Understanding the Significance of Cable Laying

Cable Laying

Many of us utilize devices like computers or televisions daily without recognizing the intricate network of cables that supports them. Despite their importance, cables often go unnoticed by most people.

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Unfortunately, general awareness about the technology hidden within those simple wires is quite low. Indoor cables, in particular, face substantial wear and tear; from office chairs rolling over them to curious pets nibbling at them.

Outdoor cables endure significant environmental stress, including varying temperatures and extreme pulling forces during their installation. It might seem that thicker cables are sturdier, but both thick and thin cables are subjected to similar stresses and limitations.

This article aims to heighten awareness regarding cables by elucidating concepts such as bending radius, temperature tolerance, and allowable pulling forces. Readers will also find invaluable guidelines for proper and safe installation.

Key Parameters to Consider

Initially, the notion of upgrading or expanding a network arises. An engineering firm is consulted to convert this concept into a viable plan. It’s essential to define basic parameters and goals alongside the client while also considering various technical specifications essential to infrastructure.

During the implementation phase, multiple contractors collaborate closely, and one of the key roles involves the installation of the physical network of wires and cables. The contractors responsible for laying the cables must take into account the following parameters:

• temperature range of the cable,
• bending radius of the cable,
• maximum tension of the cable,
• weight of the cable, and
• storage and preparation for cutting.

Temperature Range

The temperature range of a cable is crucial for both users and installers. Cables have to perform efficiently across a variety of temperatures, and during installation, considerable mechanical forces act upon them. The type of plastic used largely determines the limits of operation within temperature extremes.

Excessively high temperatures can soften the plastic, risking irreversible changes, while extremely low temperatures can lead to rigidity, making the material inflexible. Such conditions can result in tears, allowing moisture ingress that further deteriorates transmission capabilities.

Specific temperature ranges for laying and using these cables can usually be found in the manufacturer's technical documents. During installation, these ranges differ, offering greater flexibility as mechanical strain is typically lower once cables are laid.

The VDE regulations provide the following guidelines:

During Cable Laying

PE-sheath: From -20 °C to +50 °C
PVC-sheath: From -5 °C to +50 °C

Before & After Cable Laying

PE-sheath: From -20 °C to +70 °C
PVC-sheath: From -5 °C to +70 °C

Cable Bending Radius

When discussing the bending radius, it’s important to differentiate between multiple bends (during installation) and final positioning bends. Cables are often laid under tension around guides, which can subject them to significant stress from compression and stretching. Maintaining minimum bending radii—typically ten times the outer diameter for multi-bends—is critical to prevent permanent damage.

Final bending, where the cable is set in its permanent position, requires less stringent tolerances. For instance, the irreversible bends should be at least 7.5 times the cable's outer diameter. Exact standards can again be referenced in the cable manufacturer's documentation.

Tension

It is critical to closely monitor the tension applied to cables during installation. Excessive force can inflict damage, necessitating replacement. The maximum tension a cable can endure primarily hinges on the cross-sectional area and the tensile strength of its conductors.

For cables with structural support, such as steel or copper armoring, it is the internal conductor that dictates the maximum tension, while the armoring may add weight without contributing to tensile strength.

Cable Weight

As the diameter of cables increases, they can weigh significantly, often exceeding nine tons per kilometer (without the reel).

Storage & Cable Cutting

Cables intended for shipment and cut cables should be safeguarded against moisture, ideally through the utilization of shrink caps fitted with fusible glue. Provisional arrangements like loosely fitted caps or simple adhesive tape fall short of providing properity against water ingress, leading to corrosion and signal transmission degradation.

For any temporary connections, the establishment process should occur promptly with sufficient moisture protection, such as canopies for installation.

Further Reading

Cable Pulling Equipment

Thorne & Derrick provides a wide variety of Cable Pulling & Laying Equipment, aimed at ensuring secure installation for both fiber and copper cables within the telecommunications sector. Properly installed cables minimize operational interruptions and maintenance demands, ensuring uninterrupted service. Available products include cable spiking tools, conduit rods, cable lubricant, and rollers.

More Information | Cable Drum Handling & Laying Cables | A Guide from Nexans

Understanding Underground Cable Laying

The push for nature conservation, aesthetic integration, and spatial efficiency has made underground cable laying a necessary practice. This method offers advantages such as reduced transmission loss and a decreased likelihood of service disruption during extreme weather events.

What is Underground Cable Laying?

In densely populated or constrained areas, underground cable laying emerges as an efficient solution. It allows for seamless power and telecommunications infrastructure beneath the surface, avoiding the visual clutter associated with overhead installations. A systematic approach ensures trenching and proper installation to meet operational standards without compromising service quality.

Advantages of Underground Cable Laying

Given climate patterns, having reliable infrastructure to weather unpredictable conditions is essential. The advantages of underground cable systems are substantial:

• Extended Lifespan: Underground cables typically outlast their overhead counterparts.
• Lower Maintenance Costs: Less exposure to adverse weather conditions translates to simplified upkeep.
• Safety Improvements: Grounded cables are less likely to cause accidents, protecting the public from electrical hazards.
• Continuous Service: Shields from environmental variables contribute to uninterrupted supply.
• No Obstructions: With cables buried, they pose no physical barriers to buildings or landscaping.
• Space Efficiency: Underground installations minimize land use against traditional pole structures.

Installation Techniques for Underground Cable Laying

The success of underground cable systems hinges on proper laying methods, quality connections, and the resilience of cable joints. There are three common methods of installation:

Direct Laying

This straightforward method involves excavating a trench to a specified depth, followed by layering sand for protection before placing the cables within. It is straightforward but requires careful maintenance over time.

Pros:

• Simple and cost-effective.
• Facilitates effective heat dissipation into the ground.

Cons:

• Can incur higher maintenance costs over time.
• Locating faults can prove challenging.
• Revisions to cable networks require significant effort.

Draw-in System

This approach involves placing conduits or ducts at intervals along the cable route, allowing for future cable pulling with minimal disruption.

Pros:

• Easy access for future repairs and alterations.
• Reduced maintenance costs.
• Built-in mechanical protection fosters fewer faults.

Cons:

• Higher initial installation costs.
• Limitations in heat dissipation due to cable grouping.

Solid System

This method entails placing cables within durable pipes or troughs, typically made of strong materials, ensuring added mechanical protection.

Pros:

• Offers robust mechanical protection.

Cons:

• High demand for skill and labor can escalate costs.

Challenges of Underground Cable Laying

While beneficial, underground cable laying does face specific challenges:

1. High Installation Costs: Initial expenses can be substantial, including road restoration.
2. Regulatory Approvals: Extensive permissions are needed before commencement.
3. Difficulty in Modifications: Changes in line layouts can be complex due to hidden structures.
4. Cable Route Obstacles: Plan must accommodate any hindrances in the terrain.
5. Insulation Needs: Extensive insulation is imperative to handle high voltage flows.

FAQs

What is the minimum depth for cable laying?

Depth varies by cable type; low voltage cables should be at least 0.75m, while higher voltage cables have respective depths of 1.05m and up.

What cable laying methods exist?

Whole cable networks rely on installation techniques that include direct lay, draw-in systems, and solid systems, each with distinct methodologies.

How deep should cables be buried?

Typical depth requirements range from 30 to 42 inches based on terrain and environmental conditions.

What advantages does direct laying hold?

This method is efficient, cost-effective, and minimizes disturbances while ensuring rapid network establishment.

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