Safety Petrol Tanks.
Page 6
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Interesting Experiments with a very Simple Preventive Device.
The serious consequences of an explosion within a tank containing such a highly-volatile liquid as petroleum spirit cannot be too fully appreciated by engineers and others connected with the storage of small or large quantities of petrol. In the event of the bursting of a tank due to the application of external heat, the contents are spread over a large area, and to this distribution of inflammable liquid the rapid spreading of the area of conflagration at many recent fires can be attributed. It is many years, now, since Davy and Stephenson separately invented the miner's lamp, the use of which enables workers safely to enter chambers which are filled with explosive gases ; yet, it is but recently that we have heard of the application of the same principle which governs the construction of the miner's lamp to the safeguarding of petrol-storage tanks against the risk of explosion arising from the presence of lire. The Safety NonExplosive Reservoir Company, Limited, of Ciz, Frith Street, Soho, London, W., is now making such a device (Henze patents) in this country. The use of this fitting has for some time been compulsory in Germany, Austria, and Hungary. The protective effect of the device, which in this country is known as the " Snercold " safety fitting, is due to the fact that, when a flame is surrounded by a good conductor, the heat is carried away faster than it is generated, and the result is that the temperature falls below that necessary for the combustion of the gases to continue on the side of the conductor remote from the flame. Thus, the vapour which arises from the petrol within a tank may be ignited at the mouth of the filling socket, but, if that socket be provided with a fine-gauze partition, it is impossible for the gases within the tank to be ignited. This effect of the gauze would, however, break down if the partition became heated by direct contact with a flame, or if the vessel were placed in a draught which might cause the flame to be blown through the meshes of the gauze, or if the gauze become torn or otherwise damaged. The " Snercold" device is, however, fitted inside the tank, and the gauze is protected by perforated metal shields which prevent damage by handling; it is, therefore, impossible for any one of these three conditions to vitiate its function. Another and equally important detail in the company's fitting is a small safety plug, and this is soldered into the filling-socket cap by means of soft solder which fuses at a temperature of about 85 degrees Centigrade. Should the tank become heated from the presence of a fire in its vicinity, the soft solder quickly melts and releases the internal pressure.
A representative of "THE COMMERCIAL MOTOR," on Thursday last, witnessed some very convincing and comparative tests with this device, in an open field at Wembley. The first test consisted of the lighting of a bonfire, in which was •placed a steel drum containing about 13 gallons of
petrol ; needless to say, the tank was fitted with the safety device. Within a very short space of time, the safety plug had blown out ; but, although the fire raged fiercely for some minutes, there was no danger of explosion. The vapour arising from the barrel through the aperture lately occupied by the safety plug was of course ignited by the flame and burned steadily. The surrounding fire was easily put out with a hose, and the flame from the tank was extinguished by the placing of a wet sack over the hole. After the extinguishing of the flames in this manner, the vapour arising from the tank was again ignited, by the application of a lighted match, and a further demonstration was given ; in this test, petrol was poured from a two-g-allon can (which, by the way, was also fitted with the safety device) into the barrel, and, although the stream of petrol was enveloped in flame, there was no suggestion of an explosion.
After demonstrating in this manner the fact that petrol can be handled with perfect safety in the presence of fire, provided that the vessels be fitted with the safety device, a comparative test was undertaken. In this test, two electricallywelded steel drums of precisely-similar shape and strength were mounted on an iron gantry. Each drum had a capacity of five gallons, but only three gallons of petrol were placed in each of them. One of the drums was fitted with the" Snercold safety device, whereas the other was provided with a plain screwed-down cap. A bonfire was built up round these two drums, and in a few moments the safety plug of the protected tank fused and freed the drum from internal pressure. Four minutes later, the other tank exploded with a loud report, blowing one end of the drum 30 yards in one direction, and the barrel of the drum about 40 yards in the opposite direction. The contents of the exploded drum were spread to a radius of some io or 15 yards, and the grass within this area was for a few moments one mass of flame. 'The protected drum was not even moved off its gantry, and, after the fire had been extinguished, it was found that thesafety device was quite intact, and undamaged.
The value of this device has already been recognised by the London Fire Brigade, which has fitted the device to all vessels used for the storing of petrol, whether in the stations or on motor engines and vehicles, and we understand that the Admiralty is also giving the invention its serious consideration. So convinced of its effectiveness are some of the insurance companies, particularly the Municipal Mutual Insurance, Limited, that they are prepared to make a reduction of from to per cent. to zo per cent, on all insurance against the risks from fire or explosion on garages and other premises, and on motor vehicles, where the " Snercold "safety device is fully installed.