Intelligent Local Ventilator

System Overview

The intelligent local ventilation system for coal mines is an automated control device that offers multiple functions in one unit, boasting high efficiency and energy savings—essential for ensuring normal production in coal mines. It integrates the local ventilation control system with the local ventilation fans themselves. Moreover, the locally designed ventilation fans, equipped with specially engineered monitoring sensors and connected to other monitoring signals, are linked to a PLC-based automatic control system for closed-loop control. This system addresses the current domestic situation where local ventilation fans operate without effective monitoring and surveillance, seamlessly integrating efficient mine management with safe and reliable equipment operation. As a result, the hazards posed by gas at mine excavation faces have been significantly reduced. While enhancing the safe and stable operation of equipment, this system also guarantees the continued normal production of the mine.

The system consists of a host computer, local ventilation fans, a variable-frequency speed control device, intelligent control systems, and air distributors.

Composition and Function

(1) Product Composition

The device consists of a frequency converter, PLC, switching components, a gas concentration sensor, a temperature sensor, a wind speed sensor, a carbon monoxide sensor, a dust sensor, a broadcasting system, a network system, and the fan unit itself. (See Figure 2 for details.)

The explosion-proof switch is placed at the underground distribution point and connected to the underground ring network switch, ensuring both uninterrupted power supply and smooth operation of the main network. From the explosion-proof switch to the intelligent variable-frequency drive, you can choose either a network cable or fiber optic cable—opt for a network cable if the distance is within 100 meters, and fiber optic cable if the distance is greater. The intelligent variable-frequency drive is pre-equipped with both Ethernet and fiber optic interfaces; video and sensor data are transmitted via Ethernet to the host computer in the dispatch room.

(2) Function and Principle

Operating mode of the speed control device: The control mode is set based on the collected signals for gas, temperature, wind speed, CO, dust, and other parameters.

According to the "Regulations," conventional speed control is set based on gas concentration and features three operating modes: "automatic ventilation mode," "automatic gas discharge mode," and "manually controlled frequency-setting mode."

Automatic ventilation mode

For low-gas mines, when the gas concentrations at the working face and in the return airway both remain below the set values, the speed-control device operates in automatic ventilation mode. In this mode, the device switches to comprehensively controlling the fan speed based on a combination of parameters including roadway airflow, temperature, CO concentration, and dust concentration. If any one of these measurement points—airflow, temperature, CO concentration, or dust concentration—exceeds its set value, the speed-control device will automatically increase the fan speed up to the upper frequency limit, thereby boosting the airflow. Once the over-limit signal returns to within the safe set range, the fan speed will automatically decrease back to the lower frequency limit. Throughout this process, the gas concentration must consistently remain below the normal operating level; if it ever exceeds the threshold, the system will immediately switch to the automatic gas-discharge mode.