Microduct Fill Ratio and Cable Jetting Air

Computes cable-to-microduct area fill, annulus, nominal duct air, and compressor free-air delivery against an entered jetting window. An 8.5 mm cable in a 10 mm duct occupies 72.2% of the area, above the ordinary 40% to 60% window. The arithmetic sizes air demand; manufacturer data and a trial shot, not a general formula, establish jetting distance.

area fill = (cable OD/duct ID)^2; annulus = pi(ID^2 - OD^2)/4; nominal duct flow = annulus x velocity; free-air delivery scales by absolute pressure ratio.

Microduct fill and nominal air-demand screen. Jetting distance is deliberately not calculated.

Circle areas and a volumetric-flow conversion.

Estimate. AHJ and licensed professional govern.

Field names used by the API: duct_id_mm, cable_od_mm, fill_min_pct, fill_max_pct, optimal_fill_pct, air_velocity_m_s, pressure_bar_absolute, fill_ratio_pct, free_air_l_min, optimal_cable_od_mm, optimal_free_air_l_min

• Nominal incompressible screen real duct flow is compressible and pressure falls along the runthe jetting-equipment supplier
• Fill window is entered cable and duct surface and stiffness alter itthe paired product data
• Distance excluded bends, elevation and surface friction prevent a general formulamanufacturer charts and a trial shot