Controlling pulling tension is critical to prevent damage and ensure the longevity of cables and conductors, whether overhead or underground. The primary methods for calculating and controlling this tension are:

I. Calculation of Pulling Tension:

• Engineering Formulas: For both overhead and underground, theoretical pulling tension is calculated using engineering formulas that account for:

  • Cable/Conductor Weight: The inherent weight of the material.

  • Coefficient of Friction (μ): Between the cable/conductor and its support (stringing blocks for overhead, conduit for underground). This is a critical factor, often determined by material compatibility and the use of lubricants (underground).

  • Length of Pull: Longer pulls accumulate more friction.

  • Number and Severity of Bends: Each bend significantly increases tension due to sidewall pressure.

  • Temperature & Environment: Affects conductor sag (overhead) and lubricant performance (underground).

• Manufacturer Specifications: Cable and conductor manufacturers provide Maximum Allowable Pulling Tension (MAPT) or Maximum Allowable Tension (MAT) specifications. These are absolute limits that must never be exceeded to avoid internal damage to conductors, insulation, or the outer jacket/sheath.

• Computer Software: Specialized software is often used for complex pulls (especially underground with multiple bends or long runs) to accurately model and predict tension profiles, optimizing pulling points and lubrication strategies.

II. Control of Pulling Tension:

• Real-time Load Cells & Digital Displays: Our modern pulling equipment (both hydraulic pullers for overhead and powerful winches for underground) are equipped with integrated load cells that provide continuous, real-time feedback on the actual pulling force. This data is displayed digitally, allowing operators to monitor tension instantly.

• Automatic Tension Control: Advanced pullers feature closed-loop hydraulic or electric systems that allow operators to pre-set a maximum tension limit. If the actual pulling force approaches this limit, the system automatically slows down, or even stops, the pull until the tension is within safe parameters. This prevents overstressing the cable/conductor.

• Consistent Speed Control: Maintaining a smooth, consistent pulling speed (without jerks or sudden accelerations) minimizes dynamic tension spikes and helps maintain stable friction.

• Proper Equipment Selection:

  • Overhead: Using correctly sized stringing blocks with smooth, well-lubricated bearings and appropriate liners (non-metallic for sensitive conductors) to minimize friction. Precision hydraulic tensioners apply controlled back-tension.

  • Underground: Utilizing effective cable lubricants, adequate conduit sizing, and appropriate cable rollers/guides in manholes/vaults to reduce friction.

• Strategic Pulling Points: For very long or complex runs, intermediate pulling points may be established to break up the pull into shorter segments, keeping tension below the MAPT.

By combining accurate tension calculation with precise, real-time control mechanisms offered by our advanced pulling equipment, we empower our clients to execute safe, efficient, and damage-free cable and conductor installations, maximizing their lifespan and performance.