In most industrial plants there are routine objective measures for important processes, but that’s often not the case with spray equipment. The mentality that "if it sprays, it must be OK" is pretty common in a lot of plants we visit. There seems to be a perception that liquid is soft and metal is hard, therefore spray nozzles don’t wear. Sprays are usually visible in a plant, and that’s the means by which they are often inspected – i.e., just by looking at them. The problem with this approach is that a spray nozzle that is worn 30 percent more than its original capacity with distribution much heavier in the center than when it was first installed looks much like it did when it was new. Without objectively measuring flow and distribution, end-users don’t find out there is a problem until there is defective product or there has been tremendous waste of water, chemicals and the energy to pump them. So again, the need for routine inspection and maintenance is high. Even more effective than periodic inspection and maintenance are automated spray systems, which monitor flow and can adjust as needed or provide warnings when spray performance falls outside an accepted range.
Q: From a monetary perspective, why is it important to examine the efficiency of the spraying process? Can you provide some specific application examples that demonstrate the monetary gains and/or losses that can be incurred from spraying efficiently and/or inefficiently?A very simple example of nozzle maintenance providing a quick payback occurred at a food processing plant where our customer discovered that the nozzles on their conveyor rinsing headers were worn to 15 percent over the flow capacity they desired. Changing out those 60 nozzles was a minor investment, but because the system was in use 20 hours per day, five days per week, 51 weeks per year, the financial impact was significant. The company avoided more than 3,300,000 gallons of wasted water over the course of a year. Based on average costs for water and disposal, that change saved them over $23,000 U.S. annually. Another expensive plant resource is compressed air. We worked with a bottling plant not too long ago that was using compressed-air nozzles to dry soft drink bottles after washing. The plant was operating 250 days per year, 16 hours each day, and the cost of operating this system was estimated at over $35,000 per year. High-impact, blower-fed air knives were a much more efficient answer to the plant’s drying problem and provided savings of almost $30,000 annually. Those are just two simple examples of how proper nozzle selection and maintenance can provide significant financial payback. Spraying Systems offers an online calculator to help users understand how much money they can save by optimizing their spray system. This calculator can be found at www.spray.com/save.
Q: Why is drop size an important consideration in many spray applications? How does the process of atomization affect spray quality? Two good examples of applications where drop size is critical are dust control and gas conditioning/cooling. Dust control is most effective when dust particles collide with water drops of an equivalent size. Drops that are too large won’t collide with the smaller dust particles, and drops that are too small evaporate too quickly and simply release the captured dust particles back into the atmosphere. So understanding the particle size of the dust and the droplet size are both critical to the effectiveness of the system design.In gas conditioning applications, problems can result from premature or incomplete evaporation. If drops are too small, they evaporate quickly and the desired level of absorption may not occur, thus resulting in less efficient or damaged downstream equipment. If drops are too large and don’t evaporate quickly enough, wetting will occur, entrained liquid may result, and dust can accumulate in the duct or tower and obstruct gas flow.Q: What is on the horizon in terms of spray technology? How will the spray technology of tomorrow be more effective/efficient than the spray technology of today?The future will bring more advances in precision spray nozzles, spray control technology, and spray modeling. We’ll see more intelligence built directly into the nozzle – things like thermal sensors, acoustic sensors, and vibration sensors that will provide real-time monitoring. New spray controllers will take advantage of improved sensors like these and others to tightly monitor and control the quality and moisture content of things, such as tissue paper and roofing shingles and the amount of chocolate sprayed on an éclair. Modeling software and the spray input data will continue to improve as universities and leading industry spray experts cooperate to model new flow characteristics of droplet behaviors for new products, such as injection systems, drug inhalers, and high-efficacy process towers.
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