I. Overview of the No-Stop Fan Changeover Function

The coal mine main ventilation fan no-stop changeover system is designed to overcome the various shortcomings of the ventilation equipment structure used in most mines. This system allows the standby fan to start in advance before the original running fan is shut down, i.e., entering "hot standby before changeover", improving the fault tolerance of the changeover process. If the standby fan can start normally, the ventilation network can be switched after it runs stably. If the standby fan cannot start normally, it can be stopped first, because the original running fan has not stopped, so it will not affect the downwind ventilation, and there is sufficient time to find the cause. In addition, allowing the standby fan to start and run in advance, in terms of the impact on the ventilation system, can change the system shutdown or breeze throughout the changeover process in the current "shutdown changeover" mode to a reasonable fluctuation of the downwind volume in the short time of ventilation network switching, realizing "no-stop main and standby fan changeover." It eliminates the problem of intermittent ventilation shutdown caused by shutdown changeover in the mine.

This system has the functions of automatic no-stop main ventilation fan changeover, "one-button" operation, and automatic identification and changeover of the running ventilation fan failure. Through the detection and control system, the logic control quickly opens or closes the self-sealing new-style airlock to achieve rapid changeover of the ventilation fan, shortening the impact on the ventilation system during the changeover process from the "system shutdown" in the traditional method to "air volume fluctuation", and shortening the changeover time under fault conditions.

II. Function Introduction

(1) "One-button" Changeover:

Using a dual-machine hot standby mode and optimizing the control system to achieve switching control of two fans without stopping the downwind ventilation power, achieving "one-button" changeover.

(2) Automatic Changeover in Case of Failure:

In case of failure and shutdown, the system prompts the operator to handle the operation according to the fault status, and has the function of automatic changeover in case of failure.

(3) Complete Monitoring Function (Online Monitoring Implementation):

● Real-time online monitoring of the running status of the fan motor and the opening and closing status of the airlock;

● Real-time monitoring and display of the inlet static pressure, air volume, air speed signal, inlet temperature, and fan efficiency of the fan;

● Monitoring and performance analysis of electrical parameters such as fan voltage, current (power frequency current and variable frequency current), variable frequency frequency, power, and power factor;

● Online monitoring of the bearing temperature and stator temperature of the fan motor, with overlimit alarm function;

● Monitoring, display, and analysis of fan vibration status information;

● Real-time graphical curve display of online measured and processed fan operating parameters;

● Historical graphical curve display of measured and processed fan operating parameters, and the ability to query historical data at any time;

● Query and display of online measured and processed historical operating data of the fan in the form of reports, and monitoring data of the fan within 2 years can be retrieved;

● Overlimit alarm for online measured and processed fan operating parameters in various forms:

● The parameters on the main monitoring screen turn red;

● Alarm light flashing prompt;

● Sound alarm prompt.

● Unattended operation.

(4) Automated Performance Testing:

Adjusting the air volume and pressure through the control system, automatically collecting data, and realizing automated performance testing.

● Control the opening, closing, and stopping of the fan airlock, adjusting the airlock to any angle (0 to 90 degrees), so that the fan is fixed at a certain negative pressure point;

● According to the fan performance testing requirements and the fan negative pressure range, the system can automatically adjust the airlock to obtain the negative pressure at each measurement point;

● Record the operating parameters (air volume, negative pressure, power, current, vibration, efficiency) of the measurement points, generate reports, and draw fan performance curves.

(5) Fault Diagnosis:

Establish an expert system that can correctly judge and output alarm signals and automatic diagnostic conclusions when the fan operation is abnormal.

● Fault diagnosis of bearing temperature and stator temperature of the motor;

● Fault diagnosis of horizontal and vertical vibration of the fan;

● Fault diagnosis of sudden increase and decrease of fan air volume;

● Overlimit diagnosis of gas concentration at the fan inlet.

(6) Remote Communication Function:

Supports remote monitoring with third-party remote devices (inverters or other control devices). Supports multiple communication protocols, such as MODBus RTU, MODBus TCP, FTP, WEB, OPC SERVER, etc., with multiple communication schemes, and can easily upload monitoring data to the comprehensive automation system currently used in coal mines to achieve integration of the coal mine information system.

III. No-Stop Changeover Airlock Operation Instructions

The no-stop changeover execution system mainly consists of multiple functional airlocks and execution power units, also known as: air short-circuit airlocks and vertical hanging network regulating airlocks, which are installed in the mine ventilation roadway. For easy maintenance, another normally open standby airlock can be added in front of the vertical regulating airlock near the ventilation shaft (can be added according to the actual situation).

According to the starting characteristics of the ventilation fan, the magnitude and duration of the starting current are related to the wind resistance. As shown in the figure, a horizontal adjustable air short-circuit airlock is added to the original ventilation system. Through this airlock, the resistance during the fan hanging network start-up in the original "shutdown changeover mode" can be reduced, reducing the fan starting wind resistance and improving the success rate of the fan motor start-up.

In order to further overcome the uncertainty of whether the standby ventilation fan can start normally in the traditional "shutdown changeover" mode, the no-stop changeover project adopts hot standby of the coal mine ventilation fan. The standby fan is started without stopping the original running fan. After normal start-up, reliable hot standby can be achieved. If a problem occurs that prevents start-up, the changeover operation can be paused to check and repair the fault first, because the actual changeover process has not yet started, it will not affect the normal operation of the original network. Therefore, the change from cold standby to hot standby further improves the success rate of the changeover.

Workflow Description:

● Fan No. 1 is operating normally. Open the No. 2 horizontal air short-circuit gate and start the standby fan No. 2. (At this time, the fan is in idle operation. Idle operation means that the airflow enters through the horizontal short-circuit gate window and exits through the outlet, realizing hot standby before starting.) After checking (control system self-check) that the standby fan No. 2 is operating normally, open the No. 1 horizontal air short-circuit gate and close the No. 1 vertical hanging net gate at the same time, so that the original operating fan No. 1 transitions to the idle operation state.

● Open the No. 2 vertical hanging net gate next to the operating standby fan No. 2 and close the No. 2 horizontal air short-circuit gate at the same time, so that it transitions to the normal operation state with the underground ventilation network.

● After checking that the standby fan is operating normally on the network, stop the original operating fan and complete the shutdown.