Non-metallic – tough and practical
Though metallic conduit can provide
excellent EMC screening, inherent low fire
hazard properties, better crush resistance
and high mechanical strength, non-metallic
alternatives can offer increased flexibility,
are easier to cut to length and are easier to
install.
Nylon corrugated conduits also offer high
impact strength and crush recovery, making
them suitable for applications requiring
high impact resistance or fatigue life. They
also do not rust or corrode, and have no
exposed metal that needs bonding. PVC
smooth or helically-formed flexible conduits
offer high compression strength and
polypropylene conduits are acid resistant
and available at a lower cost.
Non-metallic and polymer-coated metal
conduits should be considered carefully
when specifying for installations subject
to high UV exposure. When degraded by
UV radiation, incorrectly specified system
material can become cracked and brittle,
resulting in less impact strength and
flexibility.
To avoid this, specifiers should select
products designated ‘UV resistant,’ which
have undergone extensive UV testing.
There is no technical standard governing
UV resistance, so product performance
claims can differ drastically. Flexicon, for
example, ensures maximum, market-
leading protection by subjecting its conduit
solutions to 1000-hour Xenon arc testing
from UL 1660 (Underwriters Laboratories)
to support its claims of UV resistance
performance.
Using metallic or composite
Though non-metallic solutions offer
excellent protection, metallic and
composite systems are necessary
in applications requiring very high
compression or pull-off strength, or heavy
duty applications. Composite products such
as plastic sheathing on metal conduits to
increase the ingress protection, or metal
over-braiding on non-metallic corrugated
for EMC, or metal threads on plastic fittings
can offer the ideal combination of light
weight, high strength and fast installation.
Specified correctly, liquid-tight metallic
flexible conduit systems combined with
flameproof barrier glands can offer the best
possible mechanical strength and ingress
protection for hazardous areas, with high
levels of chemical and corrosion resistance.
These systems are available in nickel-plated
brass and 316L stainless-steel, with the
latter preferred in installation environments
subjected to high levels of corrosion.
In conclusion, advances in cable protection
technology mean a wide variety of metallic,
composite or non-metallic solutions are
now available. By carefully specifying and
correctly applying system components, it
is possible to commission cost-effective
systems that offer the correct levels of
performance.
For further information about
selecting the appropriate flexible
conduit system for your installation,
please visit www.flexicon.uk.com or
contact [email protected]
Issue 36 PECM
61