Keeping chlorinated solvents in the loop

Closed-loop method enables safe use of chlorinated solvents

By Paul Simons

December 19, 2011

Chlorinated solvents have proven to be the best cleaning medium in many applications to achieve the highest-quality required cleaning results. However, chlorinated solvents come with environmental and safety risks. A closed-loop cleaning process offers a safe and environmentally responsible method for handling chlorinated and nonchlorinated solvents.

Cleaning metal components to be free of contaminants for optimal function is an important production step in the aerospace and other industries.

Cleaning metal components is an important production step in the automotive, aerospace, electronics, medical, and optical industries (see lead image).

High-precision cleaning is necessary to obtain a clean and contaminant-free surface for optimal function. It is also necessary to prepare products' and components' surfaces for downstream processes for proper adhesion of paint and other coatings, welding, and so forth, in order to produce high-quality products and assemblies that meet regulatory and safety standards (see Figure 1).

In many applications, chlorinated solvents, such as trichloroethylene, perchloroethylene, and methylene chloride, have proven to be the most effective chemicals to achieve the required, highest-quality cleaning results.

However, open handling and exposure to chlorinated solvents can come with environmental and safety risks.

Manufacturers considering aqueous solvents and biodegradable cleaners as alternatives to chlorinated solvents may find that so-called green solvents are sometimes less effective or do not meet the cleaning requirements for the product being manufactured. Aqueous and many alternative solvents typically have been less studied than their chlorinated counterparts; therefore, their long-term impact on health and safety is often less understood.

A new closed-loop cleaning process offers a safe and environmentally responsible method for handling chlorinated and nonchlorinated solvents. The system greatly reduces worker exposure to the solvents while also reducing solvent consumption and waste.

How the Closed-loop Cleaning Process Works

The closed-loop process uses sealed cleaning equipment technology combined with a safe delivery and handling system. The containers are connected via a hose with the closed-cleaning machine, allowing solvents to be pumped automatically in and out of the machine in a closed loop (see Figure 2). This method drastically limits vapor emissions and prevents spills and contact with the solvent.

The system includes two double-walled containers—one supplying fresh solvent, the other collecting used solvent for recycling.

The system includes two different, specially designed double-walled containers for the safe transport, storage, and use of solvents. One is exclusively designated for the supply of fresh solvent and the other for the collection of used solvent for recycling (see Figure 3).

The outer steel box protects the drum, preventing damage or spills. The containers also have specially designed fittings and couplings to prevent vapor emission during use and solvent transfer.

The used solvent is collected in a safety container system for professional recycling to close the loop, reducing solvent consumption and thus waste.

Active solvent maintenance includes on-site testing, lab analysis, and stabilization to enable manufacturers to benefit from the internal recycling within the cleaning machine. This extends the solvent life while maintaining high-quality cleaning results over a long period of time.

Complies With Standards. The closed-loop system helps manufacturers to meet regulatory requirements, including the National Emission Standards for Hazardous Air Pollutants (NESHAP) for air emissions; Occupational Safety and Health Administration (OSHA) for worker exposure; and the Resource Conservation and Recovery Act (RCRA) and Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) for spillage during storage and handling.

In an independent study1 done by the European Commission, the environmental and economic consequences of the introduction of additional Chemical Product Services in the field of metal cleaning were analyzed. The results were significant. While 754 kilograms of solvent was needed to clean 100 kg of oil using open-top cleaning machines, the amount of solvent needed to clean 100 kg of oil in closed-cleaning equipment, together with the safe supply and maintenance of the solvent with special service elements, was reduced to 15 kg. This represents a reduction of 98 percent.

A closed-loop cleaning process can help manufacturers achieve the high-quality cleaning results they require using chlorinated solvents while still operating within a safe and sustainable manufacturing environment.

Note

1. European Commission, Directorate-General Joint Research Centre, Institute for Prospective Technological Studies (2006): EUR 22213 EN, Technical Report Series, Chemical Product Services in the European Union, pp. 58-65.