Of all the chemical exposures that
can affect the life and performance of electrical cables, oil is one of the
most damaging. Used as a coolant and lubricant in many industrial and
infrastructure settings, oil can inflict molecular damage on the polymers used
for cable insulation.
Degradation Happens. When insulation polymers are exposed to oil
over time, two degradation mechanisms can occur. Some polymer formulations will
absorb the oil, causing the polymer to swell and soften. A loss of tensile
properties results. Other polymers will lose their plasticizers when exposed to
oil, causing a loss of flexibility and elongation.
Either way, oil exposure renders
many polymer compounds ineffective as insulators. This attack on polymer
properties can result in downtime, costly repairs and, in the worst case,
hazardous electrical conditions.
Temperature extremes and other
chemical exposures can exacerbate the damage caused by oils. The greater the
intensity of the oil exposure and the operating temperatures, the faster oil
will degrade insulating polymers.
Lasting Damage. Once it gets underway, oil damage is not
reversible. But it can be prevented by selecting cables with inherent oil
resistance.
Without a deep knowledge of the
specific polymer compounds used in the cable you’re considering, it can be
difficult to know which products can stand up to oils and for how long. Making
matters worse, individual polymer formulations may not offer equivalent
performance even if they have the same family name. Not all PVCs are created
equal, for instance.
And that’s why testing is so
important. To avoid oil resistance problems, engineers should pay close
attention to UL tests, which help determine how a cable will react in the
industrial oil environment.
