Ask the Expert Question-and-Answer Archive

by Ron Joseph

August, 2009

Water Wash and Airflow

Q. I am a new Industrial Engineer at a company that has a large spray lacquering process. The process consists of a rear ventilation system that flows air to a water wash booth and out a ventilation duct powered by an exhaust blower. We use a conveyor to drive parts through a system of rotators that spin and spray the part.

This process is suffering heavily form overspray because the water wash booth’s design is not correct for this application and the air ducts cannot keep up with exhausting the amount of overspray. My goal is to optimize the system that is currently in place without spending much capital. My question is how to determine the amount of water GPM should the water bath pump out and how to maximize airflow to optimize ventilation. Thank you for the help.

A. Do you still have there original drawings of the booth? Do you know who manufactured the booth? The booth manufacturer should be able to tell you what the water flow rate should be. However, there are other factors that might be influencing the efficiency of the booth:

Are you treating the water with chemicals to detackify the paint sludge?
Have you looked behind the water curtain to see how much paint sludge has built up?
Have you checked the water piping and pump to see if they are plugged with overspray?
Is the water level in the trough at the correct level? If it is too low or too high, the efficiency of the booth will be impaired.
Is the exhaust fan pulling at the optimum CFM?

These are just some of the parameters you should check.

Regards,

Ron Joseph