A stringing pulley block is a special device used in overhead line transmission projects (power lines, telecom lines, etc.) to facilitate the installation of conductors (wires). It ensures that conductors can be pulled (strung) smoothly along towers or poles without damage.
A pulley with a grooved wheel (sheave) mounted in a frame, used to support and guide conductors, OPGW (optical ground wire), or earth wires during stringing.
The conductor runs inside the groove of the pulley, which is usually lined with nylon, aluminum alloy, or polyurethane to reduce friction and prevent conductor surface damage.
It is hung on the insulator cross-arm of a transmission tower/pole before conductor pulling starts.
Often comes with hooks, clamps, or swivels for easy installation.
Single Sheave Block – One groove, used for one conductor.
Double Sheave Block – Two grooves, used for two conductors (twin bundle).
Triple/Quadruple Sheave Block – For bundle conductors (3, 4, or more).
Pilot Pulley – Smaller, used for pilot rope stringing before conductor pulling.
Special Blocks – For OPGW, river crossing, angle towers, etc.
When selecting for an overhead line transmission project, consider:
Conductor Size & Type
Groove diameter must be ≥ 1.5 times the conductor diameter.
Groove material (nylon/urethane for AAC/ACSR, aluminum alloy for heavy conductors).
Number of Conductors per Phase
Single, twin, triple, or quad conductor → choose block with corresponding number of sheaves.
Working Load / Safe Load
Pulley must withstand the tension force of conductor pulling.
Choose a block with Rated Working Load (RWL) ≥ max pulling tension × safety factor (usually 2.5–3.0).
Sheave Diameter
Larger sheaves reduce bending stress on conductors.
Typically, 30–40 times the conductor diameter is recommended.
Frame Type
Fixed frame (standard towers).
Suspension or angle pulley blocks (for deviation or large angle towers).
Lining & Protection
Nylon/urethane lining to avoid scratching or corona damage.
Ball bearings for smooth rotation.
Terrain & Special Needs
For river crossing or long-span → large diameter pulleys.
For OPGW → pulleys with protective liners to avoid fiber damage.
✅ Example:
If your project uses ACSR 400 mm² conductors (diameter ~ 26 mm):
Sheave diameter should be at least 26 × 30 ≈ 780 mm (choose ~ 800 mm sheave).
Single sheave for single conductor, quad sheave for 4-bundle line.
Frame should withstand pulling tension (say 20 kN, so block rated ≥ 50 kN).
A stringing pulley block is a special device used in overhead line transmission projects (power lines, telecom lines, etc.) to facilitate the installation of conductors (wires). It ensures that conductors can be pulled (strung) smoothly along towers or poles without damage.
A pulley with a grooved wheel (sheave) mounted in a frame, used to support and guide conductors, OPGW (optical ground wire), or earth wires during stringing.
The conductor runs inside the groove of the pulley, which is usually lined with nylon, aluminum alloy, or polyurethane to reduce friction and prevent conductor surface damage.
It is hung on the insulator cross-arm of a transmission tower/pole before conductor pulling starts.
Often comes with hooks, clamps, or swivels for easy installation.
Single Sheave Block – One groove, used for one conductor.
Double Sheave Block – Two grooves, used for two conductors (twin bundle).
Triple/Quadruple Sheave Block – For bundle conductors (3, 4, or more).
Pilot Pulley – Smaller, used for pilot rope stringing before conductor pulling.
Special Blocks – For OPGW, river crossing, angle towers, etc.
When selecting for an overhead line transmission project, consider:
Conductor Size & Type
Groove diameter must be ≥ 1.5 times the conductor diameter.
Groove material (nylon/urethane for AAC/ACSR, aluminum alloy for heavy conductors).
Number of Conductors per Phase
Single, twin, triple, or quad conductor → choose block with corresponding number of sheaves.
Working Load / Safe Load
Pulley must withstand the tension force of conductor pulling.
Choose a block with Rated Working Load (RWL) ≥ max pulling tension × safety factor (usually 2.5–3.0).
Sheave Diameter
Larger sheaves reduce bending stress on conductors.
Typically, 30–40 times the conductor diameter is recommended.
Frame Type
Fixed frame (standard towers).
Suspension or angle pulley blocks (for deviation or large angle towers).
Lining & Protection
Nylon/urethane lining to avoid scratching or corona damage.
Ball bearings for smooth rotation.
Terrain & Special Needs
For river crossing or long-span → large diameter pulleys.
For OPGW → pulleys with protective liners to avoid fiber damage.
✅ Example:
If your project uses ACSR 400 mm² conductors (diameter ~ 26 mm):
Sheave diameter should be at least 26 × 30 ≈ 780 mm (choose ~ 800 mm sheave).
Single sheave for single conductor, quad sheave for 4-bundle line.
Frame should withstand pulling tension (say 20 kN, so block rated ≥ 50 kN).
