Engineering business solvents and hazardous waste reduction

'Swarf' is metal waste contaminated with oil, water and other substances. The waste is considered hazardous but it is also a resource which can be reused either in-house or by another business - for example, a foundry or recycler.

You should reduce the cutting fluid content of swarf to increase its reuse value, make storage easier and safer, and avoid disposal, which has to be carried out by a specialist organisation. There are various methods for doing this:

• Dry machining techniques have been developed to eliminate the need for cutting oils. Dry swarf is produced and the potential hazards associated with handling cutting fluids are removed.
• You can use a centrifuge to separate the liquid from the swarf. Automatic machines have a continuous feed from a conveyor and generally deliver the swarf directly to a bin or a skip. You can send the coolant for cleaning and recycling.
• You can use magnetic separation for steel swarf in systems where the swarf is transported by flowing cutting fluid. The swarf is removed from the fluid by a strong magnet and then scraped mechanically from the magnet. Steel swarf has little value, but you can recycle the cutting fluid.
• You can dry swarf in a kiln to reduce cutting fluid contamination. Waste heat - eg from a compressor - can be used as a source of energy. This technique is normally only worthwhile for a business reusing the swarf itself.

When swarf is left in a bin or a skip, some of the excess cutting fluid will naturally drain under gravity. Use a bin with a mesh layer above the base and a tap to drain off the cutting fluid. Shovelling the swarf out of the bin instead of tipping it will keep the swarf drier. Use a skip with drainage holes, taking care to ensure the skip is within a bunded area to avoid polluting the soil or water sources with cutting fluid.