A good fan curve is more than just a line on a catalogue; it is a clear picture of how a fan behaves in real ventilation systems. From a design and operations perspective, a good fan curve is one that is smooth, stable and efficient over the range of flows and pressures you actually need, and that allows you to match the fan closely to your system curve.
On a typical fan curve, airflow is plotted on the horizontal axis and pressure on the vertical axis, often with additional curves for power and efficiency. One key characteristic of a good curve is that it is monotonic and smooth in the region of interest: pressure should generally fall as flow increases, without sudden dips, jumps or unstable regions. Irregular shapes or portions where pressure rises with increasing flow can indicate potential instability or operating points that should be avoided.
A good fan curve also includes a well-defined efficiency peak that is reasonably broad rather than extremely sharp. This allows the fan to operate efficiently over a practical range of duty points instead of only at a very narrow sweet spot. For mining and industrial ventilation, where system resistance can change over time as layouts evolve or filters load, having a fan that remains efficient across a range of flows is a significant advantage.
In addition, a good curve provides complete and clear information. It should show total pressure, not just static pressure, where total pressure is relevant to the application. It should include power input and efficiency curves, and ideally sound data. Curves should specify the speed, air density and test standard, so that engineers can correctly adjust performance for different site conditions such as altitude and temperature in underground mines.
From a system-design perspective, a good fan curve is one that intersects the system curve at a stable operating point near the efficiency peak. When you plot your ventilation system curve (pressure vs. flow) on the same axes, the intersection should lie in a region where the fan operates reliably, with acceptable power, noise and margin against stall. If the only intersection points are at very low or very high efficiencies, the curve may be accurate but the fan is not a good match for your system.
In summary, a good fan curve is smooth, free from unstable regions in the operating range, provides clear pressure, flow, power and efficiency data, and allows a stable duty point near high efficiency when matched to the system curve. Such a curve is an essential tool for selecting and managing mining and industrial ventilation fans.
