1x37 Galvanized Steel Strand 6-12mm High Strength Messenger for Transmission Lines

1x37 galvanized steel strand, 6mm to 12mm, for transmission line messenger and earth wire duty where sag has to stay predictable for decades.

A 1x37 strand exists because thirty seven wires give a better balance of strength and surface smoothness than the more common 1x7. There are more wires in contact with clamps and suspension hardware, the outer layer is finer, and the strand runs through a stringing block without the deep surface marks that a coarse seven wire strand picks up during installation.

The application dictates the specification. On a messenger or earth wire the strand sits under constant tension in wind and ice, so we control lay length and zinc mass rather than only the breaking load. We draw 60# and 70# high carbon wire, galvanize by hot dip, and close with tension control so the wires share load evenly. A strand closed with uneven tension will show one proud wire, and one proud wire becomes a corrosion cell.

• Thirty seven wires for a smoother running surface: The finer outer layer sits better in suspension clamps and is far less prone to nicking during stringing. On retrofits and line upgrades this reduces the number of rejected spans after installation.
• Low sag behaviour under design tension: High carbon wire with controlled lay gives a predictable modulus, so the sag tension stringing chart the engineer prepared is what appears on site rather than something ten percent away from it.
• Hot dip zinc rather than electro plate: Coating mass is 215 to 260 grams per square metre in the standard class. That is a coating you can measure on a section after ten years in service and still find metal, which is the practical definition of a coating that works.
• Consistent lay length along the reel: Lay pitch is checked at the start, middle and end of every production run. A strand that changes pitch along its length twists differently at the two dead ends and loads the clamps unevenly.
• Tension controlled closing: Each of the thirty seven wires is closed with individual tension control, so the finished strand is round and no single wire carries a disproportionate share. Out of round strand is what makes clamps slip.
• Cut lengths on site without birdcaging: Ends are welded or served before packing. When your crew cuts the strand at a pole, the end stays together instead of opening into a cage that has to be cut back a metre and wasted.

The main use is messenger and earth wire on overhead transmission and distribution lines, including upgrade work where an existing line needs a stronger carrier without changing the tower hardware. It is also used for heavy stayed poles and for static wire runs on industrial sites.

Outside the power industry the same strand is bought for structural guy systems on masts and chimneys, and for long span barrier and safety net anchoring where a single continuous high strength element is preferred over a rope with splices.

• Overhead transmission line messenger and earth wire
• Distribution line carrier and static wire runs
• Mast, chimney and tower guy systems
• Long span barrier and safety net anchor strand
• Industrial static wire and catenary support

Zinc coating mass is checked by the stripped weight method on samples from both ends of each lot, not by an assumed figure. Breaking load is tested on a universal machine with wedge grips and the fracture position is recorded, because a break at the grip is not a valid result.

Diameter and ovality are measured at three points per reel, and the strand is inspected over its full length for broken wires, proud wires and lay irregularities. Torsion and wrapping tests are run on the wire before stranding to catch wire that would crack in service.

Wooden or iron reels of 500m to 3000m, wrapped in VCI film and strapped, with the reel marked for size, length, grade, breaking load and lot number. Export packing is fumigated timber and the reel bore is sized so a standard stringing trailer spindle will pass through it.