Evaluating fan performance means checking whether a fan installed in a mine or industrial plant is delivering the airflow and pressure you expect, and doing so efficiently. Proper evaluation requires a combination of measurements, corrected calculations and comparison with the manufacturer’s fan curves. Done correctly, it confirms that your ventilation system is working as designed and highlights opportunities for improvement.
The first step is to clearly define the duty point: the required airflow (Q), pressure (P) and operating density (air temperature, altitude, gas composition). In a ventilation design, this is usually expressed as m³/s and Pa (or CFM and inches wg). The fan manufacturer provides fan curves showing how Q, P, power and efficiency vary with system resistance at a given speed for standard air. Using density corrections, you convert your required duty to the equivalent point on the standard-air curve.
To evaluate actual performance in the field, you then measure airflow and pressure. Airflow can be measured with Pitot tube traverses in ducts, venturi nozzles, flow grids or in-mine roadway traverses using anemometers. Static or total pressure is measured using manometers or differential pressure transmitters across the fan or across key parts of the system. From these measurements you can calculate actual volume flow and pressure at the operating point.
At the same time, you should record the fan’s electrical power and speed. Power is obtained from kW meters or from voltage, current and power factor readings at the motor. Speed is measured with a tachometer or checked from a variable-frequency drive display. These data allow you to determine the actual input power and, together with airflow and pressure, to estimate fan efficiency at the operating point.
Next, compare the measured duty point with the manufacturer’s fan curve. If the measured airflow and pressure fall near the expected point (after correcting for density and speed), the fan is performing as specified. If the measured point lies far from the curve or at a much lower efficiency, possible causes include incorrect duct connections, higher system resistance than expected, damper positions, fan rotation direction, build-up on blades or wear and erosion.
In mining and heavy industry, fan performance evaluation should also consider system interactions. Multiple fans operating in series or parallel, changes in mine layout or process modifications can all shift the operating point along the system curve. Regular surveys of airflows and pressures throughout the network help confirm that the main and auxiliary fans still match the actual system requirements.
In summary, to evaluate fan performance you define the required duty, measure actual airflow, pressure, power and speed, correct for air density, plot the operating point on the fan curve and assess efficiency and deviations. This structured approach turns raw readings into a clear picture of how well your mining or industrial fan is really working.
