Duct cable installation refers to the process of laying and securing cables inside protective ducts or conduits. This method offers several advantages, such as enhanced cable protection, easy cable management, and future scalability. To ensure a successful duct cable installation, here's a step-by-step solution:
Generally, there are six approaches for optical cable installation into a duct, pulling method and air blowing method.
In this method, cables are pulled through the duct manually or using mechanical pulling equipment. Pulling cables require the use of pulling grips or lubricants to reduce friction. It is suitable for shorter distances or when the duct is not obstructed.
Limitations: Optical fiber cables must be handled in compliance with their stated design ratings. Handling crews must be familiar with the cable's design ratings and the critical events during installation where design limits may be approached.
This method involves blowing or floating cables through the duct using compressed air or special lubricants. The cables are attached to a pulling device, and compressed air or lubricant is used to push or pull them through the duct. This method is often used for longer distances and larger diameter ducts.
Limitations: Special air blowing equipment are required for air blowing method. Air blowing of fiber cable into duct systems requires continuous run of inner-duct and pressure testing for integrity. Quality of inner-duct joints is critical to the success of air blowing techniques.
Site conditions, availability of machinery and resources are crucial factors for choosing cable installation method. The differences between pulling method and air blowing method for optical fiber cable installation are shown in the table below.
|Factors||Pulling Method||Air Blowing Method|
|Rope or not||Pulling rope pre-installed||No pulling rope to install|
|Power side||Equipment and manpower at two sides||Equipment and manpower at one side|
|Possibility of cable damage||High sidewall forces on cables and ducts may lead to cable damage.||Cable and duct can be monitored and controlled to minimize the cable damage.|
|Main forces||Manual pulling||Large compressor and/or hydraulic power pack|
|Main forces||Straight duct route||Duct route with multiple bends and undulations|
|Distance||Suitable for short distance (few 100 meters) installation||Preferred for long distance (over 2 km) installation|
As a rule of thumb, air blowing method for fiber optic cable installation is more favored than pulling method due to improved installation efficiency, particularly in longer ducts with multiple bends and undulations and savings in manpower and installation time.
The jetting method utilizes water or air pressure to propel cables through the duct. A jetting machine creates a high-pressure stream of water or air that pushes the cable along the duct. This method is commonly used in underground duct installations.
The pushing method involves manually pushing cables through the duct using flexible rods or fish tapes. This method is suitable for shorter distances and smaller diameter ducts.
In some cases, pre-installed ducts are used to simplify the cable installation process. These ducts are manufactured with pre-installed cables or empty conduits, which can be easily accessed and utilized for cable installation.
Cable pulling equipment such as cable pullers, winches, capstans, and cable rollers can be used to assist in the installation process. These tools provide mechanical advantage and help overcome friction and other installation challenges.
General precautions should always be applied when handing optical fiber cable, such as not exceed the cable’s stated maximum pulling tension and stated bending radius, as well as not exceed the cable’s maximum crush load, and etc. In addition, other general safety precautions should be paid much attention as well. Before installation begins, construction planning also should be initialed. Last but not least, necessary equipment and materials are required for every installation, including inner-duct, cable pulling lubricants, a pulling eye or grip, a swivel, the cable blower equipment, and etc. For detailed information about preparation for duct installation, you should read installation manual carefully.
Step 5 to Step 11 are about setting up inner-duct and cable blower unit(s). Please refer to detailed equipment procedures on manual.
Fiber optic cable installation into the duct provides both extra protection for optical fiber cable and an opportunity for future cable expansion. Optical fiber cable installation into the duct has widely been applied for telecommunication application so far.
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