Pacific Northwest Pollution Prevention Resource Center Pracfical

Pacific Northwest Pollution Prevention Resource Center Practical Solutions for Economic and Environmental Vitality. PARTS WASHERS Aqueous-Based vs. Solvent-Based Parts washers are commonly used in auto repair shops to Mineral spirits are classified as VOCs that contribute to clean parts or components. Parts washers include cold photochemical smog. The solvents also contain toxic cleaning units, vapor degreasers and conveyorized de- components like benzene, toluene and xylene. Benzene greasers. Cleaning solutions used in parts washers in- is an established human carcinogen; toluene causes cen- clude: 1) solvents, and 2) aqueous cleaners. tral nervous system damage; and xylene causes birth defects. The low vapor pressure blend contains a chemi- Solvent Cleaners. Solvents clean by dissolving cal called n-methyl pyrrolidone which is a reproductive away dirt. Solvents include petroleum-based solvents and developmental toxin. These solvents pose a toxic such as mineral spirits, stoddard solvent, and petrole- risk to workers and the surrounding community. If the um naptha, and organic solvents such as trichloro- solvents are improperly handled, they can contaminate ethane, trichlorethylene, benzene, and xylenes. the site. Aqueous Cleaners: Aqueous cleaners are pH- Why Use Aqueous-Based Cleaners? neutral or alkaline water-based solutions that break Water-based cleaners and operation systems are a viable down and remove dirt from part surfaces. Semi- alternative to mineral spirits used in repair and mainte- aqueous solutions that contain small amounts of sol- nance parts cleaning operations. An aqueous-based parts vents are also available. washer is much like a large dish washer. It uses water and detergent combined with heat and mechanical ener- What’s Wrong With Petroleum Solvents? gy to provide the cleaning action. A solvent style parts washer is filled with several gal- lons of solvent that is stored in a settling pan at the bot- Aqueous cleaning products are water-based solutions tom of the washer. A small flame-tight electric liquid that, unlike petroleum solvents, are non-flammable and pump is immersed in the solvent and skims clean sol- non-hazardous. Instead of dissolving grease, aqueous vent from near the top of the settling tank, and pumps it parts washer units utilize heat, pressurized water, soap at low pressure through a stiff flexible nozzle onto a action, and agitation to break up dirt and grease. metal grating above the liquid where the metal components rest. Dirt and dissolved heavy greases fall into the Although they clean differently, aqueous cleaners per- bottom and settle to the bottom of the tank. form as well as solvents in most cases. Some units are even fully automated, thereby reducing labor costs and Mineral spirits and other chlorinated solvents are com- increasing productivity. monly used for parts cleaning because of their effective- ness in removing oil, grease, grime, and burnt-on car- Advantages of Using Aqueous-Based Solvents bon. However, their continued use raises significant environmental, health, and economic concerns: Lower hazardous waste generation and management costs; Chlorinated solvents can contaminate used oil, re- Little or no solvent vapors or aerosol mists that can sulting in costly disposal; be harmful to your workers' health; Petroleum and chlorinated solvents contain chemi- Equal or better cleaning performance; cals that may be toxic if inhaled, and some solvents Reduction in cleaning labor with some aqueous may increase the risk of cancer; cleaning units; Petroleum solvents evaporate quickly, making Large cleaning capacities; worker exposure difficult to control; Elimination of fire hazards; Solvent cleaning units are often the largest source of Longer solution life. a facility’s hazardous waste; and Some solvents leave an oily residue, requiring addi- Cleaning Systems tional cleaning prior to painting or finishing. There are five major cleaning system types commonly Petroleum solvents are highly flammable. used today: This product was funded through a grant from the Washington State Department of Ecology. While these materials were reviewed for grant consistency, this does not necessarily constitute endorsement by Ecology. Sink-On-A-Drum flushes the parts and cleans them just like a dishwasher. This type is the most common used in auto repair shops. It This is a more aggressive cleaning method than the other is a sink with a brush mounted on a drum which contains systems. The formulation can be neutral or alkaline since the water-based cleaner. The sink has a faucet and flow the workers’ hands do not contact it. The formulation is brush for cleaning the parts. The water-based cleaner is generally heated to between 120° and 180°F. These units heated to about 105°F. Many units have filters for remov- are made of metal and often have filters or oil skimmers. ing particulates and oil; some units have oil skimmers. The Spray cabinets, because they are automated, reduce labor units are made of metal or plastic. Because the workers’ costs for cleaning. (NOTE: never use mineral spirits in a hands contact the cleaner, the formulations used with a sink spray cabinet as this could create a fire/explosive hazard.) -on-a-drum must have a neutral pH to prevent skin damage. Advantages Disadvantages Advantages Disadvantages --High level of cleaning performance --Moderate to high initial start-up cost Ideal for light-duty cleaning activities Difficult to clean heavy or stubborn soils --Ideal for heavily soiled parts --Uses more electricity than solvent Lower initial start-up costs unit Not suitable for large parts --Large cleaning capacities available No toxic vapors, less irritating to skin --May require rust prevention for steel --Automatic units reduce labor costs parts (rust inhibitors, additional dry- Minimal waste production --Lower waste management costs ing) --Excellent for aluminum parts Enzyme Cleaning System These systems are generally modified sink-on-a-drum units. They are made of plastic and the cleaner is heated to Ultrasonic System about 105 degrees F. The system includes an enzyme This type of system relies on sound energy to accomplish cleaning formulation that supports the growth of microbes cleaning. Through a process called cavitation, the energy which are introduced either directly into the cleaning for- causes bubbles to form; these bubbles explode in crevices mulation or in a filter. Because there are microbes, the for- and holes to clean the parts. These systems are most appro- mulation is of neutral pH. The microbes biodegrade the oil. priate for cleaning complex parts like transmissions and An advantage of this system is that the bath cleans itself carburetors. Higher pH cleaners can be used in these units and may last indefinitely without requiring changeout. The since workers’ hands do not contact the cleaner. Like the majority of debris, oil, grease, and dirt should be removed spray cabinet, these systems are automated so they reduce prior to placement in cleaning unit. Heavily soiled parts labor costs for cleaning. Similarly, you should avoid using may overload the system. mineral spirits in this kind of system. Advantages Disadvantages Advantages Disadvantages Ideal for light-duty cleaning activities Microbial units require more mainte- Ideal for hard to clean parts with blind High initial start-up cost nance to keep microbes alive holes or hidden surfaces (transmissions, Lower initial start-up costs carburetors) Difficult to clean heavy or stubborn No toxic vapors, less irritating to skin soils Very high performance cleaning Minimal waste production Not suitable for large parts Significant reduction in cleaning labor Immersion Parts Washer Managing Your Aqueous Cleaning Wastes This type of unit consists of a sink with a false bottom. The Aqueous wastes are typically less toxic than petroleum sol- bottom can be removed or opened so the parts can soak in vents and, therefore, managing those wastes are often easi- the reservoir. Like the sink-on-a-drum, there is a faucet and er and less expensive. Proper management of aqueous flow brush for hand detailing the parts. The units are heated wastes depends on the type of cleaning solution used, type to about 105°F and can contain filters and oil skimmers. of equipment, and the type of wastewater treatment system Both metal and plastic units are available. in the facility. (Note: It is illegal to dispose of any parts washer solutions into drywells, onsite septic systems, storm Advantages Disadvantages drains, or onto the ground). Reduces scrubbing time and reduces More expensive than Sink-On-A-Drum labor costs units. Onsite Septic Tanks: No type of industrial waste may Allows for extended soaking time May be difficult to clean ever be disposed into on-site septic systems. This may contaminate your septic tank or drain field, which may result in a costly system failure. Spray Cabinet Oil/Water Separators: Since parts washers emulsify oils In this type of system, the parts are placed inside a cabinet and greases, disposal of aqueous solution into an oil/water and the door is closed. High pressure spray from nozzles separator is not effective. When emulsified, oils are not sepa- rated and will simply pass through the system. This product was funded through a grant from the Washington State Department of Ecology. While these materials were reviewed for grant consistency, this does not necessarily constitute endorsement by Ecology. Municipal Sewer System: In some cases, aqueous solu- Frequently Asked Questions tions may disposed into the municipal sewer system. How- ever, special permission is required from the sewer utility, Q1: Are aqueous-based cleaners more expensive than miner- who may also require laboratory testing of the waste. Al- al spirits cleaners? ways contact your municipal wastewater utility before utiliz- A: Companies can reduce labor costs by utilizing automatic ing this disposal method. aqueous parts washers. Start-up costs may be greater initially, but Evaporation of Aqueous Solutions: Since most aqueous many units can pay for themselves with increased productivity.

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