STATIONARY FIRE PROTECTION METHODS USED IN GERMANY
Illustrations of Devices Used to Protect Buildings and Some Large Machinery Installations—Resembles American Sprinkler Systems
J. Brand, Muenich, discusses in the “Zeitschhrift des Vereines deutscher Ingenieure” of June 4, 1927, pp. 835-836, some of the applications of stationary fire protection equipment which is used in Germany. The drenching or rain-wall equipment is less known in that country. Its application is illustrated in Fig. 1. The drenching sprays are located above each window. During a fire these sprays are placed in service by opening a valve. The system is shown in operation in Fig. 2. In order to meet the large requirement for water, a storage tank is placed overhead, or an air pressure tank may be used.
Very high and large rooms are equipped with rain making apparatus as is done in theaters. The main valve is located outside of the danger zone. The water is sprayed from copper tubes which are perforated to one-third of their circumference, or from valveless sprinkler sprays. For long pipe lines a feed supply is arranged at both ends. Recently this system has also been applied to benzine or gas tanks.
Closed-in rooms may be protected with steam. This, however, requires a steam generating plant which must be kept under pressure for instant service. The system has proven satisfactory for extinguishing fires in the coal bunkers of steam operated ships. There is also the possibility of filling the hollow space in liquid storage tanks with steam in case of fire.
In some cases neither liquid nor solid fire preventatives are desirable. Carbonic acid gas has proven desirable, as for instance in the protection of electric generators, as shown in Fig. 3, which illustrates the fire protection system of the generator at the Walchenseewerk hydro-electric power plant. There is a breaking strip (a) on each switchboard. As soon as this is disengaged, the fire dampers (b) and (c) are closed automatically. At the same time the cord (d) opens the valves of a battery (e) containing carbonic acid flasks. Thus the cooling duct (f) of the generator is quickly filled with a fire-preventive gas and the fire thus extinguished.
In connection with this illustration it is of interest to know of the results of testing various insulating materials in electrical machinery in many fire-preventative gases and mixtures of gases, as reported in a recent issue of the Siemens-Zeitschrift. Engineer Fritz Liebscher of the experimental station in the dynamo works of the Siemens-Schuckert-Werke reports the following results in summary in the article, “Protection of Electrical Machinery Against Burnouts.”
For protection of electrical machinery equipped with circulating cooling against burnouts, a very rapid decrease in oxygen in the cooling plant by the introduction of inert gases is recommended. This is Inst done by injection of the liquid carbonic acid. Cut off valves are used to cut the machine off from the balance of the cooling plant in case of necessity.
Tests have shown that the independent combustion of insulating material (cotton strips, excelsior strips, paper, shellac) is impossible when the gas contains only 14 to 15 per cent oxygen. In order to reduce the oxygen percentage from the 21 per cent to 14 per cent, that is one-third, one-third of the air chamber volume must be replaced by the injected gas. This requires a gas volume equal to one-half of the air chamber volume. More gas is required if the cooling plant leaks; less gas is required if the flow of gas which is poor in oxygen, is increased.
From 90 to 120 grams of insulating material burned in one cubic meter of air. The use of carbonic acid as a fire extinguisher has, as compared to nitrogen gas, the advantages of more rapid expansion in the machine, less demand on the compressed flasks in storage, less cost and easier availability. The full enclosure of electrical machinery and cooling in view of the above results will insure against burnouts due to short circuits.
In high speed combustion engines the essential danger of fire is located in the carburetor. Various stationary fire prevention equipment is available for these engines. Fig. 4 shows a carburetor of a motor vehicle equipped with a rain maker. The tank (a) contains a fill of metyl-bromide with a pressed-on nitrogen buffer as the driving mechanism. After the handwheel (b) is opened, the extinguisher flows through the pipe line (c) to the carburetor (d) to extinguish the fire. Besides the Tetra, an extinguishing powder may also IKused. As shown in Fig. 5, an extinguisher supply line is also placed below the motor housing in the case of airplane motors.
Large benzine or gasoline tanks are protected with foam flooding. In a building which is isolated from the gas station, there is a cylindrical tank which contains dry chemicals for the production of carbonic acid foam. In case of fire, water passes through the apparatus to dissolve the chemicals. The foam flows from a circular rain attachment from the top of the tank downward. Thus each tank is covered with a protecting, cylinrical veil of fire extinguisher. Often the work is assisted by vapors of steam or carbonic acid. More recently the extinguishing method which operates with carbonic acid snow is becoming popular for protection of tanks.