Q&A WITH HELU: OIL & CHEMICAL RESISTANCE
Not all environments where you find cables and wires are the same. Factors that must be considered for cables in an IT closet or running through an office building are not the same as the demands placed on cables in an industrial environment. Harsh chemicals, oils and other lubricants are just a few of the challenges that cables that deliver power or transmit data in industrial environments must overcome to keep operations online. Regional Sales Manager David Newton of Helukabel USA goes into detail and answers some of the questions he hears in the field about industrial cables and their resistance to substances found in the industrial sector.
Q: In which industries do cables need to be resistant to organic and inorganic substances?
a: Many industrial markets must consider the environmental impact of the cables and wires they use. Machine tools, chemical plants, food and beverage processing, manufacturing and assembly, oil and gas, and renewable energy – solar and wind – are just a few industries that expose cables and wires to highly aggressive chemicals, detergents, solvents, oils, greases and other lubricants that can render the equipment they support inoperable if the cables are not protected or resistant to these organic and inorganic substances. Compared to the general market, the industrial segment requires cables and wires to be manufactured with the most technically advanced compounds to withstand the chemicals and oils found in industrial environments, while still maintaining flexibility and UV and flame resistance.
Q: What negative effects can oils, solvents and chemicals have on the performance of cable sheathing?
a: Did you know that oil is an ingredient in the production of rubber? And if you park or store your car tire in a puddle of oil, the tire will lose its protective properties and warp or wrinkle. The same goes for certain aggressive chemicals and oils: the longer an outer casing is exposed to these substances, the worse it will become. Depending on the substance to which the casing is exposed, the plasticizers added during the production of the casing are displaced or absorbed by the substance they come into contact with.
UL, CSA, and VDE are just a few of the independent testing agencies that provide guidelines for cables to ensure they perform well in applications involving aggressive chemicals and oils. Some common oil tests used in UL 62, UL 1277, MTW, and Oil Res I and II test the resistance of a cable by completely immersing it in oil for various temperatures and periods of time. These tests are used on cables to achieve various UL-specific approvals, such as machine tool wire (MTW), tray wire (TC), and service cord (ST, SO, and DLO). Cable jacket assemblies that meet these approvals include PVC, PVC/nylon, TPE, or rubber.
If the inner conductors or even the bare conductor are exposed due to sheathing
If a cable breaks, there is a risk of short circuit or fire if it is not maintained in time.
Q: What are some visual indicators that a cable's sheathing or insulation is being compromised by exposure to oil and chemicals?
a: There are four key indicators that the outer casing is being compromised by exposure to oil and chemicals and should prompt the user to consider replacement during scheduled maintenance to prevent unexpected failure and subsequent unplanned downtime. These indicators are:
Cracks – Oil or chemical exposure has resulted in the complete removal of plasticizers. This hardens the insulation and sheathing, making them brittle and more susceptible to cracking/breaking.
to swell – Exposure to oil or chemicals has caused the oil to migrate into the plasticizers. This results in a noticeable increase in the diameter of the insulation and sheathing.
Melting – Oil or chemical exposure has been absorbed and combined with the plasticizer, causing the bond to become softer and more elastic than intended.
Discoloration – Oil or chemical exposure has caused the plasticizers to spread along with the dye from the insulation and sheathing.
Q: What other factors can exposure to oil and chemicals worsen the life of a cable's sheath and insulation?
a: Cables used in industrial environments are exposed to a variety of environmental and mechanical conditions that can further accelerate the degradation of the cable’s sheathing when oils and chemicals are added. From an environmental perspective, temperature and UV exposure are the most important factors. There are certification tests for oil exposure that must be passed in order to receive specific approvals that give engineers operational parameters for how a cable will perform at certain temperatures over different time frames. The same goes for cables exposed to the sun outdoors. UV-approved cables are generally more resistant to the long-term effects of continuous sun exposure than non-UV-approved cables, such as not drying out or becoming brittle as quickly, exposing the inner conductors or the actual copper and/or aluminum strands. When it comes to mechanical stresses, any movement that causes cables to break through abrasion or twisting can allow oils and chemicals to seep into places where they shouldn’t, making the cable susceptible to potential failure if not addressed quickly.
Q: What sheathing options are available that are resistant to the effects of oil and chemicals?
a: There are many types of thermoplastics used to resist oil and chemicals, such as polyvinyl chloride (PVC), polyurethane (PUR), fluorinated ethylene propylene (FEP), and thermoplastic elastomers (TPE), to name a few. Choosing the right material – PVC, FEP, TPE, PUR, rubber or blends – is important to prevent downtime on the factory floor or in the field.
In the industrial machine tool industry, for example, PUR cables used to provide motor power and feedback can often be immersed in synthetic oils and cutting fluids 24 hours a day. Their performance has made them the standard in the machine tool market for over a century.
However, PVC based cables have become a growing business for cable manufacturers due to advances in compounding additives and blends (different types of plastics) to achieve different performance characteristics. Recent changes in UL certification, i.e. the expanded use of exposed run cable trays (TC-ER) approvals, have opened up more applications for these cables in the industrial floor.
Knowing how, where and to what the cable will be exposed will help you work with your cable supplier to select the appropriate jacket material that is best for your specific application.
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