Quality Waterjet Newsletter

Quality Waterjet Newsletter – 6/21/2005

Review On Surface Preparation with Waterjets --- Part One

In 1999, Dr. Lydia M. Frenzel, a very active and well-respected educator in the cleaning industry, gave a paper* at the 10^th American Waterjet Conference on the subject of surface preparation. A review is done on this article as the first one of a mini-series on this subject. This review will highlight the important concepts presented in her article.

Here are definitions directly quoted from her article to some terminology frequently used in this industry:

Low Pressure Water Cleaning --- Cleaning performed at pressures less than 5,000 psi;

High Pressure Water Cleaning --- Cleaning performed at pressures from 5,000 to 10,000 psi;

High Pressure Water Jetting --- Cleaning performed at pressures from 10,000 to 30,000 psi;

Ultrahigh Pressure Water Jetting --- Cleaning performed at pressures above 30,000 psi;

Surface Preparation --- Creating the situation so that the coatings will perform as expected.

Dr. Frenzel emphasized an important but often overlooked issue for a successful surface preparation and coating project. All three parties, the owner/operator, the contractor, and the coatings manufacturer, must share the same points of view for the process and the outcomes. And this should be achieved through education.

The main body of her article talked about the three components of surface preparation: Visible Cleanliness, Anchor Profile, and Invisible Contaminants. A major advantage of water jetting is the ability to remove the invisible contaminants (salts), especially in the cases of badly pitted and corroded surfaces. Anchor profile is needed for coating adhesion. Water jetting alone cannot create the anchor profile, which is usually created with abrasives. However, water jetting can give surfaces a “deep cleaning” and increase the surface area per square unit area. As a result, the coatings adhere better and last longer. Surfaces prepared with water jetting may not look as good as those prepared with abrasives due to the fact that flash rusting often occurs very quickly after water jetting. Information about visual references as acceptance standards was provided in her article.

* Frenzel, Lydia, “A Comparison of Surface Preparation for Coatings by Water Jetting and Abrasive Blasting,” Proceedings of the 10^th American Waterjet Conference, Houston, Texas, August 14-17, 1999, pp. 645- 660.

Unusual Cut

It is not unusual for a cleaning job to be automated for cleaning, but there are applications that have nothing to do with waterjet cleaning. Mike Gracey refers an application where a high-pressure pump was used for something other than cleaning showed up in 1988 when a lawn mower manufacturer wanted to use nozzle to inject chemical into the soil as they mowed. Around 1995 a Houston company wanted to build a riding lawnmower with nozzles mounted on them to inject fertilizer into golfing greens. It is interesting to go out to the golf course and watch the riding lawn mower punch holes into the green with a solution of water and fertilizer. These applications worked well using a small pump in the 1500 to 3,000 psi range.