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Wind Towers

Why we blast wind towers

Wind towers are normally erected with a 25-30 year life.  They are in remote areas and also very tall so very difficult to access which makes them costly to maintain.  The reason we blast is to get an excellent surface preparation and long coating life.

The coatings we are putting on them are expected to last the entire life of the tower, which is 25-30 years.  It is a big ask for a protective coating in inclement weather conditions, particularly near the coast and some are mounted out at sea.

Abrasive media used on wind towers

Because wind towers are normally blasted in a blast chamber in sections, normally three sections per tower, they are typically using GMA Garnet, imported garnet or steel grit.  The inside of the tower is also done but they don’t have the same corrosion issues.  Often steel grit is used where a hot metal spray coating is used on the external of the tower.  It is never used on the inside.  The fact that garnet can be used and it is very fast to use, it is the best abrasive.  GMA Garnet is almost always the best abrasive to use inside and out.

Basic equipment requirements

Painting equipment

If doing metal spray you are using hot metal spray equipment, otherwise in a shop, the best equipment to use is airless for the zinc and plural component spraying for the epoxy because you are doing large volumes in a fixed area to minimize your coating use and maximize coating coverage and quality atomization, get even, consistent finish and air assisted airless for a nice finish for the urethane top coat.

Robotic blasting equipment

Because they are being done in blast rooms and it is repetitive work, robotics from BlastOne have proven to reduce production costs massively and give excellent consistency. Robotics on the outside and also robotics on the inside. Those robotics need to have equipment behind them of large bore, high flow, high pressure production equipment to get the maximum productivity out of the robot. This typically means large port Thompson Valves, large bore blast hoses, large air compressors and large blast pots.

Typical coatings for wind towers

Typically with metal spraying, it is usually a zinc metal spray straight onto the surface.  On top of that is a coating of epoxy or urethane coating and that is a very expensive coating, but has been proven to get good coating life.  The other is a three coat system where you are putting on a zinc rich primer, an epoxy build coat and then a urethane top coat.  The reason you have the urethane top coat is to maintain good gloss and cleanliness so you don’t get contaminants sticking to the surface and the chalking that typically comes with epoxy coatings.

Normally in the coating, just without the metal spray, typical DFT is a total of 350-500 microns which is 14-20 mils.  With the metal spray, because it is a very rough finish, the coating on top of metal spray is normally 16 mils.

Safety and Other Considerations

You need to be aware that this is very repetitive work and if you’ve got manual operators you can get misses.  There are nice flat areas but it means the guys often don’t get a break and because they are in there for hours and hours at a time without having to stop to turn the steel, they may get weary and so you may get areas where you may need to go and re-blast, so you need to inspect very carefully

With large rotating equipment you need to make sure you stand out of the way when you are rotating the pipes.   When you have robotics you need to make sure that you are keeping out of the way of the robot because the robot doesn’t know that you are there.

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