The storage tank can be arranged with a float which will permit the oil suction line to be below the fluid level at all times and yet never touch the bottom where the water rests. This may be in the form of a barrel float, Fig. 180, where the oil line, at the point where it enters the tank, has a short rubber connection. The other end is plugged and is fastened to a keg while a tee and nipple above the keg allows the oil to enter the line. The keg floats on the surface and, even if the tank is almost empty, the angle at which the keg rests prevents the suction nipple from touching the bottom. The only attention required is the occasional re newal of the rubber hose.
When an engine ceases functioning in all the cylinders, it is usually an indication either of no fuel or of water-logging. If there is no fuel, the engine ordinarily first runs irregularly before stopping. With water entering the cylinder the cessation of ignition is almost instantaneous.
Ash.—The damage resulting from the presence of ash in the . fuel is over-estimated. This residue remaining unburnt in the engine cylinder is of a mineral character, being silicate, quartz or iron oxide. There is no doubt that any decided percentage of these substances will score an engine cylinder. Fortunately no oil is offered for Diesel fuel that has an ash percentage above .05 per cent.; this amount is so slight that its presence is not revealed through any engine trouble.
Viscosity.—The viscosity of an oil has no bearing on its adapta bility as a Diesel fuel. The thickest, most sluggish oil can be made quite free flowing through the application of heat. In the Northern states every oil storage tank should have heating coils for use in the winter months. If these coils are connected with the discharge cooling water before it enters the cooling tower, the heat abstracted is ample to make the oil free flowing. In the cold climates it is always advisable to have a tank inside the building of at least one barrel capacity. If shut-downs are of more than a few hours duration, the engine should be run on kerosene or stove oil until the heavy oil becomes fluid. It is necessary to drain the fuel pump and lines on a shut-down to pre vent clogging of the lines with congealed oil.
Acid.—To avoid corrosion in the pumping and cylinder parts the oil should be devoid of any trace of acid.
Engine Oil engine should be supplied with an individual oil tank. This tank is best elevated with its base at least 5 feet above the engine fuel pump. This places a pressure head on the pump suction that does much to eliminate air leakage into the pump. The tanks are often of two com
partments, one of which holds kerosene for starting purposes.
The employment of kerosene for starting is advisable in all plants. It reduces the liability of the engine refusing to fire and eliminates the tarry deposits that frequently occur when the heavy fuel oil is injected into a cold engine: The kerosene should be fed for ten or fifteen minutes on starting and for four or five minutes before stopping. At the latter time, the kerosene cuts the carbon deposits and prevents freezing of the piston rings.
The tank, in every instance, dught to have a level indicator fitted to it. A simple indicator can be made out of a galvanized float, two pulleys and a light-weighted pointer. The oil can be pumped into this tank from the storage tank by either a hand or motor-driven pump. For a plant of less than 300 h.p. the quantity of oil handled does not justify the expense of a motor-driven pump; a hand rotary pump proves quite suitable and is low in cost.
Oil Storage Tanks.—The capacity of the together with its location largely determines the type of oil storage tank. If the plant consumes less than 12,000 gallons per year, two steel tanks of 6000 gallons each are probably the most advisable size to install. The employment of two tanks provides means whereby a damaged tank can be repaired without a plant shut-down. It allows a thorough cleaning of the tank after each emptying. Figure 181 covers the steel tanks that are of commercial sizes.
If steel tanks are installed, they should be set in a pit and covered to eliminate any fire risk. Figure 182 illustrates a convenient method of placing the tanks. Concrete saddles are placed in the pit; the tanks rest on these saddles. The earth is filled in and a 2- to 4-inch layer of concrete is formed around the tank, completely encasing it. This concrete layer prevents any corrosion of the steel plate by excluding all air and moisture.
Where the ground is inclined to be marshy or water-logged at periods of wet weather, an empty steel tank has sufficient buoyancy to float on this water and, rising up above the ground, will break the pipe connections. To avoid this danger, in ground of this character, a heavy concrete slab can be run about the upper half of the tank or concrete beams laid across the top of the tanks and tied to the saddles with long rods. The weight of the concrete then overcomes the buoyancy of the tank.