Baghouse Air-to-Cloth Ratio, Bag Count & Can Velocity

The formula

This is the expression the tool evaluates. Every term is named underneath, with the unit it must be supplied in.

How the result is derived

Step by step, from the values you type to the figure on screen.

1. The 7 inputs are read from the form on every keystroke: Gas Flow at Filter Conditions, Target Air-to-Cloth Ratio, Bag Diameter, Bag Length, Bags Installed, Compartments and Housing Cross-Section at the Bags.
2. Each value is checked against the accepted range in the input table below. A value outside its range stops the calculation rather than producing a misleading figure — the results blank out and a message appears.
3. The validated values are substituted into the expression above, which resolves Air-to-Cloth Ratio together with every supporting figure in one pass — no value is carried over from a previous entry.
4. The supporting outputs — Air-to-Cloth Ratio, Cloth Area per Bag, Total Cloth Area, Ratio with One Compartment Offline, Bags Needed for the Target Ratio, Bags Short of the Target, Can Velocity between the Bags, Free Area between the Bags and Gas Flow — come from the same pass, so they always describe the same case as the headline figure.
5. Results are rounded for display only. The full-precision value is used throughout the chain, so reading a rounded intermediate figure back into the tool by hand can shift the last digit.

What each input means

Where to read each value on the floor, the unit it must be in, and the range the tool accepts.

What the tool returns

The headline figure and every supporting value it is built from.

Worked example

Substituting

Bringing the flow up to 90,000 m³/h lifts the ratio to 1.24 m/min, just over the target, and the can velocity to 47 m/min: the first fix is longer bags, which add cloth without taking free area.

How to use it

1. Work through the input groups in order — Gas and Bags & Housing. The defaults are a realistic case, so you can change one value at a time and watch what moves.
2. There is no calculate button. Every figure recalculates as you type or drag, which is what makes this usable for a what-if sweep rather than a single answer.
3. Read Air-to-Cloth Ratio in the dark results panel — that is the headline figure, expressed in m/min.
4. Check the supporting rows underneath (Air-to-Cloth Ratio, Cloth Area per Bag, Total Cloth Area, Ratio with One Compartment Offline, Bags Needed for the Target Ratio, Bags Short of the Target, Can Velocity between the Bags, Free Area between the Bags and Gas Flow) before acting on the headline — they are where an implausible input usually shows itself first.
5. Reset to defaults returns every field to the reference case, which is the quickest way to check whether a surprising result came from the tool or from an input you had changed earlier.

Where this is used

• Process planning — establishing Air-to-Cloth Ratio before a trial is booked, so machine time and material in Filtration, Separation & Gas Dynamics are committed against a calculated figure rather than an estimate.
• Costing and quotation — Air-to-Cloth Ratio is an input to the cost sheet, and quoting from a worked number rather than a remembered one is what keeps a margin intact.
• Troubleshooting — when the floor result drifts from plan, entering the measured values (starting with Gas Flow at Filter Conditions) shows how much of the gap in Air-to-Cloth Ratio each variable explains.
• Teaching and study — the accepted ranges bracket normal Filtration, Separation & Gas Dynamics practice, so moving one variable at a time shows the shape of the relationship rather than a single answer.

Reading the result

Typical bands and what each one is telling you.

Assumptions and limits

• The US EPA fact sheets for fabric filters (EPA-452/F-03-025, pulse-jet; EPA-452/F-03-026, reverse-air) define the air-to-cloth ratio as the ratio of volumetric air flow to cloth area and make it the number that sets baghouse size; its selection depends on the particulate loading and characteristics and on the cleaning method, a heavy loading needing a larger baghouse to avoid an excessive dust cake and pressure drop. Pulse-jet units clean online, row by row, and so achieve higher gas-to-cloth ratios than the compartmented types; they use felted (nonwoven) fabrics because they do not rely on a dust cake. Typical fabric filter pressure drop is 100 to 250 mm of water column (AWMA, 1992, as cited in the sheets). The target ratio here is yours: the tool prints no typical values. Cloth per bag is the cylinder wall only; pleated bags and cartridges carry more area per metre. Can velocity is the gas rising through the free area between the bags; too high and dislodged dust is carried back onto the cloth instead of falling to the hopper. **Choose the ratio from your dust and cleaning type; this sizes the cloth that delivers it.**
• Every input is bounded to the range normal practice occupies (Gas Flow at Filter Conditions 10 to 10000000 m³/h, Target Air-to-Cloth Ratio 0.1 to 10 m/min and Bag Diameter 50 to 500 mm, and so on for the rest). Those bounds are guard rails against typing errors, not a claim that the formula fails one unit outside them.
• The calculation is deterministic: the same inputs always give the same result. It carries no allowance for machine condition, operator skill, ambient conditions or lot-to-lot material variation unless an input above explicitly represents one.
• Nothing is sent anywhere. The maths runs in your browser, so the numbers you type never leave the page.

Standards and further reading

• US EPA Air Pollution Control Technology Fact Sheets EPA-452/F-03-025 (fabric filter, pulse-jet cleaned type) and EPA-452/F-03-026 (reverse-air cleaned): the definition of the air-to-cloth ratio and what its selection depends on.
• ISO 11057, Air quality: test method for filtration characterization of cleanable filter media; the media test behind a supplier's ratio.
• EN 1822 / ISO 29463 apply to HEPA and ULPA media, not to cleanable baghouse cloth; do not read their velocities across.

Questions people ask