Subway tunnel ventilation systems are required to keep subway tunnels well ventilated with fresh air and passengers comfortable. These ventilation systems comprise multiple fans and equipment to ensure suitable ventilation. The Chongqing Subway project in China required a permanently installed condition monitoring solution to monitor more than 64 tunnel fans for vibration (e.g., bearing failure, unbalance, bracket looseness) in the subway line plus 20 subway stations. With all the fans installed in the subway tunnel roof, at a height of 5–7 meters from the tunnel floor combined with an active subway system, regular maintenance and periodic inspection is both difficult and hazardous.
GE experts worked closely with the Chongqing Subway to develop a system-based approach that met Chongqing’s requirements and “must-have” features, such as monitoring and protection simultaneously. The Bently Nevada 2300 series combined with System 1 software is a flexible and powerful monitoring platform, allowing roller bearing diagnostic, analog input at 4–20 mA, Modbus, and relay output capability suitable for any subway application. The 2300 two-channel capability provided optimal use of channel counts in a cost effective manner while the standard TCP/IP and Modbus seamlessly communicates to PLCs and System 1 for the desired protection and condition monitoring connectivity without adding additional hardware.
Safety: By using a traditional “run to failure” approach, maintenance is only possible when the subway trains are all idled, not always possible with an unforeseen failure, decreasing tunnel ventilation. Without sufficient ventilation, the subway cannot operate safely. In addition, catastrophic failure of the fan accessories or brackets becomes a physical hazard to trains, passengers, and crews.
Reduced maintenance time and cost: Predictive maintenance enabled by GE's proven Bently Nevada proven sensor technology reduces the time and expense for maintenance work in the tunnel. For example, without CMS, should a motor bearing failure occur, a crane is required to inspect the problem; then in a second step parts must be obtained (sometimes requiring months if not inventoried), and finally re-positioning the crane in the tunnel to perform the maintenance. With a predictive maintenance CMS approach, the problem can be identified weeks or months in advance, allowing the maintenance to be planned with other scheduled idle time of the subway. For Chongqing, this amounts to $9000 USD per fan motor in costs savings, not including the labor costs!