Static Pressure
Pressure used to overcome system resistance such as ducts, elbows, filters, dampers and outlets.
Velocity Pressure
Pressure associated with air velocity in a duct or outlet. It changes with air speed and duct area.
Total Pressure
The sum of static pressure and velocity pressure. Some fan curves are rated by total pressure.
Selection Rule
Always match airflow and pressure at the same operating point, and confirm whether the curve uses static or total pressure.
Pressure Must Match the Real System
In fan selection, pressure is not a single simple number. Buyers may see static pressure, total pressure, duct resistance or pressure drop in different documents. If these values are mixed incorrectly, the selected fan may not deliver the required airflow after installation.
What Is Static Pressure?
Static pressure is the pressure available to overcome resistance in the air system. For industrial fans, this usually means duct friction, elbows, filters, dampers, silencers, dust collectors, scrubbers, heat exchangers and final discharge resistance.
When a buyer says a fan needs 2,500 Pa static pressure, the value should ideally represent the resistance of the complete system at the required airflow. If part of the system is missing from the calculation, the fan may lose airflow after installation.
What Is Total Pressure?
Total pressure is the sum of static pressure and velocity pressure. It describes the total mechanical energy in the airflow at a measurement point.
Some fan curves are based on total pressure, while some project documents require static pressure. Before comparing a fan model, buyers and suppliers should confirm which pressure value is being used.
Total Pressure = Static Pressure + Velocity Pressure
Common Mistake: Comparing Static Pressure with Total Pressure
A common selection mistake is comparing a static pressure requirement directly with a total pressure fan curve, or comparing a total pressure requirement with a static pressure curve. The result may be an oversized or undersized fan.
Only checking fan model
Model name cannot confirm the required operating point.
Mixing pressure terms
Static pressure and total pressure should not be treated as the same value.
Confirm curve basis
Check whether the fan curve and project requirement use static pressure or total pressure.
Example: Dust Collection Fan Pressure Review
A dust collection system may require 18,000 m³/h airflow. The duct route, elbows, baghouse filter and stack create total resistance. If the fan is selected only by airflow, the system may not capture dust effectively.
| Item | Example Value | Selection Note |
|---|---|---|
| Required airflow | 18,000 m³/h | Confirm simultaneous working points. |
| Duct and elbow loss | 800 Pa | Depends on route length and fittings. |
| Baghouse resistance | 1,200 Pa | Check loaded-filter condition. |
| Outlet and margin | 400 Pa | Include stack or discharge loss. |
| Fan pressure direction | About 2,400 Pa | Check fan curve at 18,000 m³/h. |
Which Pressure Should Buyers Provide?
For quotation and preliminary fan selection, buyers should provide the pressure value stated in the project design or equipment requirement. If the pressure basis is unclear, provide all available system data so QIYUE FAN can help review the fan direction.
Related QIYUE FAN Product Directions and Guides
FAQ About Static Pressure and Total Pressure
Is static pressure the same as total pressure?
No. Static pressure is used to overcome system resistance such as ducts, elbows, filters and outlet loss. Total pressure equals static pressure plus velocity pressure.
Which pressure should I provide for fan selection?
Provide the pressure value shown in your project specification and clarify whether it is static pressure or total pressure. If you are not sure, send the full duct, filter and outlet information for review.
Why does fan airflow drop after installation?
A common reason is underestimated system resistance. Long ducts, elbows, dampers, silencers, baghouse filters or outlet stacks can increase resistance and reduce actual airflow.
Can I select a fan only by pressure?
No. The fan must meet airflow and pressure at the same operating point. Pressure without airflow, or airflow without pressure, cannot confirm the correct fan model.
Should baghouse filter resistance be included in static pressure?
Yes. For baghouse dust collector systems, filter resistance and loaded-filter pressure drop should be included. Clean-filter resistance alone may not represent real operating resistance.
What should I send to QIYUE FAN?
Send airflow, static pressure or total pressure, duct layout, filter resistance, working medium, temperature, voltage, frequency, outlet angle and installation requirement.
Need Help Checking Fan Static Pressure?
Send your required airflow, static pressure or total pressure, duct layout, filter resistance, working medium, temperature, fan speed and motor standard. QIYUE FAN can help review whether the fan pressure direction matches your real system resistance.
QIYUE FAN CO., LTD. | Industrial Fan Manufacturer | Tel / WeChat / WhatsApp: +86 15653305981 | Email: sales@qiyuefan.com