Q. I am exploring the possibility of using polypropylene balls as thermal insulation in some of our process tanks. Can you share some of your general insights on this practice? What are some concerns I should have? Finally, do you have any special advice in regard to implementing the practice?—M.O.
A. The use of covers for plating process tanks is a good idea. By covering process tanks you will save energy and reduce emissions. An excellent article regarding covers was published in Products Finishing in 2011. This article discusses the use of solid lids on plating process tanks. Numbers generated in this study showed impressive energy savings. If you don’t want to consider mechanical covers, the use of “floating thermal insulation”—a fancy name for the use of polypropylene floating balls—will also give you savings in terms of energy and reduction of objectionable fumes and odors.
Polypropylene balls can reduce exposed tank surface area by as much as 90 percent. Polypropylene is resistant to most chemicals and can withstand temperatures of over 200°F. I recommend solid balls over hollow ones. The hollow balls tend to damage more easily and if punctured can fill with liquid and no longer float effectively. The balls are available in a number of different diameters. Some data that I dug out of my files suggest that use of
1 1/2-inch- diameter balls will give you as much as 75 percent energy savings at a temperature of approximately 190°F.
The only downside that I am aware of with using floating balls is that they can get lodged in crevices of the parts placed in the tank. Larger diameter balls are less likely to get lodged in the parts.
A clever variation of the balls is a hexagonal shaped float called “Hexies” that are available in a couple of different sizes. They are reported to give a heat loss reduction of as much as 80 percent.
My overall advice is to go for it.
Choosing the best process for your operation.
Why is it important for you to know this?
An overview of precious metal electroplating processes.