Laying Of Underground Cables: A Beginner's Guide
The most commonly used tool for this purpose is the fish tape. Fish tape consists of a long, flat metal or fiberglass strip wound inside a spool. One end features a hook or eyelet.
Underground cables form the backbone of many critical systems. Unlike overhead cables, underground installations benefit from better protection against weather extremes and visual clutter but require a detailed understanding of soil conditions, environmental challenges, and careful planning. This guide provides clear direction, helping readers navigate through key steps in cable installation.
Notices for Laying Underground Cables
Environmental Considerations
Before beginning any underground cable project, it is critical to assess the environment. Areas subject to severe acid or alkali conditions or those exposed to stray currents can lead to electrochemical corrosion. Avoiding such regions or applying specialized protective measures is essential. For instance, working in areas with a high likelihood of termite damage or where external mechanical forces may impact the cables demands extra precaution.
Protection Against Corrosion and Damage
To ensure the durability of cables, they must be laid with ample protective layers. Recommended practices include laying cables in trenches lined with soft soil or sand that is at least 100 mm thick on all sides. Additionally, installing a concrete protective plate extending at least 50 mm beyond each side of the cable significantly reduces risks. In some scenarios, placing a detectable warning tape above the protective layer adds an extra level of safety.
Warning Markers and Trench Requirements
In suburban and open areas, it is important to install clear directional markers or stakes every 100 meters along long stretches, as well as at every turn or cable joint. These markers help with future maintenance and repairs. Depending on the site's specific requirements, using tools such as a Cable Conveyor during cable installation can help ensure the cable’s path remains consistent and precisely measured.
Required Cable Burial Depths
General Guidelines
For effective protection, standard guidelines dictate that the vertical distance from the bottom of the cable sheath to any underground structure should be no less than 0.3 meters. Meanwhile, the depth from the top of the cable jacket to the ground surface typically should be no less than 0.7 meters. These depths help mitigate risks from accidental digging and external environmental factors.
Special Considerations for Unique Regions
In areas with heavy traffic, cultivated lands, or sensitive environments like permafrost zones, deeper burial may be necessary. Under roadways or agricultural fields, the recommended burial depth increases to at least 1.0 meter to prevent disruptions from surface-level activities. In permafrost regions, additional protection measures such as placing cables below the frozen soil layer or using well-drained backfill soil are crucial. Using equipment like the Engine Powered Winch or Optical Cable Puller can significantly aid in installing cables at these challenging depths.
Key Considerations When Laying Underground Cables
Traction Methods and Equipment
When dealing with large-core plastic cables, installing a secure traction head on the cable end is a must. This head, when sealed properly, prevents moisture ingress and ensures that the cable remains free from twists or damages during installation. For this purpose, using specialized Cable Grip tools and a Cable Reel Stand can facilitate smooth handling and pulling, ensuring the cable maintains its structural integrity while in motion.
Cable Traction and Pulling Techniques
Proper traction is essential to prevent overloading the cable’s rated pulling force. In areas with long conduit sections, mechanical traction—supported by devices like the Optical Cable Puller—provides consistent performance and minimizes cable stress. Sometimes, when space is limited, manual traction may be used as a last resort; however, caution should be exercised to ensure that the pulling force does not exceed 80% of the cable’s maximum capacity.
Protective Measures and Lubricants
Applying lubricants such as talcum powder or paraffin oil helps reduce friction on the cable surface during installation. It is crucial to avoid organic solvents which can damage the cable’s plastic sheath. Additionally, protective materials like steel plates or cloth padding are essential when cables are exposed to potential abrasion. Cable Laying Tools such as Cable Rollers help support these measures by easing the movement of cables and reducing physical stress during
Essential Equipment and Tools for Cable Laying
- Cable Conveyor: This tool aids in moving cables through trenches or conduits, ensuring the cable is laid out in a controlled manner. It is particularly useful in long stretches where manual handling might prove impractical.
- Cable Roller: With a focus on reducing friction, a Cable Roller helps the cable glide smoothly across surfaces or through conduits. It minimizes potential damage that could result from dragging or improper handling.
- Cable Reel Stand: Equally important is the Cable Reel Stand, which holds and stabilizes the cable reel during the laying process. It provides an organized system where the cable can unwind evenly, reducing the likelihood of twists or tangles.
Additional Tools and Their Uses
- Cable Cutter: Precision is key. A Cable Cutter ensures that cables are cut cleanly and to the exact lengths required, which is critical for ensuring secure terminations.
- Optical Cable Puller: Ideal for long or complex installations, an Optical Cable Puller aids in maintaining a consistent pulling force, which is especially helpful when cables must navigate bends or curves.
- Engine Powered Winch: When dealing with heavy-duty cables or extended distances, an Engine Powered Winch provides the necessary strength and control, making the cable pulling process both safer and more efficient.
- Cable Grip and Wire Steel Rope: These tools ensure that cables are held securely during the installation process, minimizing movement and reducing stress on the cable.
- Come Along Clamp and Connector Shackles: These accessories contribute to the overall safety and manageability of the cable laying process, allowing for secure fixation and easy adjustments as needed.
Methods for Laying Underground Cables
There are several methods for laying underground cables, each suited for different environmental conditions and project scales. Selecting the appropriate method can make a huge impact on the installation process and long-term performance.
Direct Laying Method
Step-by-Step Process:
1. Trench Excavation:
Begin by excavating a trench approximately 1.5 meters deep and 45 centimeters wide. The trench dimensions provide enough space for both the cable and the protective layers.
2. Initial Protective Layer:
Lay a 10 cm thick layer of fine sand at the base of the trench. This layer acts as a cushion, protecting the cable from moisture and direct contact with potentially abrasive materials.
3. Cable Installation:
Carefully place the cable onto the sand bed. When dealing with multiple cables, maintain a horizontal or vertical spacing of around 30 centimeters between them to minimize thermal interference and prevent faults from propagating.
4. Covering Layer:
Add another 10 cm layer of sand on top of the installed cable before covering it with bricks and finally backfilling the trench with soil. This layering helps protect the cables from mechanical damage and environmental disturbances.
Integrating products like the Cable Roller and Cable Conveyor during this process can help guide and protect the cable as it moves into position, ensuring that every step is controlled and precise.
Draw-In System
Manhole and Duct Installation Techniques:
1. Pre-Installed Ducts:
Cast iron or concrete ducts are pre-laid along the designated route. These ducts act as a pathway for cables, reducing direct contact with the soil.
2. Installing Cable Rollers:
Cable Rollers or Cable Conveyor systems are positioned at intervals to facilitate smooth pulling of the cable.
3. Cable Pulling Through Manholes:
Using an Optical Cable Puller, cables are carefully drawn through the ducts via strategically placed manholes. The spacing of these manholes is critical—they must be frequent enough to ease the installation while ensuring enough room for the cable to adjust.
This system is particularly effective when cables require extra protection. Using a Cable Reel Stand to organize the cable during these operations can also streamline the process, ensuring that cables remain untangled and properly aligned.
Solid System
Open Trough Technique and Protective Sealing:
1. Constructing the Trough:
Open troughs made of cast iron, stone, asphalt, or treated wood are prepared for cable placement.
2. Cable Positioning:
Place the cables carefully within the trough. Due to the nature of this method, the protective characteristics of the trough itself reduce the need for additional shielding, though a lead sheath is typically applied to the cable for extra protection.
3. Sealing the Trough:
Once positioned, the trough is filled with a bituminous compound—commonly asphalt—to secure the cables in place and protect them from mechanical damage and environmental factors.
While the solid system is less common due to its higher costs and sensitivity to weather conditions, it remains a viable option for scenarios requiring maximum protection from potential disturbances.
Conclusion
Laying underground cables is a vital process that supports the seamless operation of modern power, communication, and transportation systems. From environmental considerations to the careful selection of the right tools and equipment, every step plays a crucial role in the long-term reliability of your network. Whether you opt for the direct laying method, the draw-in system, or the solid system, integrating state-of-the-art cable laying tools such as Cable Conveyors, Cable Rollers, Optical Cable Pullers, and Engine Powered Winches can greatly enhance both efficiency and safety.