Surge in centrifugal fans

I understand the OP’s question now! I just want to ask whether both of these parameters need to be satisfied simultaneously for surge to occur, right? Firstly, the word “and” is used in the original text; the triggering conditions for such devices generally require that both thresholds be reached simultaneously, though there may be slight differences in the design parameters of fans from different manufacturers. For fans in use in chemical plants, the gas medium and temperature under actual operating conditions also affect the threshold at which surge occurs. It is best to refer to the manufacturer’s operation manual for confirmation. If it is necessary to adjust the anti-surge design, it is advisable to seek help from a professional equipment engineer; the specific parameters should always be based on the official guidelines provided by the manufacturer.

Haha, I happened to look into relevant information while working on a chemical engineering project earlier! I understand your question. You’re asking whether both outlet pressure and power conditions need to be met simultaneously for surge to occur, right? Firstly, the thresholds provided in the textbook are likely general reference values; for such operating conditions, it is usually necessary for both conditions to be met simultaneously before entering the low-flow range where surge is likely to occur ； However, in practice, different brand and model of fans, the type of gas being transported, as well as the resistance in the pipelines on site, all affect the actual critical operating conditions; therefore, this value cannot be used directly. For project design, it is better to refer to the performance curves provided by the fan manufacturers, or to consult a professional equipment engineer for verification, which is a more reliable approach.

The fan here has a pressure of 16 KPa and a power rating of 45 KW. I discussed this with the client, who said that variable frequency control can be used, so there’s no need to worry about surge problems.

Variable frequency can indeed effectively avoid the surge zone! However, it is still recommended to pay attention to three points: 1) The frequency range should cover the surge critical speed (which is usually indicated in the manufacturer’s manual); 2) A sudden reduction in frequency may cause the system to temporarily enter the surge zone; 3) Long-term operation at low frequencies may affect the lifespan of the bearings. Your 45KW power level provides a safety margin compared to the threshold specified in the guidelines, but it would be best to have the client provide the speed control curve of the frequency converter for verification~