"Cable blowing" or "jetting" refers to a cable installation approach that employs high-speed air flow and added mechanical force. In this process, optical fiber cables are placed into pre-installed ducts. By injecting compressed air into the duct after inserting a length of cable, the cable is propelled forward. The swift airflow moves through the duct, propelling the cable along with it. The main force application occurs near the cable's entry point, aided by a pushing device. This technique is suitable for various cables, including micro-duct cables, and allows installations over distances exceeding 1000 meters, depending on the duct route. There are two discussed methods for this process.
Approach 1: High-Velocity Air Blowing
This technique involves initially propelling the cable using a tractor mechanism, achieved through traction rollers within the blowing device, for a limited distance – typically a few hundred meters. Subsequently, compressed air is introduced to create a floating effect for the cable within the duct. This ingenious method minimizes friction by limiting the contact area between the cable's outer surface and the inner walls of the duct, leading to reduced frictional resistance. Refer to Figures 1 and 2 for a visual representation.
Approach 2: Push/Pull (Piston) Blowing
This methodology employs a specialized blowing unit where an air-tight piston is affixed to the leading end of the cable. As compressed air propels the piston, it effectively "pulls" the cable along with it, as illustrated in Figure 3. It's imperative for installers to recognize that a pulling force is inherent in piston blowing and must be maintained within acceptable limits, avoiding excessive cable tension. This technique is particularly well-suited for more spacious ducts, such as those of sizes 32/40mm and 42/50mm, and is most effective in "straight" trajectories, enabling considerable cable blowing distances.
