Specifying Flexible Conduit with Extreme Temperatures in Mind

<b>Introduction</b><br>Most electrical wiring and conduits operate 
within a “comfortable” range of operating temperatures, but there are 
also many others that experience either extremely low or high 
temperatures or both. All of these cases require conduits specially 
designed to deliver their rated performance, including flexibility and 
protection, under conditions beyond those of standard types. Electri-Flex


Most electrical wiring and conduits operate within a “comfortable” range of operating temperatures, but there are also many others that experience either extremely low or high temperatures or both. All of these cases require conduits specially designed to deliver their rated performance, including flexibility and protection, under conditions beyond those of standard types.

The number and types of applications that require these conduits are diverse, ranging from chemical production, to offshore drilling platforms, pipelines, steel production, robotics, refrigeration, and aerospace. For example, offshore oil platforms and wind turbines, wireless communications towers, weather stations, and defense systems, can experience temperatures ranging from -40° F to more than 120° F.

In steel production, very high temperatures are routine in foundries, forges, rolling mills, and arc furnaces, and, in the food and pharmaceutical industries, low temperatures are encountered in all refrigeration systems and those using liquid nitrogen for flash freezing reduce temperatures much further.

One of the most demanding applications is aerospace where platforms such as fighter aircraft can rapidly experience temperatures cycling over a range of 120° F in a matter of minutes as they change altitude. Fortunately, there are solutions to all these challenges, but it’s essential that the proper type of conduit be chosen to address the characteristic of specific situations. Electri-Flex offers conduits tailored to serving extreme temperature ranges while also withstanding rugged environments, contact with or immersion in oils, chemicals, and other aggressive substances, or even exposure to fire.

Accommodating Extreme Temperatures
When selecting the proper type of flexible conduit, many people specify only the high end of the operating temperature ratings but fail to specify the low temperature range or understand conduits’ low temperature limitations. The basic process is the same, regardless of whether low or high temperatures must be addressed. This entails determining the range of temperatures the conduit will be exposed to as well as the lowest or highest possible temperature that might be reached over short periods. In all cases, conduits must retain their flexibility, protective properties, and structural integrity while sustaining impacts and crushing even at the most extreme temperatures in their operating range.

For example, valves and other hardware on a pipeline in the Arctic are typically exposed to temperatures as low as -40° C intermitting to -60° C. If those occasions are infrequent and of short duration, a conduit with a -40° C operating temperature, such as Electri-Flex Types ATLA or AT can be used. However, when temperatures are frequently at -60° C or lower, then Electri-Flex Type ATX should be used instead. If RFI and EMI shielding are also required, Types EMS and EMCS provide this and are rated to -55° C. If low temperature operation and non-metallic conduit are required, Type LNM-P is the best choice, as it has an extremely low operating temperature limit. Information about the various types of conduit offered by Electri-Flex is described in the section below.

Flexible Steel Conduit
AT: Non-UL conduit that has a special PVC jacket that remains flexible at very low temperatures and has slow aging characteristics at elevated temperatures. Temperature range is -55° C to +105° C, with short-term spikes to +120° C.

ATLA: Designed for extreme hot or cold environments, uses a PVC jacket that remains flexible at low temperatures, and resists aging at elevated temperatures. It is UL and CSA approved, sunlight resistant and accommodates temperatures of -55° C to +105° C dry, 60° C wet, and 70° C in oil.

ATX: Has a thermoplastic rubber jacket that is virtually unaffected by temperature extremes and is rated for low-smoke zero halogen (LSZH) conditions with a flammability rating of UL 94-HB. Temperature range is -60° C to +150° C with spikes to +165°C

The above listed flexible steel conduits are also available with a stainless-steel core (ATSS and ATXSS).

Non-metallic Flexible Conduit
NMHT: Designed for high-temperature environments and contains rigid PVC spiral reinforcement within the wall of the conduit. Temperature range is -20° C to +105° C dry, 60° C wet, and 70° C in oil. It is also UL and CSA approved.

LNM-P: Well suited for continuous flexing situations and often specified for use in power track or cable carrier installations and on industrial robots. It does not contain a metal core that could fatigue from repeated flexing or vibration but rather a seamless inner core of flexible PVC bonded to another layer of flexible PVC, between which is a woven nylon mesh for added reinforcement. The PVC is flame-retardant and resists oils, mild acids, and exposure to sunlight. Temperature range is -55° C to +105° C and is also UL and cUL approved.

The Corrlok system is a family (Types CL, CLR, and CLFR) of lightweight flexible raceway alternatives that withstands harsh environments and is made from specially-formulated Nylon that is non-toxic and self-extinguishing, making it well suited for confined areas where fire can be a concern. It is LSZH rated, flame resistant, has high impact and crush strength, and is resistant to many chemicals and sunlight. Temperature is as broad as -40° C to 105° C with spikes to 150° C.

Keeping Interference in Check
Radio frequency interference (RFI) is a constant problem in many places where conduits are located, from wireless telecommunications towers to factories, and the problem will only increase in the future as more services operating at more frequencies come into service. In addition, as the Internet of Things (IoT) transitions from simply an acronym to installations throughout the world, hundreds of wireless-enabled sensors communicating among themselves and to the outside world will be present in factories and other facilities, and adding a new element of the already-crowded electromagnetic spectrum. The result for conduit manufacturers like Electri-Flex has been to design conduits whose shielding provides very high levels of resistance to the entrance of signals into the conduit but keeping signals carried by conductors within the conduit from exiting it.

Type SLA, EMS, and EMCS flexible conduits from Electri-Flex can be specified to meet both extreme temperature requirements while also providing exceptionally high shielding resistance (Figure 1). Type SLA has a temperature range of -30° C to 80° C dry (60° C wet and 70° C in oil) and Types EMS and EMCS are specified for operation between -55° and 105° C. Each of the three product families provide different levels of shielding effectiveness to meet the needs of specific applications. Type EMCS in particular offers signal attenuation of nearly 130 dB over a frequency range from 100 MHz to 3 GHz and 100 dB to 6 GHz, covering all wireless and broadcast bands and many other emitters.

Figure 1: Electri-Flex Types EMS and EMCS provide very high shielding from DC through 18 GHz. Type SLA offers less attenuation but still provides at least 60 dB of attenuation and up to 80 dB over many frequencies.

Solutions for Other Hostile Environments
In addition to extreme temperature and electrical and RF interference, there are other challenges some conduits must face, and Electri-Flex provides solutions to address them. They range from exposure to fire, oils and greases, salt spray, various forms of precipitation, and intense sunlight. Once again, each requires conduit materials specifically designed to withstand these hostile conditions without degradation that could destroy the wiring inside.

When exposed to fire, polyvinyl chloride (PVC) and similar polymers widely used throughout the industry produce toxic gases called halogens such as hydrogen chloride, hydrogen fluoride, and hydrogen bromide, as well as with other deadly combustion products. As a result, there is an increasing trend toward the use of low-smoke zero-halogen (LSZH) conduit materials that reduce these gases to negligible amounts in places such as aircraft, ships, recreational vehicles, tunnels, mass transit vehicles, elevators, and many other confined spaces.

Electri-Flex offers three LSZH product lines (Types ZHLA, CEA, and ACEA, all at -40° C to 80° C) designed for these applications as well as exposure to temperature extremes and the other hostile environments described above. Its proprietary formulation of thermoplastic polyurethane combines low smoke, flame retardation, and toxicity generation characteristics. Test results on this material conducted by an independent laboratory meet and typically exceed performance requirements in the most widely-respected standards.

Whether you’re operating equipment at 200° C or drilling in arctic conditions, you’ll need to consider the effects of these extreme environments. While specifying the proper flexible conduit for a given application might initially appear daunting, the process becomes straightforward once the requirements of the application are known. A variety of products can assist in any of your applications regardless of operational environment. Flexible steel conduits, non-metallic flexible conduits, PVC, and similar polymers are among the many solutions for protecting your operations. Armed with this information, what remains is only to select the desired model from Electri-Flex, which offers the industry’s most comprehensive product line, covering almost any likely application and operating conditions.

Photo courtesy of Electri-Flex