Why dehumidification is must for surface preparation and coating?

  • Industry News
  • Jul 30,22
Improper surface preparation accounts for 60 to 80% of premature coating failures. A proper dehumidification system in place helps in achieving the temperature, relative humidity, and dew points necessary for optimally performing coating/painting, says Sanjoy Guha.
Why dehumidification is must for surface preparation and coating?

The operations being carried out in power plants and oil refineries are very complex and critical. Blasting, painting, and coating form an essential part of the mechanism and require a properly controlled environment. In the process, even the slightest presence of moisture can intervene with the efficiency of the entire plant as a whole. Therefore, climate control becomes imperative for carrying out processes in tanks, bullets, columns, reactors, coke drums, vessels, pipelines, etc. 

Moisture has an adverse effect on the processes and many times is inconvenient leading to inappropriate coating. As coating forms a protective layer in the tanks, it is very important to ensure its tangibility. The high levels of humidity foster poor surface preparation, which leads to blistering, cracking, peeling, and cratering on the surface. Improper surface preparation accounts for 60 to 80% of premature coating failures. It substantially reduces the life of the coating system where there is coating failure arising from improper adhesion between the substrate and the coating. 

In a factory setting, tanks are places where highly sensitive and reactive chemicals like petrochemical, chemical gases, etc. are stored. Here, the improper coating has a damaging effect on the surface with the potential to dilute and contaminate the products inside. As a result, during monsoon, the coating process is delayed and at times halted due to the high proximity of humidity in the air. Compounding the already existing problems, humidity stimulates condensation on the metal surface during the night as a consequence of cold weather. This is responsible for corrosion commonly known as rust blooming or flash rust. All the factors together delay the completion of the project and impair the productivity of the plant acutely. 

Here, installing dehumidification solutions enables blasting, painting, and coating throughout the year irrespective of the surrounding weather conditions. The downtime of the plant due to bad weather is eliminated successfully and contributes majorly to reducing the project time and cost by 35%. In case the dehumidification system is not employed then blasting is conducted in a phased manner which is immediately followed by painting to avoid any condensation in the time interval. This is a hectic process that is costly as well as time-consuming. On the other hand, conducting such processes in the presence of a proper dehumidification system supports the entire blasting of the tank as a whole in a single go which is followed by the complete painting of the tank in a continuous process. This approach where each step follows suit in a synchronised manner is way more economical and saves time. 

Looking at the destructive impact of the moisture, a proper dehumidification system in place helps in achieving the temperature, relative humidity, and dew points necessary for optimally performing coating/painting. It is adept at meeting the temperature and humidity conditions as per the technical specifications of the industry which enables timely completion of the project. In the process, the advanced technology also ensures a clean and stable environment providing the prerequisite conditions for industrial coating. 

The advanced dehumidification technology maintains the RH inside the tank at less than 55% while keeping the temperature within the thin bracket of 30°C to 35°C for the entire blasting, painting, and coating jobs and during the night as well. It is highly adept at achieving a constant dew point differential of -5°C between the air and the surface temperature of the sheet to be coated. Along with this, the system maintains a -12°C dew point difference between the air enclosed within the tank or silo and outside air.

Adding on to the advantages, opting for a dehumidification solution for the coating process is comparatively 2-4% lower than the total cost of corrosion preventive painting. Hence, it is the most cost-effective and simple solution permitting proper surface preparation and coating application. By maintaining the humidity level within a very narrow range, the moisture from the coating system is eliminated. This is a very important measure in preventing condensation and rust bloom throughout the blasting and painting process. It intervenes with the prospects of blistering, and curing failures and provides anti-corrosive painting that strengthens the inter-coat adhesion that increases the coating life by 1.5 to 2 times. 

While ensuring effective surface preparation to ease the process of coating, the ventilation systems in the technology achieve a conducive environment for comfortable working environment inside the tank. Considering that tanks can be categorized as confined areas with innately dangerous settings, working in an enclosed space is very risky. Therefore, it is imperative to make arrangements for the safety and welfare of the workers working inside. Additionally, during blasting certain hazardous fumes and inflammable vapors are released which only raises the temperature inside. The ventilation system controls the temperature and renders a safe confined space for the safety and productivity of the workers. 

Cumulatively, the dehumidification system is essential for reducing the downtime of the refineries and power plants. It provides ideal solutions for seamless conduction of all the critical operations concerning blasting, painting, and coating along with other intricate processes in the plant.

About the author:


Sanjoy Guha is the Chief Operating Officer of Technical Drying Services Asia Pvt Ltd (TDS) - a part of Pahwa Group.

           

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