I. Overview of the Continuous Wind-Reversal Machine Function
The no‑stop‑fan‑reversal system for main mine ventilation fans is designed to address the various shortcomings inherent in the structural configurations of ventilation equipment currently employed in most mines. In this system, the standby fan is started in advance—before the operating fan is shut down—thereby entering a “hot standby” state prior to the reversal. This enhances the fault‑tolerance of the fan‑reversal process: if the standby fan starts up normally, it is allowed to reach stable operation before the ventilation network is switched; if, on the other hand, the standby fan fails to start properly, it can be stopped without affecting underground ventilation, since the operating fan remains running and no disruption to airflow occurs, thus providing ample time to identify and resolve the root cause. Furthermore, by initiating the standby fan ahead of time, the impact on the ventilation system is transformed from the prolonged system shutdown or reduced airflow that typically accompanies the entire fan‑reversal process under the conventional “shutdown‑and‑reversal” mode, into a brief, controlled fluctuation in underground airflow during the network‑switching interval. This achieves a true “no‑stop‑fan‑reversal” operation, effectively eliminating the intermittent ventilation interruptions caused by traditional shutdown‑and‑reversal procedures.
This system features automatic fan reversal without shutting down the main mine ventilation fan, “one-button” fan reversal operation, and automatic fan reversal in response to detected faults in operating fans. Through its monitoring and control system, the logic controller rapidly opens or closes self-sealing, state-of-the-art damper valves, enabling swift fan switching. As a result, the impact on the ventilation system during fan reversal is reduced from the conventional “system shutdown” to “airflow fluctuation,” and the time required for fan reversal under fault conditions is significantly shortened.

II. Feature Overview
(1) “One-Click” Switching:
A dual-unit hot-standby configuration is adopted, and the control system is optimized to enable seamless switching between two fans without interrupting underground ventilation power, thereby achieving one-button fan reversal.
(2) Automatic failover:
In the event of a fault-induced shutdown, the system prompts the operator to perform appropriate corrective actions based on the fault status and features automatic rollback functionality upon fault occurrence.
(3) Comprehensive monitoring functions (online monitoring implementation):
● Real-time online monitoring of fan motor operating status and damper opening/closing status;
● Real-time monitoring and display of the fan’s inlet static pressure, airflow rate, air velocity, inlet temperature, and fan efficiency;
● Monitoring of electrical parameters such as fan voltage, current (both mains-frequency and variable-frequency currents), variable-frequency drive frequency, power, and power factor, along with performance analysis;
● Online monitoring of bearing temperature and stator temperature for fan motors, with over-limit alarm functionality;
● Monitoring, display, and analysis of fan vibration condition information;
● Displays online-measured and processed fan operating parameters as real-time graphical curves;
● Displays measured and processed fan operating parameters as historical trend curves and allows retrieval of historical data for any given time;
● Query and display historical operating data of wind turbines measured and processed online in report format, with the ability to retrieve monitoring data for the past two years.
● Implement limit-exceedance alarms for online-measured and processed fan operating parameters in multiple forms:
◇The parameters on the main monitoring screen are displayed in red;
◇ Alarm light flashing alert;
◇Audio alarm notification.
● Achieve unattended operation.
(4) Automated Performance Testing:
The airflow and static pressure are regulated via the control system, with data automatically collected to enable automated performance testing.
● Control the opening, closing, and stopping of the fan damper, and adjust the damper to any angle between 0° and 90° to maintain a fixed negative pressure at a specific point.
●Based on the fan performance test requirements and the fan’s negative-pressure range, the system can automatically adjust the damper to obtain the negative pressure at each measurement point.
● Record the operating parameters of measurement points (airflow, negative pressure, power, current, vibration, and efficiency), generate reports, and plot fan performance curves.
(5) Fault Diagnosis:
Establish an expert system that can accurately diagnose abnormal operating conditions of wind turbines, issue alarm signals, and generate automated diagnostic conclusions.
● Fault diagnosis of motor bearing temperature and stator temperature;
● Fault diagnosis of horizontal and vertical vibrations in fans;
● Fault diagnosis for sudden increases and decreases in fan airflow;
● Over-limit diagnosis of gas concentration at the fan inlet.
(6) Remote communication function:
Supports remote monitoring in conjunction with third-party remote devices, such as variable-frequency drives or other control equipment. It supports multiple communication protocols, including MODBUS_RTU, MODBUS_TCP, FTP, WEB, OPC SERVER, and other connection methods, offering a variety of communication solutions that enable convenient uploading of monitoring data to the integrated automation systems currently used in coal mines, thereby achieving seamless integration of coal mine information systems.

III. Operating Instructions for the Non-Stop Fan Reverse Air Door
The continuous wind-reversal actuator system primarily consists of multiple functional dampers and actuating power units; it is also referred to as the “air-short-circuit damper” and the “vertical mesh-adjustable damper.” Both types are installed in the mine’s main intake airways. For ease of maintenance, a normally open standby damper may be additionally installed on the side of the vertical adjustable damper closer to the shaft (this can be added based on actual conditions).
Based on the starting characteristics of fans, the magnitude and duration of the inrush current are influenced by the airflow resistance. As illustrated in the figure, installing a horizontally adjustable, short-circuit air damper in the existing ventilation system can reduce the resistance encountered during the fan’s grid-connected start-up under the conventional “shutdown–reverse-start” mode, thereby lowering the starting resistance and increasing the success rate of motor startup.
To further address the uncertainty surrounding the reliable startup of standby ventilation fans under the conventional “shutdown-and-switch” method, the no‑downtime fan‑switching project adopts a hot‑standby configuration prior to the fan‑switching operation. Under this approach, the standby fan is started while the primary operating fan remains online; once the standby fan successfully starts, a reliable hot standby is established. Should a fault prevent the standby fan from starting, the switching procedure can be temporarily suspended to allow for fault diagnosis and maintenance, since the actual switching process has not yet commenced and the normal grid‑connected operation of the primary fan is unaffected. Consequently, transitioning from cold standby to hot standby significantly enhances the success rate of fan switching.

Workflow Description:
●Fan No. 1 is operating normally. Open the horizontal bypass damper for Fan No. 2 and start standby Fan No. 2. (At this point, the fan is running under no-load conditions; “no-load operation” means that the airflow enters through the horizontal bypass damper and exits through the outlet, thereby maintaining thermal standby prior to startup.)
● After inspection (self-check of the control system) confirms that standby fan No. 2 is operating normally, open horizontal bypass damper No. 1 and simultaneously close vertical mesh damper No. 1, thereby transitioning the originally operating fan No. 1 to no-load operation.
● Open the No. 2 vertical meshed damper located next to the standby No. 2 damper, and simultaneously close the No. 2 horizontal short-circuit damper to the atmosphere, thereby transitioning to normal operation with the underground ventilation network in place.
● After verifying that the standby fan is operating normally on the network, stop the original operating fan to complete the switch.
 

Schematic Diagram of the Layout of the Fan Shaft for the Non-Stop Ventilation System