Hot dip galvanising processes are prescribed for local authority pollution control under Section 2.2 of Schedule 1 of the EPA (prescribed processes and substances).
The collection of the emissions created by the galvanising process are generally achieved by either a total enclosure over the galvanising bath or peripheral extraction around the sides of the galvanising bath.
The total enclosure of the galvanising bath is the most efficient method of collecting emissions and virtually ensures complete removal of fumes.
A number of designs can be used, dependent on the actual layout of the galvanising bath and the work hoists.
Normally design air volumes are based on 1500-2000[m.sup.3]/hr/[m.sup.2] of galvanising bath area because little 'tramp' air is being extracted.
The total enclosure of the galvanising bath is usually only practical when the direction of flow of the work is along the length of the bath.
Emissions from galvanising baths should be continuously monitored for particulate matter to indicate a filter bag failure or any malfunction with the system.
When, for various reasons, it is impractical to totally enclose the galvanising bath, peripheral extraction is often the only method available.
Peripheral extraction generally takes the form of low level hoods, incorporating a series of suction slots, fitted around the sides of the galvanising bath.
This technique results in much larger air volumes for a given galvanising bath size.
The system fan can be provided with a pole changing motor or with a frequency converter, as the high suction capacity is only required during the actual galvanising process.