Virtual Flexo Plant

Parts Washer


Solvent sinks, commonly known as “parts washers,” are used in a print shop for the parts of the press that can be removed and placed in the parts washer to be cleaned. Solvent is typically supplied from a 30-gallon barrel and is re-circulated. The solvent is often filtered in the sink and used until it is dirty and no longer effective. Solvent sinks can be purchased and maintained by the printer or may be leased from a service company. If leased, the solvent sink is generally serviced by the equipment provider. that will remove and replace ineffective solvent on a regular schedule, typically using recycled solvent. The service company must be a licensed supplier and solvent recycler.

The benefits of a solvent sink include a reduction in the use of fresh solvent and improved worker safety because there is less handling of solvent-soaked shop towels to clean press parts. A solvent sink can be justified by the savings associated with reduced use of shop towels and solvents, as well as reduced waste disposal costs. In selecting a parts washer, be sure that it is large enough to contain the appropriate parts to be washed, such as ink trays.

Best Management Practices & Pollution Prevention

  • Purchase or lease a parts washer with an integral filtration unit.
  • Use solvents that are compliant with current state regulations. Many states now regulate parts washers as a cold solvent cleaner and have set a vapor pressure limit 1.0 mm Hg at 68oF.
  • Use solvents that have a flashpoint above 100oF to avoid OSHA regulations and ideally above 140oF to help avoid EPA hazardous waste regulations.
  • If not using a service for the solvent and a specific rule does not apply, use one that is either compatible or identical to the press cleaning solvent so that the used press solvent can be used in the parts washer prior to recovery or disposal.
  • Used solvent can be recycled on site with a solvent distillation unit. This unit will significantly reduce the amount of hazardous waste generated, with only the still bottom that has to be disposed of as a hazardous waste.
  • Solvent should only be replaced when necessary. Service provider schedules may need to be adjusted according to in-plant usage.
  • Keep lids closed when not in use to reduce solvent evaporation, which leads to fugitive VOC emissions.
  • Consider using a water-based (aqueous) cleaning solution parts washer.
  • Use drip racks or trays to increase drainage from small parts to minimize solvent loss.
  • Pre-clean parts with a rag or wire brush if possible.

For access to vendors who may supply alternative materials and equipment, see the PNEAC Vendor Directory.

Environmental Regulations

Air Emissions

The solvent used in parts washers is commonly naphtha or other similar solvent blend. Alternative low vapor pressure solvents are commonly a source of VOC emissions and should not be overlooked when considering emission calculations and reporting.

Measure the emissions from the solvent parts washer through a mass balance formula. Maintain records of the amount of solvent provided by the parts washer service provider. Compare the amount of solvent disposed of to the amount of new solvent provided during the previous delivery in order to measure the evaporative loss. If make-up solvent is added to the tank, maintain records of the amount of solvent added each time. These records should be compared to the previous amount of solvent added to calculate the evaporative losses.

Hazardous Waste

Typically, the waste solvent from solvent parts washers is classified as a hazardous waste due to the flashpoint of the solvent. Include this waste stream when calculating a facility’s waste generator status.

Hazardous waste solvent containers must be properly labeled with the EPA Hazardous Waste labels and must be manifested according to state and federal environmental regulations. The containers must also be labeled with the appropriate DOT labels (i.e., flammable warnings) and the transporter must have all appropriate DOT placards in place.

Health & Safety

Chemical appropriate gloves, apron and eye protection should be worn when using a parts washing unit.

Ample air ventilation should be provided.

The equipment should be properly grounded to reduce the risk of fire if the flashpoint of the solvent being used is less than 100oF.

Additional Information

Fact Sheet

The Flexo Environment