Sizing of Systems
The major difference is in the airflow calculations. A C-17 paint barn has a cross-sectional area of 210 feet by 70 feet (14,700 square feet). Even if only part of this area is ventilated, the air volume is around 1.1 million CFM. An aircraft paint booth requires 200 feet by 25 feet (5,000 square feet) and only 500,000 CFM of airflow. This is a significant difference in the amount of utilities required. The horsepower required for a paint barn is about 1,850. The horsepower required for a paint booth is only 860.
If humidity and temperature control are required, the refrigeration load of the paint barn is about 4,000 TR. The size of the mechanical plant for this tonnage is impressive and of great significance. It requires a couple of very large chilled water systems, pumps and expansion tanks, and large piping systems. In addition, a cooling tower system is required to cool the condenser of the chillers. The cooling tower requires much of the same ancillaries, such as piping, reservoir, water treatment and pumps.
All of this large equipment requires much floorspace and probably a separate building to house and maintain the equipment. The electrical plant is also quite significant, involving a substation and high-voltage distribution. The engineering of the electrical plant is quite significant. With a paint booth, the refrigeration load falls to about half of that figure, proportional to the airflow.
If recirculation is used in either arrangement, the installed horsepower stays about the same, but the refrigeration load falls to a quarter of the above numbers. In the case of the paint booth, approximately 500 TR is required to cool the booth. This is a much more manageable proposition and may even be accomplished with standard, packaged chilled water systems.
Paint Booth Lighting
Lights are carefully arranged to produce maximum intensity in the area where paintable surfaces are located. In addition, lights are only 7 to 8 feet above the fuselage at this point and lighting is extremely good. The large number of lights is also arranged to cast light onto the floor in strategic locations, allowing for reflectivity to the underside of the fuselage and wings.
Sidewall lighting further augments the reflected lighting to offer a highly visible surface at any point on the airplane. This helps the painter eliminate skippers, runs, dust and dirt inclusions. More importantly, areas where corrosion would originate are discovered and repaired.