Reasons for mine conveyor belt
fire There are many reasons for conveyor belt fire, some caused by its own failure, and some caused by external fire sources. This paper mainly analyzes the cause of fire caused by its own fault.
1.1 Roller slip causes fire
(1) The rubber or wood lining covered by the driving drum is worn (a basic type of component failure) seriously, which reduces the friction coefficient and causes the conveyor belt to slip.
Storage and transportation conditions of rubber conveyor belt: In storage and transportation, fire should be isolated, sharp instruments and corrosive chemicals should be avoided, and long-term storage under the sun should be avoided.
2) The wet surface of the driving drum will cause the conveyor belt to slip, such as coal out of water.
(3) Coal buried at the head of the machine will cause coal to enter between the surface of the drum and the conveying, which will reduce the friction coefficient and cause the conveyor belt to slip.
(4) The tensioning force of the tensioning device is not enough, resulting in the decline of traction force and causing the conveyor belt to slip. According to the different use environment, the conveyor belt is divided into ordinary conveyor belt and includes (ordinary type, heat resistant type,
Refractory type, burning resistant type, acid and alkali resistant type, oil resistant type), heat resistant conveyor belt, cold resistant conveyor belt, acid and alkali resistant conveyor belt, oil resistant conveyor belt, food conveyor belt and other models.
(5) The driven roller bearing is damaged and stuck, resulting in the driven roller's speed decreasing or not rotating, causing the conveyor belt to slip relative to the roller.
Whether driving drum or driven drum, as long as the occurrence of skid phenomenon, the surface temperature of the drum will rise rapidly. According to statistics, the conveyor belt skidded for about 40min, and the surface temperature of the drum reached 320℃
Around, the conveyor belt will begin to smoke. 320℃ is the critical ignition temperature. Therefore, the roller skid is very harmful, long time skid can lead to the conveyor belt fire,
This may cause security accidents. Heat-resistant conveyor belt is made of multi-layer rubber-cotton canvas (terylene cotton) or polyester canvas covered with heat-resistant or heat-resistant rubber, and bonded together by high temperature vulcanization.
Suitable for conveying hot coke carbon, cement, slag and hot castings below 175℃.
Idlers cause fire. In recent years, the temperature rise of idlers caused by idlers not rotating is one of the main causes of coal mine conveyor belt fire. The rubber conveyor belt runs with the coal on the roller,
It is both a traction mechanism and a bearing mechanism. There is no relative movement between coal and conveyor belt, which eliminates the friction resistance between coal and conveyor belt. Because the roller is equipped with rolling bearings,
There is rolling friction between the heat resistant conveyor belt and the roller, and the running resistance is very small. However, due to poor underground environmental conditions, it is easy to enter coal dust inside the roller bearing, which will cause the bearing to stick.
After the conveyor belt is stuck on the surface of the roller friction running, will make the roller temperature rise. It is observed that the conveyor belt fire caused by the friction of idlers is generally after the shutdown. Before shutdown, the belt runs at the speed of 1 ~ 3trds.
The contact time between the fixed point on the conveyor belt and the surface of the roller is short, and the temperature of the conveyor belt increases very little. Moreover, the air flow generated during the operation of the conveyor belt can also reduce the surface temperature of the roller.
Therefore, in normal operation, even if there is friction, the conveyor belt is not easy to fire. After shutdown, the lower roller will stop rotating, do not turn down
Roller is the main cause of fire. Because there is a certain amount of pulverized coal around the lower roller, surrounded by pulverized coal, the heat dissipation condition of the roller will become worse, so as to cause fire, especially in the easy to sprinkle coal
Unload the lower supporting roller at the drum and tail drum.
1.3 Necessity of drum friction test
The so-called drum friction test means that when the conveyor belt sample passes the drum friction test, flame and flameless combustion shall not occur in any part of it, and the surface temperature of the drum shall not be greater than 325℃.
The conveyor belt sample was installed in the drum friction test device, and the upper and lower covering layers were tested in the static air and the flowing air respectively. A tension of 343N was applied during the test.
The roller rotates away from the fixed end of the sample at a speed of (200.4-5)r/min. If the conveyor belt sample breaks within 60min, the test will be stopped; if it does not break, the test will continue until 60min.
During the test, the test personnel should stick to the test site, observe whether the sample has flame combustion or flame combustion phenomenon at any time, and record the test time and the highest temperature of the drum surface.
The drum friction test simulates (definition: the virtual of a real thing or process) the most severe environmental conditions during the operation of the belt conveyor (also known as the belt conveyor).
That is, the conveyor belt directly fricts with the steel rolling Jane, and the conveyor belt cannot have flame burning and flame burning phenomenon. In the laboratory of flame retardant conveyor belt roller friction test, fabric whole core flame retardant conveyor belt
The smoking temperature is about 220 ~ 250oC, the smoking temperature of the wire rope core flame retardant conveyor belt is about 250 ~ 280oC, and there is no flame combustion and no flame combustion phenomenon. But there will also be temperatures that exceed the regulations
The temperature reaches 360oC or higher, with combustion phenomenon. Here it is worth noting that the fire temperature of the whole fabric core flame retardant conveyor belt and the wire rope core flame retardant conveyor belt
At 280300℃ and 320-340oC respectively, and the temperature has been close to the pulverized coal smoking temperature of 330 ~ 350o
C, fire temperature 420 ~ 440oC, such as improper management and use of conveyor belt is easy to cause fire. Fire is the most serious accident of belt conveyor, once it happens, it will cause significant personnel
Casualties and massive property damage. Therefore, it is very necessary to carry out the roller friction test before the conveyor belt goes down the well.
2 Maintenance Management
Daily inspection, shorten storage, pay attention to do high temperature prevention, corrosion prevention, moisture and other regular inspection.
Before use, the conveyor belt shall be inspected by the relevant units to ensure that the conveyor belt used conforms to the "Coal mine Safety Regulations" and the relevant technical standards.
Conveyor inspection, the roller should rotate flexibly, fasteners firmly, bearing lubrication is good; Body rollers (supporting conveyor belt and material weight) should be complete, flexible rotation; H frame, beam frame should be stable, no skew phenomenon;
The tensioning device should be complete, the tensioning is suitable, the conveyor belt does not slip; The cleaning device should work well, especially the cleaning device at the unloading drum and tail drum, so that there is no floating coal and sundries on the surface of the conveyor belt after cleaning.
Protective device, conveying machine to install temperature, speed, smoke, coal and other protective devices, the device should be sensitive and reliable, in order to stop the problem in time, reduce the scope of the accident.
Improve the environment of the roadway, in order to improve the environment of the roadway, it is necessary to reduce the roadway water, as far as possible to make the water flow down the shaft wall, when necessary, but also adopt waterproof plugging, grouting plugging or engineering sealing measures.
For acid ore water to prevent the main, try to avoid acidic water dripping on the conveyor belt. The roadway should be kept clean and sanitary, especially the slime under the conveyor belt at the bottom of the conveyor should be cleaned often.
Ensure the bottom roller (supporting the conveyor belt and material weight) normal operation.