ACETYLENE AND INSURANCE.
AT a recent meeting of the Philadelphia Fire Underwriters’ Association, Mr. Chas. A. Hexamer gave his views on acetylene gas, as viewed from the insurance standpoint:
“Acetylene gas burns with an exceedingly luminous flame of much greater candle-power than the best city gas. If furnished to the consumer through underground pipes in a manner similar to the present system of city gas supply, there would be no greater risk from its use than from the use of city gas. In order to cheapen its use, however, it is proposed to supply acetylene gas to consumers in cylinders,in a liquefied state, under a pressure variously estimated at 750 to 1,000 pounds. It is stated that a cylinder of gas, 4 inches in diameter, 5 feet high, will contain enough gas in a liquefied state to supply an ordinary ten-room dwelling with gas for three months. These cylinders it is proposed to connect directly with the gas pipe in a building ; when empty, to be disconnected and a new’ cylinder substituted. It is necessary to reduce the 1,000 pounds pressure in the cylinder to a small fraction of a pound at the burners. This is done by a Pirtsch valve, a rather complicated mechanism.
Two important questions present themselves at this point ;
- What would be the result if a possible fire in the building should reach the acetylene cylinder?
- What would be the result if the reducing valve failed and the entire gas pressure in the cylinder were suddenly thrown into the gas pipes in the building ?
It is stated that, while it is true that an increase of temperature involving the gas cylinder would produce increased pressure, before the pressure would cause a rupture of the cylinder (which is said to be tested to 3.000 pounds) decomposition of the acetylene gas into carbon and hydrogen would result, with no explosive effect. This result, it is claimed, has been obtained by heating a small cylinder of liquefied gas in a fire to a cherry-red heat. While this may be true (and similar decomposition of gases—notably hydrogen sulphide, which in a cylinder subjected to heat deposits free sulphur and liberates hydrogen—are known), it remains to be demonstrated whether cylinders of liquefied acetylene gas can safely be heated without disastrous results, the fact being that the quantity of hydrogen liberated equals in volume the acetylene decomposed; the danger of a rupture of the cylinder, therefore, is not eliminated by the decomposition of the acetylene. The result of failure of the reducing valve, which operates automatically, can be easily imagined. The liberating of a gas at nearly 1,000 pounds pressure into gas pipes not intended to carry more than a few pounds pressure must necessarily produce disastrous results.
From the above it will be seen that the points of interest to the underwriter are the presence of cylinders of liquefied gas in buildings in case of fire, and possible failure of the valve intended to reduce and regulate the slight pressure of gas necesssary at the burner. There is no reason why the objection from these points should not be overcome. Cylinders of compressed gas can, and should be located outside the building, and a safety valve can be provided to empty the cylinder, discharging the gas into the open air outside of the building, in case the reducing valve refuses to act.
Besides furnishing acetylene in liquefied state under pressure, it is proposed to introduce small gas machines intended to generate acetylene directly from the calcium carbide. Apparently, no special hazard attaches to this plan, provided the gas machine be located outside the building, and provided the calcium carbide be stored in a dry place and free from an accidental contact with water, which, generating the gas. might cause a fire or an explosion by coming in contact with an open light.
It is too early to formulate rules and requirements for safe introduction of acetylene gas for illuminating purposes. The subject has hardly passed the experimental stage. The result of an accident to a cylinder of the compressed gas brought it forcibly to the attention of the underwriters. That the disaster was the result of the accidental and possibly careless breaking of a valve being experimented with cannot be allowed to modify the deduction to be drawn. As an illuminant, acetylene is so far superior to ordinary city gas, that, if the claim made as to the relative cheapness of its production can be substantiated, its general introduction may be expected. A careful consideration of the subject by underwriters’ associations is necessary. In the meantime, underwriters are wise who carefully consider each application for the use of this new gas in its present state of development, and, until proper regulations and requirements have been formulated for its safe introduction, refuse to grant permission for its use in buildings covered by their policies.”