Q. I’m interested in knowing if there is a formula that can be used to determine contact time for soak or immersion cleaning verses impingement or spray cleaning? K.S.
A. Unfortunately, there is no direct relationship between the two. This would be impossible to even approximate since the fundamental process steps will often be significantly different between the immersion and spray process. For instance, it is unlikely that you could utilize the same cleaner in both applications. Immersion cleaners are formulated with standard surfactants that typically allow some amount of foaming. In the case of the spray cleaner, the choice of surfactants is narrowed significantly by the fact that you need to make use of a low foaming version to make sure you do not build up a large and sustained foam blanket that would like spill out of your machine.
Another difference with the surfactants may be the tendency to emulsify or split lubricant out of the cleaner. The spray wash may utilize a splitting surfactant package since it will pump from below the liquid surface, allowing the use of a skimmer on the side of the tank.
Spray cleaners are usually not run at the same temperature, with the spray cleaner being run at the lower temperature due to the evaporative cooling effect that takes place during the spraying process. You may be able to develop an empirical relationship between a specific pair of immersion and spray cleaners, but that relationship would be applicable only for those two compounds under very specific operating conditions.