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ATEX fans for combustible dust & textile fibres

05 September 2022

Combustible fibre accumulation is an issue in dusty and textile industries but automated dust collection, high airflow systems and ATEX fans can prevent explosions from happening.

Dust explosions can occur in any activity in which solid materials are treated and finely divided. Small sized particles are produced during manufacturing processes. Large particles fall while smaller particles remain suspended for unlimited periods. Powder is measured in microns. A micron is a unit of length equal to 10-4 (0,0001cm). Material handling fans are required where solid and bulky materials need to be handled or conveyed, for example in food processing or biomass applications. In food processing applications the likes of flour, sugar and grain need to be transported effectively and efficiently to manufacture the final product, it is likely that in these scenarios, an ATEX material handling fan is required due to the combustible nature of the solids.

The transport of textile fibres in air

Transporting fibres by air is an important process, and one with little alternative, in textile industries. In the production of non-woven fabrics, sometimes the used fibres are processed and carried along long distances to be distributed to machinery such as mixers and packing machines. The air is used as the method of transportation to carry a potentially large volume of fibres and as such the fan chosen should be able to continue in operation having carried these textile materials through the impellers while continuing to produce the pressure and airflow required to prevent a blockage in the system. Optimisation of the entire system depends on selecting the right size fan with appropriate straight bladed impellers. In the industrial fan marketplace, we call these radial bladed fans, radial fans, or material handling fans.

Many industrial fans can handle dusty or slightly dust air but only a limited range can work with textile fibres.

Combustible fibres in the textile industry

All textile processing, whether spinning, reeling, or blending, produce fibre. When not managed responsibly the fibres created during this intensive process, can pose a hazard to buildings and employees as fibres can quickly accumulate. Dust can collect on surfaces such as rafters, roofs, suspended ceilings, ducts, crevices, dust collectors, and other equipment. When the dust is disturbed and under certain circumstances, there is the potential for a serious explosion to occur. The build-up of even a very small amount of dust can cause serious damage. Combustible fibre accumulation remains an issue in the textile industry but automated dust collection systems, high airflow systems and ATEX fans can create a proactive solution to prevent explosions from occurring.

The MBZM P/R and AAZA P/R offer effective and efficient airflow and the safe explosion proof transportation of textile fibres.

What is combustible dust?

Combustible dust is any material that can disperse in air and catch fire when exposed to an ignition source.

Combustible dusts can include but are not limited to most solid organic materials (sugar, flour, grain, wood etc). carbonaceous materials (charcoal, soot, textiles (lint, cotton), many metals and some non-metallic inorganic materials. Some of these materials are not “normally” combustible, but they can burn or explode if the particles are the right size and in the right concentration. Learn more about ATEX gas and dust zones on our website.

What other workplaces are at risk of dust explosions?

- Dust explosions have occurred in many different types of workplaces and industries, including:
- Agriculture (e.g., fertiliser plants, composting facilities, grain elevators, silos, etc.)
- Food production (e.g., sugar factories, bakeries)
- Chemical manufacturing (e.g., rubber, plastics, pharmaceuticals)
- Fabric products manufacturing
- Woodworking facilities
- Metal processing and manufacturing (e.g., zinc, magnesium, aluminium, iron)
- Recycling facilities (e.g., paper, plastics, metals)
- Coal mining, processing, or coal-fired power plants
The disguised explosiveness of dust
According to Dr. Luca Marmo, Ada Ferry & Enrico Danzi in their published paper: Journal of loss prevention in the process industries they state: “There’s a diffuse feeling that the risk of dust explosions in the textile industry is limited or even negligible.”

The reality is that the risk is not negligible. Explosions are happening in this industry and causing loss of products, facilities, and lives.
According to Dust Safety Science, the paper reviews some case studies of dust explosions in the textile industry. The first one they mention is a 1987 linen dust explosion Harbin, China. On March 15, 50 people were killed and 177 injured in a series of explosions so violent that the seismographic records registered nine peaks. There was one primary explosion followed by eight secondary ones, all of them so devastating that 13,000 square meters of the factory were damaged.

The explosion originated in one of the nine dust collection units. Although the ignition source was not identified, the authors hypothesized that electrostatic discharge or a localised, glowing nest of material ignited the explosion, which propagated from the dust collector through the ductwork and involved all the other units in the carding section. The pressure lifted the dust layers on the floor, causing secondary explosions in the carding and spinning sections and underground textile stock areas.

The second case study referenced in the paper is a 2001 nylon flock explosion in Italy. This incident, started in a dryer after it had been shut off so that threads could be retied. When the dryer was powered back on, the resulting explosion propagated back to the dust collector, and the other dryers and blew out the side of one of the ducts. There were also flash fires that injured three workers.

The third incident covered is a 1995 flock fire and explosion at Malden Mills in Massachusetts. 27 people were injured and over 40% of the plant was damaged. The cause was an electrical spark created by the electrostatic grid system at the beginning of the production line.

The last case study covered in the paper is a 2001 wool dust explosion in Italy. This facility, which carried out washing, carding, and wool combing activities, was full of dust containing vegetable residues. When smouldering combustion started in the basement, where several filtering cells were present, a huge deflagration occurred and caused a 20 to 30-meter flash fire, which was fuelled by the layers of dust. In this case, the impurities and oil vegetable residue on the wool fuelled the explosion.

MBZM P/R Medium Pressure Centrifugal Fan with Straight Impeller

Material handling fans with a straight impeller also include the medium pressure MBZM P/R. The fan manufactured in Fe360 sheet. The fan paint finish is a Qualicoat polyester powder coating stoved at 200 °C with an average film thickness of 70 microns. The average heat resistance of the coating is 180°C with peaks at 200°C.  The housing is fully welded and joined. The simple inlet straight blade impeller is also made of Fe360 sheet statically and dynamically balanced. The impellers are painted with epoxy primer that can resist temperatures of up to 300°C. The motor is a standard asynchronous squirrel cage motor with IP55 protection and class F insulation. Manufactured with standard voltages: 230V 50Hz in single phase motors and 230/400V 50Hz in three phase motors up to 2kW and 400/690V 50Hz. The standard orientation for the MBZM P/R is LG270, this can be adjusted in models 220 to 620. In sizes 710 to 1000 the orientation is fixed.

The MBZM P/R is designed for dusty, very dusty, solid material and textile fibres.

Designed with inline installation in mind The MBZM P/R series is suitable for solid material transport and textile material transport. The MBZM P/R’s maximum working temperature of carried air is 130°C and ambient air 60°C.

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