Ontario Region Environmental Protection Branch POLLUTION PREVENTION FACT SHEET Pollution Prevention Program - Federal Programs Division Fact Sheet #13: Pollution Prevention for Cleaning and Degreasing This Pollution Prevention Fact Sheet is one in a continuing series prepared under the Pollution Prevention Program of the Federal Programs Division of Environment Canada, Ontario Region. This Program is intended to help federal departments in Ontario become model environmental citizens by managing beyond compliance. This Fact Sheet presents the following: An introduction to cleaning and degreasing methods; Explanations of why changes are needed; New products and technologies; How to choose an alternative; Success stories; and Further sources of information. Introduction Cleaning and degreasing of metal parts is most often done to remove soils that interfere with the operation or performance of equipment, or to prepare equipment for subsequent procedures such as painting, plating or coating. Cleaning and degreasing is also carried out for purely cosmetic reasons to remove soils which cause an undesirable appearance. While most federal facilities use cleaners and degreasers for general maintenance and repair, some use them in the manufacturing of products. For example, the Royal Canadian Mint uses degreasers in the manufacturing of coins. Departments such as National Defence and Transport Canada are large consumers of cleaners and degreasers for the maintenance and repair of vehicles and aircraft. Most federal facilities are required to routinely clean and repair vehicles and equipment used in the operation of their buildings and the maintenance of their grounds. Common Methods of Cleaning and Degreasing Metal Parts Cold cleaning is generally performed in a tank of cleaner at room temperature. Usually, the items to be cleaned are agitated mechanically or ultrasonically. A varsol dip tank is an example of a cold cleaning system. Wipe cleaning or spot cleaning refers to localized cleaning of a workpiece. Typically, a lint-free cloth saturated with cleaners is used to manually clean the part. When the cleaning operation has been completed, the excess cleaner is left to evaporate from the workpiece. Vapour degreasing uses a partially full container of cleaner heated to its boiling point. The parts to be cleaned are suspended in the vapour cloud above the boiling liquid. The vapour condenses on the cooler parts, dissolves the contaminants and flushes the liquid mixture back into the hot liquid. When the cleaning process is complete, the parts are removed from the tank and they quickly dry in air.
Why Changes Are Needed Traditionally, chlorinated and halogenated hydrocarbons, mineral spirits and petroleum distillates have been used as cleaners and degreasers. These products are recognized for their high cleaning, fast drying performance. However, a number of commonly used solvents are ozone depleting substances. The use of many of these solvents is restricted or banned. Others which are still in use are scheduled for phase-out in just a few years. (See Fact Sheet #12 - Ozone Depleting Solvents). Other common solvents contribute to the creation of low level ozone, a component of smog produced when the volatile organic compounds in the solvents evaporate into the atmosphere. Many solvents are highly toxic to humans and wildlife. They may have chronic or acute effects, and some are carcinogen or teratogenic. The human health risk can be quite pronounced as workers are often in close contact with solvents for extended periods of time. Without proper safety equipment or ventilation, airborne concentrations of solvent vapour can easily reach dangerous levels, not just for workers, but for others in the same building. Avoid or Reduce Avoiding the use of cleaners or degreasers is always the most environmentally responsible option. Before spending time and effort looking for alternatives, step back and take a good look at why you are using harmful cleaners or degreasers in the first place. Ask yourself if there are any steps your organization can take to eliminate or, at least, reduce the use of these harmful substances. For example: 1. Attempt, as much as possible, to eliminate or reduce cleaning operations. 2. Try to find an alternative to the actual cleaning process using either a new technology or a new solvent. 3. Finally, if no alternatives are applicable, some changes can be made to the existing cleaning and degreasing equipment. To improve solution efficiency in the cold cleaning process, a "closed loop" system, including a filter and an oil skimmer, should be installed. Such a system will extend the life of the solution and at the same time decrease the amount of solution to be disposed of. To reduce air emissions in the vapour cleaning process, the following add-on controls should be taken into consideration: Slowing down the rate of entry or removal of the work load from the vapour degreaser. Improving the rack design to ease the part s drainage. Increasing the freeboard height 1 of the tank. Adding refrigerated coils on the freeboard. Installing simple flat or rolling covers. Alternatives to Solvents It is often very difficult to completely eliminate the need for cleaning or degreasing operations. Fortunately, a wide range of alternatives are available. The following is a description of different options that are presently available. New Products Aqueous Cleaners are mixtures of water, detergents, surfactant, emulsifiers and other additives that promote the removal of organic and inorganic contaminants from hard surfaces. They can be used to remove light oils and residues left by other cleaning processes, as well as to remove heavy oils, greases and waxes. When using aqueous cleaners, rinsing and drying may be required. To prevent corrosion, a rust inhibitor will have to be added to the cleaner or to the rinse water. The new process may also occupy more floor space. Enzyme Cleaners are a particular group of aqueous cleaners. Enzymes are mixed with warm water and can be used in any process that uses aqueous or semi-aqueous cleaners. Their principal advantage is that after use, if they have not been contaminated with hazardous products, they can be disposed directly in the sewer system. Enzyme cleaners are new products, and some testing might be necessary to determine the optimal conditions for cleaning and degreasing. Semi-Aqueous Cleaners are comprised of a group of cleaning solutions composed of natural or synthetic organic solvents, surfactants, rust inhibitors and other additives. They include terpene, esters, glycol ethers, 1 Freeload height is the distance between the surface of the liquid and the top of the tank. 2
and N-methyl-2-pyrrolidine (NMP). The term semiaqueous refers to the use of water in some part of the cleaning process, such as washing, rinsing, or both. In general, they have a good ability to remove heavy grease, waxes and tar. Their low surface tension allows them to penetrate small spaces. Some also have a low vapour pressure and thus have low volatile organic compound (VOC) emissions. Depending on the type of cleaner, adverse effects will vary; some may be toxic to aquatic life, others are highly flammable or need rinsing and drying. Before making a final decision, more investigation will be required on the selected product. Petroleum Hydrocarbons include petroleum distillates and paraffinic hydrocarbons. The principal advantage is that they do not produce wastewater and are recyclable by distillation. However, they are flammable or combustible, and some have very low flash points. Hydrochlorofluorocarbons (HCFCs) were designed to lower the emission of ozone-depleting substance in the cleaning process, however, they still have an ozone depleting potential. Therefore, they are recommended only as short-term solutions to the use of chlorinated solvents. Solvent uses of HCFCs will be banned in Ontario effective July 1, 2000. New Technologies The Completely Enclosed Vapour Cleaner (CEVC) is an alternative to the conventional vapour degreaser. In a CEVC, the work load is placed in an air tight chamber into which solvent vapours are introduced. After cleaning is complete, the vapours are evacuated and captured. Using that process, solvent air emissions are virtually eliminated. No significant changes are required in the operator routine, but each batch will take more time to be cleaned. The operating cost will be reduced due to the significant recovery of solvent, however the initial capital cost and the energy requirements are relatively high. Automated Aqueous Cleaning and Aqueous Power Washing are two new systems that replace cold cleaning and vapor degreasing processes. They both eliminate solvent hazards by using an aqueous or semi-aqueous cleaner. They are easy to install and operate but require wastewater treatment. The Automated Aqueous Cleaning system is used to clean small parts like the ones usually cleaned by the vapour degreasing process. The washer sprays an aqueous or semi-aqueous solution across the parts to remove oil and debris. The parts travel through a series of chambers, each with different concentrations of cleaning and rinsing solutions. Excess sprayed solution is recovered and reused. Because water and cleaning solutions can be reused, the operation of an automated aqueous cleaning system will reduce water and soap consumption. However, the initial capital cost and the energy requirements are relatively high. Aqueous Power Washing systems are being used in a variety of industries to clean large parts such as jet engines, electric motors, landing gear parts or even a whole battle tank. The parts to be washed are placed on a turntable inside a power washer unit. As the turntable rotates, the parts are sprayed from all angles with water at high pressure and elevated temperature. Aqueous power washing systems provide more efficient cleaning compared to manual tank cleaning, and cleaning times are drastically reduced. When combined with an oil skimmer and a filter, the aqueous power washing unit will significantly reduce water and soap consumption. Ultrasonic Cleaning applies high frequency sound waves to the liquid cleaning solution. The sound waves generate zones of high and low pressures throughout the liquid. In the zones of negative pressure, the boiling point decreases and microscopic bubbles are formed. As the sound waves move, this same zone becomes positively pressured, thereby causing the bubbles to implode. This is called cavitation and is the basis of ultrasonic cleaning. Cavitation exerts enormous local pressure and temperature on parts. When using this method, parts with small crevices can be cleaned more easily to meet cleaning standards. By making aqueous cleaners more effective, ultrasonic cleaning eliminates the need for strong solvents. The problems associated with ultrasonic cleaning are that parts to be cleaned must be immersible. Thick oils and greases may absorb ultrasonic energy and may not be removed. Testing must also be done to obtain optimum solution and cavitation levels for each operation. In the electronics industry, cleaning flux after soldering might be a problem. The use of Low-Solid Fluxes will eliminate the need for cleaning, and Inert 3
Atmosphere Soldering totally eliminates the need for flux. These two new technologies will eliminate solvent use. In the avionic industry, solvent stripping of surface coatings has historically been used. This can be avoided by using Media Blasting Technology. Many types of blasting media are available for paint stripping. The most common type is plastic, but wheat starch or dry ice can be used as well. The greatest advantage of media blasting is that it does not produce wastewater. On the other hand, spent media containing paint chips may have to be disposed as hazardous waste. Fortunately, some plastic media are recyclable. How to Choose an Appropriate Alternative The first step in choosing an alternative, after a cleaning technology has been selected, is to decide what kind of detergent is best suited for the specific application it will be used for. For this Fact Sheet, we will concentrate on selecting aqueous or semiaqueous cleaners. But similar steps can be followed to choose other types of alternatives. Generally, testing of different products will be necessary to make a final decision on the exact type of cleaner to be used. But before starting any testing, a pre-selection is recommended. To do so, the person responsible for the selection should evaluate all the information provided by the different manufacturers and more specifically through the Material Safety Data Sheets (MSDS). The person responsible should look for the following information: Are there any components of the detergent on the list of Accelerated Elimination and Reduction of Toxics (ARET) substances? The ARET list should be compared with the information found under the "hazardous ingredients" section on the MSDS. If this is the case, the concentration of each of the ARET substances should be considered. If alternatives that do not include an ARET substance are available, they should be used instead. Does the detergent contain either 2- butoxyethanol or butyl carbitol as an ingredient? This information will be found under the "hazardous ingredients" section in the MSDS. Do not be surprised; 2-butoxyethanol (also called butyl cellosolve) is widely used in water based cleaners, but it does pose health problems and is likely to become regulated in the future. Also, D-limonene or other terpene(s) are sometimes used in aqueous solvents. Terpenes are biologically active, and may cause environmental and human health problems. In order to recognize a cleaner made with terpenes, it might be directly mentioned on the list of ingredients, or it may specify "strong citrus or pine odour". This is an indication that some terpene was used in the fabrication of the cleaner. Is the product classified as a volatile organic compound (VOC)? A VOC will have a vapour density greater than 1 (density of air = 1), a high vapour pressure, and a percentage volatility by volume greater than 50%. If the solution is a VOC, it should not be considered as a perfect alternative. Is the ph above 12.5 or below 2? Under "special disposal" in the MSDS does it mention that dilution is necessary before disposal? This often means that the ph is too high or too low to be safely disposed of. A component with a ph higher than 12.5 or lower than 2 will have to be considered as a hazardous waste material and disposed of as such, increasing operating costs. The ph level, along with flash point information, is usually mentioned under the "physical properties" section of the MSDS. A cleaner with a flash point lower than 61 o C is considered to be a hazardous material. Depending on the end use of the cleaning solution, a rust inhibitor can generally be added or included in the solution. If the solution is used in a power washing machine; a defoamer may also be required. Check with the manufacturer whether adding one or more of these products will affect the final solution. Remember: The choice of an environmentally friendly detergent depends greatly on the type of cleaning technology used, the parts to be cleaned, and the contaminant to be removed. Conclusion A large variety of environmentally friendly alternatives to conventional cleaning and degreasing methods is available on the market place. The choice of a specific alternative will be mainly determined by the budget available, the type of operation to be 4
replaced, the parts to be cleaned and the contaminant to be removed. In any Pollution Prevention Program, cleaning and degreasing operations should be investigated and environmentally friendly alternatives implemented to replace the use of harmful solvents. Success Stories The Royal Canadian Mint in Ottawa is the exclusive producer of collection coins in Canada. Before pressing the coins, the blanks have to go through several burnishing and cleaning operations In the past, the blanks were cleaned in a vapour degreaser which consumed large amounts of Freon. Recently, the Royal Canadian Mint acquired a new ultrasonic system using an aqueous detergent. The main incentive for switching from Freon to an aqueous cleaner is regulatory compliance, but there are cost benefits as well. In fact, the payback period of the new equipment is less than a year. The Royal Canadian Mint engineers are so pleased with the ultrasonic system that they are now looking to completely eliminate their use of Freon by installing another automated aqueous washer in the tooling area. The Société de Transport de l Outaouais (STO) is the bus company that serves the cities of Hull, Aylmer and Gatineau, Quebec. The fleet consist of over 200 buses. In the late 80's, the managers of the mechanical workshop decided to eliminate the use of solvent in cleaning and degreasing operations. They were using strong solvents in a bath cleaning process. They decided to buy an Aqueous Power Washing Machine. A Typhoon "PC" from Proceco, including a special wheel washer and a closed loop system, was installed in 1989. They now successfully use the washing machine with a mild aqueous soap. The time required and the cost associated with cleaning and degreasing operations have drastically decreased as a result of the use of the aqueous power washing machine. The workers also appreciate the improvement of the quality of their work environment. and degreasing solvent at most of the electrical and mechanical workshops at 8 Wing Canadian Forces Base (CFB) Trenton. A pilot project was set up by Environment Canada - Federal Programs Division - Ontario Region and the Base Environmental Office to reduce or eliminate the use of varsol on the Base. In 1995, two automated Aqueous Parts Washers were installed in the Electrical Mechanical Engineering (EME) Workshops to replace the varsol baths. This pollution prevention project was very successful and reached its goal of eliminating pollution at its source and replacing a harmful process by an environmentally friendly one. Many of the Base workshops have now eliminated or reduced their use of harmful cleaners and degreasers. One year after the installation of the first parts washers, the Base is now equipped with 8 automated aqueous power washers of different sizes, 2 ultrasonic cleaners, and 2 enzyme-based small parts cleaners. Success Stories Does your department have a pollution prevention success story to share? Other government departments in Ontario would like to hear about your experience in dealing with a particular problem. Please provide relevant information to the Pollution Prevention Coordinator, Federal Programs Division, Environment Canada. We will ensure that all interested parties obtain this information. Further Sources of Information Alternatives to Chlorinated Solvents in Cleaning Applications. California Environmental Protection Agency, 1995. To receive a copy contact Ron Nobes, Federal Programs Division, Environment Canada. Tel: (613) 952-8995. Guide to Cleaner Technologies, Cleaning and Degreasing Process Changes. U.S. Environmental Protection Agency, Feb. 1994, EPA/625/R-93/017 Contact: : Pollution Prevention Information Clearinghouse. Tel: (202) 260-5917 Fax: (202) 260-0178 Varsol (mineral spirit) is a hazardous material that used to be used extensively as a cleaning 5
Guide to Cleaner Technologies, Alternatives to Chlorinated Solvents for Cleaning and Degreasing. United States Environmental Protection Agency, February 1994, EPA/625/R-93/016. Contact: Pollution Prevention Information Clearinghouse. Tel: (202) 260-5917 Fax: (202) 260-0178. Web site: http://www.epa.gov/ Seminar Publication, Solvent Waste Reduction Alternatives. United States Environmental Protection Agency, September 1989, EPA/625/4-89/021. Pollution Prevention Information Clearinghouse. Tel: (202) 260-5917 Fax: (202) 260-0178 Guide to Cleaner Technologies, Organic Coating Removal. United States Environmental Protection Agency, February 1994, EPA/625/R-93/015. Contact: Department of Toxic Substance Control Office of Pollution Prevention and Technology Development. Tel: (916) 324-2659 Fax: (916) 327-4494 Web site: http://www.epa.gov/opptintc/index.html For further information about the Pollution Prevention Program for federal facilities in Ontario, please contact: Environment Canada Ontario Region - Environmental Protection Branch Federal Programs Division 49 Camelot Drive Nepean, Ontario, K1A 0H3 phone: (613) 952-8675 fax: (613) 952-8995 e-mail: fpd@ec.gc.ca All Fact Sheets can be found on the Internet at: www.on.ec.gc.ca/epb/fpd (aussi disponible en français) Water-Based Alternatives to Solvent Cleaning, An Interactive Teleconference. The Great Lakes Pollution Prevention Centre, February 11th 1993. Contact: Great Lakes Pollution Prevention Branch. Tel: (416) 973-7805 Fax: (416) 973-7438 Web site: http://www.cciw.ca/ppc/info/avail-pubs.html 6