Products Finishing

SEP 2018

Products Finishing magazine is the No. 1 industrial finishing publication in the world. We keep our readers informed about the latest news and trends in plating, painting, powder coating, anodizing, electrocoating, parts cleaning, and pretreatment.

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Page 30 of 59

PRODUCTS FINISHING — 29 CLIMATE-CONTROL BOOTHS Air make-up units (AMUs) are standard systems for replacing exhausted air. The units for this article are special, and will be referred to as HVACs. They also will range in price; this is due to the many variables in installations. HVACs can provide that climate control and dehumidification for replacement air. There is no one system that fits all, as each should be customized for the location, climate variations and coating variables. Codes also require replacement air for air that is exhausted from a booth or facility. How AMUs Work When relative humidity (RH) is too high, HVACs cool the air to remove moisture and thereby reduce the humidity in the air going into the spray booth or paint system. The air velocity through the HVAC is reduced so the moisture (water) drops into a pan and doesn't get blown down the duct. This makes the size of the HVAC unit larger; coils and other apparatuses may also increase as determined by the specifications. When RH is too low, such as in very hot, dry climates (think Phoenix), or very cold, dry climates (think Minneapolis), the air is so dry that it can flash off the moisture from the coating before it can be applied to the part. In these cases, the raw air is pulled into the HVAC through filters, then passes over the cooling coils. The air may need to be cooled below the spray temperature required in the spray booth to remove the moisture, then it is reheated to bring it back up to the right temperature for spraying. Typical Costs An AMU in an "ideal" climate, like Southern California, would likely require unheated, filtered airflow at a cost of about $0.50 to $1.00 per cfm (cubic foot per minute). So, if the volume of air required is 20,000 cfm, for example, the cost would be $10,000 to $20,000. The cost of a typical AMU with gas heat (direct-fired burner), providing heated, filtered air, would be about $0.75 to $2.00 per cfm, or $15,000 to $40,000 Conditioned Air Supply for Finishing Systems, Spray Booths or Powder Room Enclosures Air Intake Intake Filters Dry the Air Cooling Coils Mechanical, Chilled Water or Desiccant Wheel Heating Method Direct-fired Gas Burner, Indirect-fired Gas Burner, Steam or Hot Water, or Electric (seldom used) to Booth or System Evaporative Cooler (Can cool and add RH in hot climates.) Moisture Drain Air Supply Air to Powder Room Enclosure A large dehumidifier and air make-up unit (left) sits next to a standard vertical unit with no climate-controlled air make up. for our 20,000-cfm example, depending on the amount of duct required, the installation area and other factors. For hot, dry climates where it never really gets cold, an AMU with a direct-fired burner and an evaporated cooler would likely be recommended, at a cost of about $2.00 to $4.00 per cfm ($40,000 to $80,000 for required air volume of 20,000 cfm). To help better understand the complexities involved in choosing the right HVAC, a shop would be well-advised to get a psychometric chart and better understand the terms relative

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