by Deepak Pahwa, Director, Technical Drying Services (Asia)
Blasting, painting, and coating are inherently complex and critical processes in oil refineries and power plants. Here, even the slightest trace of moisture can interfere with the efficiency of the various operations. This mandates the processes to be carried out under a controlled environment in tanks, bullets, columns, reactors, coke drums, vessels, pipelines, etc. that can aid in curtailing the adverse effects arising from the presence of moisture.
Moisture being a source of inconvenience acutely meddles with the prospects of effective coating which provides a protective layer in the tanks. It is responsible for poor surface preparation giving rise to blistering, cracking, peeling, and cratering on the surface. Approximately 60 to 80% of premature coating failures occur due to improper surface preparation. It shortens the life of the coating system and can even lead to coating failure due to improper adhesion between the substrate and the coating. Tanks are used to store petrochemical, chemicals gases, etc, and improper coating can eventually lead to a damaging effect on the surface and ultimately cause dilution and contamination of the products inside.
Considering the menace moisture can create many times the coating process is delayed or halted during the monsoons when there is high proximity of humidity. Furthermore, condensation occurs on the surface of the metal at night because of the cold weather, which results in a corrosive effect known as rust blooming or flash rust. This can severely curb the productivity of the plant due to the delayed completion of projects. By employing dehumidification solutions blasting, painting and coating can be done all round the year irrespective of the weather conditions. The need for downtime due to bad weather is successfully eliminated which has a major contribution to reducing the project time and cost by 35%.
In the absence of a proper dehumidification system, the staff is forced to conduct phased-wise blasting followed by immediate painting to avoid running the risk of condensation in the time interval. This in turn is a costly and time-consuming process. A dehumidification system in place enables the entire blasting of the tank in a single go and supports the complete painting as a continuous process. Following the step in a synchronized manner proves to be economical and time-efficient.
The advanced technology addresses the issue of moisture or high humidity levels and provides a clean and stable environment for industrial coatings by meeting the temperature and humidity conditions as per the technical specifications. An adequately designed and applied dehumidification system is an ideal solution for achieving the temperature, relative humidity, and dew points required for optimum performance of the coating/painting to enable the timely completion of the project.
It comes with the most cost-effective and simplest solution that is significantly 2-4% lower than the total cost of corrosion preventive painting. The technology permits proper surface penetration and coating application. The air inside the tank is dehumidified to get rid of the moisture from the coating system and achieve and maintain the moisture level within a narrow range preventing the condensation and rust bloom during the blasting and painting process.
The dehumidification system plays an imperative role in achieving the RH inside the tank at less than 55% with temperatures between 30°C to 35°C throughout the entire blasting, painting, and coating jobs and even during the night. It effectively maintains a constant dew point differential of -5°C between the air and the surface temperature of the sheet surface to be coated and at the same time also maintains a difference of -12°C dew point between the air enclosed within the tank or silo and outside air.
Cumulatively, it intervenes with the possibility of rust bloom, blistering, and curing failures. It has an anti-corrosive painting effect which improves the inter-coat adhesion, consequently increasing the coating life by 1.5 to 2 times.
In addition to the above-stated advantages, the ventilation systems is imperative for providing comfortable working conditions inside the tanks. Considering that working inside a tank for painting or coating purposes is done in innately dangerous settings, there is a continuous requirement to make arrangements for the safety of the staff. Moreover, the process of blasting releases certain hazardous fumes and inflammable vapors while increasing the temperature of the enclosed space. Therefore, there is a constant need to provide ventilation solutions as well as control the temperature within the confined space to ensure the safety and productivity of the staff working inside.
Collectively, dehumidification, temperature contol and ventilation control are the ideal solution for ensuring the seamless continuity of all the critical operations pertaining to blasting, painting, and coating as well as other intricate processes in the refineries and power plants.
