Drum filters are cylindrical machines used in industrial applications to filter liquids with high concentrations of suspended solids. They use an internal vacuum to draw water through their outer filter surface, trapping solids on the drum surface. They can have removable screen-type filter panels or sieve holes. Drum filters are economical and have few moving parts. They can be used for micro-sieve or perforated filters, which use filter aid to trap sediment. The drum rotates against a flexible plate or knife to remove trapped sediment. Both types of drum filters are effective and cost-effective.
A drum filter is a large cylindrical machine typically used in industrial applications to filter liquids that carry high concentrations of suspended solids. The rotary drum filter works by drawing water through its outer filter surface into its inner space by means of an internal vacuum. The suspended solids in the water are trapped on the drum surface and the filtered water is then pumped out. Drum filters may use removable screen-type filter panels or have a pattern of sieve holes in their surfaces for use with a filtration aid coating. Drum filters have a minimum of moving parts and are economical to operate and maintain.
This machine typically consists of a large drum that rotates through a tub or bath filled with contaminated water. The inside of the drum is equipped with a vacuum duct in the center and a system for pumping the filtered water. Once the system is started, the rotating drum has a powerful vacuum created within it which draws the dirty water from the tub through the filter element inside it. The suspended solids are trapped on the outer surface of the drum filter to be discarded or used according to their nature.
Drum filters using fine mesh panels are typically equipped with a spray system that washes away solids collected by the filter elements as the drum rotates. This variant is commonly known as a micro-sieve drum filter and is typically used in applications where solids need to be rejected. The micro-screen drum filter is particularly useful for cleaning water contaminated by coarser solids, such as animal hair or feathers, which would clog conventional filters. The filter panels are also simple to replace once worn out.
Perforated drum filters are often used in water treatment plants that remove large amounts of fine sediment from water. They can also be used to remove wastewater from suspended sewage products. These filters operate on the same basic principle as removable panel filters, but employ a layer of regularly applied filter aid to trap sediment. The drum is perforated with numerous holes which create a sieve-like outer surface through which water is drawn. The drum is then lined with materials such as diatomaceous earth or perlite which carry out the filtration process.
The drum filter rotates against a flexible plate or knife which scrapes away the trapped sediment for later use or disposal. This knife removes a thin layer of filter aid while exposing fresh, pristine material to continue the filter cycle. This causes gradual depletion of the filter aid layer requiring regular drum coating. Both types of drum filters are not only very effective in separating heavy and dense suspensions, but can be cost effective due to the simplicity of the systems.
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