Paint Spray Guns

Cleaning

COUNTER-CURRENT CLEANING OF SPRAY GUNS

Q:  Do any paint shops practice counter-current multi-stage cleaning/rinsing of paint equipment (like spray guns) for waste reduction?

A: This would be an excellent P2 strategy, yet I have only seen one Air Force Base use this principle.  Counter-current rinsing is very common in the surface pretreatment industries, where water flows from the first rinse tank to the second.  Water in the first tank quickly becomes contaminated on account of drag out from the previous degreasing tank.  The second rinse tank gets its feed water from the municipal supply and has a low concentration of the contaminants that are drug in from Tank #1.  The makeup water for Tank #1 comes from Tank #2 and not from the municipal supply.  Overflow from Tank #1 goes directly to the drain, and from there to a POTW.

It can easily be shown mathematically that the amount of feed water required to keep the concentration of contaminants in Tank #2 low is very much less than if only a single rinse tank were used.

figure 1:  Counter Current

figure 2: Single Rinsing Tank

The same principle could be used for spray gun cleaning.  You could have two identical spray gun washers and immerse the dirty gun in the first tank, then remove it and immerse it into the second, cleaner tank.  Instead of refilling the first tank with clean solvent, you would refill it with the “dirty” solvent from the second tank.  Fresh, clean solvent would only be used as makeup for the second tank.  My guess is that solvent usage from this operation would drop dramatically.

HOME | TRAINING | CONSULTING | EXPERT WITNESS | ASK THE EXPERT | LINKS