Shielded Conduit Protects Against RFI/EMI

<i>Three kinds of shielding provide maximum choice</i><br><br>Many 
applications require shielding effectiveness from RFI and EMI 
interference. Stray voltage, current, and high frequency noise can 
damage circuits, interrupt performance, and initiate potentially 
dangerous actions. Shielding reduces these potential problems. Shielded 
conduit, especially where flexibility is required, provides a 
significant solution for the engineer. Electri-Flex

Electri-Flex

Three kinds of shielding provide maximum choice

Many applications require shielding effectiveness from RFI and EMI interference. Stray voltage, current, and high frequency noise can damage circuits, interrupt performance, and initiate potentially dangerous actions. Shielding reduces these potential problems. Shielded conduit, especially where flexibility is required, provides a significant solution for the engineer.

Electri-Flex Company manufactures a broad line of conduits that are designed to protect sensitive circuits from outside interference in a variety of applications. These applications are found in aerospace, communications, and many other industries where commercial off the shelf (COTS) products are acceptable. Shielded conduits are used in markets such as industrial, HVAC, and utilities – especially water and wastewater– use variable speed drives. Also called variable frequency drives, these devices are extremely susceptible to radio frequency interference. This conduit is also often used in building automation applications such as dampers, blower motors, and electronic controllers. It is used in data center wiring to keep power wiring from interfering with signal and data lines, and, for similar applications, in test and measurement. Flexible shielded conduit is used in transportation and in aerospace, where space is at a premium and the flexibility is an advantage, such as in trains, subways, and both military and civilian aircraft.

The graph to the right depicts a general comparative shielding effectiveness (attenuation in dBs) of all three types of Shield-Flex conduit. The dotted line indicates a comparison to standard unshielded liquidtight conduit Type LA. Tests were performed per MIL-STD-285 and in general accordance with IEEE 299. 1” trade size conduit was tested using standard liquidtight fittings from Thomas & Betts Series 5300. Results are based on controlled laboratory conditions and may vary in actual field installed conditions.

  • Good Shielding – Type SLA: UL listed, liquidtight flexible steel conduit with a tinned copper shielding braid located over an inner steel core and under its protective PVC jacket. Working temperature range -30°C to 80°C dry / 60°C wet /70°C oil. Shielding braid provides a minimum of 90% shielding coverage.
  • Better Shielding – Type EMS: Provides a better shielding effectiveness than Type SLA. Has an inner core made from a fully interlocked bronze strip and does not contain a braided shield. An all temperature PVC jacket provides a working temperature range of -55° to 105° C. 
  • Best Shielding – Type EMCS: A hybrid of SLA and EMS because it utilizes the same bronze core and PVC jacket as EMS but gets further screening protection from a tinned copper braid as found in the SLA product. Provides a working temperature range of -55° to 105° C. 
  • For a low-smoke, low-flame spread, zero-halogen version, ask for HFSLA, HFEMS, or HFEMCS. It’s ideal for field installation in confined, public areas such as subways, tunnels, etc. The jacketing material virtually eliminates the release of acidic gases found in PVC products.
Both polyvinyl chloride (PVC) and polyurethane (PU) have wide chemical resistance. For specific chemical resistance, please see the Chemical Resistance Guide on the Electri-Flex Company website.

Using flexible shielded conduit provides a widely applicable solution to the problem of noise and interference from stray voltages and current. When you need high-performance EMI/RFI shielding, these three conduit types provide the performance you need across a wide frequency range and the quality you must demand in flexible shielded conduit.


Photo courtesy of Electri-Flex