an even 120 microns of Zinc at a spray rate of up to 36 kg/hr. A final coating of epoxy paint is then applied. This is an excellent way to protect wind turbines from corrosion and offers up to 20 years protection.
The adaptability, flexibility and ease of use of the Metallisation Arc Spray equipment, has made the transition into metal spraying much easier for Molinero. One of the main reasons for selecting the Metallisation ARC140 (superseded model) is that it is easily integrated with the robot cell, which then controls the spray gun to start and stop the spraying. The 20m push / pull supplies package also allows the energiser, wire and wire dispensing system to be located outside the dusty spray booth, giving the system greater reliability.
There are many advantages of automating the spraying process. Obviously, these generally apply when there are batches of identical parts to process, as is the case at Molinero. Automatic spraying will enable a very uniform coating thickness. Not only is this beneficial to the coating quality but also as a commercial value. Typically, if components are manually sprayed and the specification calls for a minimum coating thickness of 120 microns, it is very difficult to maintain a consistent coating depth. Even an experienced operator would usually coat to a minimum of 120 microns and in places, up to 180-200 microns or more. Through automation, an even 120-micron coating is achievable, offering on average, material savings in the region of 40%. The spraying environment is also noisy and dusty. Through automation, the operator can remain outside the spray booth area.
Major advantages of the Arc Spray process are:
- That the coatings are available for almost immediate use, with no drying or curing times.
- There is no risk of damaging the component.
- The deposits possess a higher degree of bond strength than most other thermally sprayed deposits.
- The use of only compressed air and electricity mean more economic coatings.
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