Humidity Requirements for Painting in a Process Plant

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Environmenta humidity affects quality of cleaning and painting on metal surfaces. Any water on metal surface is bad for painting work. It is necessary to ensure humidity and air temperature is within particular range for good quality of painting job.

  1. Blast cleaning shall not be performed where dust can contaminate surfaces undergoing such cleaning or during humid weather conditions having humidity exceed 85%.
  2. The temperature of the Pipe/Equipment to be painted shall be at least 3 deg.C above the dew point.
  3. Desiccant type De-humidifiers shall be used to maintain the Relative Humidity and Temperature during the application of coating materials.
  4. The RH (Relative Humidity) shall be maintained at less that 60% and air temperature inside the tanks in the range of 25 – 40 deg.C shall be maintained for proper chemical curing of the two component (epoxy) internal coatings of storage tanks.
  5. The Dehumidifiers shall be based on at least two air charges per hour of the enclosure.