PRECOATING ON AIR FILTERS
Precoting is a
coating composed by microgranuels of inert materials (usually obsidian, known
as perlite or volcanic glass) very small in dimensions but sufficiently big to
not penetrate in filter fabric. Once injected in air filter intake with clean
cartridges and with clean air, they make a sheet of inertial dust on the
cartridge surface that increase their efficiency. Practically this dust acts
just like a sand layer on a sand filter.