Introduction
Tires with a diameter of 2.6m, a width of 0.8m or more, or a specification of 27.00R49 or more can be called giant tires. Pingshuo open-pit coal mine is one of the giants in the domestic coal industry. Various advanced heavy mining and transportation equipment account for a large proportion. It has more than 200 heavy-duty transport trucks of world-famous brands such as CAT and KOMATSU. Its characteristics are: high work efficiency, but relatively high maintenance costs, and these transport trucks and the most expensive spare parts of these transport trucks are giant tires. At present, the giant tire models used in Pingshuo mining area are: 27.00R49, 36.00R51, 37.00R57, 53/80R63 4 specifications. Among them, the price of a 53/80R63 tire for KOMATSU930E truck is as high as nearly 300,000 yuan. According to statistics: Pingshuo mining area consumes more than 1,000 giant tires every year, with a value of nearly 100 million yuan, which is a huge expense. The price of giant tires has been rising year by year in the international tire market in recent years, and the supply is in short supply. Therefore, whether the giant tires are used reasonably or not directly affects whether the trucks can operate normally, and is related to mining costs and raw material consumption. As the main consumables of open-pit coal mines, the safety performance and cost reduction of giant tires have attracted increasing attention. Only by the correct use and perfect management of tires can the normal dispatch of trucks be guaranteed. Only by reducing the loss of giant tires can production costs be saved, and it also plays an important role in safe production.
The rainy and snowy season is the season with the most serious tire damage. According to the records of giant tire scrapping in Pingshuo Mining Area in recent years, it is not difficult to find that the number of giant tire scrapping in these two seasons is particularly prominent, accounting for more than 65% of the total number of giant tire scrapping throughout the year. The above data fully shows that tire management in the rainy and snowy seasons is very important. Strengthening the management of giant tires in the two seasons can reduce tire damage to a minimum, laying a solid foundation for saving tire costs throughout the year.
1 Analysis of the causes of damage
During the rainy and snowy season, heavy trucks driving on slippery, muddy and icy roads will bring certain hidden dangers to production safety and affect the life of giant tires. The following is an introduction to several common damages caused to giant tires by trucks driving in rainy and snowy weather.
1.1 Cutting and peeling
Cutting and peeling refers to the phenomenon that the giant tires are not disassembled and repaired in time after being cut during operation, but continue to run for a period of time, causing partial peeling, emptying, and falling of the tire tread. According to statistics, the giant tires scrapped due to cutting and peeling in the rainy and snowy season in Pingshuo Mining Area account for more than 30% of the total scrapped tires throughout the year. At present, the tires of heavy trucks used in Pingshuo Mining Area are all steel wire radial tires, and their transportation trunk roads are all uneven gravel roads. Due to the exposure of sharp stones in some sections or sharp stones on the roadside, in case of rainy and snowy days, the transportation trunk roads are prone to water, snow and ice accumulation, which accelerates the ability of stones and water to cut tires. In bad weather conditions, drivers do not know enough about the road conditions and are prone to cutting tires under the rolling of trucks. If not discovered in time, the stress on the tires of trucks during driving is uneven, causing the wound to spread. Due to the strong permeability of air and water, the water gradually penetrates into the steel wire layer along with the tire wound under the scouring of rain or snow water, causing the steel wire layer to be rapidly oxidized, corroded, and broken, and gradually separated from the tread rubber, thereby causing the wound to continue to grow and deepen. If not repaired in time, it will cause partial peeling, falling blocks, and even scrapping of the tire, which is a specific manifestation of early tire damage. If the tire is not leaking, it is a big mistake to continue using it. The tire wound is peeled off and emptied due to surface peeling. It can no longer resist external impact. In case of abnormal cuts or collisions, it will cause the tire to burst, which brings great hidden dangers to safe production.
1.2 Local wear
Local wear is commonly known as local wear. It is caused by uneven wear energy due to the tire pattern convexity. The specific manifestations are local wear of the tread, exposed steel wire, etc. According to statistics, the number of giant tires scrapped due to partial wear in Pingshuo Mining Area accounts for more than 30% of the total annual scrapped tires. This kind of wear directly destroys the tire structure and is fatal to the tire life. If such wear occurs, the tire can neither be repaired nor refurbished, and can only be scrapped. The phenomenon of partial wear of tires is most prominent in the rainy and snowy season, mainly because the road surface is slippery on rainy and snowy days, and there is occasional ice. When the truck starts, brakes, and goes uphill or downhill, the tires will slip. It directly causes the tires to shift and run off, and the damage to the wear resistance and carcass strength of the tires is very serious. According to the actual situation in Pingshuo Mining Area, some drivers increase the speed very high when starting, which causes the forward thrust of the tire to be greater than the adhesion, and the tire will slip on the spot; when the truck goes uphill under load, the rear wheel is overloaded, and the truck slips laterally and longitudinally with the tire. This phenomenon is usually called “the car falls off its butt” by the driver. When the truck brakes, it is best to use the point brake method. If the truck brakes suddenly, the friction temperature between the tire and the ground will rise sharply, directly destroying the various properties of the tire. Long-term braking will make a piece of the tire tread rubber wear flatter and flatter until the steel wire layer is exposed, and finally the tire tread and the ground lose the circumferential rolling effect. This phenomenon fully shows that the tire has been partially worn. In addition, the inertial force of the truck moving forward will be consumed by the rubbing and cutting stress in the carcass, which seriously damages the carcass structure and strength, resulting in uneven depth of the tread groove. In order to ensure safe production, tires damaged by local wear must be resolutely scrapped and must not be used as a makeshift.
1.3 Impact burst
When a tire hits an object under load, it will cause a sharp deformation and produce a very large stress concentration in the carcass, then the tire may be damaged. If this collision happens to occur when the truck is overloaded or speeding, when the tire hits a sharp stone or obstacle, the stress and deformation it bears are too large, which often causes the tire to burst. According to statistics, the giant tires scrapped due to impact bursting in the rainy and snowy seasons in Pingshuo Mining Area account for more than 5% of the total scrapped tires throughout the year. Although the proportion is not large, this kind of damage brings great hidden dangers to safe production. The following situations can also cause tire impact burst, such as: partial steel wire damage, local wear, cuts, peeling, etc. Tire impact burst is extremely serious for heavy trucks. Giant tire bursts generally occur on the rear wheels of transport trucks. When a tire on one side suddenly bursts, the driver should stop the car immediately. The shock wave generated at the moment of tire burst will seriously harm the surrounding people or equipment and the surrounding environment. Wait until all situations are clear before getting off the car for inspection. If it is under heavy load, the goods should be immediately cleared and returned to the maintenance workshop for inspection and treatment; if it occurs on the two front wheels of the truck, when one of the tires bursts, it may cause the heavy truck to overturn, the beam to twist, the suspension and the horn shaft to be seriously damaged, etc. The direct loss is immeasurable, which brings great hidden dangers to safe production.
The above three causes of tire damage are the most common in rain and snow seasons. Tire damage directly affects the service life, and is also related to safe production and cost consumption. Only by using tires scientifically, safely and correctly can they achieve their maximum economic benefits.
2 Preventive measures
2.1 Level the main road and clean the road surface
In the Pingshuo mining area, some loading and dumping sites have long transportation distances. In case of high temperature weather, tire thermal peeling can be directly caused; the road surface of the transportation main road is uneven, sharp stones can be seen everywhere, and they slide off the truck from time to time. If it rains or snows, it is easy to accumulate water, snow, and ice. If it is not cleaned in time, it will cause tire cuts or even impact bursts. These problems directly affect the normal use of tires. As the saying goes, “It is better to repair the road than to repair the car.” It is recommended that the relevant departments reasonably adjust the transportation distance between the loading and dumping sites, reduce bends, reduce slopes, and comprehensively carry out the standardization of mine engineering quality, especially for the work on the transportation main road. First of all, there should be enough width. On the basis of leveling, the center of the transportation main road should be used as the base point and extended to both sides with a slope of 3% to prevent road water from freezing and ice, and dig drainage ditches on both sides of the road to completely solve the tire damage caused by road water accumulation in rainy and snowy seasons. In addition, we implement the responsibility system for transport trunk roads, and strengthen the leveling and maintenance of on-site roads by road graders and bulldozers.
2.2 Strengthen measures to ensure smooth traffic
In rainy and snowy weather, trucks will experience adverse phenomena such as truck slippage and tire idling when going uphill, downhill or turning, especially on the working surface of transporting loess. These problems will cause serious damage to trucks and tires. It is recommended to make full use of scrapers to spread stones on transport trunk roads, ramps, and curves when it rains or snows, so that the tires can increase the friction with the ground, minimize the occurrence of truck slippage, and make the transport trucks run smoothly, safely and smoothly.
2.3 Strengthen training and improve quality
At the mining site of open-pit coal mines, electric shovel drivers, truck drivers, bulldozer drivers, road grader drivers, etc. have relevant contacts with tires. Problems in every link will cause abnormal tire consumption. For example, when the shovel driver loads the truck, if the truck is overloaded or unbalanced, the abnormal wear of the tire will be accelerated. Therefore, the loading quality of the shovel is particularly important for the tire. The truck driver is the first person responsible for the use of the tire. The truck should bear the main responsibility for the cuts, wear and bursts of the tires during operation. This requires the truck driver to check the condition of all tires before and after the shift change. If there is a problem, it should be reported in time and detailed records should be kept. When driving, it is necessary to start at a low speed, move forward at a constant speed, and brake with a point brake, and try to avoid rolling over stones or other obstacles. The bulldozer driver takes into account the cleaning of the working surface of the dumping site and the loading site, and should try to avoid the phenomenon of rolling over stones and other debris after the truck enters the working surface. The road grader driver is in the closest contact with the tire, and the quality of his work directly affects the service life of the tire. First of all, we should follow the working methods such as “quantitative road repair and regular inspection” and deal with problems in time when they are found. Only by cooperating with each other and caring for the above four types of work can the tires be used safely and reasonably at the mining site, so that the equipment drivers can form a sense of responsibility of “loving tires and saving tires”. The above employees should be trained regularly to improve their professional quality, strengthen their sense of responsibility, and contribute to ensuring the normal use of giant tires.
2.4 Regular maintenance and filing for future reference
Planned maintenance work is currently the most advocated work idea in the maintenance industry, and it is also feasible for tires. Planned maintenance of tires is divided into two parts: First, strengthening daily inspection of tires is a preventive measure to ensure the normal operation of tires. Through daily maintenance, equipment refueling, etc., the tire pressure and wear degree of trucks should be carefully checked, and detailed records should be made and fed back to the workshop. Every truck and every tire must be known, and the tires that need to be replaced should be replaced in a planned manner; second, comprehensive preventive repair of tires should be carried out, which means that the tires should be repaired in time after being cut. If the cut of the tire is not discovered in time, the wound will become larger and larger as the use time increases. When it develops to peeling and falling pieces, it will lose the value of repair. This work requires full cooperation from equipment drivers, tire workers, and maintenance workers. Strengthen the inspection of tires during daily inspection, oiling and inflation to extend the service life of tires. If necessary, some reward and punishment measures can be taken to improve the enthusiasm of staff.
2.5 Strict assessment, clear rewards and punishments
The quality of tire-related work directly affects the service life of tires. The implementation of the economic responsibility system for tire workers is the fundamental guarantee for managing tires well and reducing costs. A comprehensive safety and quality standardization work system for tire assembly, disassembly, replacement, repair, inflation, etc., and formulate relevant job responsibility systems to encourage every tire worker to complete the work under safety and standards. Regularly organize relevant management personnel to assess the safety and quality of tire work, and the teams and individuals who have safety and quality problems in the assessment must be rewarded and punished clearly, so as to fully mobilize the enthusiasm of on-site tire workers.
3 Conclusion
Through the analysis of the most common causes of damage to giant tires in rainy and snowy seasons, and the implementation of the above-mentioned practical preventive measures. In 2008, Pingshuo Mining Area achieved good results. First, the service life was extended, with an average service life of nearly 700 hours; second, the number of scrapped tires was reduced, 45 fewer than the same period, equivalent to an amount of more than 5 million yuan, accounting for about 10% of the annual tire cost; third, safe production was ensured, and a good foundation was laid for tire-related work in the coming year.
