In industrial ventilation systems, accurate calculation of airflow and static pressure is essential for selecting the right blower. Whether you are designing a dust collection system, fume extraction unit, or industrial ventilation setup, understanding these parameters ensures efficiency, durability, and energy savings. This is why experienced Centrifugal blower manufacturers in India emphasize proper engineering calculations before recommending a blower model.
In this blog, we will break down airflow and static pressure calculations in a simple and practical way.
Understanding Airflow (CFM)
Airflow refers to the volume of air a blower moves within a specific time. It is usually measured in:
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CFM (Cubic Feet per Minute)
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CMH (Cubic Meter per Hour)
Airflow depends on the application. For example:
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Dust collection systems require high airflow.
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Combustion air systems need controlled airflow.
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Chemical exhaust systems require continuous steady airflow.
Basic Airflow Calculation
To calculate airflow, you need:
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Duct size
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Air velocity
The formula is:
Airflow (CFM) = Duct Area (sq.ft) × Air Velocity (FPM)
Step 1: Calculate Duct Area
For a round duct:
Area=π×(D/2)2Area = π × (D/2)^2Area=π×(D/2)2
Where D is duct diameter.
For a rectangular duct:
Area=Length×WidthArea = Length × WidthArea=Length×Width
Step 2: Multiply by Velocity
If the duct area is 2 sq.ft and air velocity is 1500 FPM:
Airflow = 2 × 1500 = 3000 CFM
This means the blower must handle 3000 CFM.
Professional Centrifugal blower manufacturers in India use this calculation along with safety factors to ensure optimal performance.
Understanding Static Pressure (SP)
Static pressure is the resistance the air faces while moving through ducts, filters, bends, dampers, and equipment. It is measured in:
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mmWC (millimeters of water column)
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Inch WC
Higher resistance means the blower must generate more pressure.
Components That Create Static Pressure
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Duct length
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Elbows and bends
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Dampers
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Filters
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Cyclones or dust collectors
Each component adds pressure loss.
How to Calculate Static Pressure
Static pressure is the sum of all pressure losses in the system.
TotalStaticPressure=DuctLoss+ElbowLoss+FilterLoss+EquipmentLossTotal Static Pressure = Duct Loss + Elbow Loss + Filter Loss + Equipment LossTotalStaticPressure=DuctLoss+ElbowLoss+FilterLoss+EquipmentLoss
1️⃣ Duct Pressure Loss
Duct friction loss depends on:
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Duct diameter
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Air velocity
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Duct length
Friction loss charts are typically used for accurate calculation. As a general rule:
Longer ducts = Higher pressure drop
2️⃣ Elbow Loss
Each elbow adds resistance.
For example, one 90° elbow may add 0.25 to 0.5 inch WC depending on velocity.
3️⃣ Filter Loss
Clean filters may have 0.5 inch WC resistance.
Dirty filters increase pressure significantly.
Example Calculation
Let’s assume:
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Duct loss = 1.2 inch WC
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3 elbows = 0.9 inch WC
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Filter loss = 0.8 inch WC
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Equipment loss = 0.6 inch WC
Total Static Pressure =
1.2 + 0.9 + 0.8 + 0.6 = 3.5 inch WC
The blower must deliver required airflow at 3.5 inch WC.
Reputed Centrifugal blower manufacturers in India always design blowers according to both airflow and static pressure to avoid underperformance or motor overload.
Why Both Airflow & Static Pressure Matter
Many industries make the mistake of focusing only on airflow. However:
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High airflow with low pressure = System may not overcome resistance
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High pressure with low airflow = Poor ventilation
The correct blower selection depends on the performance curve.
A centrifugal blower operates based on a performance curve that shows:
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Airflow (X-axis)
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Static Pressure (Y-axis)
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Efficiency
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Power consumption
Matching system requirements with the blower curve ensures:
✔ Energy efficiency
✔ Low vibration
✔ Longer motor life
✔ Proper ventilation
Role of System Design
Proper system design reduces static pressure and improves efficiency. Good practices include:
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Using smooth duct interiors
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Avoiding sharp bends
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Minimizing duct length
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Proper duct sizing
Experienced Centrifugal blower manufacturers in India often provide technical guidance to optimize system layout before finalizing blower capacity.
Importance of Safety Factor
Industrial applications require a safety margin. Typically:
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Add 5–10% airflow safety factor
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Add 5–10% pressure safety margin
This ensures stable performance even when filters become partially clogged or future system modifications occur.
Common Mistakes to Avoid
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Ignoring filter resistance
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Undersizing ducts
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Not considering temperature or gas density
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Selecting blower without performance curve review
Professional manufacturers always request:
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Required CFM
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Total Static Pressure
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Air temperature
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Application details
This data ensures accurate blower selection.
Final Thoughts
Calculating airflow and static pressure is the foundation of proper blower selection. A blower must meet both volume and resistance requirements to perform efficiently.
For industries such as cement plants, chemical factories, food processing units, and dust collection systems, accurate calculation ensures:
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Reduced energy consumption
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Longer equipment life
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Consistent industrial performance
That is why leading Centrifugal blower manufacturers in India focus on engineering precision, performance testing, and system compatibility before delivering a blower.
If you are planning to install or upgrade an industrial ventilation system, always calculate airflow and static pressure carefully — or consult experienced professionals to ensure the right selection.
Proper calculation today means efficient performance tomorrow.