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Finishing Academy Paint Booth Training


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1.1 Introduction

1.2 Crossdraft

1.3 Downdraft

1.4 Airflow

1.5 Filter Replacement

1.6 Temperature and Humidity - Controlled Booths

1.7 Equipment

1.8 Fire Protection

1.9 Conclusion

1.6 Temperature and Humidity - Controlled Booths

 

The cost of heating, cooling and humidification of the replacement air in a paint booth is a cost adder to consider. Temperature and humidity requirements are best defined by the type of paints being used. Optimizing the temperature and humidity to what the paint manufacturer recommends improves the overall quality of the finish, reduces dry times thereby increasing throughput, and decreases paint defects.

The ability to control temperature and humidity in a paint booth can be done by adding HVAC to the air make-up unit. The cooling portion of the AMUs can operate from electric using DX cooling or chilled process water from a cooling tower. The heating and humidification portion of the AMU can operate via electric heaters, direct or indirect fired gas burners, or steam.

Adding HVAC to a booth that utilizes 100% outside air is possible, though it can be very costly. Air moving through the booth ranges from 50-fpm upwards of 125-fpm depending on local Air Quality Management requirements. A stream of processed air passes through a booth in less than a minute in most cases, passes through the filters in the exhaust chamber, and is then exhausted to the outside air. It takes a significant amount of energy with very large equipment to process that much air as quickly as required.

The best way to reduce the size of the HVAC equipment and reduce energy is to recirculate. In cases where booths recirculate, as much as 70% to 80% of the processed air passes through the exhaust chamber filters, and is then recirculated back into the booth, leaving only 20% to 30% of newly processed air required. This significantly reduces the size of the HVAC equipment thereby saving cost and energy. Though some costs are added back because of the addition of recirculating fans, ductwork, and controls.

Depending on local Air Quality Management requirements, the recirculated air may need to pass through Carbon filters and in some cases, even HEPA filters before it is able to enter back into the booth. Carbon is used to reduce Volatile Organic Compounds (VOCs). Paint booths are set up with monitors that measure VOCs in order to ensure that they remain below the Lower Explosive Limits (LEL).

The use of recirculation fans adds some heat to the recirculated air. That means there will be temperature variations between the recirculated air and the incoming fresh air. That temperature variation could cause stratification of the intake air. This can be reduced or eliminating with a well-engineered intake plenum design that allows the air to mix and balance before entering the booth.

Another method to conserve energy to install energy recovery to reclaim cooling from the exhaust air and transfer it to the incoming air. This has been successfully done in a number of installations. The airflow patterns of a humidity controlled paint booth must be carefully analyzed to promote complete mixing of incoming air.

 

 

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12731 Norway Road • Osseo, WI • 54758 • info@globalfinishing.com • 800-848-8738