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A 19 m long small-scale model representing a mine gallery has been designed and constructed at the Central Mining Research Institute in India to study the complex phenomenon of open fires in simulated underground mine conditions. It comprises a 10 m brick-lined rectangular segment of internal cross-section 13 x 13 cm and a 9 m circular section of 30 cm diameter. Two sets of experiments were carried out at air velocities of 1.0 and 1.5 m/s: a fire was artificially started at one end of a zone of coal lining blocks and governing parameters such as gas concentration, temperature, pressure drop across the fire zone, air velocity and dust concentration were continuously monitored for 8-9 h. Conclusions are presented regarding the rates of CO, CO2 and heat generation, the occurrence of explosions and the throttling effect of ventilation., A 19 m long small-scale model representing a mine gallery has been designed and constructed at the Central Mining Research Institute in India to study the complex phenomenon of open fires in simulated underground mine conditions. It comprises a 10 m brick-lined rectangular segment of internal cross-section 13 x 13 cm and a 9 m circular section of 30 cm diameter. Two sets of experiments were carried out at air velocities of 1.0 and 1.5 m/s: a fire was artificially started at one end of a zone of coal lining blocks and governing parameters such as gas concentration, temperature, pressure drop across the fire zone, air velocity and dust concentration were continuously monitored for 8-9 h. Conclusions are presented regarding the rates of CO, CO2 and heat generation, the occurrence of explosions and the throttling effect of ventilation.

Knowledge of the air permeability of individual pillars can contribute to the prevention or control of fires caused by spontaneous combustion within the pillars. A methodology is presented by which permeability can be determined using specially designed sampling pipes, through which air samples can be drawn at varied known pressures following leak-proofing of the surface area around the pipe hole. Average coefficients for air permeability and air-leakage rate were calculated for eight holes drilled in a pillar., Knowledge of the air permeability of individual pillars can contribute to the prevention or control of fires caused by spontaneous combustion within the pillars. A methodology is presented by which permeability can be determined using specially designed sampling pipes, through which air samples can be drawn at varied known pressures following leak-proofing of the surface area around the pipe hole. Average coefficients for air permeability and air-leakage rate were calculated for eight holes drilled in a pillar.

Stoppings, of vital importance for effective ventilation and isolation of areas susceptible to fire, are generally made of brick in cement mortar but may be very hard to build in inaccessible areas. A methodology adopted in Indian mines to make underground plugs through boreholes from the surface is outlined and the experimental procedure for measuring air leakage described. Data from the Jambad and Kajora seams at Moira and the Niga seam at Kuardi 11/12 colliery, Eastern Coalfields, shows that in the case of poorly constructed stoppings as much as 27.5% of outbye air was leaking to return through only six stoppings. A remotely placed cement concrete plug had far less leakage than even well-built stoppings when pressure differences were below 140 Pa, though further treatment would be required if high pressure differences were likely to be applied., Stoppings, of vital importance for effective ventilation and isolation of areas susceptible to fire, are generally made of brick in cement mortar but may be very hard to build in inaccessible areas. A methodology adopted in Indian mines to make underground plugs through boreholes from the surface is outlined and the experimental procedure for measuring air leakage described. Data from the Jambad and Kajora seams at Moira and the Niga seam at Kuardi 11/12 colliery, Eastern Coalfields, shows that in the case of poorly constructed stoppings as much as 27.5% of outbye air was leaking to return through only six stoppings. A remotely placed cement concrete plug had far less leakage than even well-built stoppings when pressure differences were below 140 Pa, though further treatment would be required if high pressure differences were likely to be applied.

Conventional methods of improving ventilation in many Indian coal mines are risky because of problems such as shallow depth, multiple seam workings, and thin partings. Many mines have fire-affected areas connected to different ventilation circuits, and increasing fan pressure to improve air circulation risks reinitiation of heating. To avoid this, the pressure difference between the sealed area and the area outside it must be kept below a critical value. Improvements to the conventional pressure balancing technique in a mine in the Kacchi Balihari colliery of Jharia coalfield, India, have improved the working environment without increasing the risk of fire in the sealed panel. The technique is applicable to other mines with similar conditions., Conventional methods of improving ventilation in many Indian coal mines are risky because of problems such as shallow depth, multiple seam workings, and thin partings. Many mines have fire-affected areas connected to different ventilation circuits, and increasing fan pressure to improve air circulation risks reinitiation of heating. To avoid this, the pressure difference between the sealed area and the area outside it must be kept below a critical value. Improvements to the conventional pressure balancing technique in a mine in the Kacchi Balihari colliery of Jharia coalfield, India, have improved the working environment without increasing the risk of fire in the sealed panel. The technique is applicable to other mines with similar conditions.

Reversing the direction of air flow to isolate a fire is reported to have saved many lives in America but has not been adopted in Indian coal mines, despite it being stipulated in the regulations for both coal and metalliferous mines in India that main mechanical ventilators shall be capable of such reversal. The arrangements for reversal of different fan types are outlined, work carried out in countries outside India reviewed and the law relating to reversal of ventilation in different parts of the world discussed. The effects of reversal on goaf gases and adjustment of air flow from the surface are also considered., Reversing the direction of air flow to isolate a fire is reported to have saved many lives in America but has not been adopted in Indian coal mines, despite it being stipulated in the regulations for both coal and metalliferous mines in India that main mechanical ventilators shall be capable of such reversal. The arrangements for reversal of different fan types are outlined, work carried out in countries outside India reviewed and the law relating to reversal of ventilation in different parts of the world discussed. The effects of reversal on goaf gases and adjustment of air flow from the surface are also considered.

In mines with cracks connected to the surface, improving climatic conditions by increasing fan capacity is a risky proposition. It may lead to spontaneous heating in the mine as a result of leakage from the surface caused by the increase in cumulative pressure drop. A new method of ventilation has been evolved for such situations. It can be superimposed on the existing ventilation system of a mine without much modification or any adverse effect on the ventilation of the remaining districts. The method involves converting the affected area into a chamber by closing cross-connections, installing an axial-flow fan of suitable capacity amd using two regulators of variable aperture to create a pressure difference across the panel and raise the pressure of the chamber to the desired level. Such a system was successfully implemented at the 1&2 Incline, Jhanjra project, India to reduce air leakage from the surface so as to control a fire in a working longwall panel and to improve mine climate., In mines with cracks connected to the surface, improving climatic conditions by increasing fan capacity is a risky proposition. It may lead to spontaneous heating in the mine as a result of leakage from the surface caused by the increase in cumulative pressure drop. A new method of ventilation has been evolved for such situations. It can be superimposed on the existing ventilation system of a mine without much modification or any adverse effect on the ventilation of the remaining districts. The method involves converting the affected area into a chamber by closing cross-connections, installing an axial-flow fan of suitable capacity amd using two regulators of variable aperture to create a pressure difference across the panel and raise the pressure of the chamber to the desired level. Such a system was successfully implemented at the 1&2 Incline, Jhanjra project, India to reduce air leakage from the surface so as to control a fire in a working longwall panel and to improve mine climate.

Nitrogen has a number of advantages over CO2 and combustion gases for fire fighting: CO2 may be absorbed by strata or reduced to CO and is not available in large quantities, which combustion gases need cooling and seriously compromise monitoring of the fire by gas analysis. Nitrogen generators may be based on pressure swing absorption of O2 from air or its diffusion through a semi-permeable membrane. Nitrogen requirements will depend on the rate at which air leaks into the fire area, which can be controlled by equalising pressures in the adjoining mine workings. A number of cases in which nitrogen was injected into Indian coal mines are described, with details of the problems encountered., Nitrogen has a number of advantages over CO2 and combustion gases for fire fighting: CO2 may be absorbed by strata or reduced to CO and is not available in large quantities, which combustion gases need cooling and seriously compromise monitoring of the fire by gas analysis. Nitrogen generators may be based on pressure swing absorption of O2 from air or its diffusion through a semi-permeable membrane. Nitrogen requirements will depend on the rate at which air leaks into the fire area, which can be controlled by equalising pressures in the adjoining mine workings. A number of cases in which nitrogen was injected into Indian coal mines are described, with details of the problems encountered.

A large number of powered supports and other equipment were trapped when part of the roof suddenly collapsed at longwall panel no.3 in Smala seam, Kottadih colliery, India. Out of 83 chock shields, 55 were badly damaged and heating in the panel threatened to cause heavy leakage of hydraulic fluid. Liquid and gaseous nitrogen were infused into the sealed panel through boreholes and pipes already in place and dynamic pressure balancing was used to detect and reduce leakage. The temperature was kept below 40 degrees C and the panel was successfully reopened after 19 days, allowing safe recovery of the undamaged supports and other equipment., A large number of powered supports and other equipment were trapped when part of the roof suddenly collapsed at longwall panel no.3 in Smala seam, Kottadih colliery, India. Out of 83 chock shields, 55 were badly damaged and heating in the panel threatened to cause heavy leakage of hydraulic fluid. Liquid and gaseous nitrogen were infused into the sealed panel through boreholes and pipes already in place and dynamic pressure balancing was used to detect and reduce leakage. The temperature was kept below 40 degrees C and the panel was successfully reopened after 19 days, allowing safe recovery of the undamaged supports and other equipment.

A laboratory study was carried out on coal samples from four different Indian seams. It was found that carbon monoxide emission started at 40 degrees C in all samples and that CO concentration increased and O2 concentration decreased with temperature. Emission of hydrocarbons began only when temperatures reached more than 120 degrees C. Emissions of C1- C4 hydrocarbons may therefore be used to assess the status of fires in sealed panels, whereas CO is the best indicator for early detection of spontaneous heating for Indian coals., A laboratory study was carried out on coal samples from four different Indian seams. It was found that carbon monoxide emission started at 40 degrees C in all samples and that CO concentration increased and O2 concentration decreased with temperature. Emission of hydrocarbons began only when temperatures reached more than 120 degrees C. Emissions of C1- C4 hydrocarbons may therefore be used to assess the status of fires in sealed panels, whereas CO is the best indicator for early detection of spontaneous heating for Indian coals.