Aqueous Parts Washing Equipment

Background Information

There are two basic approaches to aqueous cleaning, batch processes and continuous processes. The approach your company decides upon will be based on the production levels that you require. For a high production level a continuous process is probably the better choice, while batch processing is sufficient for moderate and lower production level.

Batch Processing
The parts are loaded into the washer in batches. A cleaning operation (washing, rinsing, drying) must be completed for a batch before another operation can be started. Batch processing is labor intensive, so it will require an employee to operate.

Continuous Processing
Parts are loaded continuously into the washer system and are moved through the cleaning system by a conveyor type system. Continuous systems are not labor intensive, so the washer would not need an operator at all times.

The other distinction between models of aqueous parts washers is the method of cleaning that is used. The most commonly used methods of cleaning are immersion cleaning, spray cleaning, and ultrasonic cleaning. These methods are briefly described below.

Immersion Cleaning
The parts are dipped into cleaner-filled tanks. The cleaning solution may be agitated and/or heated to improve cleaning. Immersion is often a batch process.

Spray Cleaning
Spray cleaners increase the cleaning ability by combining the cleaning chemistry with physical cleaning (sprayer). Spray cleaning may be batch or continuous.

Ultrasonic Cleaning
Ultrasonic cleaning is a special type of immersion cleaning in which high frequency vibrations are transmitted through the solution to produce a scrubbing action. It is effective in cleaning very small parts.

Purchasing Guidelines

The following equipment purchasing guidelines were developed by the Wisconsin Department of Natural Resources to help Wisconsin businesses identify and evaluate pollution prevention opportunities. Although it is not possible to cover every aspect of equipment selection, the list covers some of the more important points and provides considerations for evaluating aqueous parts washing equipment.

• What is the configuration and size of the part to be washed?

• Does the configuration or size lend itself to spray washing or immersion?
• Does the part have grooves or cavities that may require a special cleaning method?
• Will the configuration of the part promote "drag-out"? Drag-out is contamination of the rinse solution by dirty wash solution that remains on the part after it has been removed from the wash stage.

• Does the material from which the part is made make it susceptible to damage from the washing method you are considering?

• What is the quantity of parts to be washed?

• Smaller quantities can be handled efficiently in batch systems, while large quantities may be more efficiently handled in a continuous process system.

• What specific functions must the cleaning equipment perform?

• Will the cleaning solution need to be heated?
• Is a dryer system necessary to remove moisture from the part immediately afterwashing?
• Is a multi-stage process necessary to increase the cleanliness of the parts?
• Is an oil separator/skimmer an available equipment option?

• What are the contaminants that need to be removed?

• Is the proposed cleaning agent compatible with the type of equipment to be used?
• If immersion cleaning is going to be used, will the contaminants be suspended in the cleaning solution or will they settle to the bottom of the tank?
• Would the contaminant be more easily removed with the aid of physical or mechanical treatment?

• What are the time constraints on the process?

• Is the cycle time required in seconds, minutes, or hours?
• Will a batch system be fast enough or will a belt-driven or monorail-driven continuous process be required?
• Could an ultrasonic cleaner reduce the cycle time?

• Will the equipment manufacturer provide a test cleaning of your parts for your inspection?

• Will the cleaned parts meet the cleanliness standards of your clients?

• What are the wastewater treatment requirements for the contaminated cleaning solution and rinse water?

• If you discharge to a public sewer, contact your Wisconsin DNR wastewater pretreatment specialist and your local publicly owned wastewater treatment plant (POTW) to determine wastewater regulations.
• State law requires that plans and specifications be submitted to the Wisconsin DNR before installation of wastewater treatment equipment!

• What are the wastewater requirements if I am not on public sewer?

• If you discharge to a subsurface soil absorption system (septic tank system), you may only want to consider closed loop cleaning systems. In order to avoid groundwater contamination discharges of industrial wastewater to a septic systems are restricted. If discharging is not outright prohibited, then pretreatment of wastewater and a DNR Wisconsin Pollution Discharge Elimination System (WPDES) permit will be required. The pretreatment process must remove all petroleum, volatile organic chemicals, metals, emulsified oil and any toxic wastes prior to discharge to the septic system. Periodic sampling may be required. Contact your DNR wastewater specialist for more information.
• Direct discharges of industrial wastewater to surface waters of the state (streams, lakes and the storm sewers and ditches that lead to them) also require a DNR WPDES permit. Contact your DNR wastewater specialist for more information.

• What operations are to be performed immediately after cleaning?

• Will the parts be painted, plated, or galvanized?
• Will these operations be affected by the aqueous washer?

• Will the parts need to be handled automatically or can they be handled manually?

• Are there any local, state or federal health and safety or environmental regulations that apply to the use of this equipment?

• Depending on the type of industry using this equipment, there may be categorical effluent standards that apply to discharge of process wastewater.

Suppliers and Manufacturers Lists

The Wisconsin Department of Natural Resources (DNR) Hazardous Waste Minimization Program developed the following lists of suppliers and manufacturers of aqueous parts washing equipment as a service to Wisconsin businesses. This is not a complete list of available suppliers/distributors and manufacturers. The lists also are not an endorsement of any of the specific manufacturers or suppliers listed. The DNR, by providing the list, makes no representation that the products will or will not ensure compliance with environmental and safety laws in any specific application. Hazardous waste generators are advised to thoroughly evaluate the services and compliance status of any company or equipment that they use to manage their hazardous wastes. Contact your local waste-water treatment plant to determine any applicable discharge requirements and avoid discharging industrial wastewater to septic systems. Other local, state, or federal laws may also apply. If you have questions or corrections regarding this list contact the Hazardous Waste Minimization Program at 608/267-3763.

AQUEOUS PARTS CLEANING EQUIPMENT: LOCAL SUPPLIERS AND DISTRIBUTORS*

* Includes companies located in Wisconsin and companies that have participated in UWEX's Cleaning Expositions and other Wisconsin cleaning workshops. For other distributors contact the manufacturer directly.

AQUEOUS PART CLEANING EQUIPMENT: MANUFACTURERS

Additional Publications on Aqueous Parts Washing and Solvent Reduction Available from the DNR Hazardous Waste Minimization Program's Pollution Prevention Clearinghouse

General

SW-223 • Cleaning, Opportunity Checklist (DNR 4 pp) 89
SW-259 • The Good, the Bad and the Banned: Solvent Red. (Univ of TN 80 pp) 91
SW-261 • Industrial Cleaning Source Book (UWEX SHWEC 54 pp) 93
SW-700 • Metal Parts Cleaning--Waste Minimization (EPA 50 pp) 530-SW-89-049
SW-751 • Reduction of Toxic Organic Discharges and VOC Emissions Using Plastic Media Blasting (EPA Proj Sum 8 pp) 600-S2-87-014
AM-172 • Solvent Parts Cleaning Environmental Overview (DNR/DOD 7 pp) 95