Industrial Dust Collection, Fabric Filtration & Fan Sizing
Pulse-Jet Baghouse Gross vs Net Air-to-Cloth Ratio Formula
Calculate Pulse-Jet Baghouse Single-Bag Area (ft²), Gross Air-to-Cloth Velocity (fpm), Net (N-1 Compartment Offline) Air-to-Cloth Velocity (fpm), and Filter Cake Pressure Drop (in. w.g.).
Size fabric filter bags on Net (N - 1) offline-compartment cloth area—not Gross cloth area!
Air-to-Cloth Ratio (A/C = Gas_Flow_ACFM / Cloth_Area_ft2, in ft/min or fpm) is the single most critical sizing parameter in industrial pulse-jet baghouses: exceed ~4.0–4.5 fpm on fine mineral or cement dust and particles drive deep into the felt media, blinding the bags permanently! Whenever a multi-compartment baghouse isolates 1 compartment offline for bag changeout or pulse cleaning, all gas diverts into the remaining (N_comp - 1) compartments—raising Net Air-to-Cloth Ratio by N_comp / (N_comp - 1) and boosting filter pressure drop Delta_P = S_drag * V_net proportionally!
Verify on a 6-Compartment Cement Baghouse—Gas_Flow = 60,000 ACFM (B2), Cylindrical_Bag_Diameter = 6.0 in (0.50 ft, B3) by Bag_Length = 12.0 ft (B4 -> Area per bag = PI() * 0.50 * 12 = 18.85 ft² in E2), Total_Compartments = 6 (1 offline -> 5 active, B5), Bags_Per_Compartment = 160 (960 gross bags = 18,095.57 ft²; 800 net bags = 15,079.64 ft², B6), and Effective_Filter_Drag S_e = 1.20 in. w.g./fpm (B7): Gross A/C Ratio looks gentle at 3.32 fpm (E3), yet Net (N-1) A/C Ratio reaches 3.98 fpm (E4), producing 4.77 in. w.g. Tube-Sheet Pressure Drop (E5)!
| Baghouse Sizing KPI (60,000 ACFM, 6"x12' Bags, 6x160 Bags, Se = 1.20) | Formula | Verified Output |
|---|---|---|
| Cloth Area per Filter Bag (ft²) | PI() * (Bag_Diam_in / 12) * Bag_Length_ft | 18.85 ft² |
| Gross Air-to-Cloth Ratio (fpm) | ACFM / (Bag_Area * N_comp * Bags_Per_Comp) | 3.32 fpm |
| Net (N-1) Air-to-Cloth Ratio (fpm) | ACFM / (Bag_Area * (N_comp - 1) * Bags_Per_Comp) | 3.98 fpm (4.97 fpm @ 5 Comp) |
| Net Tube-Sheet Pressure Drop (in. w.g.) | Effective_Drag_Se * Net_AC_Ratio | 4.77 in. w.g. (5.97 @ 5 Comp) |
Net (N - 1) Offline-Compartment Air-to-Cloth Formula
Validate Gas_Flow > 0, Bag_Diam > 0, Bag_Length > 0, Total_Compartments >= 2 (so N - 1 >= 1!), Bags_Per_Comp >= 1, and Filter_Drag > 0!
=LET(q_ac, B2, d_in, B3, l_ft, B4, n_cp, B5, b_cp, B6, s_dr, B7, IF(OR(q_ac <= 0, d_in <= 0, l_ft <= 0, n_cp < 2, b_cp < 1, s_dr <= 0), "Invalid Baghouse Input", LET(a_bg, PI() * (d_in / 12) * l_ft, a_nt, a_bg * (n_cp - 1) * b_cp, ROUND(q_ac / a_nt, 2))))Undersized 5-Compartment Bid Check (Set Total Compartments = 5)
Cut Total_Compartments B5 from 6 to 5 (a low-CapEx vendor quote with only 4 compartments online during maintenance): Net Air-to-Cloth Ratio E4 spikes to 4.97 fpm and Tube-Sheet Pressure Drop E5 climbs to 5.97 in. w.g.—pushing the bags into high-blinding territory!
=IF(ISTEXT(E4), E4, ROUND(B7 * (B2 / (PI() * (B3 / 12) * B4 * (B5 - 1) * B6)), 2))Try the example
Use the original values or change them to test your understanding.