Cooling Water Pipe Lining
As part of the 650,00 sq.ft cooling tower coating project for NTPC / NBCC at NTPC’s 2 X 500 MW Simhadri Thermal Power Plant listed above, Amchem was chosen to internally line several large diameter steel pipe (from CW duct to towers) carrying sea water with 2,000 microns Purethane® Coating. The steel pipes carry approx. 60,000 m³/hour (60 million litres/hour) of Seawater and range from 2.4 metres to 3.2 metres in diameter.
Amchem designed and deployed specialized automated blast cleaning and coating rigs for the project. These rigs were motorised for linear travel and contained special rotary blasting/ spray heads. Travel and rotation speeds were controlled by precision variable speed AC drives. This allowed setting of optimum speeds for travel and rotation in accordance with required blast standards (SSPC SP-10), coating thickness and tip spray rates. Coating thickness was very even using the automated system with spot variation of not more than 100 microns.
Regular field tests conducted on adhesion reported results of up to 16 N/mm² (2,300 Psi) against the 8 N/mm² minimum specified. The pipe lining was holiday tested at 6,000 V and a pinhole free coating was provided. 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 exceeded the specified parameters. The pipe has been in operation since 2001 with zero defects or maintenance.
Water from the condenser is brought into the Cooling Tower through 3.2m diameter MS Pipe up to Cooling Tower bottom, which is bifurcated into 2 pipes of 2.4m rising up to a 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. Afterwards the water is sprayed downwards from the AC pipes through PVC fills where incoming air from gaps in the racker column cools the water, and collects in the basin. We coated the pond walls and floors last after the fill support structure was completed. NTPC’s Simadhri Thermal Power Plant project was logistically and technically challenging, however Amchem received great praise and our performance and coating was highly acclaimed by NTPC/NBCC.
15ᵗʰ Anniversary Revisit
Purethane – Performance on Steel
For NTPC’s 2 X 500 MW Simadhri Thermal Power Plant, Amchem has carried out the
following Large Diameter Seawater Pipeline coating with 2,000 Microns Purethane ®
- Simhadri-I, 2002: Unit 1 & 2; 2 X 500 MW) | 2.4 & 3.2m MS Pipe Of Cooling
Tower, through M/s NBCC Ltd. In service for the past 15 years.
- Simhadri- II, 2012: Unit 3 & 4; 2 X 500 MW | 3.2m MS CW Pipe, through
M/s Kirloskar Brothers Ltd. In service for the past 5 years.
Amchem had used first of its kind (in India) automation for blast cleaning and coating using
custom designed equipment. Even though sand was a permitted abrasive in the specification, we instead chose to use Granulated Copper Slag, which was much more expensive, on technical grounds at our own cost. As part of the long-term performance review exercise, Amchem personnel visited the plant towards the end of June 2017, after more than 15 years of operation. We had the following insights in retrospect:
- The Purethane coating is fully intact and working properly, continuing to protect the
pipeline, many man years after the installation.
- There have been no repairs carried out ever on the installed coatings since
Pipelining Track Record
Since the first project at Simhadri, Amchem has emerged as the preferred vendor for lining large diameter cooling water pipelines for the power generation sector. This is due to the high quality of its Purethane®, 100% Solids Polyurethane Coating materials as well as the application/ technical capability of Amchem crew. All operations – blast cleaning & lining are fully automated, whether above ground or in the trench. Our product performance, delivery as well as documentation & response time has been rated excellently by customers – we are very proud of this achievement!
- NTCEL Vallur, IVRCL | 3.2 and 2.2m diameter pipe
- NTCEL Vallur, Gammon India | 2.2m diameter pipe (replacing failed vendor)
- NTPC Simhadri, ERA Infra | 3.2 m diameter pipe
- NTPC Simhadri, KBL | 3.2 m Dia Pipe (replacing failed vendor)
- APGENCO Krishnapatnam, Tata Projects | 0.9 – 3.7m diameter pipe
- MEIL, Turicorin Power Project | 1.2m diameter pipe
- BHEL, Maitree Power Project | 1.2 – 3.3 diameter pipe