The Role of Performance Testing for Backward-Curved Stainless Steel Centrifugal Fans in Condition Monitoring

Establish an effective monitoring mechanism for the operational efficiency of backward-curved stainless steel centrifugal fan equipment to eliminate energy waste.For example, a unit's hot air system was originally designed for an airflow of 46,000 Nm³/h. After technical upgrades and optimization, the system's required airflow decreased to approximately 28,000 Nm³/h, achieving energy savings. However, during the system overhaul, the backward-curved stainless steel centrifugal fans within the system were not correspondingly adjusted. To reduce airflow, valves within the system had to be partially closed. This caused all backward-curved stainless steel centrifugal fans in the hot air system to operate in an inefficient "overpowered" state, resulting in extreme instability. Particularly concerning were the two fans handling furnace gas backflow, whose operating points approached the surge point, leading to frequent failures. In 2005, improvements were implemented for the backward-curved stainless steel centrifugal fans. Through performance testing of backward-curved stainless steel centrifugal fans, their operating points were determined. Based on this, a new type of backward-curved stainless steel centrifugal fan with lower air pressure but suitable for the current operating conditions was selected. This expanded the safe operating range of backward-curved stainless steel centrifugal fans. It ensured the safe operation of backward-curved stainless steel centrifugal fans while saving energy. This facilitates the effective configuration of backward-curved stainless steel centrifugal fans with ductwork systems. Backward-curved stainless steel centrifugal fans always operate in conjunction with their ductwork systems. After gaining external work within the backward-curved fan, the relationship between pressure increase and flow rate follows the patterns depicted in the fan's performance curve. When gas flows through the ductwork, the relationship between pressure increase and flow rate adheres to the ductwork's characteristic curve. Therefore, the airflow characteristics of the backward-curved stainless steel centrifugal fan are entirely equivalent to those of the pipeline network. Simultaneously, the total pressure generated by the backward-curved stainless steel centrifugal fan is partially used to overcome resistance within the pipeline network, while the remainder is converted into kinetic energy of the airflow at the pipeline outlet Ft. The effective power of a backward-curved stainless steel centrifugal fan is proportional to its total pressure. When the static pressure portion used to overcome pipeline resistance increases, the kinetic energy of the airflow at the pipeline outlet decreases, resulting in reduced flow rate of the backward-curved stainless steel centrifugal fan. Consequently, poor pipeline network layout adversely affects the performance of backward-curved stainless steel centrifugal fans. Structural elements such as pipe joints, elbows, and valves, or sudden expansions, contractions, and sharp bends in the pipeline, increase local resistance losses while reducing the efficiency of the backward-curved stainless steel centrifugal fan system. Pipeline pressure losses comprise both along-the-line resistance losses and local resistance losses. Linear resistance loss is determined by air velocity, duct length, duct cross-sectional area, and wall roughness. Local resistance loss relates to duct cross-sectional area and transition configurations. Therefore, by measuring the network's flow rate, static pressure, and dynamic pressure, defects in the duct system can be identified. This enables rational selection of duct cross-section, length, inner wall smoothness, and transition configurations between ducts of different cross-sections. This effectively reduces pressure loss in the ductwork and enhances the system's transportation efficiency. When the pressure or flow rate of a single backward-curved stainless steel centrifugal fan fails to meet system requirements, necessitating the parallel connection of multiple units, the system's operating point pressure and flow rate should be tested using the performance testing method for backward-curved stainless steel centrifugal fans. This ensures the correct selection and matching of the fans.