Why the laying depth for underground cables is important
Why the Laying Depth for Underground Cables Matters
Hello! Today, we would like to discuss a crucial topic when it comes to laying underground cables: laying depth. The proper installation depth is essential for the safety, reliability, and longevity of underground cables. In this article, we'll clarify why installation depth is vital and how to ensure your underground cables are installed correctly.
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Protection Against Mechanical Damage: The depth at which underground cables are installed plays a significant role in protecting them from mechanical damage. Sufficient depth safeguards the cable from accidental damage caused by excavators, construction vehicles, and other activities. This protection helps maintain the integrity of the cable insulation and reduces the chances of power failures or short circuits.
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Weather Resistance: An appropriate installation depth also provides defense against weather-related effects. Underground cables face various conditions such as rain, frost, and solar radiation. A proper installation depth offers better protection from these elements, enhancing both the durability and performance of the cables.
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Regulatory Compliance: The laying depth of underground cables often falls under legal guidelines and regulations. Such regulations are designed to ensure the safety of cable networks and the public. Understanding local regulations and ensuring compliance with the installation depth requirements is crucial to avoid legal issues and safety hazards.
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Current Carrying Capacity: The installation depth can influence the current carrying capacity of underground cables. Adequate depth facilitates improved heat dissipation which, in turn, boosts the cable's current carrying capacity. This is particularly important for high-voltage or power-intensive applications, minimizing the risks of overheating and power loss.
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Future-Proofing and Maintenance: The installation depth of cables significantly affects the future maintenance and upgrade flexibility of the cable network. Adequate depths simplify maintenance tasks without necessitating the exposure or relocation of cables, which saves time and cost for future repairs or upgrades.
Conclusion: The laying depth is a decisive factor in guaranteeing the safety, reliability, and durability of underground cables. It plays a pivotal role in protecting the cable from mechanical damage, weathering, and ensuring compliance with regulations. Sufficient installation depth further enhances the current carrying capacity and promotes easier maintenance and upgrades for the cable network.
When laying underground cables, careful planning of the laying depth in accordance with local regulations is essential. Should you have any questions or require assistance, do not hesitate to reach out to us.
Sincerely,
Your Lingen Construction Machinery Team
Pre-planning the Cable Pull Saves Time and Increases Efficiency
In the world of cable pulling, ideal scenarios are a rarity; thus, installers and technicians must employ creative solutions and ingenuity at every turn.
Bruce Foreman and Rick Keeler,
Fishel Technologies
The practice of cable pulling is certainly not new; however, adequate planning is frequently underrated, leading to increased costs and workload for installers and technicians alike. A little foresight can prevent the expense of efforts needed to re-pull cables that may have suffered damage during initial installation. Moreover, coordinating multiple cable runs concurrently will reduce the labor costs associated with each installation.
Each cable pull presents a unique challenge, and various factors must be considered during the pre-planning phase; nonetheless, the following step-by-step installation procedure can act as a guideline for efficiently preparing for the cable pull. The process can be categorized into eight important steps:
- Identify the environment where the cable pull will take place;
- Determine the cable type and its specifications;
- Establish the cable route;
- Install the necessary hardware for cable support;
- Prepare the cable reels and cable cart;
- Label accordingly to the Tia/eia-606 standard;
- Position the technicians for the cable pull;
- Finally, execute the cable pull.
Before installers or technicians commence work at the job site, it is crucial to identify the type of environment or building structure for cable placement. According to the Bicsi Telecommunications Distribution Methods Manual, five different systems for horizontal cable distribution are identified: underfloor duct, poke-through, conduit, raised-floor, and ceiling distribution.
In retrofitted buildings, the overhead ceiling distribution system is the most prevalent. This type of environment involves drop-ceiling tiles, locked ceiling tiles, solid ceilings with access panels, solid ceilings with cable raceways, and overhead conduit systems.
For new building projects, architects and engineers typically recommend overhead distribution systems. The date of construction is a significant factor affecting ease of installation; for instance, older buildings might have locked ceiling tiles or solid ceilings with access panels, making access more challenging compared to drop-ceiling tiles. School buildings built in the 1960s might lack overhead ceiling space, leading technicians to utilize conduit systems or surface raceways for cable routing.
A common horizontal cable distribution system in new construction is the underfloor method. The two primary underfloor systems are poke-throughs and underfloor ducts.
Regardless of whether the distribution system is overhead or underfloor, identifying the necessary tools and methods for that specific type of cable pull is crucial.
Identify Cable Type
The second vital step in preparing for a cable pull is identifying the cable type and specifications. Most installations typically include Category 3 cables for voice, Category 5 cables for data, and possibly coaxial or fiber-optic cables for video applications. As data rates and bandwidth demands continue to soar, fiber-to-the-desktop solutions are increasingly becoming the norm in end-user environments.
Based on the pathways and spaces designated for cable placement, selecting a plenum or non-plenum jacketed cable can greatly affect the pull's complexity. A plenum cable might be mandated if the cable is to be placed in a return airspace. Some plenum cables constructed from Teflon or fluorinated ethylene propylene offer easier installation compared to others, given the variations in jacket material compounds which can affect the overall diameter and slickness of the cables. The same considerations apply in a poke-through conduit system. Although plenum cables generally incur higher costs, limited conduit space with multiple cables may leave installers with little choice.
Cable specifications also play a critical role in cable pull preparations. Important characteristics to consider include:
- Pulling tension
- Bend radius
- Maximum distance
- Outside diameter of the cable
- Conduit-fill ratios.
The Tia/eia-568A standard specifies that the pulling tension for Category 5 cabling must not exceed 25 lbs. Exceeding this pulling tension may alter the electrical characteristics of the cable and degrade its performance. Tests for Category 5 compliance reveal that any cables stretched beyond the 25-lb pulling tension may fail performance tests, necessitating a re-pull.
The bend radius is another key element to consider while preparing for the cable pull. Neglecting the recommended bend radius may compromise the electrical characteristics of the cable as well. Manufacturers suggest the minimum bend radius based on the cable jacket's outside diameter. Note that when bundling cables, sharp 90-degree bends must be avoided.
Additionally, the Tia/eia-568A standard dictates a maximum distance of 90 meters for 100-Mbit/sec applications in a Category 5 channel model. If distance limitations are exceeded, compliance tests for Category 5 will fail, once again requiring a re-pull. Noncompliance with these standards can double the rework required and result in frustration for installers.
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The overall diameter of the cable is another crucial factor affecting how many cables can be pulled simultaneously. A large cable bundle is challenging to pull, especially in conduit. To avoid cable-jacket burn and excessive pulling tension, consult conduit-fill ratio tables before setting up for the cable pull.
In the third stage of preparing for the cable pull, installers are required to establish the cable route, mapping out the most efficient pathway – provided that the distribution system hasn't yet been determined. The cable route should navigate along main passageways such as hallways and corridors while following the building’s structural lines.
The primary cable route should maximize the number of stations pulled; for example, various stations may branch off the main route to optimize the effort put forth by cable installers. It's crucial to keep 90-degree bends to a minimum — ideally, no more than two bends within a 100 ft cable span without a pull point. Excessive bends on the main cable route necessitate additional technicians at each turn. Additionally, to minimize disruption to office employees in nearby areas, it is advisable to avoid routing the main cable bundle across offices.
Prior to beginning the cable pull, installers should scrutinize the route for potential trouble spots where the cable could snag. To mitigate electrical interference and potential cable damage, it is advisable to steer clear of electrical cables, fluorescent lighting, sprinkler systems for fire alarms, and hot water pipes. Difficult locations such as excessively high ceilings also elevate the physical strain on installers; therefore, choosing the cable route cautiously is essential to reduce unnecessary work.
The subsequent step in preparing for the cable pull involves installing cable support hardware. Numerous hardware options exist, with the most commonly used being bridle rings, J-hooks, cable trays, conduit, and cable raceways. Some may provide easier or more cost-effective solutions depending on the environment; however, bridle rings or J-hooks in overhead structures often offer the most economical options. It’s crucial to securely attach the necessary beam clamps and bridle rings to adequately support the weight of installed cables.
Setting Up and Labeling
Now that installers are ready to set up for the cable pull, they need to determine the optimal location to start the pull. Installers essentially have two options: either pull from the telecommunications closet on each floor to the individual workstations, or pull from the largest cluster of workstations back to the telecommunications closet.
The cable cart should always be configured to mitigate cable strain; for instance, sharp angles into the conduit or the first bridle rings must be avoided. In pre-existing buildings, small, lightweight cable carts may be preferable compared to larger ones, depending on the specific environment.
Labeling, the sixth step of the process, is critical. Without proper labeling, technicians will need to tone and tag cables, which can double the time spent on the job. A labeling scheme that clearly identifies the location, cable, and jack position at the workstation is recommended. An example of an effective labeling technique is an alphanumeric system, such as 1A, 1B, 1C, and so forth. Consistent and standardized labeling methodologies can facilitate future pulls following the same format effectively.
It is advisable to print labels clearly or utilize a labeling machine to ensure that technicians and end-users can easily read the labels. Avoid confusion during cable termination by labeling cables, cable reels, and field blueprints simultaneously before commencing the cable pull. It's recommended to use white glass tape and a sharp-point permanent marker, marking distinguishing numbers like six (6) and nine (9) with a line underneath to tell them apart. Lastly, affix labels about three feet from the cable end to ensure that they remain intact when cutting off the cable bundle head.
When bundling multiple cables, stagger their arrangement to prevent the cable bundle head from becoming too bulky, which can lead to snagging on the bridle rings. Reducing snagging can also be accomplished by securing the jet line or pull string with a half-hitch and taping down the cable bundle. To expedite the next pull along the same route, cable installers should trail the cable bundle with an additional jet line.
Among the most critical steps to guarantee a successful cable pull is the positioning of technicians. Ideally, one technician will monitor the reel cart while another is assigned to pull the jet line to the desired location. Furthermore, it is beneficial to have a technician at each 90-degree bend. In cases where there aren't enough technicians on-site, technicians should pay out sufficient slack to the first 90-degree bend and continue pulling slack to each subsequent bend until the cable bundle reaches its destination.
The final step calls for careful monitoring and patience. To avert cable stress or cable-jacket burn, installers must pull slowly and steadily. The technician at the reel cart must feed the cable, ensuring that sufficient slack is available to reduce drag and stress on the cables.
It is pertinent to remember that if pulling tension exceeds 25 lbs, the Category 5 cable may not conform to the Tia/eia-568A standard, which necessitates a re-pull. Pre-lubricating the cable head when necessary can reduce friction in tight conduit pulls.
Two-way radios can be invaluable when multiple stations are being pulled over long distances. Constant communication between technicians helps ensure a smoother cable pull and diminishes frustration levels. A few additional tips to keep in mind include:
- Leaving adequate slack at each cable end for routing down walls to the desired location.
- At the telecommunications closet, ensuring enough cable length remains to connect to the termination field.
- When organizing cables in the telecommunications closet, planning their path beforehand to allow for sufficient slack.
Remember that aesthetics are also important; maintaining a clean and organized workspace creates a positive impression. Coiling pulled cable bundles neatly prevents confusion, especially for larger installations. If cables must be stored overnight before termination, they should be coiled with electrical tape at station locations. If cables are to be left in ceilings, it’s wise to tie-wrap coils to the ceiling structure to keep them clear of other tradespeople. When cables are loosely piled together, tangling inevitably occurs, and installers will then need to waste time untangling them prior to termination.
Eight Steps to Prepare for the Cable Pull:
- Identify the environment where the cable pull will take place;
- Determine the cable type and specifications;
- Establish the cable route;
- Install the necessary hardware for cable support;
- Set up the cable reels and cable cart;
- Label according to the Tia/eia-606 standard;
- Position the technicians;
- Ready, set, and pull!
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