It is important to keep the solutions in tanks A and B separate until they meet in the mixing chamber.
Figure 71 also shows a hose extinguisher for small fires, which may occur on the outside of a tank, on the tank farm.
Figure 72a and b shows an actual example of the system at work.
Steam.—Another extinguishing system, not so desirable as Foa mite, consists of turning steam into the top of the tank to snuff out the flame. Steam lines are run from the boiler plant. These open into the tanks and, in case of fire, the steam is turned in. If used early this method is effective, but in big tank farms such a system is impractical, as the boiler plant is far away from some of the tanks and could not deliver steam enough to snuff out the flames.
Sump holes are built around storage tanks. In case of fire it is often necessary to turn the water from the bottom of the tank into the sump, as the fierce heat of the burning oil generated steam from the water in the bottom of the tank and might cause an explosion that would spread the fire. Clearance of at least 200 ft. should be maintained between tanks on tank farms.
Fires in Oil Fields.—Fires in oil fields are due to a number of sources. Derricks catch on fire because of friction of the crown pulley from bailing. Cigarettes, cigars or matches cause fires around the oil rigs. Crossed wires may cause sparks. Spon taneous combustion of waste or rags, grass fires, or leaking gas lines all cause fire. These causes can be removed readily by a little care and vigilance.
Once a derrick starts burning it is only a few minutes (10 to 15) before it will fall over. It may be desirable to control the fall of a derrick to save buildings, and this can be done by pull ing on the guy wires in the desired direction.
Friction of the flowing oil may heat the top of the casing and cause combustion, or a fire may start because of the carelessness of some workman, through a lighted match, cigarette or cigar. Once on fire, a flowing well is a difficult problem to fight. Con trol valves should always be placed on drilling or producing wells where flowing oil or gas wells are expected. If the fire starts it can be extinguished by closing the valve and shutting off the supply of oil or gas.
When a well is not equipped with such appliances the first method used is to try to smother or snuff the flame with steam.
A battery of boilers is quickly assembled and steam lines laid near the burning well. Then the steam from the battery is turned on all at once and the fire may be smothered; or a gust of wind may carry the flame above the oil or gas for an instant, and the steam will snuff the flame.
Where the fire is too vicious for the ordinary steam method, tunnelling to the casing has been tried, and control has been gained by crushing in the casing by means of jacks until the flow is reduced sufficiently so that the steam could snuff out the flame. In other cases a stream of mud has been played into the crater formed by the burning well until the mud finally extinguished the flame.
In November, 1914, a 30,000-million gasser in the bottom of the Cimmaron River Bed in the Dropright Pool of the Cushing Field was extinguished by an ingenious method. Steam had been tried without success. Then a wire cable was suspended from a derrick on one bank to one on the other. A heavy boiler smokestack, open at the top, was hung on this cable and pulled over to the burning gas well. The idea was to drop the smokestack over the gas well and control the flame so that it could be snuffed out by steam. A number of attempts were made to swing the stack in to place, but the gas pressure and the volume were so great that the plan was abandoned the first day. Later efforts succeeded, however, and the flame was snuffed out and the well controlled.
No rules for fire fighting can be laid down, but rigid rules regarding smoking around wells can be enforced and other pre ventive measures employed. Boilers should be placed far enough away so that gas from an unexpected sand cannot be ignited from the boiler fire.
Also, the bits should be dressed outside of the derrick floor, especially in areas where the depth to gas or oil-sands is unknown. Where such depths are known the bits may be dressed, and fires can be maintained until the sands are nearly reached. Even in such cases, however, great care must be exercised.
Grass fires sometimes cause the burning of derricks, and all grass should be cut from around derricks, tanks, and oil sumps. Moreover, the habit of looking for leaks in gas lines with an open flame should be discouraged, as grass fires are sometimes caused that way.