Painting Q&A: Importance of Drain Stage Length

Q. What is the importance of drain stage length in pretreatment systems?

A. Many people in the industry do not believe that drain length is important because it’s not a process. But it is a process. Simply put, it is the process of drainage. In manual systems, drain time is not as important because many times overflow is sent to waste. In inline systems, everything is governed by time/line speed, and for drainage, how far the water flows in either direction.

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Chemical processes are designed by chemical strength, temperature and takt time. Rinses need to be clean water (city water, RO water, DI water and so on). Try not to rinse with dirty water, and remember that some city water and tap water is not clean enough for industrial use. Lack of chemical strength due to dilution does not provide the correct process function. Contaminated rinse water does not rinse and does not allow the next process to be properly performed.

Drain time and stage length keeps the next tank clean and does not dilute chemical concentration. Everything in a system is designed to provide the end result that you the customer has deemed important. Make sure to hang your parts to watch how far water drains in both directions and how far it “shoots” off the part. Design the drain stage to capture this draining water so the process parameters will remain where they are supposed to be.

Global Finishing Solutions' Martin Powell has 33 years of experience in the finishing industry. He has bachelor’s degrees in marketing and business administration with a minor in international management. He has been published in several trade journals. For information, please call GFS at 800-848-8738.

Originally published in the November 2015 issue.