METHODS OF FIRE FIGHTING IN UNDERGROUND WORKINGS OF MINES

METHODS OF FIRE FIGHTING IN UNDERGROUND WORKINGS OF MINES

Teaching of Miners in Fire Prevention, and Rescuing, Important—When a Mine on Fire Should Be Sealed and Unsealed

WITHOUT a doubt the most hazardous mine fire to combat is one occurring in a dry, dusty bituminous coal mine, which, in burning, generates explosive gas in the fire area. Fortunately this condition does not exist in Ontario, as we have no coal mines in the province, and a fire in a metal mine is not as hazardous to combat as a fire in a coal mine; explosive gas is rarely found and explosive dust is not a factor in metal mining; the gases given off during metal mine fire however, are generally much more difficult to control because the ventilation in most of such mines is inadequate and poorly controlled.

The methods for attacking a mine fire can only be taught in a general way and no fixed rule can be laid down for the control and extinguishing of every fire; each fire is an original problem.

The principal causes briefly stated may be catalogued as follows: Open lights; smoking; defective wiring; faulty electrical installations; ignition of gas; blasting; (especially when done with black powder) incendiarism and spontaneous combustion.

Miners Taught Fire Fighting, Rescuing, Etc.

It is of course understood, that the best method to fight fires whether on the surface or underground is to prevent them by eliminating every possible hazard, and, as this is an impossible task, the Workmen’s Compensation Board, the Department of Mines and the mining companies have united to produce an efficient organization with the most up-to-date equipment so that the miners can be taught the various methods of fire fighting, rescuing entrapped miners, recovering bodies and recovering the fire area after the fire has been extinguished.

Today, Ontario can boast that, while she has the youngest mine rescue organization on the American continent, it certainly is not the least efficient as more than five hundred men have been trained in the use of mine rescue apparatus.

Methods of Fighting a Mine Fire

Despite all precautions that may be taken to prevent fires, preparation should be made to fight them if and when they occur. The methods of fighting a blaze are:

  1. direct attack with water, chemicals or sand;
  2. flooding the mine or fire area:
  3. inclosing the stricken area with tight seals:
  4. pumping silt into the area and flushing same:
  5. Killing the affected area with an inert gas such as carbon dioxide.

Many mine fires are extinguished in the first or incipient stage by direct attack with water. Failure to fight the blaze successfully by this method is generally due to late discovery, a lack of water or improper attack in the initial stages. If the attempt to control fire in the incipient stage fails, one of the other methods of control is tried, with the exception of using an inert gas. as this is an expensive and often unsuccessful method. The most practical method and the one most often used is by inclosing the fire area with air-tight seals, excluding air and slowly but surely extinguishing the fire through lack of oxygen to support combustion.

Sealing a Fire in Metal Mines

Mine fires should be sealed when progress can not be made by fighting them by direct attack, or when other conditions, such as inaccessibility and dangerous conditions, make sealing necessary. In sealing a fire area in metal mines the seals should be placed as close to the fire as possible. The question of when and how to unseal mine fires is of the first importance to the mining industry as a whole. If a mistake occurs and a seal is opened too quickly the hazard to life and property is increased; and throughout the world, this practice is only too often carried out. The control of fires by scaling and the time an area should remain sealed is firmly established by experience and chemistry with the aid of the chemist fully experienced in the analyzing of fire gases; thus a fairly accurate knowledge is obtained and the opportunity to determine the potential hazard and the best time to unseal the fire area.

When to Unseal a Mine

Scientific study and experience has shown that no attempt should be made to unseal a fire until

  1. the oxygen content of the sealed atmosphere is low enough to prevent any explosion occurring.
  2. Until Carbon monoxide, the combustion indicator has entirely disappeared. to make sure that the area has had sumcient time to cool to minimize the possibility of the fire rekindling when ventilation is resumed.

Some of the factors briefly stated that govern the time to unseal an area are:

  1. Extent and intensity of fire at time of sealing;
  2. Tightness of seals and inelosed area;
  3. Sampling and analysis of the atmosphere under seal.

The extent and intensity of the fire at the time of sealing will have a hearing upon the reduction of the oxygen in the sealed area; for example, a large amount of burning or heated material will reduce oxygen faster but will require longer time to cool; a fire that is active at the time of sealing will cause oxygen to diminish more rapidly than one that is smouldering.

Tight Seals Are Essential

Tight seals are essential for the control of oxygen If possible they should be made of incombustible material such as brick; concrete or tile well hitched into the floor, roof and sides of the drift. Every care must be taken when building these seals, as it is impossible to build one absolutely airtight.

Necessity of Proper Sampling

It is of the utmost importance that proper sampling and accurate analysis be made of the atmosphere behind the seals so that they without a doubt indicate the composition of the gases present. These samples should be collected at least once every twenty-four hours for the first few days later when the analysis shows that the stoppings are tight and the fire is controlled they can be made at longer intervals, every two or three days. Portable field apparatus may be used for the analysis, where extreme accuracy is not essential, as it should be accurate to approximately 0.20 of the per cent of the volume so tested. If greater accuracy is required, the samples should be sent to a laboratory equipped for accurate work, where analysis as close as 0.01 or 0.02 can be made.

(Excerpts from a paper read before the annual convention of the Dominion Association of Fire Chiefs, by Chief R. Mathieson, Kirkland, Ont., Can Excerpts from the first part of this paper, treating of aboveground hazards of a mining camp, was published in the last issue.)

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