The present invention relates to a local methane gas detector for hazardous areas. The present invention particularly relates to a portable methane gas monitoring and power cut-off system for improving safety of underground coal mines. The present invention more particularly relates to an intrinsically safe system which is capable of accurate and continuous measurement of methane gas concentration, date and time-wise data storing, view current instrument’s reading at a remote and safe place, providing evacuation warning to miners, and switching off the power supply of an area where concentration of methane exceeds the permissible limit to avoid explosion.
Local methane detector for hazardous area of the present invention is a monitoring and power cut-off system for underground coal mines, when concentration of methane gas exceeds the permissible limit, wherein infrared methane sensor is provided with microcontroller unit to monitor methane gas. The present invention consists of different sub-units for various functions. The present invention uses a microcontroller unit for controlling all sub-units of the system. The mine atmospheric air is sucked by a suck-in fan inside the gas sensor chamber, and where infrared methane sensor is used for accurate and continuous measurement of methane concentration present in the said gas chamber. The loud audio alarm and visual display are provided for giving evacuation warning to miners working in highly explosion prone area when concentration of methane gas crosses the permissible limit, which is controlled by said microcontroller. The system uses a relay for cut-off power supply in case of methane concentration reaches the explosion limit, which ultimately prevents methane explosion in gassy underground mine, and saves valuable life and property. The battery power supply with 5 days backup is provided in addition to intrinsically safe power supply of 110 volt AC supply normally available in underground coal mines. A remote read out unit is used for viewing instrument’s reading at a safe place away from hazardous monitoring location.
Local methane detector for hazardous areas of the present invention is particularly useful for accurate and continuous measurement of methane gas concentration present in underground mines. The present invention would provide a loud audio visual warning and automatically cut-off the power supply of the particular area of an underground mine, when infrared sensor measures the gas concentration above its permissible limit. Use of the present invention would help in date and time-wise storing of methane gas concentration data. This would also help in saving valuable human lives and loss of huge property caused by explosions in underground coal mine.
The hitherto known prior art generally related to portable equipment for continuously detection of methane gas present in underground mines is referred to herein below.
Reference may be made to patent number: WO2005003756 entitled “Gas monitoring apparatus”, wherein a system has been described and claimed for gas monitoring in a mine working. Gas monitoring apparatus comprises of a sensor module and an associated display module, which can be physically connected together or separated. The sensor module contains gas sensors, which is used to detect the concentration of gas. The sensor module transmits readings wirelessly to display module, which includes a display to show the reading. Each sensor unit can communicate with multiple display units and vice versa.
The drawbacks of the above said patent number: WO2005003756 is that the system is specially designed for monitoring gases only. The system has no facility for power cut-off of the particular area of an underground mine when concentration of methane gas exceeds the permissible limit. The system has no high brightness alphanumeric LED display unit for long distance viewing of methane concentration and evacuation alarm. The system does not use infrared sensor, hence it can’t provide accurate measurement during continuous monitoring over a longer duration due to inherent limitations of the used sensor.
Reference may be made to patent number: US3879717 entitled “Portable methane monitor and alarm system”, wherein a system has been described and claimed for a portable, battery-operated, continuous methane monitor and alarm instrument. It includes a semi-conductor gas sensor which in response to an increase in concentration of methane gas, exhibits a lowering of its resistance. A push-pull oscillator provides an alternating current at 3-5 kHz to the heater of the gas sensor. It senses methane gas of sufficient concentration (0.8 - 1.2%), the gas sensor produces a voltage when compared with a reference voltage to actuate two alarm oscillators, one of which actuates an audible horn circuit and the other of which actuates a visual flashing-light signal circuit.
The drawbacks of the above said patent number: US3879717 is that the system is designed for methane monitoring and alarming system. The system is not work in normal 110 V AC power supply of mine and also not capable of power cut-off system in particular hazardous areas of underground mines. The system has no high brightness alphanumeric LED display unit for long distance viewing of methane concentration. The system does not contain remote read out unit facility to view instrument’s reading at a safe place away from unsafe monitoring locations. It is not capable of data storing and recording. The system does not use infrared sensor, hence it can’t provide accurate measurement during continuous monitoring over a longer duration due to inherent limitations of the used sensor.
Reference may be made to patent number: JP57100338 entitled “Monitoring system for gas”, wherein a system has been described and claimed for monitoring gases in a semi-closed space. The system uses a single laser beam passage. By passing the laser beam through the area to be monitored, the system detects the variation of absorbed quantity of infrared rays of this laser beam. The system uses a spectroscopic analyser to measure the methane concentration.
The drawbacks of the above said patent number: JP57100338 is that the system is specially designed for monitoring methane in semi-closed space. The system cannot continuously monitor methane concentration present in mines. The system is not capable of alarming and switching off power of a particular hazardous area. The system is not intrinsically safe for using in hazardous mining environment.
Reference may be made to patent number: US4870025 entitled “Method of sensing methane gas-I”, wherein a system has been described and claimed for sensing methane gas. The system uses electrically interconnecting platinum and palladium catalysts to obtain an electrical output reading, electrically interconnected catalysts to a temperature in a range from 350-450°C. Passing the gas stream over electrically interconnected catalysts, methane gas contained in the gas stream being oxidized only by palladium catalyst while all other oxidisable components of the gas stream being oxidized by both catalysts, whereby palladium catalyst will be heated to a temperature proportionately higher than platinum catalyst based on the percentage of methane gas contained in the gas stream.
The drawbacks of the above said patent number: US4870025 is that the system is not designed for continuous monitoring of methane. The system is not work in normal 110 V AC power supply of mine. It has no alarming system and no power cut-off system for a particular area where methane concentration exceed its permissible limit.
Reference may be made to patent number: GB1111951 entitled “Mine gas determination apparatus including radio transmitting and receiving equipment for sending monitoring signals”, wherein a system has been described and claimed for monitoring gases and radio transmission in underground mine. The mine gas determination apparatus comprising a mobile instrument with a coupled radio transmitter in which reception of signal by a receiving unit causes an associated transmitter to send a message received signal on another frequency to the transmitting unit concerned.
The drawbacks of the above said patent number: GB1111951 is that the system is specially designed for monitoring gases and radio communication only. The system is not able to cut-off the power supply of the particular area of an underground mine to prevent methane explosion. The system does not use infrared sensor, hence it can’t provide accurate measurement during continuous monitoring over a longer duration due to inherent limitations of the used sensor.
Reference may be made to an Indian patent application numbers: 174/DEL/95 entitled “A data acquisition system useful for underground mines” and 149/DEL/2003 entitled “A multi-channel intrinsically safe real time environmental monitoring system for underground mines”, wherein systems have been described and claimed for acquisition of environmental data from underground mines. The systems are capable of providing real-time monitoring of different environmental parameters such as temperature, air velocity, machine status, methane, carbon monoxide at a plurality of locations in an underground mine. The systems provide on-line visual representation of trend of all the monitored parameters and give audio-visual warning signal when a particular parameter crosses the respective threshold limit.
The drawbacks of the above said patent application numbers: 174/DEL/95 and 149/DEL/2003 are that the systems specially designed for monitoring environmental parameters from surface only. The systems are not portable and hence cannot be placed in any desired location in a gassy underground mine. The systems are incapable of switching off the power supply of the particular area of an underground mine when methane concentration exceeds the permissible limit to prevent methane explosion.
Reference may be made to an Indian patent application number: 1320/DEL/2007 entitled “Portable gas monitoring and power cut-off system for underground mines”, wherein a system has been described and claimed for a portable system to use in hazardous gassy underground mine environment, characterized in that it comprises in combination an intrinsically safe multi-channel environmental monitoring unit, an automatic power cut-off unit and an intrinsically safe power supply unit. The system is capable to monitor gases continuously in underground mine, and automatically cut-off power supply of the particular area in an underground mine when concentration of methane exceeds more than the permissible limit at two or more sensor locations.
The drawbacks of the above said patent application number: 1320/DEL/2007 is that the system is it does not use infrared sensor, hence it can’t provide accurate measurement during continuous monitoring over a longer duration due to inherent limitations of the used sensor. The system has no in-built data storing facility. Further, the system has no alphanumeric high brightness LED display for long distance viewing and remote monitoring.
Reference may be made to patent number: US4606219 entitled “Gas detectors”, wherein a system has been described and claimed for a gas detector which comprises a housing, a gas cell transducer mounted in the housing, an electrical monitoring circuit supported in the housing and electrically connected to the transducer which is arranged to produce signals corresponding to the electrical characteristic of the transducer, and a remote control station electrically connected to the monitoring circuit which supplies power to the monitoring circuit and receives the monitoring signals indicative of the concentration of the gas, the monitoring circuit including circuit meant for producing monitoring signals. The monitoring circuit will cause an indication at the remote control station of a dangerous gas concentration having a maximum value when the concentration of gas is at a predetermined minimum, and which reduces value as the concentration of gas increases toward a predetermined maximum.
The drawbacks of the above said patent application number: US4606219 is that the systems are specially designed for detection of carbon monoxide concentrations in the housing. The system is not designed to detect methane in underground mine. The systems are incapable of switching off the power supply of the particular area of an underground mine when methane concentration exceeds the permissible limit to prevent methane explosion.
Reference may be made to patent number: CN1096846 entitled “Gas monitoring and controlling system”, wherein a system has been described and claimed for monitoring gases and automatically turned off the outer equipment when a certain gas density is reached. The system comprises monitor and controller. In the monitor, the sensor in the gas chamber transfers the gas density into electric signal, which is amplified, and voltage and current value is transformed to drive meter to indicate the gas density. In case that a signal gas density reached, the monitor gives voice, acoustic and optical alarm. The electric signal fed to controller is received by ground receiver or microcomputer. When a certain gas density is reached, the outer equipment is turned off automatically.
The drawbacks of the above said patent number: CN1096846 is that the system is specially designed to monitor gases and generate audio-visual alarm. The system is not able to cut-off the power supply of the particular area of an underground mine to prevent methane explosion. The system is not able to store data and work in available 110 volt AC power supply in mines. The system does not use infrared sensor, hence it can’t provide accurate measurement during continuous monitoring over a longer duration due to inherent limitations of the used sensor.
Reference may be made to patent number: US4567366 entitled “Method and apparatus for measuring methane concentration in gas”, wherein a system has been described and claimed for measuring the methane concentration in a gas, transmitting light having at least one wavelength band selected from a band of 1.6 µm and a band of 1.3 µm through an optical fiber having a small transmission loss in wavelength bands to a measuring cell where a gas whose methane concentration is to be measured passes in and out, separating the light into at least one light having the methane gas absorption wavelength, to be measured, and at least two lights having other reference wavelengths, determining the intensity ratio of the light having the wavelength to be measured to the lights having the reference wavelengths, and calculating the methane gas concentration in the measuring cell.
The drawbacks of the above said patent application number: US4567366 is that the system is specially designed for measuring the methane concentration in a liquefied natural gas tanker, or a small pit of a coal mine. The systems are incapable of switching off the power supply of the particular area of an underground mine when methane concentration exceeds the permissible limit to prevent methane explosion and there is no alarming system.
Reference may be made to patent number: US20080029702 entitled “Method and apparatus for detecting methane gas in mines”, wherein a system has been described and claimed for remotely detecting concentration and distribution of methane gas in mines. The system consists of one tenable laser source wherein the wavelength of source can be tuned across one of methane optical absorption peaks, and photons of the laser source are emitted towards mine walls; at least one light detection device, wherein photons reflected from mine walls are collected and converted into electronic signals; one signal process and control unit, operatively in connection with optical source and light detection device, for analyzing signals with tuneable laser spectroscopy technology and tomography algorithms, and determining existence, concentration and distribution of methane gas in mine.
The drawbacks of the above said patent number: US20080029702 is that the system is designed for instantaneous methane detection in mine. The system is not capable for continuous monitoring of methane concentration present in mine atmosphere. The system has no features of switching off the power supply of the particular area of an underground mine when methane concentration exceeds the permissible limit, and also there is no alphanumeric high brightness LED display for long distance viewing as well as no loud audio alarm system.
Reference may be made to patent number: US4064498 entitled “Electrical circuitry for detecting a combustible mixture of gas in a mine atmosphere”, wherein a system has been described and claimed for electrical circuitry for detecting a combustible mixture of gas in a mine atmosphere, that operates continuously at selected locations in the mine for a selected time interval to generate output signals that are proportional to concentration of combustible gas in the mine atmosphere and actuate an alarm device when an undesirable condition occurs.
The drawback of the above said patent number: US4064498 is that the system is not portable and continuous methane gas detection in underground mine is not possible by the electrical circuitry. The system has no data storing facility. It has no arrangement to view instrument’s reading at a safe place away from hazardous monitoring location as well as no high brightness visual alarm system for long distance viewing.
Reference may be made to patent number: US3104320 entitled “Apparatus for gas analysis”, wherein a system has been described and claimed for an ionisation chamber for gas analysis comprising of a hollow body defining a cavity, an electric terminal contends of cavity for holding a radioactive source of radiation of sheet form against the walls of cavity, a radiation-passing liner spaced inwardly from the walls of cavity, and a gas outlet spaced from gas inlet by cavity. Ionisation chamber that includes a radioactive source of radiation and means for electrically energising an electrode therein, whereby the device may operate as a detector for fluid traces carried by a carrier gas through a chromatography column.
The drawbacks of the above said patent number: US3104320 is that the system does not have the featured of methane detection in underground mine. The system is not capable to store historical database of methane concentration date and time-wise in external memory device. The system is not capable of switching off the power supply of the particular area of an underground mine when methane concentration exceeds the permissible limit to prevent methane explosion.
Reference may be made to patent number: US3496558 entitled “Methane and coal dust detection”, wherein a system has been described and claimed for a light source and an oppositely disposed photoelectric cell are located adjacent to throat of venturi and are used to determine quantity of coal dust present in the sampled air as measured by the quantity of light reaching the photocell. A gas detector located within the venturi accommodates measurement of the amount of methane in the air passing through the venturi as measured by the change in resistance of the detector filament as methane contacts the filament surface within a shielded region of the gas detector.
The drawbacks of the above said patent number: US3496558 is that the system is not portable and continuous methane monitoring in underground mine is not possible. The system is not capable of work in normal 110 V AC power supply available in mine and also not capable of power cut-off in particular hazardous areas of underground mines where methane concentration exceeds the permissible limit to prevent explosion in underground mine. There is no loud audio and high brightness visual alarming arrangement for long distance viewing.
Reference may be made to patent number: US3714421 entitled “Gas detector and analyzer”, wherein a system has been described and claimed for a portable, self-contained gas detector and analyzer. It includes a carrier gas supply, and electrical power supply, a sampling loop and a chromatographic column with an electron-capture detector. A preferred embodiment is adapted to respond to a pre-selected tracer gas. If the tracer is included in a closed system whose integrity is suspect, the detector can first be operated to detect the presence of the tracer and then can signal the rate at which the tracer is being provided to a predetermined and limited volume.
The drawbacks of the above said patent number: US3714421 is that the system designed is based on chromatographic column with electron-capture detection in mine. The system has no facility of high brightness visual and audible alarming arrangement to alert the miners. The system has no facility for viewing instrument’s reading at a safe place away from hazardous monitoring location. The system can’t work in normal 110 V AC power supply of mine and also not capable of power cut-off arrangement in a particular hazardous area of underground mine.
Reference may be made to patent number: US 4063895 entitled “Methane analyser”, wherein a system has been described and claimed for passing the gas sample through an enclosed space having a source therein emitting light energy including wavelengths approaching but not less than 147 nm at a flow rate sufficiently slow to cause any hydrocarbon molecules in the gas sample to attain a super-active state; adding moisture to the gas sample prior to step of passing the gas sample through an enclosed space having a source therein emitting light energy whereby the gas sample will contain a minimum moisture level of 2% saturated vapour pressure.
The drawbacks of the above said patent number: US4063895 is that the system is not capable of continuous monitoring of methane concentration in underground mines. The system is not capable of switching off the power supply of the particular area of underground mine when methane concentration exceeds the permissible limit to prevent methane explosion. It is not capable of storing historical database of methane concentration date and time-wise in external memory device.
The main objective of the present invention is to develop a local methane detector for continuous monitoring of methane gas concentration in underground coal mines, and provide a portable system for improving miner’s safety, which obviates the drawbacks of the hitherto known prior art as detailed herein above.
Another objective of the present invention is to provide measurement of methane gas level upto 10%, which can further be enhanced upto 100% as per the requirement of user.
Still another objective of the present invention is to provide an infrared (IR) sensor for accurate and continuous measurement of methane gas concentration throughout long life of around 5 years.
Yet another objective of the present invention is to provide an intrinsically safe (IS) system with ingress protected enclosure for continuous operation in hazardous areas.
Still yet another objective of the present invention is to provide a remote read out unit to view instrument reading at a safe place away from unsafe monitoring location upto a distance of 1 km via digital interface.
Further objective of the present invention is to provide a detachable battery power supply of 5 days backup in addition to normal 110 volt power supply of mine so that the system can operate in highly explosive area, where normal power is not available or restricted.
Still further objective of the present invention is to provide a suck-in fan arrangement to suck the air inside instrument’s sensor chamber for representative monitoring of methane gas available in underground mine atmosphere.
Yet further objective of the present invention is to provide a data storing facility which can record methane concentration with date and time-wise for further analysis as and when required.
Still yet further objective of the present invention is to provide an extension port facility for transferring recoded readings into other memory device for subsequent transferring of data to surface computer to analyse variation of methane concentration during different working periods.
Another objective of the present invention is to provide a password protected keypad arrangement for set-reset features such as cut-off point, recording interval etc. as per the site specific user requirement.
Still another objective of the present invention is to provide a liquid crystal display (LCD) unit for continuous observation of parameter of its different sub-units, and also provide a high brightness alphanumeric light emitting diode (LED) display for long distance viewing of methane concentration reading.
Yet another objective of the present invention is to provide a loud audio and good quality visual alarm for providing evacuation warning to the miners working in highly explosion prone area.
Still yet another objective of the present invention is to provide a relay for power cut-off in underground mines when concentration of methane exceeds the permissible limit to prevent explosion in underground mine.
Local methane detector (LMD) for hazardous area of the present invention is a portable system for continuously monitoring methane gas in underground coal mine and power supply cut-off when concentration of methane exceeds more than the permissible limit, which is controlled by infrared methane sensor, microcontroller unit and relay. The present invention is provides a suck-in fan for sucking the air inside the instrument’s sensor chamber from underground mine atmosphere and where an infrared sensor continuously sense of available methane gas level in the said chamber. The loud audio alarm and visual display are used for providing evacuation warning to miners when methane gas concentration above its permissible limit which is controlled by said microcontroller unit. The system cut-off the power supply in case of methane concentration reaches the explosion limit, which ultimately prevent methane explosion in gassy underground mine, and saves valuable life and property. The system is portable, intrinsically safe, 5 days battery backup with an additional intrinsically safe power supply for normal 110 volt AC supply operation in underground coal mines, and can be used in gassy underground mine. A remote read out unit is provided for viewing instrument’s reading at a safe place away from unsafe monitoring location upto a distance of 1 km via digital interface. The system has a storing facility which can record the methane concentration with date-time for further analysis as and when required. The system is integrated with intrinsically safe power supply for long term use in underground mine without the need or frequent replacement of batteries.
The present invention is illustrated in figures 1 to 4 of the drawings accompanying this specification. In the drawings is described local methane detector for hazardous areas.
Figure 1 represents the block diagram of local methane detector for hazardous areas wherein the intrinsically safe power supply with battery backup unit (PBU) is connected to power board (PB) of microcontroller unit (MC), the microcontroller unit (MC) is sequentially connected to infra-red methane sensor (MS), memory unit (M), fan seed controller (FC), Fan (FN), alarm unit (AU) and display unit (DU).
Figure 2 represents the ingress protected enclosure of the local methane detector for proper working in hazardous areas, and enhancing durability of electronics components and circuits, infrared sensor and battery which are placed inside the enclosure. The enclosure system consist of different parts (1) to (8) for measuring and controlling methane gas present in hazardous areas and underground mines.
Figure 3 represents the schematic diagram of the remote read-out unit for viewing instrument’s reading at a safe place away from unsafe monitoring location. The remote read out consist of different parts (9) to (10) to view LMD reading at a safe place away upto 1 km from unsafe monitoring location.
Figure 4 represents the functional keypad diagram of the LMD system. The keypad arrangements consist of different function keys (S1, S2, S3, S4, S5 and S6) for operation of LMD system.
The details of the figures 1 to 4 of the drawings are given below:
Figure 1 represents the block diagram of local methane detector for hazardous area is a portable methane gas monitoring and power cut-off system, wherein the intrinsically safe input power having 110 V AC with 6 V battery backup unit (PBU) is connected to power board (PB). The said power board (PB) is connected to the voltage regulator (VR) of 3.7 V output. The said power board (PB) is also connected to a 3.7 V lithium ion battery for power supply to real time clock. The output of the said voltage regulator (VR) is sequentially connected to microcontroller (MC), infra-red methane sensor (MS), memory unit (M), fan seed controller (FC), fan (FN), alarm unit (AU) and display unit (DU). The remote read out (RU) is wirelessly connected to the local methane detector system.
Figure 2 of the drawings shows the ingress protected enclosure of the local methane detector system used for proper working in hazardous areas and improving durability of electronics components and circuits as well as infrared sensor and battery which are placed inside the enclosure. The local methane detector system for hazardous areas consist of different parts: ingress protected enclosure body (1), keypad (2), loud audio alarm unit (3), liquid crystal display (4), suck-in fan (5), instrument’s gas sensor chamber (6), visual alarm (7), and LED display (8). The keypad (2) is fitted at the side of ingress protected enclosure body (1). The loud audio alarm unit (3) is fitted on top of the said enclosure (1). The said ingress protected enclosure body (1) are fitted with keypad (2), loud audio alarm unit (3), liquid crystal display (4), suck-in fan (5), instrument’s gas sensor chamber (6), visual alarm (7) and LED display (8).
Figure 3 of the drawings shows schematic diagram of the remote read-out unit for viewing instrument’s reading at a safe place away from unsafe monitoring location. The electronic circuit and battery are enclosed in a fiber box (11). The antenna (9) and LCD screen (10) is fitted on said fiber box (11).
Figure 4 of the drawings shows the functional keypad diagram of the LMD system. The keypads arrange on a printed circuit board consists of different function keys: power on/off (S1), LED on/off (S2), menu (S3), up key (S4), down key (S5), and save/exit (S6). The functional keypad has power on/off (S1), LED on/off (S2), menu (S3), up (S4), down (S5), and save/ exit (S6) keys which are mounted on printed circuit board.
Accordingly present invention provides local methane detector for hazardous areas which comprises a portable system for continuous monitoring of methane gas present in hazardous mine area, characterized in that it comprises in combination an intrinsically safe, automatic evacuation warning with continuous methane gas level indication in a high brightness alphanumeric LED visual display, and power cut-off unit.
In an embodiment of the present invention, the local methane detector for hazardous areas is capable of continuously monitoring methane gases in underground mines, and improving miner’s safety wherein the system comprises in combination of an intrinsically safe input power (IP) having 110 V AC being connected to power supply with battery backup (PBU); the said power supply with battery backup (PBU) being connected to power board (PB); the said power board (PB) being connected to the voltage regulator (VR) of 3.7 V output; the said power board (PB) being also connected to a 3.7 V lithium ion battery for power supply to real time clock; the output of the said voltage regulator (VR) being sequentially connected to the microcontroller unit (MC), infra-red methane sensor (MS), memory unit (M), fan seed controller (FC), Fan (FN), alarm unit (AU) and display unit (DU); and the remote read out (RU) being wirelessly connected to the local methane detector.
In another embodiment of the present invention, the portable system is provided for measurement of methane gas level upto 10%, which can further be enhanced to upto 100% as per the requirements of user.
In still another embodiment of the present invention, the infrared (IR) sensor is provided for accurate and continuous measurement of methane gas concentration throughout long life of around 5 years.
In yet another embodiment of the present invention, the intrinsically safe system with ingress protected enclosure is provided for continuous operation in hazardous areas.
In still yet another embodiment of the present invention, the remote read out unit is provided for viewing instrument reading at a safe place away from unsafe monitoring location upto a distance of 1 km via digital interface.
In further embodiment of the present invention, the detachable battery power supply of 5 days backup in addition to normal 110 volt power supply of mine is provided for the system, so that it can operate in highly explosion prone area, where normal power is not available or restricted.
In still further embodiment of the present invention, the suck-in fan arrangement is provided for sucking air inside instrument’s sensor chamber for representative monitoring of methane gas available in underground mine atmosphere.
In yet further embodiment of the present invention, the data storing facility is provided for recording methane concentration with date and time-wise for further analysis as and when required.
In still yet further embodiment of the present invention, the extension port facility is provided for transferring recoded readings into other memory device for subsequently transferring data to surface computer to analyse variation of methane concentration during different working periods.
In a further embodiment of the present invention, the password protected keypad arrangement is provided for set-reset of features such as cut-off point, recording interval etc. as per the site specific user requirement.
In a still further embodiment of the present invention, the liquid crystal display unit is provided for continuous observation of different sub-units’ parameter, and also high brightness alphanumeric LED display is provided for long distance viewing of methane concentration reading.
In a yet further embodiment of the present invention, the loud audio and good quality visual alarm is provided for evacuation warning to the miners working in highly explosion prone area.
In a still yet further embodiment of the present invention, the relay is provided for power cut-off of particular area in underground mine when concentration of methane exceeds the permissible limit to prevent explosion in underground mine.
In the present invention there is provided a local methane detector for use in hazardous areas of underground mine atmosphere, particularly for continuous methane gas monitoring in underground mine, automatically evacuation warning to miners and cut-off power supply of a particular area of an underground mine when concentration of methane exceeds the permissible limit to prevent explosion and save valuable human life. The LMD system consists of intrinsically safe input power having 110 V AC, which supplies power to the voltage regulator (VR) of power board (PB). The constant output (3.7 V) of the said voltage regulator (VR) is feed to microcontroller (MC), infra-red methane sensor (MS), fan speed controller (FC), fan (FN), alarm unit (AU) and display unit (DU). The said power board (PB) has a 3.7 V lithium ion battery for supplying power to real time clock. The said suck-in-fan (FN) sucks mine atmospheric air and store in the instrument’s gas sensor chamber (6). The said infra-red methane sensor (MS) senses methane gas level present inside the said instrument’s gas sensor chamber (6) and pass the signal into the DC amplifier (DA). The said DC amplifier (DA) amplifies DC signal and transmits the same to LCD display (4) and LED display (8) units for showing the corresponding output voltage of respective amplifiers. The remote read out unit shows the concentration of methane gas present in underground mines at safe place away from monitoring location. If the permissible set value of methane gas level exceeds, then the system indicates the same by blowing the LCD display (4), LED display (8) units and generating loud audio alarm (3) simultaneously. In this situation, the microcontroller system (MC) will automatically switch off the main power supply through the relay of auto-power cut-off unit.
In a physical embodiment of the local methane detector for hazardous areas of the present invention specification of different units of the system are given below, however, equivalent components can also be used wherever required.
In physical embodiment of a local methane detector for hazardous area of the present invention the specification of the different component of the system are given below.
Local methane detector as shown in figure (1): 6 V rechargeable battery, step down transformer 12-0-12 V, diodes IN5408 and IN 4007, regulators IC-7806, IC-7809, IC-7812, IC-7912 and IC-7812. Infrared methane sensor having measuring range 0 to 10%, which can be enhanced upto 100%.
The novel features of the portable local methane detector system for hazardous area of the present invention have been realized by the non-obvious inventive steps of integrating the multi-channel real-time system with continuous monitoring of methane gas concentration, high brightness alphanumeric visual and loud audio evacuation warning technique, automatic power cut-off mechanism and intrinsically safe power supply unit for use in gassy underground mines.
The novelty of the present invention with respect to the prior art are:
1. Capable of continuous gas monitoring, which can be placed anywhere in an underground mine and can be shifted easily to other required locations.
2. Capable of accurately measurement of methane gas level upto 10%, which can be further enhanced upto 100% based upon the requirement of user.
3. Capable of continuously monitoring methane gas concentration present in underground mine using infrared methane sensor which has electrical output.
4. Capable of precisely operating in hazardous areas as the system is intrinsically safe with ingress protected enclosure and can be used in gassy underground mines.
5. Capable of wirelessly transmit instrument data to remote read out unit for viewing instrument’s reading at a safe place away from unsafe monitoring location upto a distance of 1 km via digital interface.
6. Capable of providing long power backup using a detachable battery power supply of 5 days backup in addition to normal 110 volt power supply of mine.
7. Capable of efficiently sucking of mine atmospheric air into instrument’s gas sensor chamber for representative monitoring of methane gas available in underground mine atmosphere.
8. Capable of storing data which can record methane concentration with date and time-wise for further analysis as and when required.
9. Provision of extension port facility for transferring recoded data into other memory device and further analysing variation of methane concentration during different working periods in surface computer.
10. Provision of password protected keypad arrangement for set-reset of features such as cut-off point, recording interval etc. for safety purpose.
11. Provision of long distance vision for viewing instrument current reading using a high brightness alphanumeric LED and LCD display units.
12. Capable of providing evacuation warning to the miners working in highly explosion prone area using loud audio and good quality visual alarm.
13. Capable of continuously monitoring gases in underground mine, and automatically cut-off power supply of the particular area in an underground mine when concentration of methane exceeds the permissible limit.
Use of a local methane detector system for hazardous area of the present invention should be done as follows:
The local methane detector system for hazardous area is especially designed for continuous detecting and monitoring of methane gas present in underground mine or hazardous area. The system placed in safe distance from a working face of a gassy underground mine wherein the system accurately detect methane gas concentration by an infrared methane sensor. The available 110 V AC power supply is connected to the input of intrinsically safe power with backup unit (PBU) of the invented system through armoured cable. The auto-power cut-off unit is connected with nearby power supply unit of the mine. The system continuously measures the concentration of methane gas and displays the respective concentration value in alphanumeric LED and LCD display unit, and stores data of methane concentration with date-time wise in a memory device. This data also shows in remote read out unit place at a distance 1 km away from monitoring location. When concentration of methane gas level exceeds its permissible limit, the system immediately gives loud audio and visual evacuation warning to miners and simultaneously automatic cut-off power supplies of the particular area of an underground mine.
The following examples are given by way of illustration of the working of the invention local methane detector for hazardous area in actual practice and therefore should not be construed to limit the scope of the present invention.
Example – 1
The local methane detector system for hazardous area of the present invention first experimented at laboratory with simulated conditions. The system was supplied with 110V AC power supply and operated for long time. Then simulated voltage was connected with the microcontroller unit, infrared methane sensor and detecting unit and it displays the corresponding concentration of methane gas in the alphanumeric LED and LCD display unit. This data also shows in remote read out unit place at a distance 1 km away from LMD system. Then high voltage was applied to the methane sensor than the rated voltage. The system indicated the high value by lighting the LED and LCD display unit, generated loud audio alarm in the alarm unit, and simultaneously the system disconnected the power supply of the fan by energizing the connected relay.
Example – 2
The experiment was also performed with the present invented system by using infrared methane sensor and calibrated methane gas containers. The intrinsically safe power supply (PS) of the system was connected with the 110V AC power line and the sensors were connected with the IP unit. The relay of the system was connected with the main power supply of the laboratory. The system was operated for long time. Different known methane gases concentrations were given near the instrument’s sensor chamber and the system displayed the concentration with 96-99% of accuracy. When gas concentration above the permissible limit (1.5% for CH4) was applied to the CH4 infrared sensor, the system showed the same by glowing the LED and LCD displays, and generating loud audio alarm. The system reading showed in the read out unit placed at a distance 1 km from the laboratory. When gas concentrations above the permissible limit were given in infrared sensor, the system switched off the power supply of the laboratory by the connected relay. Few experimental data of methane sensors are shown in Table-I.
Table-I: Experimental data
Sl. No. Known concentration of methane gas cylinder feed to the sensor Measured concentration of methane by the local methane detector Guideline for threshold limit values (TLVs)
1 1.5% 1.5% At 1% isolate electricity, at 2% remove personnel.
2 2.5% 2.5%
3 5.0% 5.0%
4 8.0% 8.0%
5 10.0% 10.0%

Local methane detector system for hazardous area of the present invention essentially enabled continuously monitoring of methane concentration and stored instrument readings in a memory device, and provided audio-visual alarm and subsequently automatically cut-offs power supply of the particular area when concentration of methane exceeded the permissible limit. The system was capable of monitoring methane gas using IR sensor, which had electrical output. The system is portable having a battery backup and intrinsically safe for using in any locations of gassy underground mines.
Therefore, it is conclusively shown that the novel features enabled by the inventive steps of the local methane detector for hazardous area of the present invention essentially proved useful for the mine management for improving safety and saving valuable human lives and property.
The main advantages of the local methane detector system for hazardous area of the present invention are:
1. The system easily portable, which can be placed anywhere in an underground mine and can be shifted easily to other required locations.
2. The system accurately measures methane gas level upto 10%, and which can be easily enhanced upto 100% based upon the requirements of user.
3. The system continuously measures methane gas concentration present in hazardous area using infrared methane sensor which has electrical output.
4. The system precisely operates in hazardous areas, which is intrinsically safe and can be used in gassy underground mines.
5. The system wirelessly transmits instrument data to a remote read out unit for viewing instrument’s reading at a safe place away from unsafe monitoring location upto a distance of 1 km via digital interface.
6. The system provides long power backup using detachable battery power supply of 5 days in addition to normal 110 volt power supply of mine.
7. The system sucks mine atmospheric air inside the sensor chamber to monitor methane gas concentration available in underground mine.
8. The system stores methane concentration reading with date and time-wise in working period for further analysis as and when required.
9. The system provides an extension port facility for transferring recorded readings into other memory device to analyse variation of methane concentration during different working periods.
10. The system provides a secure password protected keypad arrangement for set-reset features such as cut-off point, recording interval etc. for safety purpose.
11. The system clearly displays instrument reading data using high brightness alphanumeric LED and LCD display units which helps in long distance vision.
12. The system provides loud audio and good quality visual alarm when respective parameter crosses its permissible limit.
13. The system continuously monitors methane gas, and automatically cut-offs power supplies of the particular area in an underground mine when concentration of methane exceeds the permissible limit.

CLAIMS:
We claim:
1. A local methane detector for hazardous area continuously monitors methane gas in underground gassy mine and provides automatically audio-visual evacuation warning and subsequently cut-offs power supply of the particular area in an underground mine when concentration of methane exceeds the permissible limit; it comprises in combination of an intrinsically safe methane gas monitoring unit, an automatic power cut-off unit and an intrinsically safe power supply unit; whereas the said intrinsically safe input power (IP) having 110 V AC being connected to power supply with battery backup (PBU); the said power supply with battery backup (PBU) being connected to power board (PB); the said power board (PB) being connected to the voltage regulator (VR) of 3.7 V output; the said power board (PB) being also connected to a 3.7 V lithium ion battery for power supply to real time clock; the output of the said voltage regulator (VR) being sequentially connected to the microcontroller unit (MC), infra-red methane sensor (MS), memory unit (M), fan seed controller (FC), Fan (FN), alarm unit (AU) and display unit (DU); and the remote read out (RU) being wirelessly connected to the local methane detector.
2. A local methane detector for hazardous area, as claimed in claims 1, wherein the infrared methane sensor (MS) with intrinsically safe circuit, which continuous measures methane gas level upto 10%, which can be enhanced upto 100% as per the requirements of user.
3. A local methane detector for hazardous area, as claimed in claims 1-2, wherein the remote read out system is provided, which shows the corresponding instrument’s reading at a safe place away from unsafe monitoring location upto a distance of 1 km via digital interface.
4. A local methane detector for hazardous area, as claimed in claims 1-3, wherein the detachable battery power supply is provided in addition to normal 110 V AC power supply of mine so that the system can operate in highly explosive area with 5 days backup where normal power is not available or restricted.
5. A local methane detector for hazardous area, as claimed in claims 1-4, wherein the suck-in fan arrangement is provided, which sucks mine atmospheric air inside instrument’s gas sensor chamber for accurate monitoring of methane gas available in underground mine.
6. A local methane detector for hazardous area, as claimed in claims 1-5, wherein the data storing facility is provided, which records methane concentration with date and time-wise for further analysis as and when required.
7. A local methane detector for hazardous area, as claimed in claims 1-6, wherein the system password protected keypad arrangement is provided, which set-resets different features such as cut-off point, recording interval etc. as per the site specific user requirement.
8. A local methane detector for hazardous area, as claimed in claims 1-7, wherein the LCD and high brightness alphanumeric LED display unit are provided, those continuously display different parameters and enable long distance vision of methane concentration readings.
9. A local methane detector for hazardous area, substantially as herein described with reference to the examples and drawing accompanying this specification.

Dated this ____________day of _________________ 2017.

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SCIENTIST
Intellectual Property Management Division
Council of Scientific & Industrial Research