Art. VII.—On Fires in Coal-ships: Their Causes and Prevention.
[Read before the Auckland Institute, 6th July, 1896.]
Fires on coal-ships have become so frequent, and are attended every year with so great a destruction of property and so great a loss of life, that public attention is at last aroused to what is becoming a national calamity. Papers have been read on the causes of these fires before both learned societies and shipping associations; chambers of commerce have been appealed to; the Imperial Government set up a Royal Commission to inquire into and report upon them; and quite recently the English Board of Trade was appealed to on the matter. But, notwithstanding these efforts, no available means have yet been found for effectually dealing with fires in coal-ships, for their number is increasing year by year, and it is not too much to say that the word “failure” best represents to-day the position of the inquiries into both the causes of these fires and their prevention. So great has the pressure of these calamitous coal-cargo fires become at Newcastle, N.S.W., that it is almost impossible to insure a coal-cargo, and the cancelling of coal-charters is reported to be frequent at that port. It is not surprising, therefore, that the Government of New South Wales has set up a Royal Commission to report upon them, which is now sitting.
Now, under such circumstances, it will be readily believed that I should not have ventured to deal with this serious and important subject, but for the circumstance that for more than seven years my inquiries and investigations have been concentrated upon a somewhat kindred subject—the causes of fires on frozen-meat steamers, and their prevention. At the commencement of these investigations on the spontaneous combustion of charcoal I found myself in a very small minority, consisting of Sir James Hector, of New Zealand, F. C. Moore, Esq., president of the Continental Insurance Company of New York, Sir V. Majendie, H.M. Chief Inspector of Explosives, London, and a few eminent chemists. That very small minority has steadily increased, until it promises in no very long time to become a majority in the belief that fires on frozen-meat steamers are mainly caused by the spontaneous combustion of the charcoal with which they are insulated.
My pronounced success in these investigations has emboldened me to direct my attention to the causes of fires on
coal-ships, and their prevention. Naturally, in view of the inquiries made by so many able men, I hope it will be believed that I have approached the subject with great diffidence, and very much in the spirit of the mouse when it released the lion from the net—that is, of doing my little best to remove a very serious danger.
The grave importance of the subject will be further seen from the circumstances—(1.) That from the Port of Newcastle, New South Wales, alone, of twelve coal-laden ships which left that port from the 7th September, 1895, to the 18th February, 1896, nine ships were reported with their coal-cargoes on fire or heated. Nor is this heating of coal-cargoes confined to Newcastle coal, for Captain Andrew, of the ship “Crondale,” reports that “on his recent voyage to San Francisco the temperature of his cargo rose to 103°, the cargo being from a southern New South Wales coal-mine.” (2.) That in a letter from the Shipmasters' Society to the Board of Trade, dated the 10th February, 1896, it is stated “that twelve coal-laden vessels, representing about 20,000 tons, were abandoned at sea; seven vessels, of about 12,000 register tons, put into port in distress with cargoes shifted; and forty-six vessels, of about 70,000 register tons, were missing—unheard of—seven of the missing being steamers (period not named). The coal-cargoes of these missing and abandoned vessels are estimated at 130,000 to 140,000 tons, and the crews of the missing ships may be taken at about one thousand lost” (the latter drowned or burnt).
It must be understood that only a portion of these missing vessels were burnt, many of them having probably foundered at sea from the shifting of their cargoes, which is put down to imperfect trimming whilst being loaded.
Further on I shall treat of this question of bad stowage of coal-cargoes from imperfect trimming, but for the present I direct attention to the main subject of this inquiry—namely, causes of fires on coal-ships.
At this point it is necessary to describe the chief mode of putting coal on board ships at the great coal port of New-castle, New South Wales, which may be taken as similar to the practice in most of the great coal ports in the United Kingdom.
The coal is brought by rail alongside the ships in trucks containing from 5 to 10 tons. The box portion of the truck is then lifted by a powerful steam-crane, swung over the hatchway, and the truck-load of coal is dropped bodily into the hold. As each truck-load follows the coal is very much broken and pulverised into small coal, slack, and dust. As this dumping down of the coal proceeds, a great cone of small coal and slack is formed, and pounded into a more or less hard
mass. Down the sides of this cone other truck-loads of coal are then dumped, and, rolling down, are stowed by trimmers in the vacant parts of the hold. When the main hatch is filled, the remaining hatchways are filled in like manner with a cone of small coal and slack, and the vacant spaces stowed by trimmers as before.
Causes of Fires.
As before stated, my long investigation into the causes of fires on charcoal-insulated frozen-meat ships has led me to the conclusion that these fires are caused by the spontaneous combustion of the charcoal (carbon), owing to the well-known fact that charcoal possesses the property of absorbing oxygen, and concentrating within its pores nine times its volume of oxygen. When this concentration of oxygen occurs to the extent of even one cubic inch of charcoal, spontaneous combustion is certain to follow.
Now, coal, which may be said to be mineral carbon or charcoal combined with various gases, possesses, but perhaps in a higher degree, the property of absorbing oxygen when the necessary conditions are presented to it. In this view I am supported by eminent European authorities, such as Lewes, Richters, and Fayol. In the normal state of large or round coal, in which state it comes from the mine, coal is not subject to spontaneous combustion, as it has been known to have been stowed in bins for long periods without showing any signs of spontaneous combustion.
But under the present mode of loading coal-vessels the normal condition of large or round coal is largely absent, by reason of the cones of small coal and slack formed under each hatchway being pounded into a more or less solid condition. That small coal or slack in heaps takes fire most people who have visited a coal-mine will have seen. Even the heaps of slack from the secondary non-bituminous coal of New Zealand, containing little or no pyrites or sulphur, constantly take fire from spontaneous combustion. In bituminous coals, such as the South Staffordshire and similar coals, slack is particularly liable to spontaneous combustion, due to the rapid oxidization (absorption of oxygen) that is set up when finely-divided coal is brought into contact with air. Formerly, cases of the firing of coal-cargoes (being smaller) were not so frequent as now, yet I may state that, of four coal-ships which left a northern English port in 1858 with cargoes of coal for Aden, three were burnt. But now, when coal-ships are very much larger than formerly, fires on coal-ships are increasing to an alarming extent, as may be seen from a very able paper on “Coal Explosions on Shipboard,” by Mr. Richard Benyon, F.R.G.S., appearing in the Nautical Magazine for April, 1892,
in which he states that “where the cargo is under 500 tons, the number of carriers meeting with disaster is but one in four hundred. Cargoes between 500 and 1,000 tons show a percentage of 1¼ of fires and explosions. This increases to 3½ per cent. when the coal carried is between 1,000 and 1,500 tons, and 4½ per cent. for 1,500 to 2,000 tons, while above 2,000 tons the percentage of disasters to cargoes is no less than 9.”
In order that a clear idea may be formed of what the burning of a coal-ship at sea means, I may cite some of the latest cases recorded, that of the burning of the “Republic.”
Burning of the “Republic.”
The “Republic” left Newcastle, N.S.W., on the 22nd January, 1896, with a crew of thirty-two hands. The early part of the trip was devoid of adventure, and the discovery of a small column of smoke, which filtered through the chinks of the fore hatch on the 10th April, was the first thing to startle the crew. The thermometer in the ventilating-pipes showed a rising temperature, and, while alarm was an element still absent from the minds of the crew, it was decided to open the hatch, and when the hatch was opened very little smoke escaped, and the pumps were prepared to dispose of what was deemed merely a small blaze. The men kept up the brave struggle, labouring steadily at the pumps night and day. The battle went on without incident until the 15th April, when the gaining flames began to show their power. The sounds of small explosions of gas went fore and aft through the hold all day long, and culminated at 7 o'clock in the evening in a terrific explosion. Hatches 1 and 2 were blown overboard, the decks started, and the great vessel strained from stem to stern. The night of the 15th was a terrible one, and the crew worked on in desperation trying to subdue the fire fiend. When morning dawned a vessel was seen within speaking distance, which proved to be the ship “Hollinwood,” and Captain Kidd, who by a curious coincidence had been in trouble of a similar nature, readily agreed to stand by the “Republic.” On the following morning the explosions were renewed, and forks of flame shot up through the ventilators. On the 18th a further series of explosions occurred, and on the 19th Captain Hughes decided to abandon the ship. The two lifeboats were at once got ready, but, as it had been blowing hard since the previous night, the heavy sea running made it impossible to save anything but what the men stood up in. The mates commanded the boats, Captain Hughes remaining on the “Republic” until the crew had been transferred to the “Hollinwood,” when he secured the ship's papers and was taken on board the latter vessel. The transhipment was a
difficult operation, both boats becoming partly filled. In such a sea probably all hands would have been lost, and the “Republic” would have been posted as “missing” owing to bad stowage. The “Hollinwood” stood by the burning vessel all night, and at 8.30 p.m. her main and fore masts went over the side, the decks and standing rigging having been weakened by the fire and both rendered incapable of sustaining the strain put upon them. All through the night the fire burned with unrestrained fury, and when day broke Captains Hughes and Kidd decided that it was useless to remain longer, and the “Hollinwood” was accordingly squared away on her course for San Francisco.
Heating of the “Hollinwood's” Cargo.
Captain Kidd, of the “Hollinwood,” had a somewhat similar experience, but managed to save the ship at the expense of the cargo. The “Hollinwood,” a steel four-masted ship, belonging to McVicar, Marshall, and Co., of Liverpool, sailed from Newcastle, New South Wales, on the 10th December, with a crew of thirty-three hands all told, and a cargo of 4,060 tons of Caledonian coal, consigned to J. D. Spreckels and Co., of San Francisco. “On the eleventh day out,” said the captain, “the thermometer in the ventilating-tubes in the vicinity of No. 2 hatch registered 98°, and upon discovering that my cargo was on fire I determined to put into Lyttelton, New Zealand, which was then only two days' sail distant. Owing to contrary winds, however, five days were consumed in making the port, during which time, of course, I made every effort to keep the fire under control, and successfully. At the recommendation of the surveyors who inspected the vessel at Lyttelton, I discharged all but 1,400 tons of my cargo there. I was fortunate in reaching port when I did, for even while the work of discharging was being proceeded with the heat between decks ran up to 122°. Beyond scorching the paint in the hold, however, the ship sustained no damage, and in accordance with instructions I sailed for San Francisco on the 8th February.”
The “Knight of St. Michael.”
As supplementary to the burning of the “Republic” and the heating of the “Hollinwood's” coal-cargo, I quote the very able report of E. F. Pitman, Esq., Geologist to the Government of New South Wales (February, 1896), upon the heated coal-cargo of the ship “Knight of St. Michael.” I quote this valuable report in full, because it appears to me to describe the causes of the spontaneous combustion of coal-cargoes in a fuller and more lucid manner than any other document I have perused.
The report of the Government Geologist is as follows:—
“I have the honour to report that I have made two inspections, on the 25th and 27th instant, of the coal-cargo of the ship “Knight of St. Michael,” and have to report as follows: Previous to my visit the cargo had been inspected several times by the marine surveyors, copies of whose reports are herewith. From these reports it will be seen that the ship left Newcastle on the 1st February with a cargo of 3,216 tons of Wallsend coal. On the 2nd February the master took temperature at intervals between 8 a.m. and noon, and found that in No. 2 hatch it rose from 96° to 104°. He therefore put into Sydney Harbour, and on the 4th February the cargo was surveyed, and the temperature in No. 2 hatch was found to be 105°. The surveyors thereupon recommended the discharge of 300 tons of coal from this hatch. On the 6th February the surveyors made a second inspection, after the 300 tons had been nearly discharged, and, finding the coal still much heated on the surface, they recommended the discharge of a further quantity of about 500 tons, or until the ceiling was left practically clear. The cargo was again inspected by the surveyors on the 11th, 12th, and 14th instant, and on the latter date they were of opinion that all the heated coal had been taken out, and that the remainder was fit to be carried on. On the 14th instant the captain reported that the temperature of the coal in No. 3 hatch was rising. The surveyors confirmed this on the 17th, and also found a slight increase of temperature in the coal in No. 4 hatch. They therefore recommended-that coal be shifted from hatches Nos. 3 and 4 into No. 2 until the heated coal was reached, and that the heated portion be then removed and sold. On the 21st they reported, after another inspection, that there were no signs of heating in the remainder of the cargo, and it was therefore assumed that the difficulty had been overcome. Subsequently, however, it was ascertained that the temperature was again rising in No. 2 hatch, and I was then requested to report upon the matter. At about 9.30 a.m. on the 25th instant I found a temperature of 84° Fahr. in the centre of the coal immediately underneath No. 2 hatch, while in the hold near the side of the vessel the temperature was only 77°. It was noticeable that the coal contained a large proportion of small and dust. At about 9.45 a.m. on the 27th February I found that the temperature had risen to 88° Fahr. in the centre of the coal under No. 2 hatch, while in the hold near the side of the vessel it was 76°. At the same hour the temperature of the coal in No. 3 hatch was 79°, and in No. 4 hatch it was 73°, while the shade temperature on deck was 69°. It is clear from the foregoing remarks that the temperature of portions of the
cargo is at the present time abnormally high, and there is reason for believing that, if left alone, it would continue to increase until spontaneous combustion ensued. Samples of the coal taken by me have been analysed by Mr. J. C. Mingaye in the departmental laboratory, with the following results: From No. 2 hatch: Hygroscopic moisture, No. 1, 2.65, No. 2, 2.81; volatile hydrocarbon, No. 1, 35.80, No. 2, 35.32; fixed carbon, No. 1, 55.30, No. 2, 54.47; ash, No. 1, 6.25, No. 2, 7.40; sulphur, No. 1, 0.535, No. 2, 0.453. From No. 4 hatch: Hygroscopic moisture, 2.45; volatile hydrocarbon, 37.55; fixed carbon, 52.30; ash, 7.70; sulphur, 0.508. It may be stated, therefore, that the cargo consists of semi-bituminous coal of good quality, but containing large proportion of dust and smalls. The coal was, I am informed, screened at the pit-mouth, and its present condition is, I presume, due to subsequent handling. From the investigation of eminent European authorities, such as Richters, Fayol, Lewes, and others, there can be little doubt—(1) that the principal cause of spontaneous combustion in coal is the absorption of oxygen by the coal; and (2) that the most favourable conditions for the self-heating of coal are a mixture of small pieces and dust, an elevated temperature, a large mass or volume of coal to act as a non-conducting covering, and a certain volume of air. These conditions are precisely those which exist in the ‘Knight of St. Michael's' cargo. The cargo was, I understand, loaded during the abnormally hot weather which prevailed at the end of January, and it is probable, therefore, that it reached the hold with an initial temperature of from 120° to 150° Fahr. In loading from the trucks at Newcastle a considerable proportion of small and dust has been produced by the fall and by the process of trimming; by the filling-up of the hold the volume of coal necessary to form a non-conducting covering has been provided; while just about sufficient air has access to the hold to complete the necessary conditions. I am of opinion, therefore, that the heating of the cargo of the ship ‘Knight of St. Michael’ is due, firstly, to the fact that the coal contains a large proportion of ‘small’ and ‘dust,’ and, secondly, to its having been loaded during abnormally hot weather. The proportion of ‘small’ and ‘dust’ has no doubt been increased by the shifting operations which have taken place since the arrival of the ship in Port Jackson, and I am of opinion that considerable risk would be incurred if the ‘Knight of St. Michael’ were allowed to put to sea with her cargo in its present state.— Edward F. Pitman, Government Geologist.”
I think it is open to doubt whether the hot weather in January caused the heating of the coal in the “Knight of St. Michael,” as the temperature of the coal at the side
of the ship was only 77°, the real cause being the heating of the cones of small coal and slack under the hatchways.
Commenting on the above report, the Morning Herald and Miners' Advocate, Newcastle, New South Wales, says:—
“The case of the heated cargo of the ship ‘Knight of St. Michael’ continues to excite considerable interest in shipping and insurance circles in Sydney. There can be no doubt of the injurious effect upon the Newcastle coal trade caused by this occurrence, however northern colliery-proprietors and their representatives may endeavour to prove that more has been made of the affair than circumstances would justify, as, according to statements made to the Newcastle Herald's Sydney representative by merchants and others in the metropolis, some of them are doing. The fact that the surveyors judged it advisable that a third of the cargo should, be discharged after the ship had been in Port Jackson for a month is taken to be a full indorsement of the decision of the captain to return to port. As one gentleman put it, Captain Dodd was not likely to have put back, when he had the knowledge that such a delay would cause his owners considerable monetary loss and additional expense for harbour charges and lying idle, if there had appeared to be any safety in proceeding on the voyage. On the other hand, it is said that, by continuing his trip, the captain would have, in face of the surveyors' reports, been endangering a magnificent vessel, valued at £20,000, as well as thirty lives, for the sake of a coal-cargo worth only £2,000. It is generally agreed by shipping and insurance people in Sydney that, in the interest of the trade of Newcastle, it is advisable that the coal-owners should take steps to secure a full investigation of the matter. Otherwise, it is believed the trade of Newcastle may suffer from alarmist reports, which in many instances may not have as much foundation as in the ‘Knight of St. Michael” case.”
Causes of Combustion.
The conclusions to be drawn from Mr. Pitman's able and exhaustive report are clear enough:—
1. That the cause of the spontaneous combustion of the coal on board the “Knight of St. Michael” was the absorption of oxygen by the small coal in the hatchways.
2. That the most favourable conditions for the self-heating of coal are a mixture of small coal, slack, and dust produced under each hatchway by the dumping down of the coal from the railway-trucks, and forming a cone under each hatchway, consisting mainly of coal pounded into small coal, slack, and dust, thus presenting the conditions necessary for spontaneous
combustion of the coal-cargoes, which followed as a matter of course, as in so many other coal-ships.
Professor Lewes has laid shippers of coal under very great obligations by his highly valuable papers “On the Spontaneous Combustion of Coal-cargoes,” and “On Spontaneous Ignition and Explosion in Coal-bunkers,” read before the Institution of Naval Architects and the United Service Institution. In these valuable papers Professor Lewes says, “Newly-won coal possesses great power to attract and absorb oxygen; that small coal, weight for weight, having more surface than large, is more liable than large coal to absorb oxygen and take fire; that, as a matter of fact, fires in coal-laden ships begin generally under the hatchways, where the process of pulverising goes on till the cargo is complete. Coal shipped in rainy weather incurs additional risk—moisture causes crumbling and the exposure of fresh surfaces. Badly-broken coal offers so many more points of atmospheric contact than does a block of the same mass. Thus a cubic foot has six superficial feet of surface; but, if a cubic foot of coal be subdivided into cubic inches, the amount of surface exposed to oxidization would be 10,368 square inches, and when pulverised into slack the power of absorbing oxygen becomes very largely increased. These multiplied surfaces again increase the heat proportionately. At over 100° Fahr. the heat increases very rapidly: at more than 130° Fahr. actual ignition is only a question of days.”
Fires In Coal-Bunkebs.
Referring to the ignition of coal in bunkers, Professor Lewes says, “In the fast ocean-steamers it is now becoming an event of frequent occurrence for the contents of coal-bunkers to ignite spontaneously, and many a hand-to-hand struggle has been waged between decks without the passengers even suspecting the threatened danger.”
Seeing that 100° to 115° Fahr. is a common temperature in stoke-holes, and up to 135° is frequently met with, and that I have myself seen the temperature of a stoke-hole in the tropics at 150° Fah., yet, practically nothing has been done to prevent boiler and engine-room heat from passing into coal-bunkers.
Professor Lewes suggests the construction of double bulkheads, with the iron plates 6in. apart, and arrangements made for the slow circulation of sea-water between them to keep down the temperature in bunkers. I agree with Captain Froud, R.N.R., “that structural and other difficulties stand in the way of the adoption of the Professor's suggestion.” (See Captain Froud's admirable paper “On Heating of Ships and Cargoes,” read the 20th November, 1891, before the
Shipmasters' Society, London, and to which I am much indebted.)
On the question of the prevention of heat passing from stoke-holes or boilers to the coal-bunkers, instead of Professor Lewes's suggestion of filling the double iron bulkheads with sea-water, or filling them with air, as Captain Froud suggests, I would propose their being filled with calcined pumice; this material, with its innumerable air-cells, being indestructible and incombustible, and being one of the best and safest non-conductors of heat hitherto discovered. Captain Froud's suggestion of filling the bulkheads with air is inadmissible, because air facilitates radiation and circulation, under the influence of which the interior of the bulkheads would be heated and the air become a conductor of heat, and of no value. It is only when air is confined in minute cells, as in pumice, that it is a first-class non-conductor of heat.
The ventilation of coal-cargoes by means of iron or wood tubes, if there are no cones of small coal and slack under the hatchways, I consider unnecessary, and if cones of coal be formed in the hold these tubes often do more harm than good. If no cones are formed, surface ventilation by the removal of the hatches occasionally in fine-weather will secure all the ventilation necessary.
Causes of Explosions.
In a great many of the fires of coal-cargoes explosions of a severe and dangerous character often occur. It is an error to suppose that great quantities of this explosive gas (commonly known as “marsh-gas”) is generated and thrown off by coal in what ought to be its normal condition in a ship's hold—namely, large and round coal. When in that condition, with a normal temperature of 75° Fahr., only harmless quantities of marsh-gas will be found in the hold. This dangerously explosive gas is produced by heat, as may be seen at any gasworks, where large quantities of large and round coal are kept in bulk for considerable periods without developing heat. But when this coal is thrown into heated gas-retorts large quantities of gas are at once thrown off. So it will be in a ship's hold; if the coal is mainly large and round little or no gas will be evolved, and if no heat-creators in the shape of cones of small coal and slack (which are practically gas-retorts) be allowed to be formed in the ships' holds. It is these heated cones which generate and throw off large quantities of marsh-gas, and which cones, I have no hesitation in
saying, are solely responsible for all the fires and the explosions which occur.
The shifting of coal-cargoes at sea is doubtless responsible for some of the “missing” coal-ships, but the presumption is strong that many of them have been burnt by the spontaneous combustion of their cargoes, and no one left alive to tell the tale of misery and disaster. Coal-trimmers are, I think, often unjustly blamed. There are doubtless some cases of false trimming, and no wonder, considering the very small pay coal-trimmers receive for doing very disagreeable work.
If shifting-boards are used, and the coal-distributor hereinafter described be employed, and a fair wage be paid for trimming, the danger from shifting cargoes will be reduced to a minimum.
Prevention of Fires.
I now pass on to the consideration of the best and most available means for the prevention of fires on coal-ships.
I have endeavoured to demonstrate that fires in coal-ships are caused by the formation under each hatchway of cones of small coal, slack, and dust, into which so considerable a proportion of large and round coal is changed by the dumping of coal from trucks into the unprotected holds—and, I may add, in a less degree from shoots or baskets—and that these cones become heated and take fire from the spontaneous combustion of the oxygenized small coal and slack they contain.
This paper is already too long, and, as the appliances for preventing fires on coal-ships will shortly be put to a practical test, it is not necessary to occupy more of your time or to try your patience further than to say, generally, that I propose to fix in the ship's hold a coal-distributor at varying points, from which the coal slides off, and, in so doing, makes so small a quantity of small coal, slack, and dust, and the coal lying so loosely, that it is deprived of all liability to absorb oxygen in dangerous quantities, thus preventing spontaneous combustion and reducing the risk of fires in cargoes of coal so loaded to an inappreciable minimum.
The distributor not only prevents the formation of dangerous cones of coal under the hatchways—as by the present system of loading—but fills the spaces under the hatchways with large and round coal. The distributor will not dispense with coal-trimmers, but it will enable the trimmers to do their work properly, and will secure better and safer stowage, and much less danger of shifting, than under the present system.
In this way the coal is very much less broken, is distributed much more widely, and the hatchways are filled with
large and round coal, deprived of all power to absorb oxygen, develope heat, or generate gas; and, instead of the hatchways turning out, as now, hundreds of tons of small coal and slack, thus reducing the selling-value of the cargo, the spaces under the hatchways turn out at least a fair sample of the entire cargo, and enable the captain and owners to obtain a much better price for their coal.
By this means of loading coal, with its attendant freedom from all danger of spontaneous combustion or of gas explosions, the owners and charterers will be able to effect insurances on ships and cargoes at reasonable rates, in place, as at present, of their either not being able to insure at all or at rates beyond their power to pay. Most important of all, an enormous loss of life and property, by the burning at sea of coal-ships and their cargoes, will be prevented.