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Cutting Water Waste
Practical ways to reduce water consumption in cleaning operations.
Water can be a significant expense—the average cost per 1,000 gal is approximately $7, including sewer charges.
Jon Barber, Director, Spraying Systems Company
Nozzles that are worn by as much as 30% (below) still show no obvious signs of wear.
Clean-out needles can be used to remove debris from nozzle orifices.
Integral strainers (circled) keep debris from entering the nozzle.
Motorized and fluid-driven tank washers provide high-impact cleaning and reduce water/chemical use and labor costs.
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Efficiency in business requires a series of strategies for reducing spending and consumption. In industry, water usage plays a significant role in these expenses. In the U.S., 45% of the fresh water consumed annually is by industry, with the heaviest users in food, chemical/petrochemical, primary metals, and paper.
Lately, water costs have gotten a lot more attention from manufacturers and processors. In some areas, these costs have more than doubled in the last 10 years, leading to a push for leaner processes. But considering wastewater disposal costs, many companies still have plenty of room for improvement.
So how can users of industrial cleaning processes cut their water consumption? One of the easiest and least expensive ways is through proper system maintenance, including spray nozzle optimization, routine tank cleaning and basic system maintenance such as fixing leaks.
Optimizing Nozzle Performance
Spray nozzles are at the heart of many aqueous cleaning operations. Though seemingly simple, nozzles are actually precision components designed to yield specific performance under specific conditions. But just because a nozzle is spraying doesn’t mean that it is working optimally. Spray systems that aren’t optimized not only use too much water; they can cause other costly problems such as quality control issues, unscheduled production downtime, increased maintenance, and increased consumption of costly chemicals and electricity.
To ensure a cleaning system is operating at peak efficiency, a reputable nozzle manufacturer can perform an audit of the spray system. Audits typically are offered at no cost and may require several hours of work.
The audit can reveal problems and document ways to reduce water use through regular system maintenance and by optimizing nozzles and other aspects of their spray cleaning systems. These steps include replacement of worn nozzles, considering a more durable material, reducing spray pressure, using self-cleaning nozzles and automating tank cleaning.
Worn spray nozzles are a problem in many plants. Over time, nozzle openings erode, increasing the flow rate. Even slight nozzle wear that isn’t visibly noticeable can be extremely wasteful, costing tens or even hundreds of thousands of dollars annually in increased operating expenses. And worn nozzles spraying over capacity waste more than just water and electricity costs due to excess pump operation. Chemical consumption and wastewater disposal costs will also increase.
Abrasive or corrosive materials can compromise nozzle performance and require a more frequent replacement schedule. The cost of replacement nozzles can be far less than the cost of wasted water, even if the nozzles are only 15–20% worn.
Nozzles made from harder materials generally provide longer wear life. In addition to standard materials such as brass and stainless steel, more durable spray nozzles are often available. Specialty nozzles include models made from carbides or with ruby orifices. When possible, decreasing pressure can slow the liquid velocity through the orifice and may help reduce the rate at which the orifice wears.
Self-Cleaning Options
In many applications, orifice deterioration and clogging are caused by solid particles in the sprayed liquid. This situation is particularly common in systems using continuous spray water recirculation. Regular recycling of the water during the production process reduces the amount of clogging and prolongs the useful life of both the water and the nozzles. In an average production process, recycling of water enables approximately 17 uses before discharge, as opposed to one or two uses without recirculation.
Many applications allow for the use of self-cleaning nozzles. These are available in a number of configurations and operating styles. For example, in intermittent spraying applications where liquids tend to dry in the orifice between uses, nozzles with clean-out needles are ideal. A clean-out needle slides through the orifice to clear obstructions, and can be activated manually or automatically, depending on nozzle type. Automatic spray nozzles can be equipped with a needle that cleans the liquid orifice after each spray cycle for maximum protection against clogging.
Other self-cleaning nozzles retract a purge piston when line pressure is reduced to remove fibers and other solids from a clogged nozzle. Spray headers, with internal brushes that rotate and remove debris from nozzle orifices, are also widely used in applications that do not recycle the water and it is not as free of particulate.
Other options include nozzles with built-in strainers, which trap larger particles and prevent debris from entering the nozzle orifice or vane, significantly reducing wear. Integral strainers can be ordered as part of the nozzle itself and are available in a variety of mesh sizes, down to 200 mesh. Materials include brass, aluminum, nylon, stainless steel and polypropylene, for standard and quick-connect nozzles in flat spray, full cone, hollow cone and fine spray patterns.
T-strainers are widely used and available in many configurations. Most are designed to minimize pressure drop and provide simple, fast cleaning and maintenance. Self-cleaning versions, which allow the filtered liquid to pass through the strainer and return to the supply, are another option. Strainers are available in a variety of materials, including FDA-compliant materials for potable water usage, and for low-, medium- and high-pressure applications.
Routine Tank Cleaning
For clean-up throughout the plant, using low-pressure spray guns instead of open hoses can reduce water consumption by 50 percent or more. Ensuring water is on only when needed also significantly reduces waste.
Tanks are often cleaned manually by workers equipped with hoses or by filling and draining the tank multiple times. Depending on tank size, these cleaning methods can use hundreds of gallons of water every time the tank is cleaned.
Automated tank cleaning systems can provide an effective alternative to manual cleaning. In addition to using considerably less water than manual and fill/drain methods, automated tank cleaning offers many other benefits. These benefits include faster and more thorough cleaning, reduced use of costly chemicals, reduced disposal costs, improved worker safety, and reduced labor costs and maintenance downtime. Plants have reported savings of as much as $50,000 a year per tank by switching to automated cleaning.
Clean-in-place (CIP) systems use spray nozzles to provide controlled, thorough cleaning and rinsing. High-impact, fluid-driven or motorized tank washers and automated turnkey systems are other options.
Turnkey systems integrate pumps, sensors, motors and valves, all designed to optimize nozzle performance. Systems can be equipped to recirculate cleaning liquid in a closed loop, allowing the reuse of a portion or all water and chemical cleaning solutions.
Additional Simple Water Savers
Beyond nozzle maintenance and optimization, there are several other relatively simple and inexpensive ways to cut water use.
Leaks should be fixed. As simple as it sounds, this is often overlooked. Plants have reported as much as a 14-percent reduction in water consumption simply by fixing leaks throughout their water systems. Sub-meters can be installed to detect leaks.
Pipes that use drilled holes to create spray patterns should be replaced. An engineered manifold will improve spray performance and will save enough water to pay for itself.
The proper nozzle should be used for each application. Using the wrong spray pattern or nozzles that produce drops that are too large or too small can cause overspray, overwetting or misting. Nozzles should be properly positioned to ensure precise spray coverage with minimal waste, and check valves should be used with nozzles to prevent drips and leaks and to maintain line pressure. Solenoid valves should stop the flow of water when production stops.
Determine whether discharges from any operation can be substituted for freshwater supplied to another operation. For example, reclaimed clean water can be used to flush floor gutters.
Finally, train workers to minimize water use whenever possible. Start by implementing these simple guidelines:
- Use hoses (equipped with spray guns, of course) sparingly and only when necessary;
- Close filling lines when not in operation, and consider using flow restrictors in liquid lines;
- Turn off all flows during shutdowns unless flows are essential for clean-up. PC
Jon Barber is a director at Spraying Systems Co. in Wheaton, IL. He can be reached via e-mail at jon.barber@spray.com.
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