Manufacturers evaluate investments in plant supplies and capital equipment based on a single key measure — how quickly that investment pays for itself. As a general rule, plant executives demand to see payback within one year in order to greenlight funding.
In an effort to identify the biggest and quickest payback, production engineers typically evaluate a plant’s largest and most complex systems first. Compared to overall production expenses, spraying equipment often represents a relatively small investment, which may be why it is frequently overlooked as a source for increasing production efficiency. However, spraying systems play an important role in such critical plant applications as coating, cooling, cleaning, chemical injection and pollution control. The importance of spray technology in these critical applications offers significant opportunity to gain production and processing efficiencies and reduce operating expenses.
A spraying system that is not optimized can drain profits from plant operation. Consider the cost of wasted water alone, even in a system with a minor performance problem like worn nozzles can amount to tens of thousands of dollars annually. If wastewater needs to be captured, treated, and recirculated, the cost of waste can easily double and more likely triple.
Other costly problems resulting from inefficient spray systems include:
- Reduced product quality and excess scrap due to uneven cleaning or coating
- Unscheduled downtime and increased labor for maintenance due to clogged or caked nozzles
- Unsafe work environment resulting from overspray or misting
- Increased consumption of expensive chemicals and energy
By optimizing spray systems, plants can achieve significant payback through a relatively small investment. Spray optimization begins by identifying the most critical requirements in an application and specifying the right spray nozzle for the job. Depending on the application, users should consider performance standards for flowrate, spray pattern, spray coverage, liquid and air pressure, spray impact, drop size, construction materials, and cycle times.
Spray optimization should also include a plan to evaluate, monitor, and maintain spray systems as part of a regular maintenance schedule. The proper frequency depends on the application — it could range from the end of every batch for a food or pharmaceutical coating application to every few months for an automotive parts cleaning process. When evaluating a spray system, the following questions should be asked:
- How much are water, chemical, and electricity costs?
- How much time is being spent on maintenance?
- How much scrap is being generated?
- How much is being spent on noncompliance fines?
If the answers to any of these questions reveal unnecessary expenditures, it may be a good time to make an investment in optimized spray technology. If a manual spray system is being used, automated control may be the best strategy for achieving optimization. Dedicated spray controllers are pre-programmed with nozzle performance data so they save the time and expense of programming a PLC. Spray controllers monitor spray system variables and adjust components to compensate accordingly.
For example, a worn nozzle orifice will often cause line pressure to decrease. A spray controller can detect this immediately and adjust the pump to maintain adequate flow and coverage. By optimizing a spray system, savings can be achieved in the following areas:
- Liquid and chemicals
- Labor and downtime
- Quality and production throughput
- Regulatory compliance
- Compressed air usage and energy costs
Savings in each of these areas have been achieved across a wide variety of industries and spray applications. Following are real-world demonstrations of payback resulting from spray optimization.
LESSON 1: Liquid & chemical usage
Meat processor precisely controls flow for varying line speeds and saves $48,000 annually in chemicals
A leading processor of fresh beef, pork, and fully prepared meats uses ascorbic acid as an antimicrobial agent to extend the shelf life of its meat products. Activating the spray guns to consistently hit the moving trays was difficult, and with line speeds varying between 15 and 40 feet per minute, the spraying system was unable to apply a consistent amount of the solution to every meat tray on the conveyor. Product quality and overspray of the costly solution were major concerns to the meat processor. The system also required frequent maintenance resulting in production downtime and imprecise spraying caused by sealing problems at the packaging stage.
By upgrading its automated spray system with a dedicated spray controller, the processor was able to ensure that the correct amount of ascorbic acid was applied to the meat products every time despite the varying line speed. The spray controller manages the timing of chemical delivery to two spray guns based on feedback from a rotary encoder and optical sensors. The encoder monitors the speed of the conveyors and the sensors are used to detect the meat trays as they pass below the spray guns, thereby eliminating overspray on the conveyor.
By significantly reducing the consumption of ascorbic acid, this processor received a payback in less than six months. Additional benefits of the system include increased productivity and improved packaging.
- Reduced ascorbic acid usage: $48,000
- Reduced spray system maintenance and documentation of performance: $3,000
- Reduced scrap caused by packaging problems: $4,800
- Total annual savings: $55,800
LESSON 2: Labor & downtime
Carpet padding manufacturer reduces maintenance downtime by 75% with automated tank cleaning
In the manufacture of carpet padding, batches of resin are added to shredded foam in a mixing vessel. Frequent and thorough cleaning of the vessel is important to maintain product quality. During an evaluation of its process, the manufacturer concluded that 100 production hours were lost each year to manually clean tanks. Production value is $10,000 per hour.
The manufacturer switched to an automated tank cleaning system with a pre-programmed spray controller to monitor the cleaning cycle time, chemical injection, water temperature, liquid pressure, and flowrate. To thoroughly remove the difficult residue, the system was equipped with a motorized tank washer to provide 360-degree coverage and a high-impact, solid-stream spray.
Cleaning consistency and product quality were improved, but the biggest value resulted from the quicker cleaning cycle. The automated system reduced each cleaning cycle from one hour to 36 minutes, allowing the manufacturer to reduce maintenance downtime by 40 percent. The tank cleaning system paid for itself in approximately one month.
- Total annual savings: $400,000
LESSON 3: Quality & production throughput
Closed-loop spray system doubles throughput in baked goods production
A pastry dough manufacturer was using air atomizing nozzles to spray a butter and oil solution on its product. While spray application was a more cost-effective method than manual application, overspray and mist from the high-pressure atomization became a health concern for employees. The plant floor became dangerously slick, and employees were required to wear facemasks to avoid inhaling butter mist.
The solution was a low-mist system with a dedicated spray controller programmed specifically for food coating applications. The controller monitors and adjusts the closed-loop system by regulating extremely low-pressure liquid and atomizing airflow to the nozzles.
The low-pressure system successfully eliminated the overspray and misting problem, but the most significant payback came through an increase in dough production. The controller also regulates liquid and air heating systems to maintain the optimum temperature of the butter and oil solution. By eliminating burning of the solution and nozzle clogging, the system reduced scrap and increased production of an additional 4,000 pounds of dough each day. As a result of adding automated spray control to their existing system, the bakery saved $225,000 annually and achieved payback within eight months of system installation.
- Value of increased dough production: $155,000
- Raw material savings from reduced scrap: $47,000
- Reduced plant maintenance: $23,000
- Total annual savings: $225,000
LESSON 4: Regulatory compliance
Precision drop size control in a steel mill’s gas cooling application eliminates EPA fines
Gas cooling is a highly complex process used in many manufacturing environments, including pulp and paper mills, steel mills, power plants, waste incineration facilities, and cement plants. Insufficient gas cooling can lead to environmental problems and noncompliance fines, costly manual labor for maintenance, and unnecessary production downtime.
In steel production, hot gases and dust are created and a baghouse is often used to filter the gas stream. Prior to entering the baghouse, gas temperature must be cooled and gas volume reduced to prevent damage to the baghouse filters. The evaporative cooling process is critical to the productivity and operating costs of the mill.
Insufficient gas cooling in the duct results in overheating and damage to the expensive baghouse filters. If too much cooling water is used, bags become wet and ineffective. Excessive cooling water also wets the duct walls and causes a dust buildup that reduces airflow. The dust slurry is a hazardous waste that falls into a cleanout chamber at the base of the duct. The Environmental Protection Agency (www.epa.gov) carefully regulates cleanup and disposal of the hazardous dust slurry and imposes steep fines for noncompliance. Wetter, heavier slurry makes maintenance more difficult and increases disposal costs.
An automated gas cooling system produced effective evaporative cooling without wall wetting for one steel mill. Using closed-loop temperature control, a dedicated spray controller monitored the outlet gas temperature with multiple sensors and adjusted the flow and maintained the optimal drop size sprayed from 10 air atomizing nozzles. A small drop size is the most important factor in gas cooling because it reduces dwell time and the risk of wetting. Reduction of the dust slurry allowed the steel mill to comply with EPA regulations and damage to baghouse filters was eliminated. Annual savings approaching $200,000 provided a payback for the system in just over one year.
- Reduced hazardous waste penalty: $85,000
- Eliminated damage to baghouse filters: $50,000
- Reduced labor/maintenance costs: $60,000
- Total annual savings: $195,000
LESSON 5: Compressed air & energy usage
Energy-efficient air knives cut operating costs by almost $30,000 annually in a bottling plant
The efficient removal of excess liquid is a critical component in many spraying applications, so it is important to consider the potential savings in blowing and drying as well.
Compressed air, which is commonly used in many manufacturing plants for a variety of drying and blowoff applications, is a very expensive process. It can easily account for one-third of a plant’s total electricity usage, yet many plants are not aware of exactly how much compressed air is costing them each year.
A bottling plant was using 24 flat-fan type 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. Four 24-inch air knives fed by a 30 horsepower blower dramatically reduced energy costs — enough to pay for the new drying equipment in less than six months.
- Annual operating cost of flat-fan nozzles with compressed air system: $35,000
- Annual operating cost of air knife with blower air system: $5,900
- Total annual savings: $29,100
As evidenced in the aforementioned applications, major savings can be achieved through an aggressive spray optimization program.
To evaluate the potential payback of optimizing a liquid spray application, visit www.spray.com/save. This online savings calculator allows users to input operating variables, such as the approximate duration of a spray system operation, average labor rate, and the value of production time per hour. Based on the user inputs, the calculator provides an estimate of potential savings that can be achieved through spray optimization.
For assistance in estimating your compressed-air usage and potential energy savings, any reputable manufacturer of air knives should be able to provide a comprehensive audit at no charge. The Department of Energy (www.doe.gov) recommends the following formula to calculate the cost of compressed air:
Cost ($) = (bhp) x (0.746) x (# of operating hours) x ($/kWh) x (% time) x (% full-load bhp)
- bhp is motor full-load horsepower. (frequently higher than the motor nameplate horsepower; check equipment specification)
- 0.746 is conversion between hp and kW.
- Percent time is percentage of time running at this operating level.
- Percent full-load bhp is bhp as percentage of full-load bhp at this operating level.
- Motor efficiency is motor efficiency at this operating level.
For more tips on compressed air usage and energy savings, visit www.eere.energy.gov/industry/bestpractices/pdfs/compressed_air2.pdf.
Daniel Vidusek has more than 20 years of spray nozzle design experience, with numerous patents to his credit. He has extensive application expertise in the steel, food, and printing industries. Mr. Vidusek has presented papers at many technical conferences, has published several articles in industry trade journals, and has held a variety of engineering and management positions with Spraying Systems Co., where he currently leads a design team focused on specialty nozzles for high-tech industries. Mr. Vidusek can be reached at email@example.com or 630-665-5000. For more information, visit spray.com.