As soon as the engine is at normal speed the water injection should be started, provided the engine is of a design using water in the cylinder.
If the engine is belted to its load through a friction clutch or clutch pulley, the clutch should now be thrown in. If the engine is belted or direct-connected to a generator, the line switch should be closed and the voltage on the machine gradually built up. In two-unit plants, where the generators operate in parallel, special care should be exercised in order that the two gene rator voltages be identical before they are thrown together; this applies to direct-current machines.. If the machines are alternating current, it is imperative that they be in phase before 'IP being paralleled. The most feasible arrangement whereby the paralleling can be easily accomplished is the use of a synchron oscope. A plant with a total capacity of 50 kw. should he equipped with this instrument. In the small plants, or in larger ones where it is impossible to purchase the synchronoscope, the pilot lamp device should be used. In no plant should an engineer depend on chance in the matter of paralleling alternators.
Temperature of Cooling proper temperature of the jacket-cooling water is a matter that must be determined by experiment on the particular engine used. Engines, even of the same horsepower and same manufacture, show a decided varia tion in the water temperature most favorable for efficient opera tion. The characteristics of the fuel oil used have considerable effect. As a general rule, it may be stated that with oils under 32° Baume gravity the temperature of the discharge cooling water should be maintained around 150° to 160° Fahrenheit. For lighter oils, such as distillates up to 42° Baum& the temperature should not exceed 140° Fahrenheit, and usually 125° Fahrenheit will prove satisfactory. With the heavier oils it is necessary that the cylinder and head be kept fairly warm in order to thoroughly vaporize the fuel charge.
with the cooling-water temperature, the amount of lubricating oil that is required on any engine cannot •be stated with any degree of certainty. Much depends on the
fuel used, the condition of the engine and the particular design of the unit. Where either splash lubrication or oil cellars are used for lubrication of the bearings and crank pin, if 600 are produced per gallon of lubricating oil the oper ator can feel that he is securing efficiency in his oiling. It should be understood that usually an engine will require as much lubrication on half as on full load. Consequently, if the engine be at half load, the horsepower per gallon of lubricating oil will be one-half of the above. If kerosene or high-gravity dis tillate, usually termed "stove oil," be used, the amount of lubri cation required for the cylinder is practically doubled.
The following table represents a fair average for an engine of above 40 h.p. per cylinder Piston pin 10 drops per min.
Crank pin 30 drops per min.
Cylinder, exhaust side 40 drops per min.
Cylinder, air-port side 50 drops per min.
In engines where the cylinder is oiled at three points, the amount of oil for the three should approximate the total for the two values above. If the piston pin is lubricated by scooping up oil from the cylinder walls, of course the oil to the cylinder must be increased.
Each oil company has a particular oil that usually is suitable for low-pressure engines. It is hardly profitable for an engineer to experiment with the various oils offered, and the most satis factory oil to purchase is the one recommended by the builder of the engine. All engine builders are much interested in the lubrication problem and are in a position to conduct extensive tests on all the lubricants on the market. They seldom are prejudiced in this matter, and their recommendations can be followed with confidence. • Operation Troubles. Engine Smokes.—At least 50 per cent. of the engines in use show a decided inclination toward a smoky exhaust. Since this symptom of imperfect operation is so appar ent, the most inexperienced engineer cannot overlook it. Any one of a number of misadjustments may be the cause of this dark-colored exhaust.