Quality of water
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Abstract
For 30 years, I have received questions about the quality of water that should be used for removal of coatings. How much dissolved material or minerals gets left on the surface? Just recently after an hour lon webinar to 200 people, the questions was “What shoul the quality of the water be?” Among the first comments which I received on the WJ standards documents came from Singapore: The complaint was that we didn’t advocate cleaning with brackish or filtered seawater.” Just recently in 2015, a Sherwin Williams representative talked about the methodology in Brazil where WJ was being used for primary surface preparation, and not just potable water. However, I also received call in the mid 190’s where contractors said that they could tell the difference of quality of water between municipality sources. The better the quality of water, the better the removal, and the less flash rust. My Colleague, Andreas Momber, of Germany has a presentation where he takes the swimming pool approach, which is everything that is in the water gets left at the bottom when all of the water evaporates. However, as a rule, the industry uses municipal potable water. Checking the surface with a conductivity meter or patch or sleeve for conductivity or specific ions doesn’t indicate up a problem with respect of leaving electrolytes on the substrate. When I polled the pump industry around 2014, they almost all refer to a 1988 paper by Thomas Labus written for an intensifier pump operating 24 hours a day. This table appeared in the WJTA “Fundamentals” workshops for years. We, the industry, protect the pump and the tips. As a task group leader for NACE and SSPC, the task groups finally defined surface preparation water. Surface Preparation water is water of sufficient purity and quality that it does not prevent the surface being cleaned from achieving the WJ-1 degree of surface cleanliness or nonvisible contaminant criteria when contained in the procurement documents. SP water should not contain sediments or other impurities that are destructive to the proper functioning of the cleaning equipment. The above statement led selected vocal advocates to insist that WJ had to use distilled water, and only distilled water. This is cost prohibitive, and unnecessary. Pump manufacturers do NOT want deionized or distilled water to be used because it will leach selective metal components. The pump manufacturers are concerned with the maximum service life for the pump and the tips. Andreas Momber discusses water quality for surface preparation in his book. “For running high-pressure plunger pumps reliably and for achieving a maximum service life, pump manufacturers recommend drinking water quality..... But if suitable filter and cleaning arrangements are applied, even river water or seawater can be used. Recommended filter size depends on the sealing system as well as on the operating pressure.”i