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Fan Ventilation. Fans have long been considered as affording the best method so far discovered, in producing a ventilative current in all kinds of mines; they are found to be far superior to the furnace as a ventilative power, and are now in very general use throughout the State.
In the ventilation of a mine, the action of the fan has the effect of reducing the weight of atmospheric air in the upcast-thus causing the air in the mine to expand by the consequent diminution of its weight in the space occupied. The difference between ventilation with a fan and that of a furnace, is in the method by which the equilibrium of the air in a mine is disturbed; the furnace causes the disturbance by expansion from heat, while the fan causes it from expansion by displacement. The efficiency of a fan depends largely upon its construction and the general surroundings.
There are several fans in use at the larger mines that are doing very effective work, while at other mines not one-fourth of the fanpower expended reaches its destination, owing to leakage through defective doors and stoppings. Still another fruitful cause of waste may be found at mines where the fan is located on top of hoistingshafts, exhausting or forcing (as the case may be) through an air chamber, partitioned off from one end of main shaft, and in the effort to force the air current required through an area much too small for its accommodation, the flow of air is not only greatly retarded, but as the partitions are generally full of holes, much of the air is forced to the surface and lost, never reaching the bottom. Mine bosses are largely responsible for this, as many of them imagine that if a mine is furnished. with a good fan good ventilation is assured, regardless of the surrounding conditions; when, at the same time, if they should take the trouble to investigate and find out the amount of air circulating at the face of the workings, not 25 per cent of the work done by the fan could be detected at the face.
It requires more than a well-constructed and effective fan to secure good ventilation; for without the co-operation of a practical mine manager (though the fan may liberally perform its part), who will see that doors are properly placed, hung and attended to, the airways kept large and clean, and the speed of the fan regulated in accordance with the demands of a mine, the miners cannot hope for a healthy atmosphere to work in.
Doors in Mines. Much can be said concerning the importance of having well-constructed doors placed in mines; for even though the mine is equipped with a powerful fan or furnace for the supply of air, and it has large, clean airways, with a sweeping current of air com
ing down the shafts, yet, unless this air is conducted and circulated around the mine by the use of well-constructed doors, perfection in the other appliances will avail nothing. It is practically impossible to make the doors perfectly air-tight; this being so, their employment occasions serious loss of air, and the loss is still further increased if they are not properly built and carefully hung. For these reasons, doors as much as is possible should be avoided. All doors should be made of heavy lumber, and if pine is used, they should be made double. In hanging doors, care should be taken to have them rest closely against the framing, in order to reduce the leakage as much as possible, and the framing should be inclined for the purpose of having the door close of its own weight. At all important doors a trapper should be employed to open them when required, and to close them immediately after the passage of a trip.
During the past year a number of poorly-constructed doors came under my notice, and not only was this the case, but they were also hung wrong, and having been made of one inch pine lumber, they were continually kept partly open by the force of the air, and from this cause a large quantity of air was permitted to pass to parts of the mine, and in a direction where it was neither wanted or intended it should travel; the result being, that this loss in the volume of air robbed man and beast of the amount of air required and intended for each. Some of the mine bosses, when questioned as to their reasons for hanging doors in such manner as to shut against the air, as a rule replied that it was for the purpose of allowing the mule unaided, when passing with a trip, to open them, and thus avoid the employment of a trapper.
The canvas door has almost entirely disappeared from the main entries, and in many cases they have been replaced by the substitution of substantial wooden doors. Several of the larger mines have made such change in the system of ventilation as to entirely do away with doors on main entries. The least number of doors made use of in a mine, the better the ventilation, and although there will at all times exist a necessity for the use of doors in the distribution of the air. current, yet the excessive use of them can well be avoided by splitting the air into several divisions and carrying the return over the intake by overcasts.
Mine superintendents and bosses should give this important feature of mine management their most earnest attention.
Some very able authors, in writing on mining matters, claim that the safety-catch, under ordinary conditions, creates a false sense of security, and would rather prefer to depend on close inspection and prompt removal of doubtful ropes than on safety-catches. As far as the prompt removal of all poor hoisting ropes is concerned, I fully agree with the able author, as absolute safety is not claimed by the use of the safety-catches, and there is no certainty that they will in. variably stop the falling cage, but are to be considered as extra safeguards that should never be omitted. The fact that the cage is provided with safety-catches does not relieve the engineer of any responsibility he might otherwise feel when hoisting or lowering men in the shaft, nor does it justify the use of doubtful ropes; without them, should the rope break, the cage is certain to go to the bottom, while with the catches on, the chances are greatly against it, and if this is all that can be said in their favor, it is a sufficient reason for their employment and an offset to all objections against them.
Riding up and down through shafts must be acknowledged as dangerous, yet statistics on mine fatalities prove that only one life is lost from the breaking of ropes for every 6,000,000 tons of coal raised in England and in the mines of Europe, where nearly all the coal is hoisted through shafts; and if by the use of safety appliances this ratio of danger can be reduced, it will be almost perfectly safe to ride in shafts.
The law requiring safety-catches upon cages is largely complied with in this State. There are various forms of catches in use, but the one most generally used at the shallow shafts is the chisel-shaped lever which cuts into the front of the guides if the rope should break or the cage be resting. Another form of catch has fangs, one on each side of the guides, and should the rope break, the fangs cut into the shaft timber and stop the cage. At the deep shafts, where large engines and a high speed of the cage is attained, a better and more complete form of safety-catch is used. These catches are sectors or cams having their faces serrated or toothed like a saw, and are keyed on shafts which are placed across the top of the cage frame, one on each side of the guide. Spiral spring is placed around the shaft, which throws the cams inward against the guides; springs are held back by a chain attached to the cage and the main clevis of the hoisting-ropes, so that weight of the cage becomes the power holding back and preventing the springs from acting. If the rope should break or it should slack when the cage is resting, the springs come into action and the ca
are thrown in, the teeth bite into the timber and are wedged tight by the weight of the cage; the guides being caught on both sides cannot split or be forced out of place. This is undoubtedly the best and safest form of catch now in use, and it is generally adopted throughout the State; but they require much attention to keep them in working order.
We are sorry to state that very few of the mine operators are giving proper attention to this important safety appliance. We often find the safety-catches properly constructed and appear to be all right, but on testing their usefulness we find the springs either broken or so weakened as to be utterly useless as far as the term safety is applied. We have endeavored to have all mine owners keep their safety-catches in proper working order, but have met with only partial success.
There is no section of the law on the statute books of this State of more importance or beneficial to mine operators, than section 7061, R. S. of the mining law, which requires all mine operators employing ten or more men to make, or cause to be made, an accurate map or plan of their mines, and to add the progress and the extension of the same in January of each and every year. Yet there is no section of the law so grossly abused and violated as the above named section.
Last January a circular letter was sent out from this office to all mine operators, calling their attention to that section of the mining law, with a request to comply with the same. In response to this request a large number of paper parcels were received, with imaginary maps on some of them, which were very inaccurate and poorly drawn on common paper, with pencils, without boundary lines or scale, and were of no service whatever, to this or any other department, and only fit for the waste-basket.
Mine maps do not receive the attention their importance deserves, and mine managers are slow to realize their necessity. A good mine map will many times repay the operator for the outlay attached to it, in the trouble and expense it will save in various ways. It will show how much coal has been mined from a certain tract of land; it will show where new works can be opened up with safety in close poximity to old abandoned workings; it will serve to locate doors, cross-cuts and stoppings, and to distribute the ventilative current where it will serve the best purpose. In fact, no mine can be altogether operated successfully not properly represented by a good accurate map.
In the near future the coal seams now being worked will become exhausted, and when this is the case, no doubt the lower coal seams
will be sought and mined, which will be a dangerous undertaking when the conditions of the old workings in the upper seams are unknown; and mine owners should realize this fact, and should spare no pains to have their maps as complete and as accurate as possible. An inac curate map is almost useless, because it conveys the wrong idea of the directions of the workings, and forms an incorrect basis of estimate of amount of surface undermined. The prime object of a mine map is to show the underground workings in their relation to the boundary lines of the company's property, the amount of surface undermined, and what remains, and to serve as a complete récord of all the workings.
Property owners, as well as mine owners, have, on many occasions, applied to this Department for information in regard to certain mines, with reference to the direction the mine had been driven and what portions of the surface had been undermined. Such information, no doubt, would be valuable to the applicants, and could readily be given if the operators of the said mine had complied with the law.
The 8th Annual Report of this Department, containing this statement on mine maps, will soon be printed, and a copy will be sent to every mine owner or mine operator in the State; and I hereby notify one and all to read section 7061 R. S. of the mining law, and to comply with the requirements of the same at once, or we will be compelled to resort to extreme measures.