Abbildungen der Seite
PDF
EPUB

when the quantity has been ascertained by the eudiometer to be less, the amount of oxygen in the atmosphere ought also to be tested, and sufficient air ought to be introduced, to establish and maintain the same relative proportion of vital air in the mines, as on the surface of the earth.

[ocr errors]

Fiery mines are those in which fire-damp exists, but not in large quantities; and very fiery mines, those in which it is found to such an extent, as to render the atmosphere explosive. In the absence of better data, the measure of fire-damp in fiery mines, may be taken, at a minimum, as equal to that proportion which causes the enlargement, or elongation of the flame of a candle, or lamp, indicating the presence of one part of fire-damp to 15 parts of air, or 6.67 per cent. of fire-damp. It has been shown, that this gas ought to be diluted with 30 times its volume of pure air; then taking, as before, the mean area at 50 feet area × 6.67 per cent. 3.33 cubic feet 50 square feet,

100

=

of fire-damp which × 30 volumes gives 100 cubic feet per second, or 6,000 cubic feet per minute, as the quantity of air required to dilute this gas. But as this quantity of air is in addition to that required for dispersing the choke-damp, which is equal to 5 times the mean area, in a fiery mine the area must be multiplied by 7, to give the whole amount of pure air per second, which is required for the dilution and displacement of both these gases. In a fiery mine of 50 feet mean area the basis for calculation is (50 × 7 × 60) = 21,000 cubic feet per minute, to which must be added, the air required for respiration and combustion, and one-tenth of the whole per mile, for the length of the air-courses.'

In very fiery mines, in which the safety-lamp is used, the atmosphere may be fairly considered to be in an explosive state, and therefore consisting of 1 part of fire-damp to 8 parts of common air, or as containing 12 per cent of gas. Therefore 12.5 per cent. x 0.3 3.75 multiplier of the mean area;

[ocr errors]

=

10 per cent x 50 volumes = 5

100

6.67 per cent X 30 volumes = 2 + 5 = 7

100

12.5 per cent x 30 volumes 3.75 +5 = 8.75

100

=

but to this, the multiplier for choke-damp, must be added, giving (3.75 +5°) 87.5 as that for very fiery mines; which in a mean area of 50 feet, as before, makes the air necessary for the dilution of gases 26,250 cubic feet as the basis for calculation.

The rules inferred from the premises of this inquiry are therefore as follows:

:

In mines quite free from fire-damp, multiply the mean area by 5; in fiery mines, as described, multiply the mean area by 7; in very fiery mines, multiply the mean area by 8; which will give the quantity of air required for the dilution of choke and fire damp, per second, or multiplied by 60, the amount per minute. To this must be added the air needed for respiration. and combustion, at the rate of 20 cubic feet per minute, per man, employed in the mine; the sum of these amounts to be the basis for calculating the increased quantity required for the distance the air has to travel, one-tenth being added for every mile, or the whole quantity doubled in ten miles. By the application of these simple rules, the quantity of air required in a mine, may be always correctly ascertained. To be safe, however, the use of the eudiometer is indispensable; if the per centage of fire-damp be greater than 12, say for instance 15 per cent., the multiplier must be increased accordingly; for 15 x 0.3 = 4.5 to which if 5 be added for choke-damp, makes 100 the multiplier of the area 9 instead of 8 as before.

The quantity of air shown by these rules to be requisite, may appear large when compared with the practice pursued in some districts, but when contrasted with the ventilation of some of the large and well-conducted mines in the north of England, a near approximation is apparent; for instance, the Hetton Colliery is ventilated with 198,000 cubic feet of air per minute. Taking the mean of its areas as 54 square feet, the distance the air has to travel, 70 miles, and the number of men employed as 1,000, and supposing it to be classed as a fiery mine, 172,760 cubic feet would be required by the rule, or, if it be very fiery, 212,450 cubic feet per minute.

In Haswell colliery there are 94,900 cubic feet per minute; taking the mean area at 50 feet, the air-courses 35 miles, and the number of men at 500;-by the rules, as a fiery mine, it

requires 77,000 cubic feet, and as very fiery, 95,375 cubic feet per minute.

The ventilation of Seghill is said to be 42,708 cubic feet per minute; as a fiery mine it would require 45,680; and, as very fiery, 56,600 cubic feet per minute.

Many other instances might be given, but these, it is presumed, will be deemed sufficient to demonstrate the accuracy and general applicability of the rules proposed.

The following statement of the amount of ventilation in the several collieries named, shows the great diversity of practice which prevails, and the necessity for some certain method of determining the quantity of air really required :—

[merged small][merged small][merged small][ocr errors][ocr errors][merged small][ocr errors][ocr errors][merged small][merged small][ocr errors][ocr errors][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small]

Thus, in twenty-four collieries, the ventilation varies from 2,000 to 198,600 cubic feet per minute; and although it is quite true that one colliery may be better ventilated with 20,000 cubic feet than another with 100,000, yet there can be no doubt, that the great discrepancy observable is more than is warranted by the peculiar circumstances of each mine, and also that it may be attributed to the non-existence of rules, by which the quantity absolutely required might be readily ascertained. The insufficiency of the ventilation, in many instances, is confirmed by an examination of the records of explosions, imperfect though they are, for it appears there have been thirtyone explosions in ten of these collieries, by which six hundred and forty-six men were killed; if, therefore, a comparison be made between the ventilation herein recommended, and that shown to be adopted in the majority of the mines mentioned, and if it be found that the amount by the proposed rules considerably exceeds that allowed in many instances, it ought not

to prejudice the theory herein advanced, but to excite reasonable doubts as to the sufficiency of the existing scale of ventilation.

It has been alleged, that the fire-damp is produced in such abundance in some collieries, that it is impossible to force a sufficient quantity of air into the mine to dilute it to a state consistent with safety. This allegation is inconsistent with recorded facts and opinions. Mr. Nicholas Wood, (M. Inst. C.E.) of Newcastle-upon-Tyne, in his evidence before the Committee of the House of Lords (1849, Query 1843), says, that, 1,000 cubic feet of fire-damp per minute exceeds the quantity ordinarily produced in any mine of that district, which is the most fiery in the kingdom; therefore, the very moderate ventilation of 30,000 cubic feet of air per minute is all that is required to deprive this gas of its dangerous properties. But in addition to the gas ordinarily produced in mines, the colliery is sometimes suddenly inundated by a much larger quantity, in consequence of the workmen incidentally tapping a reservoir, or "bag of firedamp," when the gas issues in a continuous stream by what is called "a blower," or, on the fall of the roof, it escapes in large volumes. Such casualties are fraught with great danger, and imperiously require consideration in every system of ventilation. Mr. Wood states, that the blower at Wallsend Colliery discharges 120 cubic feet of gas per minute; and Mr. Mather gives the following as the greatest quantities of fire-damp that are known to have issued from blowers :

[merged small][merged small][ocr errors][merged small][merged small][ocr errors][merged small][merged small]

It is obvious that the danger arising from the sudden irruption of such large quantities of gas as even the last amount named, must be very considerably increased, when the ventilation is maintained by allowing ten, or twelve parts of air to one of fire-damp, in which state even an inconsiderable addition of gas renders the atmosphere explosive; yet this ventilation has been sanctioned by high authorities, and is, in many instances, the maximum attempted. When it is recollected, that one part

1 This word is evidently derived from the Welsh "Ogof," a cave, or den.

of fire-damp, to eight parts of common air, makes the most explosive atmosphere, the impolicy and danger of such a system must be apparent; but if, as herein recommended, the fire-damp be mixed with thirty times its volume of air, the danger in most cases would be entirely avoided: but wherever blowers are known to exist, the per centage of gas produced by them ought to be accurately taken, and a liberal addition made to the amount of ventilation in consequence, for the quantity of the air required ought always to be calculated on a maximum scale, so as to be amply sufficient, not only for good ventilation under ordinary circumstances, but also to prevent the occurrence of an explosion by such contingencies, and to preserve the men in full bodily health and vigour.

In conclusion, it may be observed, that the results of this investigation clearly demonstrate the possibility of determining the quantity of air required in mines, by the means here proposed. The rules which have been proposed, have been deduced from the scientific principles advanced, and have been so formed as to suit the varied conditions of all mines, however different their peculiar circumstances. This has been exemplified by comparing the amount of ventilation, as required by the rules, with that maintained in three collieries of different areas and lengths of air-courses, by which it appears that the results of the theory approximate very nearly to the practice pursued in well-conducted mines. The great simplicity and easy applicability of these rules can scarcely fail, it is presumed, to be a strong recommendation for their adoption, and it must be evident, that by the substitution of principles for the mere guess-work now so prevalent, a great improvement may be rationally anticipated in the ventilation of mines, upon which the happiness, or misery, and the life, or death, of so many of the industrial population of this country mainly depend.

« ZurückWeiter »