Rope properties – heat resistance and fire resistance

In technical rope design and manufacturing, materials and construction are combined to produce ropes with specific characteristics, or properties, such as strength and resistance to fire, abrasion, and more. A specific combination of properties is desired in order to best support specific practical applications of the ropes.

For ropes used in escape and rescue, two important rope properties are heat-resistance and fire-resistance. While these sound like the same thing, or at least similar, they are actually very different things.

A rope that is deemed to be “fire-resistant” is one that is constructed to withstand external impingement by fire that can melt or burn the rope. This is critical for professionals who work in and around fire, such as firefighters. A rope that is described as “heat resistant”, on the other hand, is a rope designed to withstand the heat generated during controlled descent.

Let’s take a closer look at each…

Fire-resistance. The ability of a rope to withstand insult by fire is a function of the polymers used to make the rope, the layering of fibers in the rope, and the diameter of the rope.

Of course, the proximity of the rope to the fire also affects the rope’s integrity. Obviously, the best solution to prevent rope failure due to fire is to keep the rope away from fire. The next best solution is to get down and off the rope as quickly as possible if the rope is exposed to fire. (This, by the way, is why we think a descent speed of 3 meters per second is smarter than 2 meters per second.)

Among rope polymers, Technora and Kevlar are the best in terms of their ability to withstand direct flame impingement. As a result, DEUS uses Technora and Kevlar in the core, sheath or both in our fire-resistant ropes.

No polymer is 100% fireproof. Even Technora and Kevlar fibers lose strength as a result of repeated exposure to high heat, even if the heat may not be enough to cause visual damage. Given this, it’s important that firefighters know when the personal escape ropes they carry have been weakened by proximity to fire. To help, some DEUS fire-resistant ropes are constructed with a Technora or Kevlar core and a polyester sheath. The polyester sheath acts as an early warning to signal fire exposure — if the sheath has melted, the Technora or Kevlar core has likely experienced fire damage and weakened strength.

Heat-resistance. All of the potential energy in a body at height is converted to heat during controlled descent. This heat is easily enough to melt thermoplastic polymers like Dyneema, nylon and polyester. The rule of thumb for descent over long descents is, “Once you start, don’t stop.” This is because conventional descent devices can quickly get so hot that they will melt through a rope if the rope is not moving in the device.

DEUS controlled descent devices are designed to help manage heat in two ways. First, most of the braking is done away from the rope. This keeps the component parts that are in contact with the rope cool enough that they do not melt through the rope. Second, DEUS ropes made for long descents use high-temperature polymers like Technora and Kevlar. Depending on the purpose and use of the rope, the Technora and Kevlar may be in the core or the sheath.

In general, DEUS Rescue combines different polymers, construction methods and other elements of rope design to provide a range of technical ropes with different properties, to meet a variety of needs for different markets and applications.

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