OREANDA-NEWS. In summer 2014 Alstom received an order from WSW Energie und Wasser AG to apply the erosion-resistant protective coating AmStar 888® in the steam generator of the Wuppertal-Elberfeld co-generation power plant. Following an agreed operating time of six months, or around 4,500 operating hours after application of the coating, an independent expert report has now verified the material’s stability and effectiveness.

“AmStar 888® has made a clear contribution towards significantly extending the steam generator’s operating time and thus increasing the period between scheduled downtimes,” says Volker Leonhard, Manager of the Elberfeld and Barmen power plants. “We now don’t have to replace any wearing heating surfaces, which would have taken a great deal longer than applying the protective layer. In the overall cost calculation, the Alstom coating looks financially very attractive.”

The AmStar 888® coating protects materials under high thermal strain in the boiler top casing area from erosion, particularly evaporator tubes and membrane walls. This significantly increases the interval between scheduled outages and also contributes to reduced maintenance costs throughout a power plant’s entire service life.

During an appraisal of the Wuppertal-Elberfeld steam generator last summer, considerable damage caused by mechanical impacts from the circulating bottom ash was discovered on the top evaporator wall. This was despite years of using the best available protective coatings the market had to offer at the time. As a result of this damage, the period between scheduled outages had reduced to less than six months and the damaged pressure parts were replaced several times.

The application of the AmStar 888® coating was intended to prevent deterioration in the old protective layer and the tube steel that was suffering a loss in wall thickness of up to 3 mm per year. After determining the varying level of wear in different areas, the thickness of the layer applied varied between 0.6 mm and 3.0 mm according to requirements.

This inspection confirmed and precisely calibrated the expected erosion resistance of the AmStar 888® protective layer under the extremely tough operating conditions in the steam generator. In the area suffering the greatest amount of wear, a loss of 0.7 mm on average was discovered. This means that the customer can continue operating the boiler with the remaining layer thickness without any further maintenance outlay for the next two years. Assuming another layer thickness of 2.5 mm is applied to the points suffering the greatest amount of wear that have now been precisely identified, the boiler can even be operated for a further three years, or 24,000 operating hours, without any erosion on the base material.