Engineering business solvents and hazardous waste reduction

Degreasing components using organic solvents can be a significant source of emissions and waste for engineering businesses. You can reduce costs, meet solvent emissions legislation and produce a safer working environment by changing your surface cleaning procedures.

Eliminating the need for degreasing

You could eliminate or minimise the need for degreasing by:

• keeping items well protected (eg using covers and stretch-wrap) and free from contamination between processes
• 'spinning-off' excess oils and allowing longer drain times between machining and cleaning components
• stacking components carefully before cleaning to reduce oil retention

Using alternative degreasing methods

You could also consider alternative cleaning methods to traditional acid bath and solvent vapour degreasing. The ban on 1,1,1-trichloroethane (an ozone-depleting substance) and reclassification of trichloroethylene as a Category 2 carcinogen make the following alternative methods more attractive:

• Mechanical cleaning - such as scraping, brushing, blasting, tumbling and vibration to remove dirt and grease.
• Aqueous cleaning systems - these generally have a wash stage (sometimes ultrasonically assisted), combined with rinse and hot air drying stages. This eliminates manual preparation such as hand-wiping with organic solvent.
• Biological cleaning - such as enzymes and surfactant/bacterial remediation systems.
• Controlled pyrolysis ovens - these burn off organic coatings and inks from metal surfaces at temperatures of around 930 °C. These systems have been successfully used to clean paint jigs and hangers, body panels and other metal components.

Improving solvent degreasing

Where you have to use solvent degreasing, consider making the following changes:

• use modern enclosed degreasing machines and hermetically sealed machines - open-topped vapour degreasing plant using higher risk solvents may require approval from a regulatory body
• fit cooling condenser coils below the extraction vent inside the machine to allow internal solvent capture and minimise vapour losses
• retrofit open-topped tanks with a lid - below any rim or other local exhaust ventilation extraction system - and with interlocks to ensure that extraction occurs only when the vessel is open
• rack or jig the items so that there are as few solvent traps as possible and that the items drain freely
• make equipment that transports the components through the degreasing process integral to the machine and don't allow items to carry solvent out of the machine
• turn the work in the freeboard zone to minimise solvent drag-out
• use powered hoists and lifts to ensure that the correct loading and unloading speeds are always used, ensuring minimum disturbance of the solvent surface and minimum solvent carryover
• when topping up the machine, avoid decanting losses by pumping solvents from the supply tank to the degreasing machine through a pipe system - or use sealed drums and a drum pump