Shield-Flex: What to Specify When Electrical Noise Is the Problem
Most conduit decisions are about what the jacket keeps out. Shielded conduit is about what it keeps in, and what it keeps from getting in: electrical noise.
On a modern job that noise is not a nuisance. Variable speed drives, switching power supplies, radio equipment and dense cable trays all put energy into the environment, and the circuits running alongside them are the ones carrying control signals, instrumentation readings and communications traffic. When interference reaches those circuits, the symptom is not a blown fuse. It is a reading that drifts, a drive that faults intermittently, a control system that behaves differently on second shift. Those are expensive problems to chase.
Electri-Flex built the Liquatite Shield-Flex family for exactly that condition, and released a new video and press release on the line in August. Three constructions cover the range.
Type SLA is built like standard Type LA liquidtight flexible steel conduit and adds a tinned copper shielding braid with a minimum of 90 percent coverage. Type EMS takes a different approach, using a fully interlocked bronze strip as the core, which shields better than SLA. Type EMCS combines the two ideas: the bronze core and PVC jacket of EMS, with the tinned copper braid added over it for the best shielding of the three. Electri-Flex tests shielding effectiveness per MIL-STD-285 across a frequency range from 1 MHz to 6 GHz.
There is a halogen-free version of each. Types HFSLA, HFEMS and HFEMCS carry the same shielding constructions under a low-smoke, low-flame-spread, zero-halogen jacket, which is what a transit station, tunnel or occupied critical facility is likely to require.
Two installation details matter in the field. The shield grounds directly to the drain through the connector ferrule, so there is no separate bonding step to design around, and the conduit accepts off-the-shelf liquidtight connectors. Assembled with liquidtight fittings, the run is waterproof.
The markets Electri-Flex names for the line are the ones you would expect: aerospace, defense and military, healthcare, data centers, communications equipment, industrial, HVAC, shipbuilding, renewable energy, rail and transit, utilities and variable speed drives.
Our advice to distributors and contractors across North Texas and Oklahoma is the same as always: when a shielding requirement shows up on a submittal, treat it as a question for us before you substitute or re-spec. The construction that satisfies it is usually already in the Liquatite catalog, and confirming it takes one conversation.
If you have a project with an EMI or RFI requirement on the conduit, contact your Electra Sales representative and we will work through the specification with you.
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