Armored Face Conveyor Research Articles

Analysis of the Impact of Unscheduled Downtimes on their Availability in Machine Operations

Abstract Unscheduled downtimes in machine operation are one of the main reasons behind their low availability. Such downtimes are caused by miscellaneous factors and remain difficult to identify in a number of cases. This particularly refers to enterprises that conduct their activities in changing external conditions, such as hard coal mines, where exploitation is carried out in extremely complicated, changeable and dangerous conditions. The process of coal production makes use of various machines that must be adapted to these conditions. The specificity of the working environment makes it necessary for these machines to exhibit high reliability, readiness and efficiency. These features, in turn, make the cost of the machines very high. It is therefore reasonable to make the best use of their capabilities, which translates into the effectiveness of the entire production process. The article concentrates on determining the availability of these machines. It has been assumed that availability is one of the fundamental parameters that define the effective utilisation of machines. The tests were conducted for a longwall shearer as well as an armoured face conveyor and a main haulage conveyor in one of the hard coal mines in Poland. Industrial automation systems were used to determine unscheduled downtimes in the operation of these machines, as well as their time structure and causes. The results obtained indicate that the number of unscheduled downtimes represents a serious problem in mining exploitation.

Use of IT platform in determination of efficiency of mining machines

Determination of effective use of mining devices has very significant meaning for mining enterprises. High costs of their purchase and tenancy cause that these enterprises tend to the best use of possessed technical potential. However, specifics of mining production causes that this process not always proceeds without interferences. Practical experiences show that determination of objective measure of utilization of machine in mining enterprise is not simple. In the paper a proposition for solution of this problem is presented. For this purpose an IT platform and overall efficiency model OEE were used. This model enables to evaluate the machine in a range of its availability performance and quality of product, and constitutes a quantitative tool of TPM strategy. Adapted to the specificity of mining branch the OEE model together with acquired data from industrial automatic system enabled to determine the partial indicators and overall efficiency of tested machines. Studies were performed for a set of machines directly use in coal exploitation process. They were: longwall-shearer and armoured face conveyor, and beam stage loader. Obtained results clearly indicate that degree of use of machines by mining enterprises are unsatisfactory. Use of IT platforms will significantly facilitate the process of registration, archiving and analytical processing of the acquired data. In the paper there is presented methodology of determination of partial indices and total OEE together with a practical example of its application for investigated machines set. Also IT platform was characterized for its construction, function and application.

Variable Frequency Drive and Transmission System of the Heavy Armoured Face Conveyor

Variable Frequency Drive and Transmission System of the Heavy Armoured Face Conveyor

Application of Elements of TPM Strategy for Operation Analysis of Mining Machine

Total Productive Maintenance (TPM) strategy includes group of activities and actions in order to maintenance machines in failure-free state and without breakdowns thanks to tending limitation of failures, non-planned shutdowns, lacks and non-planned service of machines. These actions are ordered to increase effectiveness of utilization of possessed devices and machines in company. Very significant element of this strategy is connection of technical actions with changes in their perception by employees. Whereas fundamental aim of introduction this strategy is improvement of economic efficiency of enterprise. Increasing competition and necessity of reduction of production costs causes that also mining enterprises are forced to introduce this strategy. In the paper examples of use of OEE model for quantitative evaluation of selected mining devices were presented. OEE model is quantitative tool of TPM strategy and can be the base for further works connected with its introduction. OEE indicator is the product of three components which include availability and performance of the studied machine and the quality of the obtained product. The paper presents the results of the effectiveness analysis of the use of a set of mining machines included in the longwall system, which is the first and most important link in the technological line of coal production. The set of analyzed machines included the longwall shearer, armored face conveyor and cruscher. From a reliability point of view, the analyzed set of machines is a system that is characterized by the serial structure. The analysis was based on data recorded by the industrial automation system used in the mines. This method of data acquisition ensured their high credibility and a full time synchronization. Conclusions from the research and analyses should be used to reduce breakdowns, failures and unplanned downtime, increase performance and improve production quality.

Multi-Body Dynamics and Vibration Analysis of Chain Assembly in Armoured Face Conveyor

Multi-Body Dynamics and Vibration Analysis of Chain Assembly in Armoured Face Conveyor

Dynamic analysis of scraper conveyor operation with external loads

A load to an armoured face conveyor (AFC) during coal mining is changeable and very difficult or even impossible to be predicted. Changes of the load to the upper scraper chain affect the load of the driving motor and generate changes in a scraper chain tension. Impact of increasing the external load to the upper scraper chain on the operation of electric motors and on the scraper chain tension is presented. The developed numerical model of the Rybnik 850 conveyor enabled identifying the places of the scraper chain high tension or places of its loosening. An impact of changing frequency of driving motor voltage on AFC’s operational conditions was tested and analysed using the AFC’s numerical model. During tests, tension of the scraper chain on the discharge end and the return end was recorded. High tension of the scraper chain and its loosening during the changeable load were also recorded on upward and downward transportation of run-of-mine material.

Armored face conveyor’s smooth velocity control for increased durability

Armored face conveyor’s smooth velocity control for increased durability

Experimental study on the welding procedure of the central groove of armored face conveyor

The central groove is a key component of armored face conveyor. Failure of welded joints in the central groove often occurs in engineering. In this article, the welding procedure parameters were analyzed to the improve strength and toughness of the dissimilar steel weld joint in the central groove. First, four types of super-high wear-resistant steel and two types of high-strength welding wire were chosen as the welding materials. Carbon equivalent method, cold crack sensitivity index method, and maximum hardness of heat-affected zone test were applied to analyze their welding properties. Second, to improve their weldability, the proper preheating temperature was determined using Y-groove cracking test and mechanical property tests. Finally, a semi-automatic CO2welding method was adopted, and a second mechanical property test was conducted to determine the proper welding wire. Results show that the chosen steels have poor weldability and cold cracking sensitivity. Preheating must be used to prevent cold cracking. When the preheating temperature is higher than 80°C, the cold crack rate can be controlled to under 20%, which can satisfy application requirements. Welding wire YMGR76 is appropriate. Using YMGR76, the preheating temperature drops to 120°C, and the strength and toughness of the weld joint are improved to 813 MPa and 112 KV2/J, respectively. This study provides a welding procedure to improve the reliability of the central groove.

Modeling and Simulation of Coal Loading by Cutting Drum in Flat Seams

Abstract This paper presents a methodology for modeling work of a coal shearer work in low longwall coal seams where the wall height does not exceed 1.5 m. In such conditions, an important issue is the process of loading the ore from shearer cutting drum on an armored face conveyor and selection of appropriate kinematic parameters to avoid choking. Discrete element method was used to model coal seam. This method allows for efficient simulation of physical systems composed of many separate components. Methods and algorithms based on existing theoretical models were developed to imitate coal cutting process. Main focus of analysis was put on coal stream movement for different variants of the shearer construction and kinematic parameters.

New Methods of Mining Technological System’s Performance Analysis

The mining production systems, both for underground and open pit extraction consist mainly in a string of equipment starting with the winning equipment (shearer loader, in case of underground longwall mining or bucket wheel excavator in case of open pit mining), hauling equipment (armored face conveyor in longwall mining or the on-board belt conveyor in case of excavators), main conveying equipment (belt conveyor in both cases), transfer devices, stock pile or bunker feeding equipment. This system of mainly serially connected elements is characterized by the throughput (overall amount of bulk coal respectively overburden rock produced), which is dependent on the functioning state of each involved equipment, and is strongly affected also by the process inherent variability due to the randomness of the involved processes (e.g. the cutting properties of the rock). In order to model and simulate such production systems, some probabilistic methods are applied arising from the artificial intelligence approach, involving unit operations and equipment, as the overall system as a whole, namely the Monte Carlo simulation, neural networks, fuzzy systems, and the Load Strength Interference methods. The results obtained are convergent and offer the opportunity for further developments of their application in the study of mining production systems.

Novel approach to and implementation of design and analysis of armored face conveyor power train

An armored face conveyor (AFC) is a key piece of equipment for a fully mechanized long-wall mining system and is currently the only means for transporting bulk material in hard coal mines. To date, the AFC power train design has mainly been based on heuristics obtained via experience, coupled with simple calculations, which cannot take the dynamic behaviors and coupling effects of the components into consideration. Therefore, model-based and simulation-driven design is preferred. In this paper, a new design and analysis methodology for an AFC power train is presented to achieve the optimal dynamic characteristics and transmission performance. A preliminary design procedure for a power train is first introduced. Then, a system-level hydro- mechatronic model of the power train is built to evaluate and optimize the preliminary scheme. Sub-models, including those for the motors, fluid couplers, gearboxes, and chain, are obtained according to their individual disciplines and assembled to form the system-level model. The chain sub-system is discretized into multiple finite elements. Governing equations are established for each element based on the Newton Euler approach and assembled according to the topological structure of the chain system. In order to make the new approach applicable for engineers, a design and analysis software is developed, with a graphical user interface that involves the whole design process. MATLAB/SIMULINK is used as the computational engine, and Visual C++ is adopted to develop the interactive software framework. Simulations for the SGZ1000/2000 type AFC are provided as an illustrative case study to validate the effectiveness and practicality of the model and software package.

Follow-Up Chain Tension in an Armoured Face Conveyor / Nadążne Napinanie Łańcucha Zgrzebłowego W Przenośniku Ścianowym

Abstract Initial chain tension in armoured face conveyors, in which operating conditions vary constantly, should be adjusted automatically to adapt it to the needs arising. The manufacturers of such conveyors are now offering a possibility of equipping a conveyor with a drive with a telescopic trough enabling stepless change of the scraper chain contour by shifting the drive frame. The work presents the outcomes of computer investigations performed using an own mathematical model of an armoured face conveyor with a main and auxiliary drive equipped with a telescopic trough and an automatic initial chain tension adjustment system with the ASTEN algorithm. The ASTEN algorithm is responding to changes in scraper chain elongation caused by changes to conveyor configuration and also by a varying mined coal load resulting from interworking with a mining machine.

Modelling of the transmission system in conveying equipment based on Euler method with application

This paper presents an approach to predict and evaluate the dynamic characteristics of the transmission system in conveying equipment under various working conditions. To solve the problems of varying mass and load, the space, which the transmission system locates, is divided into multiple space-fixed finite control volumes according to the material distribution as well as motion pattern. Each volume is further discretized into a series of finite elements. System-governing equations are obtained by the assembly of all the individual elements’ dynamic equations and the topological structure of the transmission system. Karnopp model is utilized as the basis to render the duty resistance induced by friction. As an illustrative example, the present method is applied to model a large-scale armoured face conveyor, and the corresponding simulation code is developed based on Matlab/Simulink. Simulation results show that the start-up and stop processes with empty load are relatively smooth, which is beneficial to protect the components of the system, especially the chains. Furthermore, the resulted chain-steady velocity, chain-load spectrum and minimum tension force can be directly used to predict the conveying capacity, evaluate chain strength and optimise the pretension force.

DYNAMICS OF NON-UNIFORMITY LOADS OF AFC DRIVES

Abstract The length of armoured face conveyors currently used in hard coal mines most often ranges between 200 m and 300 m. The machines are equipped with a main and auxiliary drive. Asynchronous motors mounted in conveyor drives feature the capacity of several hundreds of kilowatts. The non-uniform distribution of loads onto individual drives is observed in practice. The numerical value of loads distribution onto the individual armoured face conveyor drives is represented by a drive load distribution factor. It is defined as a ratio between the load of an electric motor installed in a given drive and the total conveyor load. The article presents a physical armoured face conveyor model intended for examining dynamic phenomena influencing the load non-uniformity of drives. Motion in this physical model is described with the system of (4 · j + 5) non-linear ordinary differential quotations of the second order. A mathematical model is obtained by adding functions describing the interwork of sprocket drums with chains and functions approximating the mechanical characteristics of asynchronous motors powered by means of frequency inverters. A large number of computer simulations was performed using this model enabling to study the impact on the load non-uniformity of drives of such parameters as motor slip, motor supply voltage drop, variations in supply voltage frequency, differences in the gear ratio of transmissions and differentiation in the pitch of scraper chain links along the chain contour.

Monte Carlo reliability simulation of coal shearer machine

In this paper the Kamat-Riley (K-R) event-based Monte Carlo simulation method was used for reliability analysis of longwall machine. Shearer machine consists of six subsystems; water, haulage, electrical, hydraulic, cutting arms and cable systems in a series network configuration. A in the Tabas coal mine was selected as case study and its all failure data were collected and used for reliability analysis of subsystems. With negligible assumption of time to repair, a flowchart was built for programming the simulation process. The Matlab mathematical programming software was used for reliability simulation process. Finally the reliability plot of longwall machine was achieved and upper and lower bound reliability were calculated. The results illustrate that the reliability of machine reduces to zero in a period of 100h. There is a 50% chance that the will not fail for the first 12h of operation. Longwall mining is a high productive underground coal mining method. In this method, coal is extracted by an automated cutting machine called shearer that moves along a track parallel to the working coal face. The cut coal falls into Armored Face Conveyor (AFC) and is transported along the working face and eventually out of the mine. Up to now, the reliability of longwall systems and equipments has been studied by few researchers (1-8). The objectives of these studies are the reliability analysis of power supports, AFC machine, drum shearer, stage loader, belt system and general production system of longwall faces. In the previous studies the classic reliability modeling and fault tree analysis techniques have been and any serious simulation approach hasn't been done on machineries of longwall mining system. This paper aimed a comprehensive reliability study on longwall machine using the event-based K-M Monte Carlo simulation method. The machine of Tabas coal mine in central desert of Iran has been selected as a case study and for data collection. Through this research, the reliability plot, upper and lower bound of shearer's reliability with 90% confidence level has been developed and discussed.

THE ANALYSIS OF THE TRIBOLOGICAL PROPERTIES OF THE ARMOURED FACE CONVEYOR CHAIN RACE / BADANIA WŁASNOŚCI TRIBOLOGICZNYCH PŁYTY ŚLIZGOWEJ PRZENOŚNIKA ZGRZEBŁOWEGO

Generally, the power and capacity of the armoured face conveyor (AFC) are determined by the motor size, pan width and chain size. It is well known that the dynamic behaviour of an AFC drive has a significant influence on tension in the AFC chain, and is therefore critical in determining the reliability of the chain and the entire AFC system. However, the chain long service life is also affected by tribological contact with the chain race plate of the AFC and with the coal. The main objective of this work was to determine the tribological properties of AFC twin chain race (top plate). Characterization of the twin chain race, made of the Hardox 450 abrasion resistant steel, included microstructural examination by light microscopy, hardness test, X-ray diffraction and examination of tribological properties. The studies were carried out on samples cut from top plate of the whitdrawn face conveyor twin chain race. It was found, that the Hardox450 steel has quite good wear resistance for such purpose as AFC twin chain race. It is possible to use more wear resistant material than Hardox 450 steel but it would cause premature wear of the AFC chain.

Dynamic Behavior Analysis on the Ring Chain Transmission System of an Armoured Face Conveyor

Armoured face conveyor is a key component of the comprehensive mechanized coal mining equipments.The ring chain transmission system is adopted to transport material from the coal face which has the characteristic of heavy duty,high power and long distance.By finite segment method and Matlab Package,the ring chain transmission system is discretized into the Kelvin-Vogit model to study its longitudinal dynamic behavior,and in the dynamic model,predefined force of the chain and two driven motor is considered.The contact model of sprocket and chains are established based on nonlinear finite element analysis via Abaqus package,and thus the stiffness coefficients of the sprocket and chain which are requisite for the dynamic model are got through the analysis.The start-up,power off and chain jam conditions of the armoured face conveyor are simulated by the model with the affects of pretension force.The minimum pretension force,dynamic tension and velocity of the chain are obtained.The methodology and simulation results help to improve the design of the machine and also offer the theoretical guide for parameter selection and match.

Dynamic Behavior Analysis on the Ring Chain Transmission System of an Armoured Face Conveyor

Armoured face conveyor is a key component of the comprehensive mechanized coal mining equipments.The ring chain transmission system is adopted to transport material from the coal face which has the characteristic of heavy duty,high power and long distance.By finite segment method and Matlab Package,the ring chain transmission system is discretized into the Kelvin-Vogit model to study its longitudinal dynamic behavior,and in the dynamic model,predefined force of the chain and two driven motor is considered.The contact model of sprocket and chains are established based on nonlinear finite element analysis via Abaqus package,and thus the stiffness coefficients of the sprocket and chain which are requisite for the dynamic model are got through the analysis.The start-up,power off and chain jam conditions of the armoured face conveyor are simulated by the model with the affects of pretension force.The minimum pretension force,dynamic tension and velocity of the chain are obtained.The methodology and simulation results help to improve the design of the machine and also offer the theoretical guide for parameter selection and match.

Finite Element Contact Analysis for Sprocket of an Armoured Face Conveyor

Sprocket has an important role in improving the transport performance and life of the armoured face conveyor, which is the key component in the transmission system of armoured face conveyor (AFC). In this paper, true stress-true strain curves of materials of the sprocket and the ring chain are obtained by computing the data of static tensile test. A simplified symmetric finite element contact model is established based on the nonlinear finite element software ABAQUS. Stress field and torsional stiffness coefficient of the sprocket are calculated according to loads and boundary conditions. Simulation results are in good accordance with the test results. The finite element model and the simulation results provide useful guidance for design and test of the sprocket. Meanwhile, accurate torsional stiffness coefficient of the sprocket is obtained for simulation of the transmission system of AFC.

Control problems in armored face conveyors for longwall mines

This paper is a tutorial discussion of the current difficulties being experienced with the performance of armored face conveyor (AFC) drive systems, as used in longwall mining. It presents the traditional approaches to the design of the drive system and highlights the inadequacies. The final part of the paper presents a possible solution approach using variable-speed drive systems, emphasizing the advantages of this approach. The paper is significant, in that it discusses, in one document, a number of problems related to the operation of longwall AFCs. Furthermore, it presents a solution path for these problems.