/images/TDUpdate.jpg/images/southwire_100x70.jpgCompressed Stranding Gives Cable New Look - 2004CompressedStrandingGivesCblNewLookSept2004.htmA new form of stranding looks different, but still delivers Southwire quality and performance.
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Compressed Stranding Gives Cable New Look - 2004

A new form of stranding looks different, but still delivers Southwire quality and performance.

You'll be seeing a new look in many of Southwire's popular utility cable products - but Southwire quality is still built into every foot of wire.

"In some utility products we're making a running manufacturing change from traditional unilay compressed stranding to a new type of compressed stranding called SIW compressed," says Nick Ware, technical director of Southwire's Energy Division. SIW stands for "Single Input Wire." The new stranding technique uses combinations of a small number of strand sizes to produce standard ASTM conductor sizes from #2 AWG to 350kcmil.

SIW goes into selected products

SIW compressed stranding will appear primarily in underground cables, but may also show up in non-load-bearing phase conductors in overhead multiplex service drops. It's a drop-in replacement for traditional unilay compressed stranding that's routinely used today by Southwire and others for these same products. The traditional unilay stranding is defined by ASTM standard B 231. SIW compressed stranding is defined by ASTM standard B 901.

What does SIW stranding mean for utility cable users? In actual applications, no real change. You can use SIW compressed interchangeably with unilay compressed stranding. If you take a cross section of an SIW stranded cable, it will look somewhat different from traditional compressed unilay, but cross-sectional areas and diameters are the same, and all the same fittings work. Connector testing in cooperation with three major manufacturers has verified complete interchangability of the two designs.

What about springback - that attribute that literally hits you in the face when training a cable into a tight location? Testing at Southwire's Cofer Technology Center shows that a #1/0 AWG, SIW stranding is actually easier to work with and train than conventional stranding.

More conductor sizes from fewer strand sizes

What exactly is the difference in the new stranding? SIW stranding produces a wide range of finished conductor sizes from a smaller range of individual strand sizes. That permits manufacturing efficiencies that will help Southwire hold the line on cable prices as materials and energy costs continue to escalate. The accompanying sketches show the cross sections you'll see in several common sizes of SIW compressed conductors.

"The first SIW compressed stranding products are slated for availability in the first quarter of 2005," says Ware. "We're pleased to be able to take this proactive step to help our customers maintain wire and cable costs."

Notes on SIW compressed stranding in specific sizes:

  • The SIW compressed size range starts with #2 AWG. A #2 AWG SIW compressed conductor looks just like a #2 AWG unilay compressed conductor with seven strands.
  • A #1 AWG SIW compressed conductor has two more strands than a conventional unilay compressed seven-wire #1 AWG conductor.
  • The #1/0 AWG SIW SIW compressed conductor is made up of nine strands and is probably the most different in physical appearance from traditional unilay compressed stranding.
  • The 350 kcmil SIW compressed conductor uses some non-traditional strand shapes in the core, but it still uses 37 wires, just like traditional unilay compressed.