Dust control
The dust produced when machining MDF is finer and more readily dispersed into the surrounding air than the dust from solid wood or particleboard. in this respect, MDF machining dust is similar to the dust produced when sanding finely textured hardwoods, both requiring a higher level of extraction efficiency. In particular, a minimum capture velocity of 20 to 30 m/sec is required at the dust generation point compared with 10 to 20 m/sec recommended for normal wood dust. The air velocity in the ducting should be in the range 15 to 20 m/sec to prevent an accumulation of dust (plugging) which could create a fire risk.
Meeting these requirements does not necessarily involve the installation of new extraction equipment for companies changing over from wood or particleboard to MDF. Experience has indicated that effective extraction of the MDF dust can be achieved in most instances by reducing the size of the collector hood openings and placing them as close as practicable to the point of dust generation. Collection efficiency will also be improved by closing off ducts connected to machines which are not in use subject to maintaining the recommended minimum air velocity in the remaining ducting. In small and medium size companies, individual extraction units fitted to each machine have been found to be cost effective. CNC machines, which by the nature of their operation, generate large volumes of dust, are normally fitted with a brush collection head to limit the spread of dust and a high efficiency extraction system.
As the fineness of MDF dust puts it in a class with sander dust, special procedures may be required to maintain adequate safety standards when the amount of MDF dust represents more than 20% of the total dust load. Extraction plant sited close to work areas inside the factory should be properly enclosed to reduce the risk of injury due to fire or explosion. Ducting should be fitted with explosion relief panels. Consideration should also be given to fitting fire detectors and automatic extinguishing equipment in large extraction systems.
Referring to personal exposure to dust from woodworking operations, some European countries have regulations limiting the amount of dust in the air in the workplace. A typical Occupational Exposure Limit (OEL) is 5 mg/m3. The recommendations in these notes relating to the efficient and safe operation of dust extraction equipment will normally result in satisfactory working conditions. Where problems arise, manufacturers should consult a specialist dust extraction company.
Companies operating wood waste burning boilers can use MDF dust as a fuel subject to certain precautions against internal explosions. Up to 20% MDF dust may be burned in combination with other more particulate waste, subject to effective mixing of the dust. Companies concerned mainly with the disposal of large volumes of MDF dust can use it in boilers fitted with injection burners as a supplement to gas or fuel oil. Advice on the selection and operation of woodwaste burning boilers should be obtained from specialist suppliers.
