A swivel is a critical component in a cable pulling setup. It's a rotating device placed between the pulling rope and the cable grip. The purpose of the swivel is to prevent the pulling rope's rotation from being transferred to the cable. As a hydraulic puller winds the rope, the rope naturally wants to twist. The swivel allows this twisting to occur freely, preventing the cable from coiling, kinking, or being damaged during the pull.

The machines used for underground cable installation can be divided into two main categories based on their function: machines that prepare the path, and machines that install the cable.

1. Trenching and Laying Machines: These machines are used to prepare the ground for the cable. This category includes:

   • Trenchers: Machines that use a digging chain or wheel to excavate a narrow, continuous trench for the cable or conduit.

   • Vibratory Plows: These machines create a slit in the ground and simultaneously feed the cable into it without the need for a wide, open trench. This "ditchless" method is faster and less disruptive.

   • Horizontal Directional Drilling (HDD) Rigs: For complex installations under roads, rivers, or existing structures, these rigs drill a pilot hole and then ream it out to accommodate the cable or conduit.

2. Cable Installation Machines: These are the machines that handle the cable itself, from the reel to the final position. Our product line focuses on these specialized machines.

Ningbo Changshi Electric Power Machinery Manufacturing Limited specializes in the machines and tools for the cable installation phase. Our range of equipment is designed to make the process safe, efficient, and precise.

• Hydraulic Cable Pullers and Winches: These are the most crucial machines for the cable pulling process. They provide a constant, controlled pulling force to draw the cable through a conduit or trench over long distances. Our models are equipped with real-time tension monitoring systems to prevent over-tensioning, which could damage the cable's conductors or insulation.

• Cable Drum Stands and Trailers: For heavy cable reels, our hydraulic drum stands and trailers provide a safe and stable way to lift and unspool the cable. They are essential for a smooth, continuous feed and prevent the cable from kinking. Our trailers also provide a secure way to transport drums to and from the job site.

• Cable Conveyors: These machines assist in pushing the cable through a conduit, working in conjunction with a hydraulic puller. They are particularly useful for long pulls or in sections with multiple bends, as they reduce the overall tension required, protecting the cable and prolonging the life of the pulling machine.

Fiber optic cable installation is governed by a set of technical guidelines that focus on preserving the cable's optical integrity. Some of the most widely referenced standards and guidelines include:

• Maximum Pulling Tension: Unlike power cables, which are pulled with kilonewtons of force, most fiber optic cables have a maximum installation pulling tension of around 2,700 Newtons (600 pounds) for outdoor cables. Our hydraulic cable pullers are equipped with tension monitoring systems to ensure this limit is never exceeded.

• Minimum Bend Radius: This is a critical factor. The standard is typically 20 times the cable's outside diameter during a pull (dynamic) and 10 times the outside diameter when stationary (static). Bending the cable too tightly can cause microbends in the fiber, leading to signal loss. Our cable rollers and sheaves are designed to provide a smooth, controlled path that respects these bend radius limits.

• Telcordia GR-20-CORE: This is a comprehensive industry standard in North America for qualifying the performance and reliability of outside plant (OSP) optical fibers and cables. Adherence to this standard ensures the cable can withstand the rigors of installation and a long service life.

Using the right equipment is the only way to meet these strict standards and ensure a successful installation. Our equipment is specifically designed to address the unique challenges of fiber optic cable.

• Tension-Controlled Pullers: Our hydraulic pullers are not just for power cables. They are precisely calibrated to apply the gentle, steady force needed for fiber optic cables, with a dynamometer to provide real-time feedback and a fail-safe against over-tensioning.

• Duct Rodders: For installations in conduit, our duct rodders are essential for feeding the pulling line through long, convoluted paths without pushing on or damaging the cable itself.

• Cable Swivels and Grips: A fiber optic pulling swivel is critical. It allows the pulling rope to twist freely without transferring that torque to the cable, preventing damage and kinking. The specialized mesh pulling grip distributes the pulling force evenly, protecting the delicate internal fibers.

By using professional-grade tools, you ensure that the cable is not just installed, but installed correctly, preserving its performance and warranty.

A professional underground fiber optic cable installation is a multi-phase process that requires meticulous planning and the use of specialized tools to protect the delicate fiber.

1. Site Survey and Planning: This is the most crucial phase. It involves a thorough site assessment to determine the best route, identify existing underground utilities to prevent damage, and calculate the pulling tension and bend radius requirements for the specific cable being used.

2. Trenching or Conduit Laying: A trench is excavated along the planned route. For most fiber optic installations, a conduit is laid inside the trench. This conduit acts as a protective pathway for the cable, shielding it from moisture, chemicals, and mechanical damage. It also makes future repairs or upgrades much easier.

3. Cable Pulling or Blowing: This is the core installation step. There are two primary methods:

   • Pulling: The most common method involves a pulling rope and a hydraulic cable puller. The rope is fed through the conduit using a duct rodder. The cable is then attached to the rope with a special swivel and pulling grip and is pulled through the conduit.

   • Blowing: A more advanced method uses a fiber blowing machine and compressed air to push the fiber optic cable through the duct. This technique is often used for long distances and complex routes with many bends, as it creates less friction and stress on the cable.

4. Splicing and Termination: Once the cable is in place, the individual fibers are connected to other cables or equipment. This is done through splicing, a process of fusing two fibers together with a machine, or termination, which involves installing a connector on the end of the fiber. This phase is critical for ensuring the signal's integrity and minimizing attenuation (signal loss).

5. Testing and Commissioning: After installation, the cable is tested using tools like an Optical Time-Domain Reflectometer (OTDR) to verify its performance. This test confirms that the cable was not damaged during the installation process and that signal loss is within acceptable limits.

The choice between pulling and blowing depends on the project's specifics, but both methods have a place in the industry.

• Cable Pulling is a traditional, well-understood method that uses physical force to draw the cable through the conduit. It's highly effective for many projects and our hydraulic cable pullers provide a controlled, safe way to execute the pull without exceeding tension limits.

• Cable Blowing is a modern technique that uses high-pressure compressed air to push the cable into the duct. The air creates a cushion that reduces friction, allowing for much longer installation runs without the risk of over-stressing the cable. This method is often preferred for long distances or for installing lightweight microduct cables.

Our company provides a full range of equipment for both methods, from hydraulic pullers with tension monitors to specialized duct rodders and accessories, ensuring a perfect fit for any project's needs.

Controlling pulling tension is one of the most critical aspects of high-voltage (HV) cable installation. Exceeding the manufacturer's specified maximum pulling tension can stretch the conductors and damage the sensitive insulation, leading to premature cable failure. To meet these stringent standards, installers must use specialized equipment.

Our hydraulic cable pullers are designed with an integrated dynamometer and a tension monitoring system. This allows the operator to set a maximum pulling limit. If the tension approaches this limit, the machine automatically slows down or stops, preventing damage. This technology is essential for demonstrating compliance with HV cable installation standards and for protecting the valuable asset being installed.

The minimum bending radius is a critical standard for HV cables, which are stiff and unforgiving. Bending the cable too tightly can cause the insulation to crack or lead to a phenomenon known as "stress concentration," which can cause electrical failure. The dynamic (during installation) bending radius is typically much larger than the static (once in place) radius.

To maintain the correct bend radius, our professional installation teams use specialized cable rollers and sheaves. These rollers are placed at bends in the trench or conduit to guide the cable smoothly and prevent it from being forced into a tight turn. They significantly reduce friction and ensure the cable adheres to the manufacturer's specifications throughout the entire pull, thereby meeting installation standards.

The integrity of an HV cable system is only as strong as its weakest point, which is often a joint or termination. HV installation standards mandate that these connections must be perfectly executed to prevent insulation breakdown and moisture ingress. Poorly prepared connections can create air voids or stress points that lead to partial discharge and eventual failure.

Our equipment is used to prepare the cable for these critical steps. The tools are designed to work with high precision, ensuring that the cable is stripped and prepared correctly, providing a perfect foundation for a professional, durable joint. This attention to detail is essential for the long-term reliability and safety of the HV network.

Installing 132kV cables is significantly more complex and demanding than lower-voltage projects. The primary challenges stem from the physical properties of the cables and the critical need for absolute precision to ensure long-term reliability.

• Weight and Size: EHV cables are much larger and heavier than their lower-voltage counterparts. A single reel can weigh several tons, making manual handling impossible. This requires specialized cable drum trailers and hydraulic drum stands for safe transport and unspooling.

• Mechanical Stress Tolerance: The insulation of 132kV cables is highly sensitive to mechanical stress. Exceeding the pulling tension or bending radius can cause micro-fractures, which are invisible during installation but will lead to catastrophic failure over time.

• Thermal Management: These cables generate a substantial amount of heat. The trench design must ensure adequate heat dissipation to avoid thermal runaway. This includes using specialized backfill materials and maintaining a specific formation (e.g., flat formation with proper spacing).

• Splicing and Terminations: The joints and terminations are the weakest points of the entire system. They require highly skilled technicians and specialized tools to ensure a perfect, moisture-proof seal that can withstand the intense electrical stress of the voltage.

The right equipment is not an option—it's a necessity. For a 132kV project, every tool must be professional-grade, reliable, and designed to handle the specific demands of EHV cables.

• Hydraulic Cable Pullers with Tension Monitoring: This is the single most critical piece of equipment. Our hydraulic pullers are specifically designed to apply a smooth, controlled force with a real-time dynamometer that provides a fail-safe against over-tensioning. This protects the conductor and insulation from damage, which is non-recoverable.

• Heavy-Duty Cable Rollers and Sheaves: Because of the cable's weight and stiffness, rollers are essential for reducing friction and protecting the cable's outer sheath. Our heavy-duty rollers and sheaves are built to handle the immense weight and are positioned to maintain the manufacturer's specified minimum bending radius at all turns.

• Hydraulic Drum Stands and Trailers: Safely unspooling a massive 132kV cable reel requires a robust system. Our hydraulic drum stands provide a secure platform to lift and control the rotation of the drum, preventing kinking or uncontrolled movement that could lead to injury or cable damage.

• Cable Grips and Swivels: The connection between the cable and the pulling rope must be robust yet protective. A wire mesh pulling grip distributes the pulling force evenly over a large area, while a high-load swivel prevents rope torsion from being transferred to the cable, avoiding kinking and damage.

Installing 230kV cables is a demanding, specialized task that requires meticulous planning and execution. The primary challenges are far more significant than those for lower-voltage cables and include:

• Extreme Cable Weight and Diameter: 230kV cables are massive. Their weight and large diameter make manual handling impossible and require purpose-built hydraulic drum stands and trailers for safe transport and unspooling.

• Thermal Management: These EHV cables generate a significant amount of heat. The trench must be designed to include specialized thermally stable backfill materials to ensure heat dissipates efficiently. Overheating can lead to rapid insulation degradation and catastrophic failure.

• Mechanical Stress Tolerance: The insulation of 230kV cables is extremely sensitive. Any mechanical stress from improper pulling tension or tight bends can cause non-recoverable damage to the insulation, leading to premature breakdown. This is why tools with real-time feedback are non-negotiable.

• Flawless Splicing: Joints and terminations on a 230kV cable are the most critical points in the entire system. Any imperfection—even an air void—can cause a partial discharge under high electrical stress, leading to a system failure. The process requires a clean environment, highly trained technicians, and precision tools.

The right equipment is not a luxury—it's a fundamental requirement for a successful 230kV installation. Our tools are engineered to meet these rigorous demands.

• Hydraulic Cable Pullers with Tension Monitoring: This is the single most important piece of equipment. Our hydraulic pullers provide a constant, smooth pulling force. Most importantly, they feature an integrated dynamometer and a tension monitoring system that automatically stops the pull if the tension exceeds the cable manufacturer's specified limit. This protects the cable from unrecoverable damage.

• Heavy-Duty Cable Rollers and Sheaves: Because of the cable's immense weight and stiffness, rollers are essential for reducing friction and protecting the cable's outer sheath. Our heavy-duty rollers and sheaves are built to handle extreme loads and are designed to maintain the required minimum bending radius at all turns.

• Hydraulic Drum Stands and Trailers: Safely transporting and unspooling a massive 230kV cable reel requires a robust system. Our hydraulic drum stands provide a secure platform to lift and control the rotation of the drum, preventing kinking or uncontrolled movement.

• Specialized Cable Grips and Swivels: The connection between the cable and the pulling rope must be robust yet protective. A wire mesh pulling grip distributes the pulling force evenly, while a high-load swivel prevents rope torsion from being transferred to the cable, avoiding kinking and damage.

The process of pulling a wire underground is a critical task that requires a systematic approach to ensure safety and the integrity of the wire.

1. Preparation and Planning: First, a clear path must be established. This involves a route survey to identify any existing underground utilities and to choose the correct conduit size for the wire. For any new conduit runs, a trench must be dug to the proper depth as required by local electrical codes.

2. Preparing the Conduit: Before pulling, the conduit must be cleared of any debris. A duct rodder is often used to feed a pull string or a pulling line through the conduit from one end to the other.

3. Attaching the Wire: The wire is then securely attached to the pulling line. A wire mesh pulling grip or "cable sock" is the ideal tool for this, as it distributes the pulling force evenly and protects the wire's insulation. For multiple wires, they are often bundled together and taped to create a smooth, tapered head that won't snag.

4. The Pull: The pulling line is then pulled, drawing the wire through the conduit. For short runs, this can be done manually, but for longer or more complex pulls, a hydraulic cable puller is essential to apply a consistent, controlled force and prevent the wire from being stretched or damaged. Using a wire lubricant also greatly reduces friction, making the pull smoother.

5. Final Checks: After the pull is complete, the wire is terminated at both ends, and continuity tests are performed to confirm that the wire has not been damaged and is ready for service.

Using the right tools is crucial for both safety and the success of the project. We offer a comprehensive range of professional equipment for this task.

• Duct Rodders: These flexible, semi-rigid fiberglass rods are used to "fish" a pull string through the conduit.

• Wire Mesh Pulling Grips: These are used to securely connect the wire to the pulling rope without causing damage.

• Hydraulic Cable Pullers: For anything more than a short, simple pull, a hydraulic puller is the safest and most efficient option. These machines apply a constant, controlled pulling force and prevent the wire from being overstressed.

• Cable Drum Stands or Trailers: For large spools of wire, a hydraulic drum stand is used to lift the reel off the ground and allow it to unspool freely and safely during the pull.

• Cable Rollers: When pulling wire through an open trench, cable rollers are placed at regular intervals to support the cable and reduce friction, protecting its outer sheath from abrasion.

The primary difference is their location and method of protection. Overhead power lines are supported by poles or towers and are exposed to the open air. Their insulation is primarily the air around them, with ceramic or polymer insulators at the support points. In contrast, an underground power line is a system of cables, conduits, and accessories that are buried directly in the ground. Their insulation is a multi-layered system within the cable itself, designed to protect the conductor from the surrounding environment.

An underground power line is more than just a cable; it's a complete system designed for long-term reliability. The key components include:

• Conductor: The core of the cable, typically made of aluminum or copper, that carries the electrical current.

• Insulation: The most critical component. High-quality materials like XLPE (Cross-linked Polyethylene) insulate the conductor, preventing current leakage and protecting it from moisture and chemical damage.

• Conduit: A protective pipe, often made of PVC or HDPE, that houses the cable. It provides a crucial layer of physical protection and allows for easier replacement in the future.

• Accessories: This includes various components that are essential for the system's operation and maintenance, such as joints (splices) to connect cable sections and terminations to connect the underground cable to above-ground equipment like transformers.