BUNKER COAL

Evening Post, Volume CVII, Issue 25, 30 January 1924, Page 10

BUNKER COAL

RISK OF SPONTANEOUS IGNITION.

The seriousness of the question of the spontaneous ignition of bunker coal is evidenced by the statement made by Mr. John H. Anderson in the course of a paper on the subject before the Institute of Marine Engineers recently, to the effect that about 200 vessels per annum are destroyed from this cause. The casuallies to British ships alone vary between 50 and 100, while the average number of American ships destroyed is over 60 per annum. AH coal has some tendency to suffer such ignition, as it is, even under normal conditions of temperature, undergoing some slight oxidation. The tendency is less with large coal than with small coal. It is increased in the presence of undue proportions of several natural impurities, such as pyrites, clay, and shale, and by the presence of extraneous waste material, such as wood and bark, sacking and cotton-waste. Even water adds to the danger. Slow oxidation generates heat, giving local rise in temperature and accelerating further combustion. Hence the need-of ventilation to keep down the temperature. In large storage heaps heavy rain with disintegrated coal seals off the bulk of the coal, and.thus encourages temperature rise. The main initiation of local heating is probably pyrites, due more to the local heating than the sum total of heat evolved. There would appear to be room for the exercise of greater precaution in the bunkering of coal. Excessive handling increases disintegration, and in badly vented bunkers temperature rises become j dangerous. Again coal appears to become more sensitive some months after' hewing. Old coal should, therefore, not be covered up by new coal. The- depth of coal should be limited—loft was suggested as an average figure in the paper —and free vents for the escape of gases provided. Bunkers should be- insulated from local sources of heat, such as steam pipes.. A ventilated air space suffices. There should be provision for temperature readings in the bunker, to be regularly made and recorded. The storage of any combustible material near the coal should be rigidly avoided. Local- fires detected by temperature readings may often be dug out, but heated coals give off explosive gases, and should only be approached with safety lamps.