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Innovation and Practice of Safety Supervision of Mine Lifting Wire Rope

Liu Shidong

Henan Xinzheng Coal Power Co., Ltd. Xinzheng Henan 451100

[Abstract] The analysis and checking of the weak links of the hoist wire rope during safety supervision can help keep the wire rope always in the safe and controlled detection state during its operation. Zhao Jiazhai Mine of Zheng Coal Group has successfully applied the leading internationally TCK.W wire rope automatic real-time online inspection system to monitor the wire rope condition, which not only solves the problems of safety supervision of wire rope, but also improves production, reduces energy consumption due to inspection, and saves the cost of wire rope as well as brings considerable economic benefits to the enterprise.

[Key words] Mine hoist, wire rope safety, weak magnetic inspection technology, wire rope automatic real-time online inspection system

The theory of intrinsic safety holds that because of the influence of many environmental parameters, as the freedom of people increases and simultaneously the safety reliability will worsen. Therefore, to ensure safety, it is necessary to adopt some kind of technology that can ensure the safety of people and property even in the case of human error, so as to achieve "intrinsic security".

The mine lifting wire rope lies in the vertical deep tunnel of the mine. In the process of equipment operation, repeated loading and release will lead to irreversible mechanical performance loss of wire rope, and for a long time there is a lack of more reliable means of prevention, so coal mine production is often trapped in the dilemma faced by "hidden danger, waste, inefficiency" because of the potential danger of lifting wire rope. Traditional manual inspection is not reliable; it is difficult to effectively find the hidden danger on the wire rope. Besides, regular rope changes cannot ensure safety, but cause a huge waste of wire rope. Furthermore, wire rope maintenance excessively used up production time, resulting in equipment idling energy consumption, and low efficiency.

1 Problem

Lugou coal mine of Zheng Coal Group had an accident three years ago because of broken wire rope, causing the loaded bucket to fall into the wellbore and interrupted production for up to 116 hours. Since then, Zheng Coal Group has checked 6 sets of large main mine individually and arrived at a conclusion: it is stipulated that the service life of all 4 multi-rope friction hoist wire rope is 2 years. And there has never been a broken rope accident. Besides, the forcedly replaced wire ropes after inspection have been found no serious defects. The service life of 5 single rope winding hoist wire rope on average is 2.7 years, and wire rope deterioration is more serious. Accidents caused by broken rope or critical broken rope have repeatedly appeared during its normal service life.

Based on the results of this investigation, Zheng Coal Group decided to take effective nondestructive testing, scientific evaluation and other technical means on the wire rope in use, so as to help the mine to improve its transport safety to its highest level.

2 Using advanced detection technology to find the hidden trouble of wire rope

Each subordinate coal mine of Zheng Coal Group first equipped with TCK.W portable wire rope nondestructive flaw detector. The instrument adopts weak magnetic detection technology, which can quantitatively detect all kinds of internal and external damage such as broken wire, wear, rust and fatigue, and accurately evaluate the residual bearing capacity and service life of the wire rope. The instrument combines a number of advanced technology, exquisite structure, light weight, good permeability, simple and convenient operation, safe and reliable use. Besides, the whole machine is suitable for more harsh working conditions with mild water resistance and anti-interference functions.

Replacing the old fashioned manual inspection with the advanced detection, immediately achieve the safety effect and economic benefit. Originally Chaohua Mine of Zheng Coal Group has one piece of imported wire rope whose service year is 4 years. However, the actual service year is less than 0.5 years. After the test, it has been found 6 serious damages, and the maximum damage value has reached 10.6% which should result in the immediate cessation of use; according to the regulations. Without this test, the rope could cause serious crash accidents at any time. Because it has been difficult to accurately evaluate the actual technical state of wire rope at home and abroad, the foreign suppliers of wire rope seriously question the basis of quality claim in the warranty negotiation. TCK.W inspection device and TCK.W inspection report presented by the mine have convinced the foreign supplier of wire rope to finally agree to compensate Chaohua Mine of Zheng Coal Group for its economic losses of 920,000 yuan.

3 Creating a new model of safety supervision for wire rope

Through further exploration and research on the safety supervision mode of wire rope, Zheng Coal Group recognizes that: although TCK.W portable wire rope flaw detector can provide a certain technical guarantee for the safe operation of wire rope, there are still many human factors in instrument operation and the problem that shutdown for inspection still affected production time due to great influence on the dynamic load of wire rope and the continuous operation of 24h in high yield coal mine, so there is still a clear gap between the actual safety state of mine lifting wire rope and the essential safety requirement. Thus it is necessary to adopt dynamic and continuous on-line real-time automatic detection scheme of wire rope in order to finally realize the scientific supervision and reliable prevention and control of mine hoisting wire rope.

In 2008, TCK.W wire rope weak magnetic detection technology has successfully been equipped with Ethernet communication, microelectronics integration, two-dimensional model analysis and other modern high-tech achievements, which can provide remote monitoring of wire rope for major production and public facilities. Zhao Jiazhai Mine of Zheng Coal Group immediately organized a core team of science and technology personnel to cooperate with TCK.W company to carry out a new technical research and finally developed wire rope automatic real-time on-line inspection system. This developed system can be applied in the magnetic field below 200mT, providing all-weather detection of mine lifting wire rope all kinds of internal and external damages, whose monitoring process is without any magnetic health consequences. The lift-off gap between the sensor and the wire rope surface can be 50mm, and the uncertainty of the loss rate of wire rope metal cross-sectional area is less than 0. 5%.

Automatic wire rope real-time on-line inspection system is equipped with 5 technical units such as mode combination detection, intelligent data collection and conversion, photoelectric meter speed measurement, automatic acoustic and optical alarm and multi-channel terminal master control. Besides, its use of expert data platform, system embedded control procedures can provide advanced functions namely all-weather automatic detection, automatic data integration and automatic generation of detection reports, which can achieve functions of "data series/damage curve/statistical chart multi-functionality", "background data operation", "automatic file", "system self-test" and "fault analysis" etc.. Besides, it will generate contingency plan integrated with mine hoist actual work environment and safe operation. Wire ropes can be inspected during normal hoist ascension. The system minimizes the human impact in the monitoring process, and the monitoring scope is further extended to areas that were not accessible to previous inspectors, thus enabling the full cycle of automatic online real-time monitoring of the wire rope and becoming the most advanced safety solution for wire rope operation.

At present, Zhao Jiazhai Mine of Zheng Coal Group has put TCK.W-SC type 4 ropes 8 measuring points wire rope automatic real-time on-line inspection system into operation for both main and auxiliary shaft. The detection head was fixed in the running path of mine lifting wire rope. During the normal lifting operation the corresponding on-line detection can be completed according to the selected route. Once during the detection process when a large damage signal is encountered, this system will automatically issue a sound and light warning in the first time, and the computer will provide "enhanced maintenance", "shutdown review" or "immediately change rope" and other equipment repair plan based on the real-time detection data to the equipment operator. Some maintenance personnel of the mine have initial doubts about the detection data of the system at an early stage, but after careful measurement, comparison and parameter adjustment, each technical parameter has been fully verified in the field, and its accuracy cannot be achieved by daily manual and traditional inspection method.

4 Effects

In July 2009, wire rope on-line inspection system for Zhao Jiazhai Mine main and auxiliary well has been put into operation. After a period of field verification, coal production has been significantly improved and the cost of wire rope is controlled. However, the detection energy consumption is nearly zero. The small investment for the enterprise has resulted in a large return and this kind of wire rope real-time on-line inspection system has become a popular use for wire rope safety supervision. The following advantages are:

(1) Wire rope is always in a safe and controlled state during production and operation

The application of TCK.W wire rope automatic real-time on-line inspection system has greatly improved the level of on-site safety monitoring, production process control and scientific management. The system enables the wire rope operation to be continuously monitored, which fundamentally eliminates all kinds of hidden dangers, ensures the safety of hoist, and becomes the most important management innovation achievement of Zhao Jiazhai mine of Zheng Coal Group.

(2) Significant improvement in production efficiency

According to the coal mine safety regulation, lifting wire ropes and tank ropes must be checked once a day. Under this request, Zhao Jiazhai mine used to consume 1.5 hours a day for manual inspection of wire ropes. The use of wire rope automatic real-time on-line inspection system can complete the wire rope detection at the same time during normal production; so that the production and testing process have been integrated as one and the past stoppage time used for manual wire rope inspection becomes effective production time, thus increasing at least 180,000t r coal production per year.

(3) Completely eliminate the idling energy consumption caused by equipment detection

The lifting height of main and auxiliary well of Zhao Jiazhai Mine is 446m and 465m respectively, whose motor power is 2800 kw and 850kW accordingly. For manual inspection, rope speed is 0.3~0.5m/s, and equipment no-load power consumption is 235kW. It needs four inspectors at the same time to conduct manual inspection and consumes power of 350kw·h. According to the effective working day of 330 days per year, the annual load energy consumption used for wire rope inspection is at least 116, 000kw h. The use of lifting wire rope safety automatic inspection system costs no idling energy consumption; instead, energy-saving profit obtained is nearly 100,000 yuan.

(4) Reasonable use of the remaining service life of the Wire Rope

The hoist wire rope of main and auxiliary well of Zhao Jiazhai Mine in the past will last 2 years before replacement. Each replacement will cost material fees of 780,000 yuan, and maintenance work fees of 250,000 yuan. The shutdown and adjustment net shortening start time has reached 3days, thus the annual cost of wire rope change is 510,000 yuan. With the use of wire rope automatic real-time on-line inspection system, the lifting wire rope of main and auxiliary well can sustain its service life, or even extend its service life to an additional year. Therefore, the annual cost of wire rope change has been reduced to 340,000 yuan and the cost of wire rope has also reduced to 1/3 of the original cost.

5 Conclusions

Zhao Jiazhai mine of Zheng Coal Group adopts the application of TCK.W wire rope automatic real-time online inspection system, and this has transformed the safety supervision of mine lifting wire rope, and achieved the goal of wire rope on-line real-time monitoring and dynamic continuous effective monitoring. It not only solves the problems of safety supervision of wire rope, but also improves production efficiency, reduces

the cost of inspection energy consumption and

saves the waste of wire rope. The direct economic benefits can be created by 81.27 million yuan per year, thus truly realizing the triple management goal for mine lifting wire rope operation namely safety, economy and efficiency.

Author profile:

Liu Shidong, Male, born in May 1963, graduated from the former Jiaozuo Mining Institute (now Henan University of Technology), electrical and mechanical engineer, who is currently the deputy general manager of Henan Xinzheng Coal Power Co., Ltd., and has published more than 10 papers. He is mainly engaged in mine mechanical and electrical equipment technology research and site management work.