Playing with fire? a guide to fire-retardant conveyor belts

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When conveyor belts fail to meet manufacturer specifications, resulting in premature wear or damage due to excessive heat and oil, the risks generally remain low, shares Sytze Brouwers, Chief Application Engineer for Fenner Dunlop BV (Dunlop Conveyor Belting) in The Netherlands. While costly, it may not pose significant safety threats. In stark contrast, if a supposed fire-retardant conveyor belt ignites and fails to provide adequate resistance to flames, the ramifications can be dire, as it could propagate fires throughout the facility.

With increasing economic uncertainties, companies in the cargo industry are feeling compelled to investigate their operational budgets, often leading to reductions in costs, including those associated with fire-retardant conveyor belts. There are serious concerns regarding whether safety is being compromised for the sake of price.

Moreover, some suppliers may create a false sense of security regarding the fire-resistance of their products. The harsh reality is that the inadequacies of a belt will often go unnoticed until catastrophic events occur.

Evidence from testing and real-world scenarios indicates that some notable users of conveyor belts in Europe, like significant ports, may be operating with belts that do not uphold their claimed fire-resistant capabilities. Increasingly, operations that should be utilizing fire-resistant belts are using inferior alternatives, often driven by economic reasons.

Insurers are also growing increasingly worried, with reports indicating that claims related to conveyor-belt fires average approximately $8 million each. To delve deeper into this complex and critical issue, insights from Sytze Brouwers, a respected authority on conveyor belting and chairman of international standards committees, have been sought.

NO CONVEYOR BELT IS FIRE PROOF

As fire-retardancy protocols and testing techniques for conveyor belts tighten, they become vastly perplexing. One crucial factor to remember is that no conveyor belt can be entirely fireproof. While manufacturers can enhance rubber using specialized additives and chemicals to improve its fire resistance, the fundamental materials, often consisting of polyester and nylon, remain flammable. Every belt is liable to burn upon exposure to an open flame, so assessing the necessary fire resistance for specific operational environments is critical.

ENVIRONMENTS WITH INFLAMMABLE DUST AND GAS

The EN standard outlines safety requirements for conveyor belts intended for general use (not applicable to underground operations). EN Category 1 serves as the basic flammability and electrical safety guideline. In environments where combustible materials, such as coal dust or fertilizer, exist, it is vital for belts to prevent the creation of static electricity that could ignite hazardous atmospheres. Dunlop adopted a strategy ensuring that all its belts are anti-static and comply with EN/ISO 284 standards, making them suitable for ATEX 95 classified zones. Contrary to popular belief, it’s not mandatory for belts in ATEX-designated areas to be flame-retardant.

ATEX assessments pertain to settings with explosion risks due to dust or gas in the surrounding air. Organizations procuring conveyor belts for ATEX-regulated areas should always request certificates from accredited testing bodies, like the German Institute Dekra Exam GmBH.

Interestingly, belts with reliable anti-static functionality often indicate higher quality rubber. Almost all black rubber types contain carbon black, crucial for optimal mechanical characteristics. Superior carbon black enhances the overall quality of the belt.

ABOVE-GROUND AND GENERAL SERVICE APPLICATIONS

Fire safety necessitates various international classification standards, with several tests employed to gauge the self-extinguishing properties of conveyor belts. Multi-ply rubber belts reinforced with textile fabrics or steelcord are the standard types utilized for transshipment and general applications. Most tests for conventional industry belts adhere to EN/ISO 340, distinguishing between fire resistance with (K) or without (S) covers.

The definition of 'with or without covers' is critical, as the degradation of the cover throughout operational life diminishes fire-resistant protections. For moderately abrasive materials like coal, K (EN Class 2A) is typically sufficient. However, more abrasive materials or substances prone to self-combustion would require opting for S (EN Class 2B) grade belts.

Both K and S grades demand that the rubber skim bonding the carcass's fabric layers be fire-resistant. Particularly for S-grade belts, thicker rubber skims are essential. Confirming the necessary specifications by obtaining data sheets from manufacturers is advisable.

Another reason for buyers to always insist on receiving technical data sheets before placing orders lies in the information concerning the level of abrasion resistance. Unfortunately, components featured in fire-resistant rubber compounds tend to adversely affect wear-resistant properties, causing fire-resistant belts to wear out more quickly. Buyers should aim for an average abrasion-resistance level not exceeding 150mm3 for purely fire-resistant belts.

At Dunlop, technicians have successfully tackled these challenges by engineering a fire-resistant rubber that also boasts remarkable abrasion resistance—50% superior to DIN Y standards for abrasion-resistant rubber. This innovation prolongs a belt's fire resistance and overall operational lifespan. Nevertheless, it is vital to acknowledge that this achievement is quite rare within the conveyor belt sector.

EN/ISO 340 TESTING

Testing under EN/ISO 340 requires exposing six belt samples to a naked flame, after which the time taken for each to extinguish is recorded. Following flame removal, airflow is introduced to the sample for a designated period, with no re-ignition permitted. For a belt to pass, visibility of flames should not exceed 15 seconds for individual samples and a cumulative total of 45 seconds across group samples. This parameter significantly impacts how effectively fire can spread along a moving belt, and it's crucial to understand the potential for fire to be conveyed to neighboring structures.

NEW CEN FIRE TEST STANDARDS TO BE INTRODUCED

Recognizing challenges surrounding existing fire test methodologies, the CEN standards committee has been strategizing over recent years to enhance these protocols. Recent discussions among technical experts across Europe led to agreements to adapt and implement smaller scale tests—including successfully testing fire safety within manufacturers' laboratories. While stringent, these new tests demonstrate a robust commitment to elevating fire-safety standards. Notably, major insurance companies are engaging with these developments, indicating promising advancements for safety-conscious entities.

DON'T PLAY WITH FIRE

Even if manufacturers provide test certificates, these may only pertain to the specific samples tested during certification. The actual delivered belts could potentially fall short of acceptable standards. For heightened assurance, consider ordering an additional meter of belt for independent accredited testing. The cost of neglecting caution in this matter is unquantifiable.

N.B. This technical overview pertains to conveyor belts utilized above ground. For inquiries specific to underground testing and standards, please seek targeted guidance.

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