Amchem completed, during January 2002, a landmark project for NTPC / NBCC at NTPC’s 2 X 500 MW Simadhri Thermal Power Project near Visakhapatnam. We finished coating approx. 600,000 sq feet of Concrete Cooling Tower with 2,000 Microns Purethane® Coatings (in NDCT – 1). It was a technologically and logistically challenging project and Amchem’s performance in this ‘first of its kind’ project was highly acclaimed.
Presently (Early 2012), cooling tower projects with area exceeding 3.6 Million Sq. Ft are ongoing.
NTPC Simadhri ProjectThe Natural Draught Cooling Towers at Simadhri are one of the largest in the world with a Height of 165.45 m. Each tower has 32,000 CuM of Concrete and 4,700 MT of reinforcing steel. Approx. 60,000 M3 / Hour ( 60 Million Litres / Hour ) of Seawater at 1.5 cycles of concentration flows through the towers.
To prevent concrete degradation and re-bar corrosion in the highly corrosive sea water immersion / splash environment, a number of measures were taken in the design. Principally, all concrete and steel surfaces in contact with sea water / sea water spray i.e up to drift eliminator level ( 15 m ) were coated with 2.00 mm of Purethane® , 100% Solids High Build Polyurethane Coating. The polyurethane coating provides a strongly bonded, tough, impermeable membrane, which prevents transmission of Chlorides, Sulphates and greatly retards transmission of Oxygen and Water Vapour into the concrete and underlying reinforcing steel. Additional corrosion protection measures include use of Sulphate Resistant Cement with 5-8% C3A content & Marine Grade CRS. Above the drift eliminator (coating line), the shell structure used an organic migratory corrosion inhibitor (MCI) .
The MCI did not prove effective in service with future design calling for coating on the entire internal shell wall. This will also prevent water percolating from the shell wall matrix into the racker columns from behind the coating.
The internal structure to be coated was very complex. It included the Fill Support Structure, Racker Columns, Baffle Walls, Duct, Walkways, Pond Floor, Pond Wall etc. At heights up to 15 metres ( 50 feet ) . The fill support structure was a maze of vertical lower columns (> 400 No’s), upper columns ( > 800 No’s ), diagonal columns and beams ( > 3,000 No’s ).
The entire structure was blast cleaned, primed using Purethane® PIV, 100% Solids Damp Tolerant Polyurethane Primer and coated in situ.
In order to access the various parts of the structure Amchem deployed specialised high reach equipment such as articulating booms, scissor lifts, manlift etc. The constrained spaces made access to the surface difficult and the high reach equipment served the purpose admirably. Three plural component airless spray equipment from Graco Inc., USA were used for the coating. In addition several blast pots and air compressors were deployed for surface preparation. The Graco equipment performed reliably as always with minimal repairs and downtime. Highly skilled crew of around 45 people conducted the surface preparation and coating application.
More than 8,000 litres of Purethane® IV, 100% Solids Damp Tolerant Polyurethane Primer and more than 135,000 Litres of Purethane® , 100% Solids Polyurethane Coating were used for the coating operations. Purethane® PIV is a specialized primer which penetrates into the concrete, sealing and consolidating the surface for improved adhesion. Water tolerance allows it to be sprayed onto damp concrete with excellent bond between the primer and concrete as well as primer and coating.
Field tests were conducted regularly for Hardness, Film Thickness, Coating Adhesion with 100% of tests meeting specified requirements. Samples were also drawn and sent to the Indian Institute of Chemical Technology (CSIR), Hyderabad for testing coating parameters like Tensile Strength, Recoverable Elongation, Water Vapour Transmission, Flexibility, Impact and Abrasion Resistance. 100% of tests far exceeded the specified parameters.
Water from the condenser is brought into the Cooling Tower through 3.2 m dia MS Pipe up to Cooling Tower Bottom, which is bifurcated into 2 pipes of 2.4 m rising up to 15 metre level. They enter the cooling tower and discharge hot water into RCC hot water ducts in each half. The hot water is further distributed through secondary ducts from each main duct and AC pipe network. The water is sprayed downwards from the AC pipes through PVC fills. Incoming air from gaps in the racker column cools the water, which collects in the basin.Pond wall and floor were coated after the fill support structure was completed.
We will be happy to provide turnkey installation on your upcoming projects!
Amchem Products Pvt. Ltd
A-79. Sector 58, NOIDA 201 301, India
Tel : 0120 - 2580121 / 4325540
Fax: 0120 - 2581351
E-Mail : firstname.lastname@example.org
Website : www.amchemproducts.com