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.Track, waterlines, power lines, and phone lines must be investigated for any evidence of flooding, flood damage, smoldering debris, or hot spots in a fire area.Ill.Reestablishing Ventilation After a Fire or ExplosionRestoring ventilation and returning fresh air to a mine area damaged by fire or explosion is the main task of the mine rescue teams in a recovery operation.Once this is accomplished, regular work crews can help with the recovery effort.If the fire area was sealed, it means unsealing the area, assessing the damage, and repairing and rebuilding the ventilation system.If the area was not sealed, the job of reestablishing the ventilation is considerably easier.It involves merely assessing the damage and making the necessary repairs to restore normal ventilation.In an area which has been damaged by an explosion, the task is the same as it is after a mine fire: to assess the damages and to repair the ventilation controls.After an explosion, a great deal of construction work is usually needed to restore ventilation to its proper function.a.Unsealing a Fire Area- Unsealing a fire area requires careful planning.To open the seals prematurely could cause an explosion or reignite the fire.Usually a detailed plan is prepared by company officials, with the, advice of federal, state, and union representatives (when applicable) for unsealing a fire area.Although mine rescue teams do not plan the unsealing operation themselves, it is important for the teams to know what the considerations and options are, as well as the potential problems in unsealing the mine.1.When to Unseal- Determining the exact time to unseal a fire area is based on the laws of physics and chemistry, plus experience and good judgment.A fairly accurate analysis and interpretation of the gases present in the sealed area is possible through the proper sampling techniques and with the assistance of a chemist experienced in mine recovery.Gas conditions and other factors must be evaluated when choosing the safest time to unseal a fire area.The main factors governing the time for unsealing a fire area are:1) The extent and intensity of the fire at the time of sealing.2) The characteristics of the burning material and surrounding strata.3) The tightness of the seals.4) The effect of the barometric pressure on the enclosed area.5) The effect of temperature on the enclosed area.6) The location of the fire area with regard to ventilation.7) The gas conditions as indicated by analysis of the air samples taken from behind the seals.Usually the gases analyzed include: oxygen, carbon monoxide, carbon dioxide, methane, hydrogen, and nitrogen.2.Preconditions for Opening a Sealed Fire AreaNo attempt should be made to unseal a fire area until:1) The oxygen content of the air behind the seal is low enough to make an explosion impossible (no matter what the quality of the combustible gases is behind the seal);2) Carbon monoxide (the gas which indicates combustion) has diminished or disappeared from the air behind the seal; and3) The area behind the seals has been given enough time to cool so when air is again introduced during the unsealing operation, it will not rekindle the fire.Achieving these goals may be difficult and may require a great deal of time.3.Preparations for Opening a Sealed Fire AreaOpening a sealed fire area requires specific preparations:1) Adjustments in ventilation should be made so that toxic and explosive gases released from the sealed area are directed into the main returns.2) Someone should monitor the operation of the main fan to ensure it is operating correctly.If the fan slows or malfunctions, the teams working underground should be withdrawn at once.Gas levels at the main returns should be monitored also.If the fan is electrically driven, precautions should be made to prevent explosive gases from coming in contact with the fan motor or any other electrical equipment used to operate the fan.3) Make checks to ensure that all electrical power in the sealed area was cut off before the unsealing process is begun.Power in the return airways near the sealed area should be locked out.4) In bituminous coal mines, all entries and crosscuts leading to and from the sealed area should be heavily rock dusted, and this should be done for a considerable distance outby the seals to be opened.5) Withdraw all unnecessary personnel from the mine.4.Methods of Unsealing Fire AreasThere are two basic methods for unsealing a fire area: progressive ventilation and direct ventilation.Progressive ventilation is the reventilation of a sealed area in successive blocks by means of air locks.Progressive ventilation is the most common method of unsealing a fire area in coal mines.The advantage of progressive ventilation is that gas conditions can be carefully controlled, and the operation can be stopped at any point if conditions become hazardous.The disadvantage of progressive ventilation is that it is a slow process.Direct ventilation is the reventilation of the entire sealed area done at once.With direct ventilation, recovery is accomplished quicker than it is with progressive ventilation, but gas conditions are less controlled.Before using direct ventilation, there should be conclusive evidence that the fire was extinguished.Direct ventilation must be used to recover mines that have been sealed on the surface [ Pobierz całość w formacie PDF ]