Dust in an atmosphere where all the basic elements for an explosion are present, a fire outbreak or a dust explosion are likely.
Potential elements such as oxygen, fuel and dust in their right size and concentration in a confined area can spark primary explosions, and then secondary explosions with its severe consequences.
In order to help avoid explosions in areas where flammable materials are handled, it is necessary to classify dust into different zones. The purpose of identifying and classifying areas where explosive dust atmospheres and combustible dust layers are present is to permit adequate assessment of ignition sources of those areas.
Doing so will help to determine the most appropriate measures against combustible dust explosions.
There are three (3) main zone classifications for dust, which includes zone 20, zone 21 or zone 22.
Zone 20 Dust Classification
Zone 20 is defined as an area where a hazardous atmosphere formed by dust cloud in air is present continuously or for long periods or frequently. Dust layers may be formed as a result.
Sources where zone 20 atmospheres can be found include containers, pneumatic conveying lines, mills, filters, pre-separators, dry mixers and sieves.
Zone 21 Dust Classification
Zone 21 is defined as an area where a hazardous atmosphere formed by dust cloud in air is likely to occur in normal operation, but not frequently and only for short period. Layers of combustible dust may be generally present.
Examples where zone 21 atmospheres are present include grinding, sanding, open charging and so on. Such atmospheres are typically a meter away from the source of release. Poor air conditions in zone 21 atmospheres make it difficult to breathe.
Zone 22 Dust Classification
Zone 22 is defined as an area where a hazardous atmosphere formed by dust cloud in air is not likely to occur in normal operation, and if so then for a short period only. Accumulations and layers of combustible dust are present.
Zone 22 is usually a meter around the source of release or may be determined by a wall. Examples include dust escaping through leaks, and forming hazardous quantities, in bags and storage areas.
Envirox provides extraction and filtration products and solutions to assist in the capturing of combustible dust in all 3 dust classifications.
Our combustible dust collectors are effective in atmospheres where dust are present continuously or for long periods of time. They capture and filter dry dust and fumes with explosion risk applications.
Products from Envirox are outlined below:
- The Nederman FMCZ, popularly called the FMC cartridge dust collector, was designed to capture and filter dry dust and fumes in continuous operation.
- The Nederman NFKZ, also known as the NFKZ3000 baghouse dust collector is a modular filter best suited for handling large volumes of air with heavy material contamination levels.
- The Nederman AUTO-MZ, is a powerful free-standing filter suitable for non - continuous duty across various industrial and commercial applications that generate light to medium volumes of dry dust.
Extraction arms for at-source extraction:
Envirox’s extraction arms are effective means of getting rid of combustible dust at source. The extraction arms for at-source extraction will be most suitable where poor air conditions make it difficult to breathe. It prevents dust from getting into the atmosphere in the first place.
Products from Envirox are outlined below:
- The NEXD combustible dust extractor is designed for applications requiring hygienic dust collection. They are ideal for applications where large amounts of dust need to be extracted at the source.
- The NEX DX dust and gas extractor arm is ATEX-approved to provide an efficient, responsive extraction of explosive dust. They are suitable for applications in the oil and gas industries.
Explosion Isolation Valve:
CARZ explosion isolation valve from Envirox prevents the transmission of dangerous effects of explosion pressure wave and flames from a downstream equipment (e.g. dust collector) to upstream areas. It serves an add-on to a comprehensive dust collection solution that will act as a barrier against approaching flame front.