Engineering business solvents and hazardous waste reduction

Reducing your use of metalworking fluids enables you to cut costs and the quantity of hazardous waste you need to dispose of.

Choosing the right metalworking fluid

Select the correct fluid for the particular operation and metal. Unsuitable fluids waste materials and time, damage machinery, and lead to poor quality products and increased waste-disposal costs. In contrast, a small quantity of specialised fluid, used as a spray mist or for minimal lubrication, can produce large cost savings and increase tool life.

You could choose a less hazardous fluid - based on vegetable oils instead of mineral oils - or an additive-free fluid, eg short-chain chloroparaffins used as lubricating agents, triazine compounds used as biocides, nitrites and secondary amines used as corrosion inhibitors. Alternatively, you could use dry machining to eliminate metalworking fluids.

Good housekeeping with metalworking fluids

Good housekeeping is essential to avoid fluid contamination, extend fluid life, avoid waste and secure safer working conditions. You should:

• Keep fluids clean by labelling all containers, vessels and pipework clearly.
• Keep fluid contact surfaces clean. Do not add clean fluid to a dirty machine or return fluid spills to the machine pump.
• Use biocide to control bacteria and fungicide to control fungi (yeasts and moulds) outside specified limits.
• Remove tramp oils - eg hydraulic and slideways oils from metalworking fluids. The most common forms of contamination are tramp oil leaking from parts of the machine, small metal particles from the cutting process, airborne particles and reuse of fluid recovered from swarf.
• Use only freshly diluted fluid at concentrations recommended by suppliers. Diluting fluids below the recommended level is a false economy as they degrade, machines corrode more easily and the surface finish is poor. If the fluid concentration is too high, this can lead to foam formation and spillages.

Monitoring metalworking fluids

Regular condition monitoring of metalworking fluids, especially for concentration and pH, enables you to extend fluid life and take corrective action at the appropriate time. For example, the build up of particulates allows other contamination to occur. You should:

• record the data on a chart and assess it for trends
• use a check sheet for solid waste to identify sources and types generated
• use a stock rotation scheme to ensure materials are used before their use-by date
• use automatic fluid management systems where appropriate

Disposing of metalworking fluids

You can use on-site treatment to reduce contaminant levels in effluent below the consent levels set by Northern Ireland Water. Treatment is essential as you must not discharge contaminated surface water directly to surface water drains and watercourses.

Spent fluids can be separated into organic and aqueous fluid by adding chemicals. You can discharge the separated water to sewer if it meets the conditions of your trade effluent consent. The sludge produced must be collected by a licensed waste treatment business.

You could consider alternative fluid disposal options such as evaporation, which concentrates spent fluid and produces a residue with potential as a fuel.