Non-Rotating Wire Rope

Rotation-resistant wire ropes, such as 18×7 (also known as 19×7) and 35×7, are specifically engineered to counteract the tendency of the rope to spin or rotate under load. These configurations feature multiple layers of strands laid in opposite directions around a specific core type, which plays a critical role in their stability and performance. This article provides a detailed look at the core designs used in these rotation-resistant wire ropes, including their construction, performance attributes, and suitable applications.

1. Understanding the Core Design of Rotation-Resistant Wire Ropes

The core of a rotation-resistant wire rope serves as the backbone of the rope, providing support to the outer strands and contributing to the rope’s overall stability. Depending on the specific configuration, rotation-resistant wire ropes can have different core types:

• Independent Wire Rope Core (IWRC)

It is the most robust and stable core type, providing excellent support, strength, and resistance to crushing and deformation. IWRC cores are typically used in wire ropes designed for heavy lifting and high-load applications.

• Independent Wire Strand (IWS):

  • An IWS core consists of a single wire strand that forms the central axis of the rope. It is primarily used in 18×7 (19×7) rotation-resistant ropes.
  • The IWS core offers moderate strength and good flexibility, providing a balanced structure that supports the inner and outer layers of the rope.

• Fiber Core (FC):

  • The FC is made from synthetic or natural fibers, offering higher flexibility and reduced weight compared to wire-based cores. It is also used in 18×7 (19×7) wire ropes for applications where flexibility is a key requirement.
  • While FC cores provide excellent handling and fatigue resistance, they lack the strength and crush resistance of wire cores, making them less suitable for extremely high-load applications.

The 18×7 (19×7) configuration typically utilizes IWS or FC cores, while higher-capacity ropes like 35×7 almost exclusively use an Independent Wire Rope Core (IWRC) due to their need for greater strength and stability.

2. Core Design and Layer Structure of 18×7 (19×7) Rotation-Resistant Wire Rope

The 18×7 (19×7) rotation-resistant wire rope is known for its balanced structure and moderate rotation resistance. This rope is commonly used in lifting applications where load stability is important but not as critical as in heavier-duty operations.

Layer Structure of 18×7 (19×7) Wire Rope:

• Core Layer:

  • The core of 18×7 (19×7) can be either an Independent Wire Strand (IWS) or a Fiber Core (FC).
  • IWS Core: Provides moderate strength and flexibility, offering balanced support to the surrounding layers. This core type is preferred for applications that require a good mix of strength and flexibility.
  • FC Core: Provides enhanced flexibility and fatigue resistance. It is used in applications where the rope needs to withstand repeated bending or where ease of handling is prioritized.

• Inner Strand Layer:

  • Composed of 6 strands laid around the core in one direction (typically right-hand lay). These strands support the outer layers and work to counteract the torque generated by the outer strands.

• Outer Strand Layer:

  • Consists of 12 strands laid in the opposite direction to the inner layer (typically left-hand lay). The alternating lay structure neutralizes the torsional forces, significantly reducing the rope’s tendency to spin or twist under load.

• Compacted and Coated Options:

  • 18×7 (19×7) ropes can be manufactured with compacted strands to increase breaking strength and wear resistance, or with a plastic-coated core to enhance internal lubrication, reduce friction, and protect against corrosion.

Application of 18×7 (19×7) Wire Rope:

• Cranes and Hoists: Suitable for lifting and hoisting applications where moderate rotation resistance and flexibility are required.
• Elevators and Winches: Ideal for elevator hoisting systems due to its flexibility and reduced rotation tendency.
• General Purpose Lifting: Commonly used in general lifting applications that demand a balance of strength, flexibility, and moderate rotation resistance.

3. Core Design and Layer Structure of 35×7 Rotation-Resistant Wire Rope

The 35×7 wire rope is a high-capacity rotation-resistant configuration designed for demanding lifting operations. It offers superior resistance to rotation and exceptional strength, making it suitable for critical applications like deep-sea lifting, offshore platforms, and construction projects.

Layer Structure of 35×7 Wire Rope:

• Core Layer:

  • The core of the 35×7 configuration is typically an Independent Wire Rope Core (IWRC). The IWRC provides the necessary support and stability for the multi-layer strand arrangement, ensuring the rope maintains its shape and structural integrity under heavy loads.

• Inner Layer:

  • Consists of 14 strands laid around the IWRC core in one direction. This inner layer, combined with the core, forms a solid base that counteracts the forces generated by the outer layers.

• Intermediate Layer:

  • Contains another set of 14 strands laid in the opposite direction of the inner layer. This counter-lay arrangement neutralizes the internal torsional forces, reducing the rope’s tendency to rotate and enhancing stability.

• Outer Layer:

  • The outermost layer includes 7 strands laid in the opposite direction to the intermediate layer. This final layer ensures smooth operation with lifting equipment, minimizing rotation and providing controlled performance.

Application of 35×7 Wire Rope:

• Offshore Lifting and Marine Engineering: Preferred for heavy-duty offshore lifting operations where precise control over rotation and stability is crucial.
• Construction and Industrial Cranes: Used in large-scale crane lifting operations due to its high load-bearing capacity and rotation resistance.
• Deep-Sea and Heavy-Duty Lifting: Suitable for applications where extreme lifting heights and heavy loads create significant torsional forces.

4. Core Design Customization Options for Rotation-Resistant Wire Ropes

In addition to standard IWS and IWRC cores, rotation-resistant wire ropes can be customized with specific core designs and treatments to meet unique application requirements:

• Plastic-Coated IWS or IWRC Core:

  • A plastic-coated core enhances internal lubrication, reduces friction between strands, and protects against internal wire abrasion and corrosion.

• Compacted Core and Strands:

  • The compaction process increases the rope’s density and strength while reducing internal friction, extending the rope’s service life and providing a smoother outer surface.

5. Choosing the Right Core Design for Rotation-Resistant Wire Ropes

Selecting the appropriate core design for a rotation-resistant wire rope depends on the specific application requirements, such as load capacity, operational environment, and the need for flexibility or strength:

• For light-to-medium lifting applications such as general lifting or elevator hoisting, the 18×7 (19×7) configuration with an IWS or Fiber Core (FC) is ideal. The FC core provides flexibility, while the IWS core offers a balanced combination of strength and stability.
• For heavy-duty lifting operations like offshore platforms, deep-sea lifting, and large-scale crane operations, the 35×7 configuration with an IWRC core is recommended for maximum rotation resistance, strength, and durability.
• Consider galvanized or plastic-coated cores for enhanced corrosion resistance and durability in marine or harsh environments.

Summary and Recommendations

The core design of a rotation-resistant wire rope plays a vital role in its performance, stability, and ability to counteract twisting under load. The 18×7 (19×7) configuration typically uses an IWS or Fiber Core, providing moderate rotation resistance and good flexibility, making it suitable for general lifting and hoisting applications. The 35×7 configuration, on the other hand, uses an IWRC core, offering superior stability and rotation resistance for critical, heavy-duty lifting operations.