Problem Solving Forum
September 30 - October 5, 2018
How do you determine if local water is suitable for use in UHP waterjetting, particularly in areas where potable water is scarce?
Lydia Frenzel of Advisory Council on
October 5, 2018:
This is a good question, but some answers could be ...read more This is a good question, but some answers could be problematic. This answer can be simple or complex, depending upon how large the job, and the actual equipment. If I give a complete answer, then it’s too complicated; if I give a simple answer- then there are more comments- “didn’t you think of this.” Minimize the water usage. The WJ industry, Pratt and Whitney, made a closed loop system around 1994 for UHP WJ under Navy Mantech funding, which lost about 50 gallons per day. It was a complete system with everything you can imagine. For practicality, get with the equipment supplier for a “closed loop” system. There are portable systems out there. How much you have to “clean” the supply and effluent water depends upon what you are expecting to find in the quality of the water. Surface preparation water should have both the solids and the non-filterable constituents out. UHP Pump manufacturers worry about the solids, dissolved air or gas in the system, and the chemical makeup of the water. Some companies use reverse osmosis (RO) to make up the supply water. RO can be so clean as to not be good for a lot of the parts in the pump. A practical suggestion: If there is any potable water available, then that is what can be used. Fill a large “baker” tank. Keep in mind that the actual nozzle time might be only 25% of the total hourly time. Direct the water bypass outlet back to a tank, not to ground. The hot effluent will need to cool before going back through the pump. Use one filled “baker” tank as the supply water with appropriate filter prior to pump for solids. Use a second tank to receive the “treated” effluent water which has been cleaned of solids, oil-grease if their presence is suspected, reduce cation-anion species if their presence is suspected. This gives the water a day to cool down to atmospheric temperature. The pump supplier can guide you through “what do I expect in the water” check list. Then use the reclaimed water for the second day. Alternate tanks each day. I have seen this cycle work on sites where lake or river water was being used in a project which lasted 2-3 months. In one case an aluminum flake paint was being removed, so a flocculation agent was in the “clean-up” side of the system. Ocean City Research, "Productivity Study of Hydroblast Removal of Coatings "NSRP 0520, Dec. 1998 described off shore WJ coatings-rust removal with filtered seawater on interior and exterior tank shells. This was followed with a fresh water rinse. They report both initial and final chlorides and conductivity. This was around 20,000 psi. Gordon Kuljian might have presented some of that at SSPC or JPCl in 1998-1999. Early in 1990’s, a refinery coatings expert called me because they were using ca 20,000 psi WJ to remove coatings as an initial trial. The resulting cleaned surface had a higher conductivity reading than the refinery wanted. The measurement wouldn’t go lower. Then I found out that they were using fire water from a pond and it was puddling on the bottom of a tank. So, they pressure washed the cleaned surface with potable water, and the measurement went to a satisfactory level. In another situation, a UHP WJ contractor was asked to use less that satisfactory quality water. He agreed to do so but added on the cost for wear and tear on the pump parts. This arrangement worked out satisfactory. Pump suppliers and experienced contractors have a good idea about how long parts should last. In the above examples, the surface was inspected for traces of ionic residues, profile, oil-grease, etc. Today, there are several pump manufacturers who make recycling systems (i.e. closed loop) to minimize water usage.
Norman Petticrew of Chlor*Rid International, Inc. on
October 2, 2018:
Test the water for high chloride levels. ...read more Test the water for high chloride levels.