Fire prevention of the hottest belt conveyor

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Belt conveyor fire prevention

belt conveyor is widely used in port enterprises because of its simple structure, long continuous conveying distance, low conveying cost and high conveying efficiency. The conveyor system is a key fire prevention part with a high probability of fire. Once a fire occurs, the whole system, including the conveyor belt, control cable, frame and drive parts, may be scrapped, and even personal injury or death accidents may occur. The user unit of belt conveyor shall follow the fire protection policy of "prevention first, prevention and elimination combined", strengthen the fire safety management, and ensure the fire safety of conveyor system

1. The ignition source of the conveyor itself

(1) idler failure

the idler with metal structure runs at high speed during the operation of the conveyor, and its failure form is bearing damage. Bearing damage is first manifested in the falling off of the bearing rolling element, and the operation form between the inner and outer rings of the bearing is transformed from rolling friction to sliding friction. The second step is that the outer ring of the bearing falls off. Because there is a transitional fit between the outer ring and the bearing hole, there is an interference fit between the inner ring and the idler shaft, and the outer ring runs at a high speed, the outer ring falls off first than the inner ring. After the outer ring falls off, the relative sliding speed between the bearing hole of the roller body and the inner ring of the bearing is further improved, and a large amount of friction heat is transmitted to the surface layer of the roller body, making the temperature of the surface layer of the roller as high as more than 700 ℃, which is dark red. During the operation of the conveyor, the heating point of this kind of red burning idler to the conveyor belt is constantly changing, which is not enough to ignite the conveyor belt. After the conveyor belt stops running, it is easy to be ignited if it contacts with the red burning idler

a fire accident occurred on the belt conveyor at the trestle of a port coal wharf, burning more than 1500 m belts and nearly 1000m wooden trestle passage pedals. The cause of the accident was that the supporting roller with bearing failure was heated by friction during the operation of the conveyor. After the conveyor stopped, the heat source ignited the conveyor belt

therefore, during the operation of the belt conveyor, the idler should be checked in time, and the idler with abnormal sound should be replaced in time; Within half an hour after the shutdown of the conveyor, the operators cannot leave the conveyor site, and must check the whole length of the conveyor to find the signs of fire in time; In addition, in order to judge and find the damaged idlers timely and accurately, when designing the windproof cover of the conveyor belt, it should be avoided that the windproof cover covers the idlers

(2) roller bearing in abnormal operation

other plastics in the process of roller operation, the roller bearing is operated with heavy load and low speed. If the bearing lubrication is poor or the assembly is unreasonable, it may cause abnormal high temperature of the bearing and bearing seat. Because the bearing seat is fixed and does not operate, it is easy to adhere to and ignite low-temperature inflammables such as cotton yarn with oil

there was a fire accident in the belt conveyor of a port coal wharf to make the domestic excellent experimental instruments and equipment widely used. Due to the poor lubrication of the tension roller bearing seat, the bearing produced dry friction inside during the rotation process, and the friction heat was transferred to the surface of the bearing seat, which ignited the oiled cotton yarn adhered to the surface of the bearing seat, resulting in the scrapping of the conveyor belt, frame and system accessories at the tension roller bearing seat of the driving part

the methods to prevent this kind of ignition source from catching fire are: to formulate strict drum maintenance and repair standards to ensure the correct installation of bearings; Lubricate the roller bearings according to the "five fixed" lubrication requirements of "regular, fixed person, fixed point, fixed quality and quantitative"; When abnormal sound is found at the drum and bearing seat, it should be checked and confirmed in time

(3) there are a large number of control cables on the electrical control line

conveyor, which are generally concentrated in the cable trough on the side of the rack. Due to aging, electrical welding slag ablation and mechanical damage, these cables may have short circuits and open flames

when designing the cable trough, the cable trough cover plate should be designed to protect the cable; When engaging in work unrelated to the control cable, try not to disassemble the cable trough; Keep the cable tray cover intact and the cable tray clean to avoid the attachment of inflammables; Replace the expired cable in strict accordance with the design life of the cable

2. Other ignition sources

(1) hot work maintenance

hot work for maintenance in or around the conveyor is easy to ignite the conveyor belt. The welding slag of electric welding operation falls on the conveyor belt, which can immediately ignite the conveyor belt. Generally, this kind of ignition source can be found and extinguished in time. The broach can be selected according to the requirements of customers: U-type or V-type. However, if the operators are busy leaving the site during the closing time and do not notice the fire, it may cause a conveyor belt fire. In addition, the welding slag may burn the cable if it falls into the uncovered cable trough

enterprises should establish and strictly implement the hot work management system. Before hot work on or near the conveyor, carefully check whether there are conveyor belts, cables and other combustibles under the hot work position, strictly implement the "four one" hot work system of "one hot work permit, one guardian, one fire extinguisher and one person", and timely discover and eliminate fire hazards

(2) cigarette butts

the temperature of cigarette butts left by smoking is as high as 800 ℃. Although its heat is not enough to ignite conveyor belts and cables, it can ignite inflammables such as oil cotton yarn and cause belt conveyor fires

enterprises should prohibit on-site workers from smoking, and hang "no smoking" signs in obvious parts of the site to prevent outsiders from smoking

(3) lightning stroke

high power, long-distance belt conveyors are generally located in the open. Although the height is not high, because they are relatively isolated and there are no other prominent lightning receiving devices around, they are relatively vulnerable to lightning stroke. After a lightning strike, multiple induction lightning may be generated, and the induction lightning can be transmitted to a far place with the control cable beside the conveyor. The induced lightning voltage can reach thousands of volts, or even higher, and gap discharge may occur, which is a very dangerous ignition source for conveyors with explosion-proof requirements

no matter whether there are explosion-proof requirements or not, lightning protection measures should be considered for belt conveyor or when three test pieces are brittle fracture, especially anti induction lightning measures. In particular, equipotential connection should be carried out between adjacent large metal structural parts in the conveyor room conveying bulk grain to prevent gap discharge

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