If you’re not evaluating your spray operations on a regular basis, you may be missing out on opportunities to boost production and profitability, minimize waste and downtime, and conserve water, electricity and compressed air.
Spray technology continues to evolve and improve. A spray system that’s been in use for several years is likely still operational, but that doesn’t mean you should wait for a problem to occur before evaluating the system to determine if process improvement is possible. A newer system may quickly pay for itself by operating more efficiently than the existing system.
You should also give consideration to replacing manual processes with automated spray systems. Many coating, washing and rinsing operations rely on workers equipped with a dispensing device, handheld spray gun or hose. Changing to an automated spray system is likely to yield better performance, provide more consistency and be more cost-effective.
But how do you know when you should change the way you spray? The following checklists may help you decide. Hereafter, you’ll find more than a dozen ideas for change that may prove beneficial in your operations.
Changes You Can Make to Improve Quality and Minimize Waste
Upgrade to high-precision automatic spray nozzles.
These nozzles provide uniform coverage of the target and eliminate costly and messy overspray. Available in hydraulic or air-atomizing versions, automatic nozzles can operate at speeds up to 10,000 cycles per minute. When used with a spray controller and monitoring sensor, each spray cycle can be documented. If a spray cycle is missed, the system can shut down automatically or sound alarms for operators.
The precise answer to this question is, of course, dependent on the specifics of your spray applications. However, it is certainly possible to save tens of thousands or even hundreds of thousands of dollars annually by changing your spray operations. Here are a few examples:
• Changing from a standard air-atomizing nozzle to a non-bearding air atomizing nozzle saved one manufacturer $60,000 per year by reducing downtime and labor.
• Using air nozzles instead of open pipe holes for drying reduced compressed-air costs by $55,000 for a metal parts producer.
• Replacing worn nozzles on an annual basis enabled one food manufacturer to reduce water consumption by 57,000 gallons per hour of operation.
• Changing to an automated tank cleaning system from manual tank cleaning boosted production time by 80 percent by returning tanks to service more quickly. The benefit to the bottom line for this chemical producer with 10 tanks translated to more than $500,000 annually.
In some instances, having experts evaluate your application for operational improvements may be the best approach. Spray performance testing with application-specific operating parameters can help determine if there’s a better way to spray. For example, in some applications, changing from hydraulic nozzles to air-atomizing nozzles may yield a performance advantage and reduce costs by operating at lower pressures, eliminating the need for high-maintenance, high-pressure pumps.
Ways to Increase Throughput and Maximize Production Time
Use a dedicated spray controller to eliminate production interruptions to adjust or change nozzles.
The spray controller can automatically adjust fan air, atomizing air and liquid pressure, cycle speed, flowrate, the number or type of nozzles spraying and more based on operating conditions and pre-stored programs. The controller can also make automatic adjustments to other system components, such as pumps and valves to automate all facets of operation and maximize overall production time.
Eliminate manual cleaning of tanks, totes, vats and vessels.
Use automated tank wash nozzles, motorized tank washers or fully automated tank wash systems to reduce cleaning time to minutes instead of hours. In addition to returning tanks to service faster, automated tank washing products clean more thoroughly and consistently than other methods and reduce the consumption of water and costly chemicals.
Change to automatic brush-type headers and clean without process interruption. Preprogrammed cleaning cycles can run without disrupting spraying operation. An internal rotating brush assembly scrubs the interior wall of the header and nozzle orifices. Debris is swept away through the flush-out valve.
Strategies to Reduce Water, Compressed Air & Chemical Consumption
Don’t neglect your nozzles.
Using worn spray nozzles — even those with slight wear — can be extremely wasteful. As nozzles wear, their orifices become larger and, at any given pressure, the flowrate will increase. Nozzles that spray over capacity can waste thousands of gallons of water per day. Using worn nozzles will also result in higher electricity costs due to excess pump operation, increased chemical consumption and more wastewater disposal costs. See Table 1 for estimates of waste resulting from using nozzles that are 15 percent worn.
Most plants use compressed air to dry, cool or move parts. Typically, open pipes or pipes with drilled holes or slits are used. While this approach accomplishes the desired task, compressed-air consumption is excessive when compared with alternate approaches. Using air nozzles, air amplifiers or air knives instead of open pipes can reduce air consumption by as much as 92 percent.
In some operations, the use of compressed air can be eliminated completely by using an air-knife package powered by a regenerative blower. Air knife/regenerative blower packages are rugged and require infrequent, minimal maintenance.
Air-knife packages are ideal for applications that require:
• High air velocity;
• Oil-free operation;
• Large application areas – more
than two feet (61 cm); and/or
• Heated air.
Minimize over-application of chemicals by choosing the right nozzles or adding a spray controller.
The over-application of chemicals is wasteful. And, in many operations, it can cause quality problems, excessive misting, worker safety issues and increased maintenance. To minimize these problems, select nozzles based on the type of chemical being sprayed, feed rate, stock width, etc. Nozzle performance may vary based on the solution being sprayed. Nozzles with automatic on-off control, shutoff needles and drip-free setups can also help control the occurrence of over-application.
Another way to eliminate the over-application of chemicals is to add spray control. The system controller ensures the proper volume of the chemical is dispensed precisely on the target when in the spray zone.
Minimize Maintenance Downtime and Labor Costs by Making These Modifications
Change to quick-change nozzles or quick-connect nozzle systems.
Quick-change nozzles consist of a nozzle body and spray tip. Spray tips can be removed by hand, without tools. Some quick-change nozzles also feature automatic alignment with tips that snap into place and lock into the correct position due to an internal stop.
Quick-connect nozzle systems feature bodies that snap onto the pipe header using a clamp or screw. Again, no tools are required for installation. Spray tips can also be installed, aligned and positioned by hand.
Automate.
Eliminate manual monitoring and adjustment of your spray system by adding a spray controller. Workers can be deployed to other tasks since the spray controller can monitor operating conditions and make automatic adjustments to ensure optimal spray system performance.
Conditions monitored by the spray controller include air and liquid pressure, automatic nozzle cycle times, liquid levels, flowrates, conveyor/line speed, temperature, humidity, etc. The controller uses these inputs to monitor the performance of nozzles, pumps, sensors and other hydraulic and pneumatic components as needed. If the spray controller cannot make the necessary adjustment, alarms can notify operators that intervention is required or system shutdown can occur.
Take steps to eliminate clogging.
One of the most common and frustrating causes of unscheduled maintenance downtime is clogging. Fortunately, there are many ways to minimize clogging. Using line strainers, integral nozzle strainers or automatic self-cleaning strainers to prevent debris from entering the nozzle orifice is always a good line of defense, especially if using recirculated water. If you’re spraying viscous liquids, using heat jackets or a heated system will help keep the liquid flowing. Other options include changing to a nozzle with open flow passages or specially designed air caps to prevent clogging or build-up/bearding.
Ensure Quality and Simplify Compliance by Adding Monitoring Devices
Detect and document worn, plugged or missing spray nozzles instantly.
Some spray controllers include built-in System Integrity Checking for instant operator notification when spray nozzle problems are detected. All system activity is automatically recorded by the controller and can be easily exported for quality control and compliance verification programs.
Verify each and every spray.
Using optical sensors in conjunction with a spray controller provides an effective way to document nozzle performance when visual inspection is difficult. When the spray controller sends a "spray" signal, a miniature optical sensor near the nozzle orifice confirms that spray emerged from the nozzle. A "spray present" signal is sent back to the controller for recording.
Replace post-tank cleaning validation tests with acoustic monitoring.
Return tanks to service more quickly by using new acoustic monitoring devices. Acoustic sensors, mounted outside the tank, "listen" for normal sounds produced by tank wash nozzles. This information is sent to a monitoring device and run through diagnostic software. When weak sound waves are detected, indicating a change in spray pressure resulting from clogged nozzles, operators are notified via audible or visual alarms. Real-time monitoring allows problems to be identified and resolved as they occur and eliminates time-consuming, post-cleaning inspections.
There are dozens of other ways to change how you spray in addition to those described here. Some of these changes may not be appropriate for your application; others may have a significant positive effect.
Bill Kohley, Ph.D., earned his bachelor’s degree in Mechanical Engineering from GMI Engineering & Management Institute (now Kettering University), his MBA from North Central College, and his Ph.D. in Organization Development from Benedictine University. Dr. Kohley has extensive experience in the chemical processing and pharmaceutical industries. He currently serves as vice president of Spraying Systems Co., where for more than 20 years he has held a variety of engineering, marketing and executive management positions. Dr. Kohley can be reached at [email protected] or 630 665-5000.
