Dr. H. Rasch, Geheimerat (Technical Councillor), Hamburg, finishes his long report as follows: -

"The accident, which did not cost any life, proves that the manufacture of the compressed acetylene-azetone mixture must be attended to with the greatest care. The pipings must in every part, especially in the joints, be made with special care, and seamless pipes of the very best material only be used, with a diameter not exceeding 9 m.m.

"The work should only be permitted to be carried out under the control and management of scientists and technically educated persons.

"The accident at Dose proves that explosions are constantly to be expected when the cylinders filled with the acetylene-azetone mixtures are exposed to fire."

Bursting of Boiler Tubes, caused by Defective Welding -

Fatal Result.

In part 7, of 15th April, 1908, the Z. f. Bayer-Revisions-Vereins describes the fatal accident at Forcheim as follows: - "The water-tube steam boiler, 300 q.m. and 12 atm., was built in 1900 by the firm Petry Dereux, in Duren, exhibited in Paris 1900, and in Dusseldorf 1902, and in 1903 installed in its present place. The boiler was alternately used with an active one to feed an engine of 800 h.p. At the inspection of 28th November, 1906, and 14th January, 1908, the boiler was found to be in perfect order. On Saturday, 15th February, 1908, one of the 193 tubes of 95 m.m. diameter burst open at a steam pressure of 11 to 12 atm., emptying the boiler in eight minutes. The mixture of hot water and steam rushed out through the damaged tube, between the fire-tubes downwards over the grate, pushing open the fire-doors, and out into the fireplace, scalding the stoker and his assistant, who nevertheless were able to go to the porter's house at a distance of almost 80 metres. Both succumbed during the night."

According to the report and the unusual situation of the crack (on one of the upper rear end tubes), the accident was deemed to have been caused by a defective welding of the seam of the tube. It is known that defective welds of tube seams frequently open even after years of use.

Acetylene Explosion.

The Z.f. Bayer. Rev. Ver., part 3, of 29th February, 1908, gives the report of the explosion of an acetylene generator. The installation, made in the autumn, 1906, was placed in a small room in the yard, and next to the general room of the hotel. The room was so small and without windows that the apparatus could only be attended to through the open door, The inspector ordered, however, amongst other alterations, that the room should be made larger and be provided with a window. A double window, 15 cm. high and 20 cm. wide, was made. The generator (Figs. 123 and 124) of the carbide-to-water type, with a capacity of 5 kilogrammes granulated carbide, dropping through the valve V into the generating chamber E. The valve rod S was provided with a packing g of indiarubber in the lid of the generator. Between the generator E and the gas-holder B is the water-safety regulator W, protected according to regulations against frost, and behind the gas-holder is the purifier R.

On the 5th January, 1908, at 7 p.m., the light was bad. The housemaid, who had to attend to the apparatus, went to the room, pulling the lever h in order to let in more carbide into the generator. The water was, however, frozen, so she tried to thaw it by means of some towels dipped in hot water. She fetched the house-butcher to help her, and probably placed the lamp in the yard about 3 to 4 metres from the door of the installation room. The butcher commenced with the thawing, while the girl remained just behind him, when an explosion, although very small and soft, took place, followed by a second one, much stronger and more sudden, heaving up the generator. The girl, and especially the butcher, were considerably wounded, with their hair burnt off. A carbide tin and the lid of the generator were fetched out by fire-hooks. Neither the gas-holder nor the purifier were destroyed, but the connection between the generator and the water regulator was blown off, and the rubber packing pushed out by the inner pressure. The small sheet soldered to the centre of the lid of the generator was melted by the heat and destroyed, and the carbide chamber was moved away and destroyed. The rear end of the house was damaged, and the roof was raised. On the lid of the generator was found some tallow, spilt from a candle, which the landlord said was left there after the explosion. The procedure seems to have been as follows: -

Fig. 123.

Fig. 124.

The water was frozen; by letting more carbide drop into the generator and the impossibility for the gas thus generated to reach the gas-holder produced a greater pressure, pushing up the rubber packing and permitting thereby the gas to escape and mix itself with the atmosphere, igniting in the candle light. This caused the first explosion. The flame then reached, through the open valve, the interior of the generator, setting fire to the acetylene contained therein, causing the second explosion.

The lesson given is this : -

The room for the plant was exposed to a freezing temperature, the use of the rubber, a most unsatisfactory packing material, on the generator, and, in spite of all stipulations to the contrary, the use of a bare candle light in the room of the apparatus, although in this particular case the light was almost indispensable by want of illumination from outside.

The case is further instructive in this respect, that the illumination of the room of an acetylene plant should always be arranged from outside, especially in such cases where the apparatus must be attended to during evenings or nights. This refers especially to private houses, and more so where the gas-holder is not large enough to take the greatest quantity of gas required during the night; this is always the case with automatic apparatus, which generally have too small a gas-holder.

That too little attention is given to the construction of the room for acetylene installations is a well-known fact, particularly in such places where frost may be expected. The walls, as well as floors and roofs, should be provided with spaces for proper insulation by peat moss, coal-dust, or other similar insulating materials; the doors should be made from double wood, and when possible be protected from the east and north winds. The installation of special heating apparatus can only be considered for central or large installations. A well-known and leading acetylene firm prefers even to build separate installation houses with insulating walls instead of using ordinary brick buildings with special heating apparatus. See "Insulators," p. 57.

Indiarubber, like glass, belongs to that kind of material which should never, or at least only with the greatest care, be used in acetylene installations, and never - as in the case just described - form part of the surface of an acetylene apparatus.

To the professional man the accident above mentioned is of particular interest, as it belongs to those very few instances of explosion taking place in the interior of the generator, such accidents occurring generally in the installation room, outside of the generator, without damaging the apparatus.

Acetylene a Great Poison.

According to Z.f. Calcium-Carbid, four persons inspected, from pure curiosity, the acetylene apparatus in Schnear, Bielefeld, and noticing some unpleasant smell, they soon left the room. Having taken ten to fifteen minutes' walk in the fresh air, they all four fell down unconscious; medical aid was soon available, and after their recovery the doctors explained the highly poisonous nature of the acetylene gas and its dangerous and speedy effect upon human life.

In its number of October 3rd, 1908, Revue des Eclairages states that ten to twelve acetylene accidents are generally reported every month, making about 130 a year. There are 13,000 acetylene installations in France inspected by the Union des Proprietaires d,'Appareils a Acetylene.