Most of the coal conveying system is transported by belt gallery, this way because of the narrow space, high location, equipment concentration, gallery wind effect, will bring the coal conveying system fire at the early stage is not easy to find, after the development of open fire quickly, it is difficult to put out and other characteristics. Therefore, the design, installation, commissioning and operation of coal conveying system have strict fire protection requirements and are important objects of concern for fire safety.

At present, rubber conveyor belt is the most widely used, in addition to the accumulation of coal will rise in temperature and cause spontaneous combustion, rubber because of the transport of coal overheating, as well as long-term friction is also prone to fire.

The flue effect of the belt gallery building, so that the wind helps the fire to form a huge updraft, blowing up the dry dust powder in the gallery, making the burning more violent, if it is high altitude erection, more difficult to put out the fire.

During the working process, there are risks of toxic and explosive gases, dust, smoke and spontaneous combustion of coal dust that endanger the safety of personnel in the belt gallery space environment, among which CO causes poisoning and methane easily triggers explosion. It is necessary to monitor the data in real time, alarm in time, and take safe rescue measures to prevent accidents.

Objects around us are only able to emit visible light when their temperature is up to 1000°C or more. In contrast, all the objects around us with temperatures above according to zero degrees (-273°C) emit thermal infrared light constantly. In particular, far-infrared radiation with a wavelength of 8-14 μm is able to collect real-time information on the temperature of coal on the conveyor belt, and the thermal imager can simultaneously generate a visual infrared thermal image. System monitoring provides timely alarms and triggers sprinklers and other related actions before open fires occur to prevent fires, and works normally in total darkness at night. Pre-detects temperature increases well before a fire occurs, well before the coal catches fire, truly preventing fires from occurring and causing catastrophic and devastating accidents.

Jinan Xiangkong control adopts the system design idea of combining software and hardware. The belt conveyor monitoring device should include two parts: infrared detection and sprinkler fire extinguishing device. The main structure should be made of new lightweight and high strength materials. The structure is light, easy to disassemble and durable. The system can be controlled and operated individually, or interlocked with the coal transportation system, and can be operated locally, or integrated into the coal transmission program control system for centralized control.

The infrared detection sensing unit is installed above or beside the belt conveyor by adjustable brackets, which should be adjustable horizontally and vertically. The installation height of the detector should be not less than 1000mm and the detection width range should cover the conveyor bandwidth.

It should be equipped with eight infrared temperature detectors, the sensitivity to meet the coal conveying process to accurately detect the high temperature area, sound and light alarm, and at the same time can chain belt shutdown, while spraying fire until the temperature is lower than the set value, the belt to start running.

The sprinklers should be installed on the belt conveyor support behind the detector and should ensure that the high temperature and fire point is within its range after the conveyor stops.

A set of gas monitoring devices is arranged every 30 meters and installed on the steel structure support nearby along the belt corridor distribution. The detectors are connected to the safety monitoring main control board independently developed by Jinan Xiangkong through 485 communication in the form of hand-holding connection. The system transmits via serial port, Ethernet and optical fiber, converts information, and realizes data acquisition and upload through various industrial advanced algorithms. The data is monitored synchronously by the field-level touch screen and the upper computer in the central control room.

System composition: explosion-proof main control cabinet, infrared temperature detector, solenoid valve, gas detector, thermal imager, and upper computer.

Function Implementation

1. The monitor is equipped with advanced imported gas detection probes, which can achieve high sensitivity and accurate detection of harmful gases under working conditions. When the concentration of gas, dust and smoke exceeds the standard, the sound and light alarm will be turned on, and the signal of touch screen and upper computer will flash. At this time, evacuate the belt gallery personnel, open the automatic ventilation system, or open the spray device.

2. Adopt dip-switch addressing mode, 485 polling meter data. Through the conversion of analog and switching signals to 485 signals, the collection of coal powder temperature and smoke alarm is realized.

3. Temperature detection is equipped with temperature detector, mounting bracket, sprinkler valve and drainage valve. When the temperature exceeds the standard, the sound and light alarm, the value flashes, while the associated relay output stops the operation of the conveyor, the sprinkler valve extinguishes the fire, and the drain valve empties.

4. Thermal imaging camera can be used to monitor coal temperature with high precision and large area, and visible light to monitor the working condition of the belt gallery.

5. Touch screen for on-site level monitoring and control, you can set the parameter alarm limit, monitor the communication status, including data display, real-time curve and historical curve query, alarm record contains alarm category, time, alarm value, alarm limit and other functional display.

6. The upper computer is set up in the central control room to synchronize the data collection and alarm monitoring, and it can make curve inquiry and sub-production of historical reports.