Painting Tube Interiors

Question:

We want to paint metal tubes with inside diameters from 2-10 inches. The tubes will be from 15-45 feet in length. Is there machinery or a system that can do this? C.L.

Answer:

Why do I always get the hard-to-answer questions? In theory, the shorter tubes can be handled easily, using existing equipment. The longer tubes will take some ingenuity.

There are spray lances available from the painting equipment manufacturers for painting inside tubes. The lances fit standard hand spray and automatic spray guns. They are tipped with nozzles that have a 360-degree spray pattern. In practice, you insert the lance in the tube and spray as you remove the lance.

When I was faced with the problem of coating the inside of 30-foot long tubes, I fabricated a wheeled spray cart to hold a solenoid operated spray nozzle. The cart was designed to hold the 360-degree spray nozzle in the geometric center of the tube. Painting was done simply by pushing or pulling the spray cart, along with its trailing hoses and control wires, into the far end of the tube, opening the spray nozzle and pulling the spray cart through the tube; painting the inside as it went along. By the way, in both cases it is important to remember to shut off the spray nozzle when it gets to your end. I ruined three shirts before I learned my lesson.