Pressure of air-blown optical cable

Air-blown optical fiber cables typically require compressed air pressures ranging from 1.0 to 1.2 MPa, depending on cable and duct dimensions, to achieve effective installation.

Typical Air Pressure and Traction Force

In air-blown cable installation, compressed air is injected into the duct to “float” the cable, reducing friction and allowing it to be pushed over long distances with minimal mechanical force . The required air pressure depends on the cable diameter, duct inner diameter, and installation length. For example, blowing a 15 mm cable in a 33 mm conduit generates a traction force of 679 N at 1 MPa and 815 N at 1.2 MPa. Similarly, a 20 mm cable in a 42 mm conduit produces 1071 N at 1 MPa and 1285 N at 1.2 MPa .

Factors Affecting Air Pressure

1. Cable-to-Duct Ratio: Optimal ratios of cable outer diameter to duct inner diameter are typically 0.35–0.6. Smaller ratios require higher air flow to maintain cable movement .
2. Cable Stiffness: Stiffer cables can travel longer distances in straight ducts, while more flexible cables handle bends better but may require careful pressure control to avoid buckling .
3. Duct Fill Ratio: A fill ratio of 50–80% is recommended for efficient air-assisted installation. Higher fill ratios improve traction but may hinder bending through turns .
4. Environmental Conditions: Air temperature affects cable flexibility. Compressed air should be heated if below 6°C or cooled if above 32°C to prevent damage to the cable or duct .

Best Practices

• Use the minimum air pressure necessary to move the cable to avoid damage .
• Attach a blowing head or bullet at the cable front to maintain a seal and improve air drag .
• Gradually increase the hydraulic pushing force as the cable progresses to prevent folding or buckling .
• Ensure duct connections are sealed to maintain consistent air pressure along the route . By carefully selecting air pressure and monitoring installation conditions, air-blown optical cables can be installed efficiently over distances exceeding 1 km, with reduced friction and minimal risk of cable damage .