DSS083: Dust Explosion Hazards in Textile Industries

In this episode of the DustSafetyScience Podcast, we review dust explosion hazards in textile industries.

In recent episodes, we’ve gone through some case studies covering dust explosion and fire incidents across various industries. The studies are a great way to illustrate what can happen, but overall industry assessments give a better idea of what could happen in the future and deliver insights that could prevent a major explosion from happening.

Today’s industry assessment is based on a paper published by Dr. Luca Marmo, Ada Ferry, and Enrico Danzi in the Journal of Loss Prevention in the Process Industries, titled ‘Dust explosion hazard in the textile industry’ it examines dust explosion hazards in textile industries.

There are a couple of reasons why this topic is a good place to start with industry assessments.

Textile materials aren’t commonly seen as combustible dusts, often even by people in these industries.
It addresses a lot of common objections in industries not traditionally regarded as having combustible dust hazards. Operators will claim that their material can’t catch fire or explode or there is no history of combustible dust explosions. While this may be true at their facility, it may not be the case worldwide.

The authors state in the paper, “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.

What are the Different Types of Textiles?

The authors group textiles into three different types:

Regenerated textiles: derived from natural resources like wood pulp
Synthetic textiles: includes nylon, polyester and acrylic
Natural textiles: includes wool, cotton, silk and linen

What Does the Typical Processing Operation Look Like in a Textile Facility?

Processing is generally a combination of opening, combing, and spinning the textiles.

Opening is the process of opening up a compact bail or the ball of material brought to the facility. It can generate dust because particles in the bail are released when it is opened up.
Carding is drawing out the material into linear threads. This is usually done with rotating drums that have small metal teeth on them.
Combing further draws out the material. This is the stage where rocks, knots, lumps, burrs, and other impurities are drawn out.
Spinning includes stretching, twisting, or winding the fibers to make threads or yarns for the textiles.

Textile Explosion Case Studies

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 localized, 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, which was covered in Episode #76, 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 smoldering 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.

Five Observations by the Paper’s Authors

Dr. Marmo and his colleagues tested various materials and came up with five observations about textiles.

The best strategy is to have a facility’s materials tested instead of making generalizations that could be seriously wrong.
Carding and combing are the dustiest processes, followed by opening the bales.
Samples from different areas of a facility can have different size and explosibility characteristics. Dust sampled from one location can be non-explosible, but more dangerous dusts could be elsewhere.
Textiles tend to settle in layers, which can affect the dispersibility of the dust. However, if a primary explosion or process upset lifts the finer dusts, they will stay in the air and lead to a large explosion.
Textiles are nontraditional, meaning that they don’t fall under the classical definitions of spherical, or particle size for combustible dusts. It’s important to note that the new definition of combustible dust in several standards include any finely divided solid that can cause an explosion irrespective of size and shape.

Conclusion

Nontraditional dusts like textiles represent safety challenges because they are not always recognized as explosible. More industry assessments can change the perception that nylon flocking explosions and similar incidents are isolated events and lead to much-needed changes in safety standards.

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