Scraper conveyor chains failure analysis and precaution

The Scraper Conveyor is the main transportation equipment for the fully mechanized mining face. The normal operation of the scraper conveyor plays a vital role in the safety production of the entire coal mine. The scraper chain is the main component of the scraper conveyor. It is an important traction mechanism. It consists of three parts: scraper, circular chain and chain link. Statistics show that the failure of the scraper chain accounts for the scraper transport. 40% of the total number of machine failures, therefore, improve the quality of the scraper conveyor scraper chain, extend the service life, vibrating screen to reduce the operating accident rate will help improve the reliability of fully mechanized mining equipment, and help increase the production of working surface. It is of great practical significance to analyze and discuss the causes and solutions of the scraper chain scraper failure.
1. Types of faults and causes
(1) Scraper damage Scraper damage is mostly bent and excessively worn, and a few are cracking. The main reason for this is that the chute laying does not meet the design requirements and exceeds the required bending angle; the joint at the chute interface is not good, causing the chute local deformation conveyor large coal or vermiculite to be squeezed during operation, causing the scraper to be subjected to Large impact force; when the spacing of adjacent squeegees exceeds the design requirements, the long-term operation will overload the squeegee.
(2) The scraper chain is detached on the sprocket. The scraper chain cannot be normally meshed with the sprocket, and the so-called "jumping" phenomenon occurs. The main reasons are as follows: the bending angle of the transition groove between the machine head and the machine head is too large; the plate in the transition groove of the machine head is not flat; the sprocket wears seriously or bites into the debris; the tightness of the two chains of the linear vibrating screen is inconsistent; the scraper is seriously skewed Or the spacing is too large.
(3) The reason why the scraper chain is pulled out in the chute is mainly because the scraper conveyor is not flattened when it is laid, but is convex and concave, excessively curved; the scraper or chute is seriously worn, so that the scraper The gap between the plate and the chute is too large; the two chains of the three-dimensional vibrating screen have different lengths and uneven forces; the excessive deformation of the scraper causes the chain length of the scraper chain to be shortened; the pre-tension of the scraper chain is insufficient, and the cutter is cut in the shearer. At the end of the scraper, the load of the scraper chain increases, the elongation of the chain increases, and the chain is caused at the tail, making the scraper easily escape from the chute.
(4) Damage to the link ring In the current situation of the continuous improvement of the reliability of the domestic ring chain, the fatigue life of the link ring is quite different from that of the ring chain. In actual use, the link ring becomes the whole The weaker link in the scraper chain. Its damage form is mainly fracture, which is mainly caused by: alternating pulsating load for a long time, fatigue damage occurs under water far below the breaking tension; the connecting bolt or pin loosening and falling off, cannot be replenished in time. Causes uneven force or can not be stressed; when used in the vertical ring, the unilateral wear is serious, if the sawtooth or arc tooth link is not replaced in time, it is easy to break; after the chain, it will generate a large dynamic load and The impact load, combined with the fluctuation of the speed of the scraper chain, makes the running of the scraper chain less stable, which causes the link ring to break; the manufacturing quality is poor, the standard is not met, the hardness is low, the wear is easy, or the stress concentration point occurs. It is prone to fatigue cracks, resulting in insufficient strength.
(5) Ring chain breakage Theoretically speaking, the various ring chains used in China's scraper conveyors should be produced according to the standard C-class chain, and the breaking load is about 10 times that of the scraper. The coefficient is large, and there should be no chain-breaking accidents, but this is inconsistent with the fact that the failure rate is large in actual use. The main reasons for this are: the manufacturing quality is not up to the standard, and the materials and heat treatment are not. Long-term withstand alternating pulsating load, fatigue damage occurs at a level far below the breaking tension, the fracture is generally at the junction of the circular arc portion and the straight portion of the chain; the chain is in operation with the chute, sprocket, and cargo Wear is caused by contact friction, weakening the cross section of the link, resulting in reduced strength. The wear is mainly manifested on the outer side of the straight part of the link, the outer part of the arc part and the inner part; the chain ring is corroded by the downhole water, causing rust and peeling. The section is reduced, the strength is reduced; the chain of the iron in the scraper chain is broken, and the chain tension is pulled out beyond the allowable value; when the spacing of the scraper exceeds twice the required spacing, when running At the head, due to the tension of the chain, the chain without the squeegee is stretched and cannot slide in the squeegee groove, and the next squeegee is also stretched with the chain, interfering with the unloading pear coal plate of the machine head, and a card chain occurs. The chain is broken; the pre-tension of the chain is insufficient, too loose, and the stack is easy to form, causing the scraper to be grooved and causing a chain phenomenon; if the chain tension is too large, the chain is too tight, which increases the initial tension of the chain and accelerates the wear of the chain. The service life is shortened, and there is no buffer space when the chain occurs; the chain is frequently started under full load or overload, so that the dynamic tension of the chain exceeds the strength limit; the tightness of the two chains is inconsistent, so that the load is concentrated therein. On a tighter chain, thus exceeding the strength limit.

2. Fault prevention and solution measures In the design, according to the working conditions, choose a reasonable scraper chain safety factor, so as to select the appropriate scraper, ring chain, link ring specifications and types, in the procurement, you should choose Products that have been verified, have good reputation and meet relevant quality standards are strictly prohibited from using unqualified scraper chains. If conditions permit, it is best to carry out necessary tests on the scraper chain. The manufacturing enterprise shall adopt the strengthening process such as surface shot peening and high load pre-stretching of the ring chain and the connecting chain to improve the surface residual stress and prevent the micro crack growth; strengthen the quality control of the ring chain and the link ring material. Considering its strength, it also considers its elongation, and then through its composite strengthening and toughening treatment, its microstructure is refined, and its mechanical properties are optimized. The chain-making process is improved, especially to avoid the link arc and the straight side. The surface damage is as smooth as possible, and the inner width of the link is controlled within the deviation range to reduce the stress concentration and slow the crack occurrence. The anti-corrosion treatment process is adopted to improve the corrosion resistance of the scraper chain.