The natural hazards especially methane, fire and rock-bump hazards make the most serious danger for present-day mines and have a crucial effect on miners’ safety and continuity of mining operations. Degree of these hazards increases with concentration of coal faces and use of high-duty mining methods for seams lying deeper and deeper. The interaction of natural hazards at seams liable to rock-bumps may lead to intensity both fire and spontaneous methane emission. The methane continuous monitoring systems in the range of 0¸100% CH4 including automatic power-off as well as the early fire detection systems based on measurements of CO, CO2, O2 and smoke are nowadays a standard. The improvement in efficiency of mine rescue operations can be achieved by quick reaction to the hazards. The issue concerns e.g. the mines in which the associated natural hazards may occur and where the bumps of definite energy requires an immediate power-off not only in the hazardous areas but also at ways of air flow and propagation of methane disturbances. The up-to-date rock-bump hazards monitoring systems use seismoacoustic and micro-seismologic methods characterized by high dynamics of signals to be registered. The roof control requires for today the support monitoring systems based for example on pressure recording in hydraulic props. The efficiency of detection and rock-bump hazards fighting may be also achieved by computer-assisted tomography on the basis of seismoacoustic equipment applied to seams in front of a longwall face and by using of cutter-loaders as a source of noises. Work safety of miners in the underground areas means also the systems of their localization and attendance in mine workings as well as the warning systems in case of hazards e.g. fire or gas and smoke propagation. The miners’ localization systems and load-speaking and alarm broadcasting communication systems should be therefore disseminated to support a mine operator to remove the staff from hazardous areas. Detection of the state of emergency requiring mine rescue operations allows a mine operator to activate the underground signalling devices and banners showing safe escape routes.
The natural hazards have a crucial impact upon the safety of the mines’ crew and continuity of routing mining operations at the mines. Degree of these hazards increases with extraction of seams at ever greater and greater depth use of heavy-duty extraction technologies. Monitoring of technological process at mines is essential from the viewpoint of supervision and control of the process’s course. Its superior objective consists in securing of continuity of the machines operation and proper operation of technological links starting from a coal winning machine and ending at coal sale and loading points at coal preparation and washing plants on the surface. It is obvious than monitoring regards not only the machines directly connected wit the production but also power supply, electrical protection and media. Monitoring and control focus on enlargement of work time and efficient diagnostics of machines utilising signalling and visual presentation of the process’s parameters.
Still more important is the control and monitoring of safety conditions, especially in underground mines. At present conditions running of safe exploitation requires complex solutions with utilisation of modern and reliable systems of monitoring, control and automatic safeguarding. In this case the utmost importance objective consists in securing of safe work conditions for the miners engaged in underground workings. That regards both the current and random monitoring of parameters and assisting the activities of the mine’s dispatchers and supervision during rescue works connected with saving of miners and protection-prevention activities.
Monitoring and control of natural hazards were treated up-to-date as autonomous subsystems of control and safeguarding. The experiences of recent years, unfortunately those tragic ones showed that in order to secure efficient methane-fire hazards prevention activities it is necessary to functionally combine all in one system. Taking the account of spatial structure of quakes origination or source of coal spontaneous heating and also occurrence of methane sources becomes indispensable. The effectiveness of safety status monitoring and warning the crew about occurring hazards as well as their rescue in disastrous situations require the engagement of the most modern information and microelectronic techniques as well as audio-visual means in modern systems of methane-fire natural hazards monitoring. On the other hand it is necessary to integrate the systems of methane - fire natural hazards monitoring, monitoring of geophysical or water hazards with the alarm loudspeaking/signalling systems and the system of locating the miners’ whereabouts.
1. MONITORING AND CONTROL
OF GAS HAZARDS
Solutions with regard to methanometric safeguarding have a decisive importance in the assessment of functionality and effectiveness of monitoring and control systems of gas hazard. The systems of automatic methanometry decide on the one hand about the safety but on the other hand have also considerable influence upon the continuity of operation of coal winning machines by switching off of electric energy in hazardous zones.
Irrespective of reduction of the total number of reported fires at Polish hard coal mines the fire hazard does not decrease. That specially regards seams prone to rock bumps where both natural quakes and distressing of the strata due to mining operations as well as due to distressing shotfiring done during hazard prevention activities increase the susceptibility to spontaneous combustion. Despite of this, thanks to, among others, application in recent years of automatic CO-metry it is possible to early detect a fire hazard and suppress it at its initial stage of development without the necessity of announcing of an emergency firefighting operation.
After a disaster at „Halemba” mine in 1991 (during which due to methane explosion 19 miners lost their lives) the investigations indicated that in the areas with high dynamic of methane emission new solutions of methanometric safeguarding are necessary. That require substitution of the old generation systems, with 4-minute sampling time commonly applied at Polish mines, with new solutions of continuous measurement mode and allowing the measurement of methane in the range of 0¸100% CH4 and faster switching off of electric energy in the hazardous zone. The idea of automatic system of ventilation control is based on continuous monitoring of the mine air parameters. The system applies a number of air parameters sensors, including, among others: CH4, CO, CO2, smoke, air velocity, absolute pressure and pressure drop, air and the strata temperature and also dust sensors. Basing on this idea the system of monitoring and control of methane-fire hazard of SMP-type was elaborated by EMAG Centre (Fig. 1) and put into use in 32 mines.
THE SMP METHANE AND FIRE
This state-of-the-art dispatcher system is a solution that utilizes Polish expertise in the field of safety and control of gas and fire hazards in the underground coal mines. The system realises continuous monitoring of significant parameters of the air, and is of modular structure that enables to adapt its functionality to the needs and size of a mine being protected. The solutions applied here are on a par with the most advanced ones in the mining industry throughout the world. All elements of underground equipment are intrinsically-safe and may operate in explosive atmosphere, and central power supply of underground devices from the surface facilitates the system’s uninterrupted operation even in the event of electric power supply breakdowns (also at the time of disasters) or failures in a mine underground.
The idea of automated system for ventilation control is based on continuous monitoring of the mine air parameters. For this purpose, in a mine ventilation network the air parameters sensors that provide current information on any variations of the mine air composition are installed. In this system a number of the air parameters sensors, are used, among them:
– Carbon monoxide analysers,
– Smoke detectors,
– Stationary oxygen-meters,
– Stationary anemometers,
– Air temperature sensors.
The system configuration shall depend on specific hazards pertaining to the particular mine and positioning of sensors in mine workings results directly from the mining industry regulations and the particular mine requirements.The CCD-1 microprocessor local underground stations operate as data concentrators. The underground station intermediates in data transmission between the underground sensors and surface station, and provides remote supply of sensors. The CCD-1 underground station is powered from the surface. The station enables to measure continuously
the mine atmosphere parameters, to monitor binary signals and also to control equipment. The station has 8 analogous inputs, 16 binary inputs and 4 control outputs. The surface central station that realises power supply of underground equipment and data transmission consists of a block of data transmission systems and supply, and a master computer system. Central computer of the SMP system is a local dispatch station (Fig. 2) for the mine safety status.
Figure 2: Methane and fire hazard monitoring system
type SMP – central station
The SMP dispatch system, implemented successfully in the hard coal mines, guarantees, among others:
q continuous monitoring and control of methane and fire hazards as well as other ventilation parameters,
q central power supply of all underground elements from the surface,
q automatic switching-off of the electric power at mine workings in case of emergency and breakdown,
q early detection of fires,
q supporting a dispatcher during rescue operation after alarm announcement, and supporting ventilation service at the time of fire extinguishing and prophylactic actions,
q monitoring and control of parameters of main fans and energy consumption.
Figure 1: Pictorial diagram of SMP-NT system
This modern mine control system is a solution completely utilising Polish experiences with regard to safety and monitoring of gas and hazards in underground mines. The system realizes continuous measure of essential air parameters and possesses a modular structure allowing for its adjustment to the size of the mine to be protected. The accepted solutions belong to the most modern in the scale of the World mining. All underground devices and instruments are intrinsically safe with respective certificates and can operate in explosive atmosphere, and the central powering of underground devices and equipment from the surface allows for non-interrupted operation of the system, even in the cases of switching off of electric energy (also during disasters) or failure in electric power supply in the underground of the mine.
2. SYSTEMS OF SEISMIC HAZARDS MONITORING
The effectiveness of natural hazards fighting requires a development of new method of hazards assessment prevention activities and prediction of their random occurrences. New methods of rock bump hazard monitoring require today the introduction of methods based in registration of dynamic phenomena and static ones taking place deep in the roof, registered in long diameter boreholes and also analyses of the borehole’s deformation in a spatial layout as well as the analysis of signals of great dynamics and brad spectrum of frequency.
For many years the EMAG Centre elaborates and develops systems for registration of crashes and quakes with the use of geophones in seismoacoustic systems (SAK, ARES - Fig. 3) and seismometers in the systems of micro seismology (SYLOK, ARAMIS - Fig. 4). Majority of Polish hard coal and copper mines apply some of these solutions. Development in this sphere regards technology in which mainly development of probes’ parameters, systems of transmission and methods and algorithms of processing. The most modern solution included digital seismoacoustic system of ARES-4D type and digital microseismic system of ARAMIS-M type with tri-axial probes utilising digital transmission of the date type DTSS.
Improvement of the effectiveness of seismic systems with regard to monitoring of quakes and location of their sources will be also possible after integration as early as at the stage of interpretation and processing of signals from seismoacoustic and seismological systems, as well as by presentation of the registered events on a uniform spatial diagram (Fig. 5).
Figure 3: Seismic-acoustic system type ARES
Figure 4: Micro-seismic system type ARAMIS
3. INTEGRATION OF SAFETY SYSTEMS
Safety of work for miners underground also means the system of warning them in case of occurring hazards, for instance, in case of a fire or propagating admixtures of gases also after a bump. Such systems need the propagation of the systems for locating the whereabouts of the miners, the system of loudspeaking communication and the alarm signalling system which, in case of occurrence of a hazardous situation, will be assisting the mine’s dispatcher in withdrawal of the crew from hazardous zones of the mine. Effectiveness improvement of endangered miners rescue system is possible due to a rapid reaction to a hazard that has just occurred and immediate transfer of messages in writing or evacuation signals. Such functions are being realised by a completely integrated system of the STAR-SMPZ type introduced for the first time at “Bogdanka” mine (Fig. 6).
In the case of mines with interacting hazards the occurrence of a bump of certain energy requires immediate switching off of electric energy not only in the affected zone but also along the route of airflow towards the uptake shaft. Therefore the structural integration of the safeguarded areas on the base of a spatial diagram of the mine is necessary and also the integration of the safeguarding systems, by now the autonomous ones, into one system (bump + methane). Such a solution is being realised at present at “Bielszowice” mine (Fig. 7).
4. CENTRAL PART OF THE PROCESS MONITORING AND VISUALISATION SYSTEMS
Data from the surface station computer of ZIST system are transmitted to the technological data server. This computer is fitted with network cards, hard disc of large capacity, monitor and printer. Computer operates in the environment of Windows NT system. Software application of SCADA has been created with tool software iFIX of Intellution Company. Program for data acquisition activated in the surface station computer creates local database which can be accessible to a variety of external users through network cards. Server of the local base of measurement data that characterise process (getting and haulage of produced coal), including those regarding longwall complexes and heading machines and binary signals, is located in central mine control room.
Software of the technological server realises the following functions:
– storage of measurement data,
– visualisation of current data,
– simplified visualisation of historical data,
– reporting and monitoring.
Data from the technological server and STAR and SMP stations are transmitted to the central database server, with the help of ADO and OPC technology. The central system (Fig. 8) consists of a group of servers, work stations and supporting devices. Applied solutions of software and hardware configuration allows the system to achieve high functionality and processing output as well as high level of reliability and safety. Multi-screen desks of the main dispatcher, designed both in the coal mine „Weso³a” (Fig. 9) and „Bogdanka” are supported by graphic wall of dimensions 2x1.5 m, with a possibility of further expansion. The graphic-wall (Fig. 10) is based on a system of rear projection, supported by Digital Light Processing (DLP), micro-mirrors technology developed by American company Texas Instrument. Thanks to the extraordinary sophisticated technology, very high technical parameters of the process state visualisation were obtained.
Figure 10: A view of graphic wall in dispatch office of WESO£A hard coal mine
As elements of the process state presentation, in dispatch office of the coal mine „Bogdanka” a graphic wall was used, while in the coal mine „Murcki” – a multiple monitor set. However, one has to remember that contemporary dispatch systems operate not only for purposes of visualisation and current supervision of process, but also serve for mine technical assets management. Therefore there is a need to give users not only tools for monitoring current state of the equipment operation, but also for their proper management and maintenance. Such requirements may be fulfilled by a system utilising relation database SQL-type, created on the central server integrated with technological server.
Presented above the contemporary dispatch system applies the most advanced developments of information technology and visualisation. The system named SD2000 proposes the innovative conception of a mine management, based on distributed structure of specialised sub-systems dedicated to the particular mine services. The principal purpose of such systems shall be management of machines operation and organisation of technical supervision services – for extension of their effective operation time. Effectiveness of control of safety state and staff warning on occurring hazards as well as rescue operation in the event of disasters requires integration of the natural hazards, monitoring systems with systems for warning/broadcasting and
localization of mine’s staff. The prototype system (of features described in this paper) with a synoptic projection table, implemented in the hard coal mine „Bogdanka”, indicates the new direction for development of dispatch systems for process supervision and control of a mine safety state.
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Figure 5: Visualisation of tremors energy distribution on the mine spatial diagram
Figure 6: Integrated system of monitoring and control of safety and alarm-loudspeaking/signalling
Figure 7: Structure of integrated SMP-ARAMIS-ARES system
Figure 8: A view of the process state visualisation on graphic wal
Figure 9: Structure of the central part dispatching system at BOGDANKA hard coal mine