“What type of particle size distribution works best in a reclaim system? For example will a powder with an average particle size of 45 microns work better than a grind with an average particle size of 58 microns. Also, what is an acceptable percentage of particles less than 20 microns(fines) in size? I am looking for numbers that would produce optimum performance with regard to fluidization. At what point will the amount of fines significantly affect fluidization? “
“Powder coating reclaim systems are designed to accommodate a wider range of particle size. There is no single particle size that is best, although finer particles are more difficult to fluidize and pump. Powders are formulated and ground to a bell shaped curve that has a range of particle sizes form 20 to 40 microns. This range accounts for the highest percentage of the particulate. However, there are particles that fall out of this range (less than 10 and greater than 50 microns) but they are few in number. The problems exist in a reclaim system when the bell shaped curve shifts toward finer particles (i.e. 50% or more less than 10 microns). Below 5 microns and the filters have difficulty capturing these particles. Remember, smoke is 15 microns, so what we are describing here is real small stuff.
Powder coating systems need smaller particles to fill the voids between the larger particles. If smaller particles were absent, then your surface appearance will have more orange peel. Imagine building a stone wall with all the same size rocks. If you don’t have small ones to fill the gaps, then the wall will have a rough surface.
Virgin powder mixed with reclaim will eliminate all reclaim problems. Most suppliers recommend a mix ratio of at least 50% virgin material. If your first pass transfer efficiency is too low, then this may pose a problem. I suggest you check your transfer efficiency and improve it to at least 50% and don’t worry about the reclaim particle size. Particle size is difficult to measure and control anyway.”