The internal design of OPGW (Optical Ground Wire) cables, particularly whether it's a central tube or multi-loose tube (also known as stranded loose tube) construction, significantly influences the stringing process and the selection of specialized equipment. Understanding these differences is key to a successful installation.

I. Central Tube OPGW Design:

• Description: In a central tube design, all the optical fibers are housed within a single, larger hermetically sealed stainless steel tube (or similar protective material) located at the core of the OPGW. The metallic strands (aluminum-clad steel, aluminum alloy) are then stranded around this central tube.

• Impact on Stringing:

  • Torsional Sensitivity: Central tube designs are generally more sensitive to twisting (torsion) during stringing. Any significant twist can cause the central tube to rotate or buckle, stressing the fibers inside and leading to optical performance degradation or damage.

  • Minimum Bend Radius (Dynamic): While the static MBR might be similar, the dynamic MBR during stringing needs strict adherence due to the single, rigid central tube.

  • Crush Resistance: Can be slightly less crush-resistant than multi-tube designs as all fibers are concentrated in one area.

• Equipment Implications:

  • Anti-Twisting Swivels: Absolutely critical. High-quality, robust anti-twisting swivels must be used between the pulling grip and the pulling rope to prevent any torque transfer.

  • Larger Diameter Stringing Blocks: Even more emphasis on using the largest possible diameter stringing blocks to ensure the cable is never bent too sharply, especially at angles.

  • Non-Rotating Pulling Ropes: Mandatory to avoid inducing twist.

  • Precise Tension Control: Essential to prevent over-tensioning which could indirectly induce torsion or micro-bends if the outer layers deform.

II. Multi-Loose Tube (Stranded Loose Tube) OPGW Design:

• Description: In this design, optical fibers are grouped into several smaller, individual loose tubes. These tubes are then stranded around a central strength member (e.g., a steel wire) along with the metallic conductor strands. This stranding can be S-Z stranding or helical.

• Impact on Stringing:

  • Torsional Tolerance: Generally more tolerant to twisting compared to central tube designs. The individual loose tubes can accommodate some degree of twisting without directly stressing the fibers, thanks to the "excess fiber length" within the tubes.

  • Flexibility: Often more flexible than central tube designs of comparable diameter due to the stranded nature of the tubes.

  • Crush Resistance: Can offer slightly better crush resistance due to the distributed protection of multiple tubes.

• Equipment Implications:

  • Swivels are still recommended: While more tolerant, using a good quality anti-twisting swivel is still best practice to minimize any torsional stress.

  • Stringing Blocks: Standard OPGW-specific large-diameter blocks with protective linings are still required.

  • Pulling Grips: Standard OPGW pulling grips are suitable.

III. Overall Considerations for Both Designs:

Regardless of the OPGW design, certain principles of stringing remain universal and require specialized equipment:

• Precise Tension Control: All OPGW requires vigilant tension monitoring to stay within the MAPT.

• Adequate Sheave Diameters: Always adhere to the manufacturer's recommended dynamic bending radius by using appropriately sized stringing blocks.

• Protective Linings: All stringing blocks must have non-abrasive, protective linings.

• Skilled Operators: Proper training and experience are crucial for understanding the nuances of each OPGW type.

Our comprehensive range of OPGW stringing equipment, including adaptable pullers, tensioners, and a wide array of specialized stringing blocks and accessories, is designed to accommodate various OPGW cable constructions, ensuring optimal performance and protection for your specific project requirements.