Possible problems in centrifugal fan selection?

When purchasing a centrifugal fan, some customers only provide the air volume and motor power, requesting the manufacturer to directly calculate the air pressure. However, the actual air pressure required by the fan depends on specific operating conditions (such as pipe length, number of elbows, and material properties), and the resistance of different systems can vary by several times. If the manufacturer relies solely on empirical formulas, the results are often highly inaccurate (approximately 90% inaccurate), which can lead to poor fan selection (such as insufficient air volume, excessive energy consumption, or equipment damage).