KTA-Tator, Inc.

Challenge 4 (Photograph 1) is a digital microphotograph (50x, taken in the KTA laboratory) of ports in the air cap of a conventional spray gun. The cap is screwed onto the end of the spray gun (Photograph 2) to atomize the paint for application. A stream of coating flows through the orifice in the center of the air cap (a portion of the orifice is shown on the right side of Photograph 1). The smaller holes to the left are two of a series of openings in the air cap that channel fine streams of compressed air into the fluid. The impinging air atomizes the fluid stream and shapes the spray pattern, allowing the coating to be applied in a smooth continuous film.

The conventional spray gun gives the operator the ability to adjust the volume of material being applied, the extent of atomization, and the size and shape of the spray pattern. Air caps are available with varying numbers, sizes, and locations of orifices for the atomization and application of most any coating material.

It is the responsibility of the contractor to properly adjust the spray gun each time is it used and to employ techniques that assure complete coverage of the applied coating. This is typically accomplished by spraying in parallel strokes that overlap each other by 50%, and sometimes using a cross-hatch pattern, which involves spraying a similar series of strokes perpendicular to the first. The distance the gun is held from the surface is ideally maintained at 6 to 10 inches, and the gun should not be arced or fanned, in order to minimize the generation of overspray and dry spray.

The final acceptance of the applied film involves verification of coating thickness using instrumentation. Visual inspections for runs, sags, overspray, dryspray, shadow through, pinholes, holidays, and other discontinuities should also be made. KTA distributes a complete line of coatings inspection instrumentation to assist in evaluating the coating film, both at the time of application and after drying. KTA inspectors can conduct tests and inspections to confirm that the coating work complies with the specification. KTA consultants are also available to evaluate the work and provide guidance, both while the application is in progress or after that fact, even years after the coating has been applied.

The Winner: This was another easy one with nearly two thirds of the responses correct. Incorrect responses included blast nozzle, vent/drain holes in end plate of pipe being galvanized, pipe flange (this one came a number of times), and the tip of a dry film thickness gage. The winner by random drawing is Joseph Horvath.