The size of the storage tank depends upon the estimated consumption of oil. If the plant is a great distance from the source of supply, a storage equal to at least one month's requirement should be constructed When the storage is far from the furnaces, it should be arranged to allow the oil to flow by gravity. It is better to pump the oil into the storage than tax the pumps to their capacity by pumping from the storage to the burners. Large suction lines from stor age to the pumps are recommended, the diameter of the suction being from 1 to 2 in. greater than the pump suction.
When necessary to heat the oil in the storage tank, this can be best accomplished by 2 in. heating coils, placed near or around the suction, inside of the tank. Pipes through the tanks should be connected by companion flanges securely fitted to the shell, and not a running nipple secured with lock nuts.
Fig. 5 shows the method of unloading a tank car by gravity. Wherever possible a "trough" should be constructed to allow the oil to flow into the storage tank as it obviates the necessity of making pipe con nection each time a car is unloaded and prevents the loss of oil before the connection can be made after the valve is opened when some foreign substance collected under the bottom valve.
Fig. 6 shows the method of pumping the oil from the tank car. In cool weather it is often necessary to heat the oil, and in tank cars having no heating coils, steam connections are made as shown.
Fig. 7 shows how a tank car is unloaded by means of compressed air. Care should be taken in using this method as many of the tank cars are only tested to 50 lb. pressure per square inch.
A swing joint and strain should be fitted to the suction line entering the tank ; the length of the "swing" being equal to the depth of the tank. The strainer can thus be cleaned after it has been pulled to the opening in the top of the tank. A small drain is necessary at the bottom edge of the tank to drain off the water that settles. A manhole on the top and also at the bottom side is of great advantage when cleaning. 'Vent pipes must be also provided to allow for the escape of any gas that might form.
The use of naked lights around the storage tanks should be absolutely prohibited. When using portable electric lights care should be taken to see that the in sulation is in good condition as otherwise an explo sion is liable to occur in case of a spark, due to the wires grounding.
Many classes of pumping systems have been de vised to handle the oil from the storage tank to the burners. As a rule they consist of two pumps mounted upon a bracket or base containing the oil heater which utilizes the exhaust steam from the pumps or live steam from the boilers, thus bringing the oil up to the required temperature. The pumps are set on a flat cast iron pan so arranged that they may be over hauled without allowing the oil or water to flow over the heater or fireroom, and deep enough to hold the oil contained in the pump cylinders. An oil relief valve is placed on the discharge line and fitted so as to allow any excess oil to return to the tank.
Oil strainers are either fitted in duplicate or the self cleaning type is used. An air tank is placed on the discharge line to take up the pulsation of the pump, thus insuring a steady pressure. The pressure is also regulated by means of a pump governor fitted on the steam line to the pumps and connected to the oil line.
By an arrangement of valves and fittings either pump may be used, the oil passing either through the heaters or directly to the burners. Any gas formed in the oil chambers may be vented through proper valves and gages and provided to show the pressure and temperature.
Fig. 8 shows a complete and very compact fuel oil pumping system. Fig. 9 shows a condensing type of oil heater.
Fig. 10 shows a pumping system and heater ar rangement for a "mechanical" oil burner installation. Owing to the high pressures and temperatures used with mechanical systems, care must be taken to have all fittings of the best quality. Fig. 11 shows a low pressure heating system, used in kitchen ranges, hot water boilers, low pressure steam boilers, and hot air furnaces.