Controlled porosity is also employed in the manufacture of metal filters and diaphragms. They have the advantage over their ceramic counterparts
- of higher strength
- and resistance to mechanical and thermal shock.
The close control over the pore size and permeability is achieved by the use of powders having a narrow range of particle size.
- Perhaps the most commonly used filter elements are made of bronze (89/11 Cu/Sn), and spherical powder are used.
The filter profile is formed by a loose packing of the powder in the mould and the inherently poor compressibility of spheres is no disadvantage. Where products are required to have limited or localised porosity, conventional pressing is necessary and irregularly shaped particles are more suitable.
- Metal filters are available in a wide range of materials including copper,nickel,bronze,stainless steel and 'Monel',
- and are widely used for the filtration of fuel oils, chemical solutions and emulsions.
They are also efficient in separating liquids of varying surface tension, and have been successfully applied to jet engine fuels, where water is removed at the same time as the fuel is filtered.
Similar devices are widely used for sound damping on air compressors and the likes.