Answer from Ningbo Changshi: This is a common and important question. While both tools guide cables, their applications are distinct.

• A cable sheave, also known as a stringing block, is a specialized pulley designed to support and guide a cable, rope, or conductor during the installation of overhead transmission lines or for vertical pulls. Sheaves are used to change the direction of a pull, lift a conductor into position, or guide it over obstacles. They are critical for overhead stringing as they reduce friction and ensure the conductor is not damaged by sharp bends or contact with the tower structure.

• A cable roller, on the other hand, is designed for underground or ground-level use. It is typically a drum or series of drums on a frame that helps to roll cables along a trench or duct run. Rollers are used to support the cable's weight and minimize friction as it's pulled horizontally.

In short, use a sheave for overhead or vertical work to change direction, and use a roller for horizontal, ground-level pulls to support the cable's path. At Ningbo Changshi, we manufacture both to the highest standards, ensuring you have the right tool for every project.

Answer from Ningbo Changshi: The material of the sheave groove is a critical factor in preventing damage to the conductor during stringing. The two primary materials used are aluminum alloy and high-strength nylon (MC Nylon).

• Aluminum Alloy Sheaves: Our aluminum alloy sheaves are lightweight, strong, and highly durable. They are a great choice for general-purpose conductor stringing. They are particularly effective when equipped with a neoprene or polyurethane lining, which provides an added layer of protection and friction reduction for the conductor. This combination is especially popular for heavy-duty applications.

• High-Strength Nylon Sheaves: Nylon sheaves are known for their exceptional wear resistance, self-lubricating properties, and low coefficient of friction. They are the ideal choice for pulling expensive or sensitive conductors, such as fiber optic ground wire (OPGW), because the material is less likely to scratch or deform the cable's outer jacket.

For maximum conductor protection, particularly with high-value conductors, we recommend using our nylon or neoprene-lined aluminum sheaves. They are a sound investment that protects your project's most valuable assets.

Answer from Ningbo Changshi: The minimum bending radius (MBR) is one of the most fundamental rules in cable installation. It specifies the smallest radius a cable can be bent without causing permanent damage to its internal structure. Sheaves must be large enough to accommodate this radius.

• Why it's important: Bending a cable too tightly, such as over a sheave that's too small, can stress and stretch the conductor strands, damage the insulation, or break the fiber strands in a fiber optic cable. This can compromise the cable's electrical or data transmission properties, leading to premature failure.

A common industry guideline is that the sheave diameter should be at least 20 times the diameter of the conductor. For example, a 1-inch diameter conductor requires a sheave with at least a 20-inch diameter. Always refer to the cable manufacturer's specifications for the precise MBR. Our extensive range of sheaves comes in various diameters, ensuring we have the perfect fit to protect your conductors and adhere to project standards.

Answer from Ningbo Changshi: A cable pulling sleeve, or grip, is an ingeniously simple yet highly effective tool for securing a pulling rope to a cable. It works on the principle of the "Chinese finger trap" . The sleeve is a woven mesh tube, usually made from high-strength galvanized or stainless steel wire. You slide the mesh over the end of the cable. As tension is applied during the pull, the sleeve's woven design tightens its grip on the cable, creating a secure, non-slip attachment point. The more tension you apply, the tighter the grip becomes.

This method is far superior to taping a pulling rope to a cable for several reasons:

• Safety and Reliability: Taping can fail under high tension, leading to a catastrophic and dangerous break during the pull. A professional pulling grip provides a secure, consistent hold that is rated for a specific load.

• Stress Distribution: The woven mesh of a pulling grip distributes the pulling force evenly over a large surface area of the cable. This prevents concentrated stress points that can damage the cable's jacket or internal conductors, which is a significant risk when using tape.

• Efficiency: A properly sized cable grip allows for a quick and easy connection and disconnection, saving valuable time on the job site.

We offer a wide range of cable pulling grips, each engineered for a specific application to ensure maximum safety and efficiency for your project.

Answer from Ningbo Changshi: Cable pulling sleeves come in various designs, each suited for a specific application. Choosing the right type is critical for a safe and successful pull. The most common types include:

• Single-Eye Pulling Sleeves: These are the most common type and feature a single eye for connecting the pulling rope. They are perfect for straight, single-cable pulls and are the workhorse of most underground cable installations.

• Double-Eye Pulling Sleeves: With an eye at both ends, these sleeves are ideal for "new-for-old" pulls, where a new cable is pulled in while simultaneously removing an old one. This design allows for a secure connection to both cables.

• Lace-Up Pulling Sleeves: This type is open along its length and can be laced onto the cable at any point, not just at the end. This is especially useful for mid-span applications, such as providing temporary support or when a cable end is not accessible.

• Swivel-Eye Pulling Sleeves: These grips incorporate an integrated swivel. . The swivel prevents the cable from twisting under tension during the pull, which is particularly important for multi-conductor cables or in pulls with multiple bends.

To choose the right one, you must consider the cable diameter, the maximum pulling force, and the type of installation (overhead, underground, or mid-span). Our technical team at Ningbo Changshi can help you select the precise grip from our extensive range to match your project's specifications.

Answer from Ningbo Changshi: The material of the pulling sleeve is a key determinant of its strength, durability, and suitability for different environments. We use several high-quality materials to meet the diverse needs of our customers:

• Galvanized Steel: This is the most common material due to its high tensile strength and resistance to corrosion, making it ideal for standard underground and overhead line pulling.

• Stainless Steel: For projects in harsh, corrosive environments such as coastal areas or underwater applications, stainless steel is the preferred choice as it offers superior corrosion resistance.

• Aramid Fiber (e.g., Kevlar): For specialized applications, we offer grips made from aramid fiber. This non-metallic material is incredibly strong, lightweight, and non-conductive, making it the perfect choice for stringing live-line conductors or in environments where a metallic grip could pose a risk, such as in the vicinity of explosives or sensitive electronic equipment.

For overhead transmission line (OHTL) work, our high-strength galvanized steel and specialized aramid fiber grips are engineered to handle the rigorous demands and high loads of conductor tension stringing.

Answer from Ningbo Changshi: This is a very common point of confusion. While the terms are often used interchangeably, they refer to different types of pulling lines based on their strength and construction.

• A pulling string is typically a thin, lightweight, and low-strength line. It is mainly used as a "pilot line" to fish through an empty conduit, which is then used to pull a stronger line, such as a rope or a mule tape.

• A pulling rope is a heavier, thicker, and much stronger line used for the actual cable pulling. It has a higher tensile strength and is designed to handle the friction and tension of a full-scale pull.

• Pulling twine is often a term for a strong, twisted cord that falls somewhere between string and rope in terms of strength, suitable for light-duty pulls.

For professional use in power line and electrical construction, we highly recommend high-strength, synthetic pulling ropes. Materials like braided polyester and polypropylene are preferred for their superior strength-to-weight ratio, low friction, and excellent resistance to mildew, rot, and chemicals. Our ropes are engineered to be lightweight yet strong enough to handle heavy cables, ensuring safety and reliability on every job.

Answer from Ningbo Changshi: While some smaller, lighter strings can be reused for non-critical, manual pulls, a professional-grade pulling rope is not designed for repeated heavy-duty use. Its lifespan is directly affected by several critical factors:

• Tensile Load: Each time a rope is used for a pull, its internal fibers are subjected to stress. Pulling a heavy cable can permanently stretch and weaken the rope, even if it doesn't break during the pull. Using a rope close to its maximum working load will significantly reduce its lifespan.

• Abrasion and Friction: Pulling a rope through tight or dirty conduits with sharp bends causes internal and external abrasion, which degrades the fibers over time.

• Chemical and Environmental Exposure: Exposure to oils, acids, alkalis, and UV radiation from sunlight can weaken a rope's material. Our synthetic ropes are treated to resist these elements, but proper care is still essential.

• Knots: Tying knots in a rope can reduce its tensile strength by as much as 50%, making it unsafe for future pulls.

For these reasons, we advise inspecting all pulling ropes before and after each use. Any signs of wear, fraying, or discoloration are indicators that the rope's integrity has been compromised and it should be replaced. This is a critical safety practice we emphasize to all our clients.

Answer from Ningbo Changshi: A measuring pull string or tape is an invaluable tool for enhancing efficiency and accuracy in underground cable laying projects. These products have a clear length marking printed directly on the line itself.

The primary benefits are:

• Real-time Measurement: As you pull the line through a duct or conduit, the printed markings allow you to instantly determine the length of the run. This eliminates the need for manual measurements with a tape measure, saving considerable time.

• Precise Cable Ordering: Knowing the exact length of a run allows you to order the precise amount of cable needed, minimizing waste and reducing costs.

• Locating Blockages: If a line becomes stuck, the markings help you pinpoint the exact location of the obstruction within the conduit, allowing you to address the problem with minimal guesswork.

At Ningbo Changshi, we offer high-strength pulling lines with clear, accurate markings to make your underground projects more efficient and professional.

Answer from Ningbo Changshi: This question gets to the core of choosing the right equipment for the scale of your project.

• A mechanical cable drum jack operates using a screw-type mechanism. A user manually turns a handle to raise or lower the spindle, which in turn lifts the cable drum. These stands are robust, reliable, and generally more affordable. They are an excellent choice for lighter to medium-duty applications and where a high degree of portability is required.

• A hydraulic cable drum jack uses a hydraulic cylinder and a pump handle to lift the drum. This design allows a single operator to effortlessly lift very heavy drums with minimal physical effort. They are indispensable for heavy-duty projects involving large, high-voltage cables where the drums can weigh several tons.

For heavy-duty projects, a hydraulic cable drum jack is the superior choice. Its power and efficiency save significant time and labor, while also providing a higher degree of safety and stability when handling massive cable drums.

Answer from Ningbo Changshi: Safety is the number one priority in any electrical construction project. A professional-grade cable drum stand should incorporate several key safety features to protect both personnel and the valuable cable.

• Integrated Brakes: A tension-braking device, often found on the spindle, provides controlled unwinding of the cable. This prevents the drum from "free-wheeling" and stops the cable from becoming tangled or damaged, which is a common cause of accidents.

• High-Strength Materials: The stand and spindle should be constructed from high-quality, high-strength steel with a durable anti-corrosion finish. This ensures the stand can withstand its rated load capacity without failure.

• Secure Locking Mechanisms: The spindle locking collars must be robust and easy to operate to prevent the spindle from slipping out of the stand's V-block.

• Stable Base Design: A wide, stable, and reinforced base is crucial to prevent the stand from tipping or shifting during a pull. For added stability, some of our models are designed with integrated forklift pockets.

All our cable drum stands are designed with these safety features, ensuring compliance with international safety standards and providing peace of mind on the job site.

Answer from Ningbo Changshi: This distinction is critically important, especially for overhead transmission line (OHTL) projects.

• A standard steel wire rope is constructed by twisting strands of steel wires together. While strong, this twisting can create rotational torque. When a conductor is pulled over a long distance, this torque can accumulate and cause the pulling wire to twist, which can damage the conductor or affect its installation.

• An anti-twist steel pulling wire, which we manufacture, is specifically engineered to counteract this torque. It is typically constructed with an even number of braided strands (e.g., 8, 12, or 18 strands) that are twisted in alternating directions. This design ensures that the twisting forces in the wire rope are balanced out, resulting in a non-rotating or anti-twisting property.

This anti-twist feature is essential for stringing high-value conductors like OPGW (Optical Ground Wire) and multi-conductor bundles, as it prevents costly damage and ensures a smooth, controlled stringing operation from start to finish. Our anti-twist steel pulling wires are a testament to our commitment to providing safe and reliable stringing solutions.

Answer from Ningbo Changshi: The choice between steel and synthetic pulling lines depends on the specific demands of your project. Each material has its unique advantages.

• Choose steel pulling wire when:

  • Maximum Durability is Required: Steel wire is highly resistant to abrasion and can withstand contact with sharp edges, rocks, and rough surfaces found in many construction environments.

  • High-Load, Long-Distance Pulls: For pulling extremely heavy or long conductors, steel offers a superior strength-to-diameter ratio and minimal stretch under high tension.

  • High-Heat Environments: Steel can withstand high temperatures better than most synthetic materials.

• Choose synthetic pulling rope when:

  • Weight is a Factor: Synthetic ropes are significantly lighter than steel wires of a comparable strength, making them easier to handle and transport, especially for manual or low-tension pulls.

  • Safety is a Primary Concern: In the event of a rope failure, a synthetic rope's energy dissipates, causing it to fall to the ground. A snapping steel wire, however, can recoil with extreme force, posing a serious safety risk.

At Ningbo Changshi, we offer both steel and synthetic options, and we can help you evaluate your project's specific needs to determine the safest and most efficient choice.

Answer from Ningbo Changshi: The longevity and safety of steel pulling wire depend entirely on proper inspection and maintenance. We strongly advise a thorough check before and after every use.

• Visual Inspection: Look for any signs of wear, such as broken wires, broken strands, excessive rust or corrosion, kinks, or crushing. Any of these signs are a clear signal that the wire's integrity has been compromised and it should be removed from service.

• Lubrication: Steel wire rope requires regular lubrication to reduce friction between the individual wires and protect against corrosion. A well-lubricated wire will have a significantly longer service life.

• Sheave and Winch Check: Ensure the sheaves, drums, and guides you are using are correctly sized for the wire's diameter. Improperly sized or worn grooves will cause premature wear on the wire rope, leading to a shortened lifespan and a greater risk of failure.

• Adherence to Standards: Always ensure that the wire's minimum breaking load (MBL) or safe working load (SWL) is well above the maximum anticipated pulling force. Adhering to standards like ISO 2408 for steel wire ropes is crucial for safety.

By following these professional practices, you can ensure that our high-quality steel pulling wires provide maximum performance and safety for years to come.

Answer from Ningbo Changshi: A breakaway swivel is a specialized safety device designed to protect a valuable cable from being over-stressed during a pull. Unlike a standard swivel, which is engineered to handle a load and prevent twisting, a breakaway swivel contains a shear pin that is designed to "break away" or fracture at a pre-set tensile load.

This is a critical safety tool, especially for delicate and expensive cables like fiber optic or high-voltage cables, which have a specific maximum pulling tension that should never be exceeded. If the pulling tension unexpectedly reaches this limit due to an obstruction or friction in the conduit, the breakaway pin will snap, disconnecting the pulling line from the cable. This prevents damage to the cable's internal structure and saves a potentially costly repair or replacement. Our breakaway swivels are available with various shear pin ratings, allowing you to select the precise breaking point needed for your specific project.

Answer from Ningbo Changshi: While the fundamental purpose of a swivel is the same—to prevent twisting—the designs are often optimized for different environments.

• Underground Cable Laying: Swivels for underground applications, such as pulling through ducts or manholes, are typically streamlined and have a smooth "bull-nose" shape. This design minimizes the risk of snagging on rough conduit edges or getting caught in tight bends.

• Overhead Transmission Line (OHTL) Stringing: Swivels for overhead work must be robust enough to handle the unique challenges of tension stringing. They are designed to withstand high radial loads as they pass over stringing blocks and pulley systems. The design ensures the swivel remains stable and rotates freely even when the pulling line or conductor is at an angle.

At Ningbo Changshi, we manufacture a wide range of swivels engineered for both environments, ensuring our clients have the right tool for their specific project needs, whether they are pulling cable through a duct or stringing a conductor on a towering pylon.

Answer from Ningbo Changshi: Proper attachment is essential for safety and efficiency. The most common and recommended method involves a direct connection between the swivel and a pulling grip, also known as a cable stocking or sock.

• Secure Connection: The pulling grip's eye is inserted into the clevis or pulling eye of the swivel. A robust, captive pin or bolt is then passed through both eyes and securely fastened. It is crucial to use the correct size pin and to ensure it is fully locked.

• Preventing Damage: For added security and to prevent the mesh of the grip from slipping, it is standard practice to use high-strength friction tape to bind the pulling grip to the cable itself. This ensures the pulling force is transmitted smoothly and evenly through the entire assembly.

By following this best practice, you create a secure, anti-torsion link between your pulling line and your cable, guaranteeing a safe and successful pull.

Answer from Ningbo Changshi: A cable drum roller stand is a specialized, low-profile stand that uses rollers to support the drum. Instead of using a spindle through the center, the drum sits directly on the rollers, which allow it to rotate.

You should use a cable drum roller stand when:

• Space is limited: The compact, low-to-the-ground design is ideal for use in tight spaces, such as inside buildings or in confined areas of a substation.

• The drum is smaller and lighter: They are best suited for smaller to medium-sized drums that can be manually lifted onto the stand.

• Portability and speed are key: They are generally lighter and easier to set up than hydraulic jacks, making them a great option for jobs that require frequent relocation.

While they may not have the lifting power of a hydraulic jack, roller stands offer a simple, safe, and efficient solution for a wide range of everyday cable pulling tasks.

Answer from Ningbo Changshi: Correct sizing is the most critical factor in ensuring a safe and effective cable pull. A grip that is too large won't hold the cable securely, while one that is too small may not fit or could be overstressed.

The proper sizing is based on the outside diameter (OD) of the cable or conductor. Our single-eye cable pulling socks are manufactured with a specific diameter range, for example, 30mm-40mm or 50mm-60mm. To ensure a secure grip, the cable's OD must fall within this specified range. If you are pulling multiple cables with a single grip, you must bundle them together and measure the combined circumference, then convert that measurement back to a diameter to find the correct sock size. We provide detailed sizing charts to assist our clients in selecting the perfect fit for their specific project needs.

Answer from Ningbo Changshi: Because a cable pulling sock is a critical link in the pulling assembly, a thorough inspection before every use is essential for safety. The key points to check are:

• Frayed or Broken Wires: Carefully inspect the woven steel mesh. Any visible signs of frayed, bent, or broken wires indicate a significant loss of strength, and the sock should be immediately replaced.

• Corrosion and Rust: Rust can weaken the steel wires and compromise the integrity of the grip. Do not use any sock that shows signs of excessive rust or corrosion.

• Eye and Thimble Condition: The single eye, where the pulling rope attaches, should be checked for any deformation, cracks, or signs of wear. The thimble within the eye should be smooth and not crushed. Pulling loads at an angle, rather than in a straight line, can damage the eye and is a common cause of failure.

• Overall Condition: The sock should not have any bulges, permanent kinks, or other signs of stress.

A damaged or worn cable sock can lead to a catastrophic failure during a pull, posing a serious safety risk. We strongly recommend that all our clients implement a rigorous inspection protocol for all their pulling equipment.