Tom Bishop, P.E.
EASA Technical Support Specialist
Volatile organic compounds (VOCs) are found in our homes, in stores, in our offices and service centers. VOCs allow paints to dry quickly and cleaners to quickly loosen and remove dirt and debris. But VOCs do have a downside in that they bring serious health and environmental risks into our workplaces. Many service centers feel that these negatives far outweigh the benefits.
In simple terms, any organic compound that evaporates into the air is, by default, a VOC unless it is listed by the applicable environmental compliance agency as an “exempt compound.” We want to minimize the use of VOCs because they contribute to air pollution.
Hazardous air pollutants (HAPs)
In addition to VOCs, another concern is hazardous air pollutants (HAPs), which are those pollutants that are known or suspected to cause cancer as well as resulting in serious health and environmental effects. Environmental and safety authorities often require reporting of the quantities of emissions of HAPs as well as VOCs. Not all VOCs are HAPs, thus reducing VOCs alone may not proportionately reduce HAPs. The best approach is to identify the VOCs and the HAPs in the products you use and reduce both types of pollutants as much as possible.
Toxic air contaminants (TACs)
Add into the mix toxic air contaminants (TACs) which, while not actually regulated by the U.S. Environmental Protection Agency (EPA), are monitored in many areas of the United States because they deplete ozone and can lead to increased global warming. Some common TACs are benzene, nickel, lead, carbon tetrachloride and ammonia. With care your use of TACs can be reduced along with the VOCs and HAPs.
In this article we will focus on VOCs; however, most of the concerns about VOCs apply to HAPs and TACs as well, and the action steps to reduce VOCs can be applied to them, too.
VOCs in general
The most common sources of VOCs in the service center are cleaning solvents, paints and varnishes. One of the primary characteristics of VOCs is that they tend to evaporate into the air quickly. When associated with cleaning, the fast evaporation of VOCs means that the part being cleaned dries rapidly, and likewise in the case of paints, the paint dries rapidly.
For winding treatment, the VOC-containing solvents in varnishes aid in the curing of the product. While fast drying is very advantageous, it also means VOCs are emitted into the air as a byproduct of the process, which isn’t good at all.
Since these released VOCs carry with them serious health risks, using VOC-containing products can also have a more direct financial impact in your bottom line in terms of insurance costs.
Health concerns should be the main reason to want to minimize or avoid use of VOCs. As an air pollutant they are not good if inhaled or absorbed by any person or living organism.
By taking steps to use alternatives to VOCs, we can reduce air pollution and avoid potential legal penalties. Using alternative products also may help control your company’s employee health and other insurance costs. While your insurance provider may not reduce your premiums because you have changed to a reduced or VOC-free product, the insurer could increase your policy cost because you are using products with VOCs.
Cleaning solvents
We will proceed to examine alternatives to each of these primary applications involving the use of VOCs, beginning with cleaning solvents. Besides their fast-drying properties, VOCs also quickly loosen and carry away dirt, debris and other contamination. The surface that is left is typically clean enough that coatings like varnish or paint readily adhere to the base material such as a winding or frame component.
Most alternative cleaners take longer to dry than solvents with VOCs and the alternative cleaners generally are not as aggressive in cleaning. That is, the cleaning process typically takes longer to remove the dirt, debris and other contaminants. There may also be a film left on the surface that must be wiped off so that varnish or paint will properly adhere to the base material. Some alternative cleaners can be heated and/or agitated to accelerate the cleaning process and make it more effective. If the cleaning process can be automated by using a machine instead of all-manual cleaning, the cleaning time labor factor can be reduced.
Alternative cleaners
Citrus-based cleaners are the most common type of alternative cleaners. There is a wide range of cleaning capabilities in citrus-based cleaners, so the best advice is to obtain small product samples and test apply them until satisfactory results are obtained. They can be used in cold (nonheated) parts cleaning equipment, such as an immersion tank or open rinse tank in which the part is bathed with the cleaner.
The base product of most citrus-based cleaners does not contain VOCs, or any substances that are considered by environmental agencies to be hazardous materials. As long as the material that is removed is also not hazardous, the residue should likewise be hazard-free. Therefore the cost and risk associated with disposal will be much less than with residue from parts cleaned with a hazardous substance. In either case, VOC or alternative cleaner, check the environmental regulations that apply to your facility’s location. Another upside of using citrus-based cleaners is that they smell nice — a vast improvement over solvented cleaners.
Another alternative cleaning method is ultrasonic cleaning (Figure 1), utilizing ultrasonic waves in a liquid to remove deposits from parts. Cleaning occurs as a result of the physical striking of microscopic gas bubbles formed by high-frequency excitation and from the chemical effect of a detergent that is added to the liquid. The ultrasonic system is most effective for cleaning parts with complex geometries and passages like armatures and components with blind holes. However, these machines are relatively expensive and used mostly for smaller parts.
Paints
Paints containing VOCs, as with cleaning solvents, dry relatively fast. However, in the process of drying, they release VOCs into the air, thus contributing to pollution and reduced air quality.
Alternative paints are usually water based and tend to take longer to dry than those with VOCs, and special care must be taken in applying water-based paints. Often a primer is needed to assure good adhesion of the topcoat.
However, the quality of the painted finish can be equivalent to that obtained with paint containing VOCs. A caution when using water-based paint is that one may be tempted to use heating to accelerate the cure, such as by placing a painted motor in the bake oven for a short period. Avoid doing that as it can cause the paint to degrade and peel or flake off — not to mention the potential to heat bearing grease to its dropping point (the oil in it literally drips out).
The solvents used to “thin” conventional paints are usually the primary source of most of the VOCs. Spray painting, whether aerosol container or spray-gun, tends to cause the most emissions of VOCs, whereas brush painting results in a large reduction in VOC emission as the relative volume of thinner is much less than with spray painting.
Brush applications
If you must use a paint containing VOCs, consider brush application. Brush application also results in better transfer efficiency. That is, more of the paint product is applied to the intended finish area, rather than being emitted into the air as with spray painting. There are drawbacks to brush painting versus spray. These include taking longer to apply, finish not as smooth, and coating tends to be thicker. The thicker coating can increase the temperature of a motor, particularly ribbed construction (e.g., TEFC), by hindering heat transfer.
And keep in mind solvents aren’t only used to thin solvented paint, they must be used to clean the painting equipment, which just adds to your costs. In many cases, you will find water-based paint is much less expensive than solvented paint, depending on the solvent used. Another option is an airless sprayer, which requires less solvent for spray applications. Both of these alternatives, water-based paint and airless sprayers, are certainly worth investigating.
Varnishes
The other common source of VOCs in the service center is the varnish used for treating windings. The VOC content of solvent-based varnishes is typically 40-50%. Changing to a 0% VOC solventless resin therefore drastically reduces the amount of VOCs emitted during the dip and bake process. As with paints, it is frequently the solvent used to thin the varnish that contains most or all of the varnish VOCs. The solvent is a necessary ingredient that allows the base varnish to penetrate the windings and to completely cure. During the dipping process the heat from the part being immersed causes VOCs to be emitted; the heat from baking likewise causes VOC emissions.
A simple yet effective method to reduce VOC emissions is to allow the excess varnish to drain from the windings (Figure 2) prior to placing them in the bake oven.
Consider non-VOC resins
Alternatives to solvent varnishes are 100% solids resins and reduced-VOC products such as some trickle resins. The 100% solids resins are available as either epoxies or polyesters, as are the trickle resins. Another benefit to the non-VOC resins is the fire safety aspect of inherently higher flashpoint.
Products containing VOCs are often more flammable than comparable resins with 100% solids. These products can be applied in the same way as with traditional solvent varnishes. That is, the dip and bake or trickle processes are no different than with products containing VOCs. The alternative products are available in higher temperature class ratings such as class F and class H.
Although they do not contain solvents, there are other components that are added to the solventless resin base product. For example, a resin may have a “stabilizer” added to it, which may have to be replenished with usage of the resin product. Similar to the way heating of a varnish causes the solvent to be given off faster than the base varnish, heating of the resin causes the stabilizer component to also be driven off.
The “good news” for the environment is that the stabilizer and other emissions from a 100% solids resin are much less harmful to the environment; and in most cases, are not substances that fall under environmental regulations.
Summary
Eliminating the use of products containing VOCs or reducing the VOC content of the paints, varnishes and cleaners you use makes good sense from a business standpoint while also addressing environmental and health issues. It’s a win-win-win (business, environmental and health) situation for you and for your employees.
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