Introduction
Belt conveyor as the most common port bulk materials such as coal, iron ore continuous conveying equipment, its conveying efficiency, work reliability is directly related to bulk materials transportation technology and economy. In recent years, with the increase of bulk cargo material loading and unloading and conveying volume of Lianyungang Xinsu Port Terminal Co., LTD. (hereinafter referred to as “the Company”), the production task of belt conveyor equipment is increasingly heavy, and the production stopper of bulk cargo transportation system caused by the damage of belt conveyor equipment is also increased accordingly. According to the statistics of production outages of bulk cargo transportation operations in 2018, nearly 70% of the outages were caused by the replacement of return idlers by belt conveyors. Therefore, how to reduce such production stoppage and effectively improve the operation efficiency of the belt conveyor is an important issue that Lianyungang Port is facing.
Return based on the in-depth belt conveyor roller, on the basis of failure cause and harm, put forward a kind of return idler belt conveyor technical retrofit scheme, through the implementation of the technical retrofit scheme, improve the ability of continuous running belt conveyor , reduce work caused by damage of belt conveyor roller system of production line stopped, to ensure the continuity of the bulk material ShuYun, and further reduce the energy consumption of the system.
1 Reasons and hazards of return idler failure
1.1 Return idler structure
In the belt conveyor, return idlers are used for return branches, including parallel lower idlers, V-shaped idlers, anti-V-shaped idlers, comb idlers and spiral idlers. Currently, the company’s 33 belt conveyor is equipped with parallel idlers consisting of two medium 159 MMX 1 000 mm short idlers supported by the crossbeam of idler support.
1.2 Main causes of return idler failure
Through the statistical analysis of the reasons for the failure of the return idler of the belt conveyor of the company, it is found that the main reason for the failure of the return idler is the wear of the idler with the accumulated material on the beam of the idler support, which leads to the damage and failure of the idler body and end cover.
In the process of bulk material conveying operation of belt conveyor, it is inevitable that some materials will be scattered on the roller support beam, and with the increase of working time, the material on the support beam is also accumulating. If the material on the support beam is not cleaned in time, the material will gradually accumulate and fill the gap between the return roller and the support beam. The accumulated materials wear the idler body for a long time, resulting in the wear and damage of the idler body and reducing the service life of the idler. On the crossbeam of the idler support, the most easy area to produce the accumulation of material is the middle of the crossbeam, that is, the connection of two short idlers. If the accumulated material here is not cleaned in time, it will wear the end of the roller for a long time, resulting in the damage and fall off of the end cover of the roller, and greatly reduce the service life of the roller.
1.3 Harm of return idler damage and failure
As the main component of the belt conveyor system, the impact and harm brought by the damage failure of the return support is not only in the roller itself, but also relates to the normal and safe operation of the belt conveyor system. Therefore, the damage failure of return idlers not only increases the cost of purchase, replacement and maintenance, but also adversely affects the technical economy of belt conveyor system operation.
(1) The accumulated material on the beam of the support will not only wear the roller body, but also hinder the free rotation of the roller body, thus increasing the running resistance of the belt conveyor and increasing the energy consumption of the system.
(2) The surface of the roller body after scraping and wearing the accumulated material on the beam of the bracket is rough and uneven, which will increase the risk of scratching the belt when the cylinder rotates and contacts the belt.
(3) The accumulated material in the middle of the support beam wears the end of the roller, resulting in the damage and fall of the end cover of the roller, which greatly increases the hidden danger of being scratched in the middle of the belt.
(4) After the damage and failure of the return idler is found, the belt conveyor system must be stopped immediately for maintenance and replacement, resulting in production suspension, which will affect the whole bulk cargo transportation operation line and bring large economic losses to the port enterprises.
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2. Technical transformation scheme and practice of return idler
2.1 Technical transformation scheme of return idler
In order to completely avoid the accumulation of materials on the beam of return roller support and effectively solve the problem of damage and failure of roller body and end cover caused by wear, the technical department of the company formulated the reform plan of return roller support mode on the basis of carrying out a wide range of technical communication and research. See Figure 4 for schematic diagram of parallel idlers supported by lug bracket. The parallel roller supported by the lug bracket is composed of two lug brackets and one 159 mm× 2 000 mm long roller. The lug bracket is arranged on both sides of the roller and connected with the load bearing member by hanging and fixing. The hanging ear roller bracket cancels the support beam to avoid the accumulation of accumulated material, which can effectively eliminate the wear of accumulated material on the return roller, and greatly reduce the risk of the end cover falling off of the roller.
2.2 Practice of technical transformation of return idler
In February 2019, with the belt line of ship unloader supporting system as the pilot, the company changed the belt conveyor’s original 1 group of 2 159 mm×1 000 mm return idlers to 1 group of 1 159 mm×2 000 mm return idlers, and changed the original return idlers’ beam support to the two side hanging lug support.
After the transformation, the beam of the original support is removed, and the accumulated material cannot be accumulated on the beam of the support, which can reduce the abnormal wear of the roller to the maximum extent and prolong the service life of the roller. Even if the end cover of the roller falls off and the middle position breaks, the normal operation of the process will not be affected and the production stoppage will be reduced.
In addition, before the reform of the supporting mode of the return idler, when the idler under the cantilever of the ship loading and unloading machine is replaced, the maintenance personnel must enter the underside of the cantilever belt with the safety belt. If the idler is replaced at night, it will be a great safety hazard. After the modification, personnel do not need to enter the cantilever belt, greatly improving the safety and operability of equipment maintenance, reducing the time of roller replacement, improving efficiency.
3. Comparison of operation comprehensive efficiency of belt conveyor before and after reconstruction
3.1 Comparison of the number of replacement idlers before and after renovation
The number of replacement idlers within 12 months after the transformation was 298, only 53% of the number of replacement idlers before the transformation (564). At the same time, the maximum number of idlers replaced in one month after the transformation is only 34, which is less than the minimum number of idlers replaced in one month before the transformation is 35. The reduction of idler replacement means the increase of idler service life, which will directly bring significant economic benefits for enterprises.
3.2 Comparison of replacement roller stop before and after transformation
The stop-time of replacement of return idler within 12 months after the transformation is 13.85h, which is nearly half of the time before the transformation. After the transformation, the number of production stoptimes for replacement of idler can be reduced to ensure the continuity of bulk cargo material transportation, improve the comprehensive efficiency of port bulk cargo material belt conveyor operation system, and provide a solid foundation for rapid and efficient bulk cargo transportation operation of port.
4 Conclusion
It has been proved by practical application that the modified return idler can avoid the grinding of crossbeam accumulator and prolong the service life of idler. Adopt single long idler to directly avoid the problem of stop caused by the falling off of idler end cover for a long time, and greatly improve the continuity of production; The change of roller support structure makes the replacement roller more efficient, safe and convenient, and greatly improves the safety of maintenance operations. In addition, the smooth implementation of the belt conveyor return roller technical transformation enables port technicians to accumulate more theoretical knowledge and practical experience in solving practical problems and tackling technical problems, which helps to improve the innovation consciousness of port technicians and promote the technological innovation and progress of the port.
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