From JPCL April 2020
Fig. 1: Using plural-component application equipment can have a number of benefits for application contractors. PHOTOS COURTESY OF THE AUTHOR
Plural-component coatings have historically presented numerous challenges for industrial painting contractors, with significant material, time and labor costs tied to mixing two or more components prior to application. After the components are mixed, logistics issues can also arise, with limited time available to apply the coating.
By switching from hand mixing (or "hot potting") two-component materials to spraying them with plural-component equipment, contractors can significantly reduce costs and improve performance. Manual processes can be automated with plural-component equipment, and electronic monitoring tools help contractors apply the materials more uniformly.
This article will outline seven distinct benefits that plural-component spraying can provide, including:
Plural-component sprayers hold the component materials in two separate hoppers and mix them together within the unit. This allows the component materials to be mixed as needed, rather than manually mixed before being poured into a single-leg sprayer.
Consequently, significant material savings can be realized with plural-component equipment. For example, if a 4-gallon mixture (2 gallons of each component) is added to a single-leg sprayer, but only 2 gallons of mixture are used, then 2 gallons of material will potentially go to waste. At a cost of $75 or more per gallon, a plural-component sprayer could achieve hundreds of dollars in savings each day by avoiding wasted material. This type of savings can become particularly valuable on small touch-up jobs, which often require less than a full batch of material.
Fig. 2: Plural-component equipment can minimize solvent usage, which can reduce solvent costs and help keep applicators safe in confined spaces.
If a quick-curing material is being sprayed, it may be necessary to flush the entire system every 30 minutes. When using hundreds of feet of hose, all the material left in the pump is wasted. This can be up to two gallons of material in 200 feet of ½-inch hose. Some materials are even recommended to be flushed after every two-to-three kits of material sprayed. If the material ends up curing in the hoses (for example, if someone forgets to flush, the material cures faster than expected or other unforeseen issues occur), the hoses, spray gun and possibly pump lower may also need to be replaced.
Along with raw material savings, plural-component equipment also reduces solvent usage. The components are mixed together in a manifold located closer to the spray gun than with traditional equipment. This means a shorter portion of hose needs to be flushed after use. Also, because high-viscosity coating mixtures often have a relatively short pot life, a single-leg pump must be flushed numerous times during the day—often after each kit mixture.
Fig. 3: For large-scale projects, plural-component equipment can help reduce time, labor and material costs.
With plural-component equipment that only mixes the amount needed, flushing can be reduced by up to 75% (5 gallons versus 20–25). At a cost of $20 per gallon of solvent, a plural-component sprayer could achieve $300 of savings per day. Another aspect that is often overlooked is the disposal cost for solvents. By using less, there is less to dispose at the end of the job.
Plural-component sprayers allow workers to focus on spraying the coatings rather than mixing the materials manually. This can significantly reduce personnel and labor requirements and increase productivity. Jobs can be completed faster if personnel are utilized on other aspects within the same job or sent to other projects, which can now be done simultaneously. Traditional single-leg equipment often requires one or more people to focus on mixing materials.
Fig. 4: Plural component setups can allow multiple applicators to spray coatings simultaneously.
For high-volume projects, additional productivity can be gained with multiple-gun configurations. Heated tanks help pre-condition the components, maintaining optimum temperature and viscosity for more efficient application. High-performance systems can provide pressures up to 7,250 psi and deliver more than 3 gallons per minute. More work can be completed in a given time, with higher flow rates and multiple workers, when compared with traditional equipment.
With single-leg equipment, manual mixing requires 3–5 minutes for each mixture. Additional time—up to 15 minutes—is required for induction, the chemical reaction that occurs after mixing components and before applying coatings. With plural-component spraying, virtually no wait time is required. A mix manifold and static mixers inside the equipment mix the coatings as spraying is conducted. Additionally, the ability to heat the materials can also reduce the entire process time by improving overall dry and cure times.
The reduced number of cleanings also saves time. With a quick-curing coating, the entire pump and hoses may require flushing every 30 minutes of spraying. Even though it may not be necessary to thoroughly and completely flush the system until the end of the shift/day, these stoppages in production equate to lost time. It may take 10 minutes or more to flush. If flushing is required every 30 minutes, 2 hours are lost to flushing during an 8-hour shift without taking into account any other periods of downtime to stage or maneuver equipment.
Manual mixing can be prone to mismeasurements and guesswork when portions of component materials are used in a given application. Manual mixing relies on the operator to make sure that all of components A and B are mixed together. For example, the operator may scrape down the sides of the container; if not done consistently, the ratio could vary from batch to batch. In another case, an operator may try to mix a partial batch of material when a full kit is not needed, resulting in guesswork on the ratio and incorrectly proportioned material. Plural-component equipment, when properly used, precisely controls mixtures and provides assurance that ratios are correct. Because the materials are mixed “on-demand,” partial batches and guesswork are not needed.
Ratios can be controlled by either fixed-ratio or variable-ratio equipment. With fixed-ratio equipment, the sprayer is linked to the two pumps at a set ratio. Controls monitor the pressures of each component to verify the ratio. Mix ratios can be adjusted by swapping out one or both of the pump lowers to achieve standard ratios ranging from 1:1 to 4:1.
With variable-ratio equipment that is electronically controlled, computer monitoring allows ratios to be adjusted as needed. Equipment can typically handle material ratios from 1:1 to 10:1.
The various features of plural-component equipment can provide more uniformity, resulting in a consistent coating application, satisfied customers and ultimately a higher-performance product. High-performance coatings often employ highly viscous materials—up to 100%-solids—and are more efficiently applied with plural-component equipment. The heated components can be mixed and applied consistently because the material remains fresh as it is sprayed, unlike a manually mixed batch of material that may still be reacting and approaching its pot life in a pre-mixed container.
With the higher pressure ratings and the ability to move the mixing point to a remote manifold, the system can handle highly viscous materials through long hose lengths, enabling workers to access hard-to-reach areas while still maintaining consistent flows and pressures. Large projects such as petroleum tanks, piping and railcars can be coated swiftly and with consistent quality, with multiple workers applying precisely controlled mixtures. Hoppers can contain up to 25 gallons of coating components, reducing the number of times workers have to stop and add components. Cure time can also be reduced due to heating and conditioning the material prior to spraying. Faster curing materials can be specified because the pot life of the material can be more easily managed with plural-component equipment.
Along with higher-performance coatings, contractors can achieve reduced rework. The variables of manual mixing, such as monitoring component ratios, temperature and product data sheet requirements, can lead to inconsistent coatings and require re-application. Ratio-assurance monitors in plural-component equipment can shut down the equipment if ratios are incorrect, preventing the spraying of material that is not on-ratio. The increased reliability can also reduce repeat inspections, helping keep projects on schedule and within budget.
Factoring in all the benefits, plural-component sprayers allow contractors to raise the bar in applying high-quality protective coatings. By automating processes previously done manually, plural-component equipment can help contractors apply materials more uniformly, significantly reducing costs and improving performance.
John Lihwa is an Area Manager for High Performance Coatings and Foam Equipment in the Applied Fluid Technologies Division of Graco Inc. He has worked in engineering, product management and sales roles with Graco since 2008. He has a B.S. in mechanical engineering and is currently pursuing an MBA from the University of Akron.
Tagged categories: Coating Application; Features; Paint application; Plural component spray
