Choosing chemical resistant structured cabling systems the smart way
The conditions under which structured cabling systems are deployed aren’t always ideal. When developing or extending a solution, there are many different factors to consider.
6 MIN READ
The environment in which the cabling and network devices will be introduced is one of the most important. Cables and components such as distribution boxes need to remain operational for decades, even in harsh environments where they might be exposed to extreme temperatures or chemicals. Certain substances can cause cables to become brittle or less flexible. After a while, the cabling sheath may crack, causing rapid deterioration. Depending on the chemicals in question, this can happen after prolonged exposure, or immediately. Fortunately, special sheathing materials can increase resistance to chemical degradation.
However, there’s more to finding a solution than just applying the most robust sheathing to every cable. Improving performance in one area might affect cabling in other areas, for example by making handling during installation harder. What’s more, cabling on a single site will often run through different areas, such as production facilities with factories as well as offices, making matters even more complicated. Cost is another consideration. So how to make smart, safe decisions without overspecifying or overspending?
What is chemical resistance?
Before we answer that question, let’s take a closer look at chemical resistance. This term generally refers to the (non-) interaction of an assessed item, or its shell, with chemical substances occurring in a given environment. A product recommendation for exposed cabling components must be based on the exact chemicals involved. Knowledge of the effects of chemical exposure on cabling components is vital to selecting the appropriate product. Furthermore, cost-benefit analysis and a worst-case impact assessment should always be carried out.
Unfortunately, chemical resistance can’t be expressed in a single number or simple formula, because so many different parameters act upon the test specimen simultaneously. The ratios and relationships that exist between these parameters are too numerous and complex to be covered completely in a single test.
Concentration, exposure, and temperature
Product selection isn’t only made based on the chemical substance in question. Its concentration in a solution or a gaseous mixture also needs to be taken into account. Generally, tests involve exposure to only a limited number of chemicals: gasoline, toluene, and related substances (olefins or olefinic solvents), oils, greases, sulphuric acid, detergents, aggressive gases, alcohols, esters, and acetone.
Another group of chemicals penetrates the molecular structure of a material, resulting in swelling. These include olefinic solvents such as gasoline, toluene, benzene, or brush cleaners. Generally, the swelling is reversible – sheathing returns to its original state once the chemical has disappeared. However, if swelling is too extreme or occurs frequently, it can lead to irreversible damage to the material. All metals are naturally resistant to this group of chemicals, but plastics are not.
Once it has been determined which chemicals may affect a cabling component, we need to specify the intensity and type of contact. In the case of liquid chemicals, this could be in the form of splashes (such as oil droplets), liquid jets (from a leaking pipe, for example), or full immersion (such as an acid bath). Short-term (five minutes or less) or medium-term (up to three hours) chemical exposures are relatively rare, temporary, and usually unplanned. Recurrent or continuous long-term influence (over three hours) are usually recurring stresses that are part of a process (such as emptying a tank).
The speed of chemical processes is strongly dependent on the ambient temperature. A temperature difference of +10° C leads to a doubling of the reaction speed. Material is thus affected by a chemical at 30° C twice as fast as at room temperature (20° C). At 40° C the reaction is even four times as aggressive. Conversely, the reaction speed is halved when cooling down by 10° C. When assessing the protective measure against a chemical, the highest operating temperature must therefore be taken into account.
Simplified, the combination of intensity and duration of the chemical exposure and the nature of the chemical substance can be interpreted as “chemical load”.
Low to medium chemical loads are caused by less aggressive chemicals such as soaps, organic acids (acetic or formic acids), highly diluted alkalis or acid solutions, alcohols, silicones, oils, lubricants or greases in the case of splash loads or occasional flooding.
Aggressive chemicals such as acids and strong bases generate in any case medium (in case of splashes) to high (flooding, immersion) chemical loads.
Choosing the ideal structured cabling solution for all parts of your project
Standard products should be capable of dealing with low and moderate chemical loads without side effects. Our ‘Resistance table’ shows the effects of certain chemicals on most commercially available materials. These chemicals include solvents, oils, fats, alcohols, acetone, and aqueous solutions. In many cases, low or medium chemical loads cause no problems, although certain materials will have an issue with higher loads.
You can find the resistance table in the Brochure ‘Chemical Resistance’ under Downloads: Cable knowledge
However, if any section of your cabling runs through an environment where it may be exposed to acids, alkalis, or aggressive gases, it is vital that you consult with experts.
In short, it is important to know which environmental factors are relevant in different locations and to understand the exact intended usage of cabling and components. In this way, you won’t need to run a cable with the most heavy-duty shielding throughout the entire environment. Instead, you can define solutions that offer the best performance where it counts, without compromising in other areas.