Humidity measurement in Paint Spray Booths

Paint booths in general

Spray painting has existed since the late 1800’s. The technique was developed in a bid to accelerate painting times compared to brush painting. Spray painting is a method of painting where paint is atomised onto a surface via a spray gun. The paint is mixed together with a solvent or water (called a carrier) so that it can be applied correctly.

Cars, aircraft, boats and other such equipment is often spray painted in a spray paint booth.

A spray booth is an enclosed room, designed for spray painting. Depending on the requirements, the booth may be equipped with filtered air to avoid getting dust in the room and an exhaust air system to clear the fumes of any evaporating solvents used during the spray painting process.

Regulations, such as the Occupational Safety & Health Administration from the United States department of Labor have a criteria for design and construction of spray booths state that a spray booth is: a power-ventilated structure provided to enclose or accommodate a spraying operation to confine and limit the escape of spray, vapour and residue, and to safely conduct or direct them to an exhaust system.

Spray paint booths regulate relative humidity, temperature, airflow and pressure to ensure a quality coating and a perfect curing.

Certain paints contain flammable solvents which release flammable fumes: in this case explosion-proof components are required for all measuring equipment that come in contact with the fumes.

Paint dry and cure times
Paint dry and cure times

Why do we need to monitor and measure in Paint Spray Booths

In order for paint to dry correctly within the paint booths, the relative humidity and temperature levels should be within the following conditions:

 – 65 to 75%rh
 – 20 to 24°C

Based upon the intake air, there may be a requirement to either dry or humidify the air in order to reach the desired values. From the temperature side, exactly the same thing: the air might need to be cooled or heated depending on the outside temperature.

Additionally, paint booths might have a  separate monitoring system inside the booths in which the different elements are painted. In order to ensure that the paint is  applied correctly to the element to be painted, it is important to ensure that the surface temperature of the element is not too close to the dew point level in the booth.

If the surface temperature of the element to be painted is close to the dew point temperature, then there will be risks of condensation forming on the surface of the element. If this were to happen, the coating will not be optimal and the drying and curing phase will not be completed properly and the results could be catastrophic.

 

Rotronic have recently launched a totally new range ATEX (Intrinsically Safe and Explosion Proof) instruments. Paint spray booths typically require ATEX certified instruments.

More details here.

Rotronic ATEX range
Rotronic ATEX range

 

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