Working Safely With Metalworking Fluids

Metalworking Fluid (MWF) is a type of coolant used during metalworking processes such as machining, grinding and milling. They are typically neat oils or water-based fluids used to reduce the heat and friction between the cutting tool and the work piece, helping to prevent burning and smoking. The fluid also helps to carry away debris such as swarf and fine metal particles. It helps to improve machining performance and prolong the life of the cutting tool, as well as provide corrosion protection for the surfaces of work pieces.

Exposure to metalworking fluids can cause irritation of the skin in the form of dermatitis, and lung diseases such as occupational asthma and occupational hypersensitivity pneumonitis.

Control by Local Exhaust Ventilation (LEV) is good practice in the handling and disposal of metalworking fluids.

Machines using metalworking fluid should be equipped with LEV to draw mists away from the operator. Some machines may come equipped with this, whereas others require LEV to be fitted retrospectively.

Effective LEV will provide the machine with adequate negative pressure so that air is drawn inside, preventing the escape of mist when the machine is opened.
Where installed, local exhaust ventilation should undergo routine checks and maintenance, all of which should be noted in a log book. Every system is required to undergo a thorough examination and test at least every 14 months as per the requirements of Regulation 9 of the COSHH Regulations.

Within the machine, the pressure and flow of metalworking fluid delivery and the cutting speed of the tool should be suitably set to reduce mist generation to a minimum. Splash guards should also be added to reduce fluids from escaping.

The use of compressed air to blow swarf and debris from machines after cutting is a significant source of exposure, as it can generate a mist and cause fluids to splash onto the skin. There is also the issue of elevated exposure to noise when open air lines are used. Alternatives to manual compressed air lines include coolant wash guns, vacuums and compressed air fixed inside the machine.

Employees should also be encouraged to use tools such as brushes and swarf hooks so that direct contact with the fluids is avoided wherever possible.

Refer to HSE documents G402 and G403 for further information.

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