Purethane coatings have excellent salt water corrosion resistance (pass > 10,000 Hours Salt Spray Test) as well as outstanding impact and abrasion resistance making them the coating of choice of the power industry for lining Cooling Water (CW) and Make Up Water (MW) Pipelines. Robotic surface preparation and lining equipment allows high quality, uniform application on site. Smaller diameter pipes can optionally be lined at the pipe manufacturer’s coating shop.
Thermal power plants use 2.2 – 3.7 m diameter Cooling Water (CW) pipes and 0.8 – 1.4 m diameter Make Up Water (MW) Pipelines. The raw cooling water is often saline/ corrosive. Most coastal power plant use Seawater for cooling which is very corrosive. These are either ‘once through’ or re-circulating systems.
In order to provide lasting protection against corrosion, Purethane Coatings are used to line these pipes. Their hydrophobic and inert nature allows excellent saltwater resistance. Hardness and Flexibility is a unique combination found only in 100% Solids Polyurethane. This combination allows them to have excellent high impact and abrasion resistance which prevents handling damage and abrasion from solids particulates in water stream.
Purethane coatings have very low permeability due to its hydrophobic nature. Low permeation prevents transmission of corrosive Ions & Gases to the substrate.In an operating power plant, shutdowns are infrequent and of very short duration (few days at most). It is practically not possible to conduct a major re-lining exercise. Therefore the lining needs to be maintenance free and provide a service life matching the design life of the power plant. Expected service life of thick film Purethane Coatings is in excess of 40 years i.e. the design life of the power station making them virtually the only practical solution for lining of these pipes.In comparison, 100% Solids Liquid Epoxy and Glass Flake Polyester Coatings are very brittle with low elongation, impact and abrasion resistance making them highly prone to damage during installation as well as in service.
These coatings also shrink during curing and ageing in the service lifetime which lays stress on the bonding surface leading to disbondment. Application of any lining to these large diameter pipes, especially onsite, requires considerable and uncommon technical skills and expertise. Amchem has developed proprietary equipment and application procedures which have been proven over the years for proper application of the coatings. Some instances of early coating failures have been witnessed in the Power sector which can be attributed directly to lack of proper technology, equipment and experience on part of the coating vendors. These have proven very costly for the operators as a single day of shut down in a 1,000 MW mega power plant due to lining disbondment can cost the operators upwards of $ 1 Million.
It is prudent therefore to select a high quality lining product and ensure proper application!