Figure 229 gives results of various tests, in which the steampressure and the oil-pressure on the burner are the two variables. It is apparent that the curves represent practically straight lines. Figure 230 shows the influence of temperature on the flow of oil through an orifice, the pressure difference remaining constant.

PRACTICAL APPLICATION OF TEST DATA

To illustrate the application of the above data in the design of the Moore Automatic Fuel Oil Regulating System, now in use in a number of prominent plants in the West, it should be stated, for those not familiar with the details of this system, that it operates on the principle of central control instead of individual control of the burners and dampers. The oil burners and valves are left wide open, or nearly so, and a variable oil pressure is maintained in the oil-burner header to given an equal pressure at all burners, the pressure varying with the load, controlled automatically by throttling the supply of oil to the header, to maintain a nearly constant steam-boiler pressure. As in most plants, burners must be designed to handle very heavy oil and also to permit heavy overloads on boilers, the average pressure at the burner at normal loads is very low and but a few pounds. To build up the pressure in the oil-to-burner header, and to prevent the friction in the header causing an unequal supply of oil to all burners, a resistance, due to a diamond-ported regulating cock, is inserted in each burner-branch pipe between the main throttle. valve and the tip of the burner and set to give such resistance that the pressure in the header at normal load on the boilers will be 20 or 30 lb. or thereabouts, depending upon operating characteristics, etc. Then a slight pressure drop in the header would have little effect on the unequal supply of oil to the various burners.

The oil pressure gauges connected to this header are located in the front of each battery of boilers, so that the firemen can tell approximately, from the reading of the oil-pressure gauge, the relative rate of firing of boilers.

A low pressure steam header is similarly connected to all burners, but generally without the diamond ported valve as a resistance, the pressure being high enough without this resistance. The supply of steam from the main boilers to the low pressure burner header, and its pressure, are controlled by means of a special throttle valve, generally known as a chronometer valve,

and this chronometer valve is in turn controlled by a steam-toburner regulator actuated by the variable oil pressure in the oil-to-burner main.

If the curve of steam and oil pressure, as mentioned above, is a straight line, then the steam pressure is equal to the oil pressure multiplied by a coefficient plus a constant. At one plant this relationship was found to be such that the steam pressure at the burner was equal to the oil pressure times three, plus thirty; thus at rating the oil pressure was 20 lb. and the steam pressure was 90 lb.; at 50 per cent. overload the oil pressure was 30 lb. and the steam pressure was 120 lb.; at half the load the oil pressure was 10 lb. and the steam pressure was 60 lb.

CHAPTER XLIII

PRESENT STATUS OF OIL BURNING POWER PLANT DESIGN

The present shortage of hydro-electric power on the Pacific Coast has created an unusual situation in that the demand for power is so great that steam plants intended originally to act merely as standby installations and to assist the hydro-electric

systems in case of trouble are now being operated at full capacity and carrying a large proportion of the total load. Other steam plants are being planned, and those already under way are being

rushed to completion so as to tide over the emergency fast becoming acute.

Fuel.-California oil is the fuel that is used almost exclusively, along the Western Coast. However, unless its production is greatly increased, in the next few years Mexican oil will be introduced into California as it has been in Arizona, Texas and the Atlantic Coast. Mexican oil is generally much heavier, dirtier and more viscous than California oil. Oil in the Panuco

FIG. 232.-Graphical display of petroleum production.

field runs in gravity about 12° Baumé and is so viscous that it cannot be unloaded from a car without being heated and must be kept up to a temperature of 120°F. (50°C.) in the pipes in order to keep it flowing. It is therefore necessary to use large pipes, covered on the outside and containing internal heating pipes through which steam or hot water is passed. Mexican oil usually contains a large proportion of silt, and it is necessary to provide strainers at both the suction and discharge of pumps as

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well as at the burners. To burn properly it must be heated up to 190°F. (90°C.) and in some cases even as high as 250°F. (110°C.) Natural gas is now being used in Bakersfield and in Los Angeles. This is the only available fuel that is superior to fuel oil. It has

all the advantages of oil, and in addition does not require atomizers or bulky storage tanks if it is piped direct from the wells. Coal is used quite extensively in the Pacific Northwest, both in pulverized form and stoker-fired. In California, however,

there is no coal marketed except for domestic purposes. If oil continues to advance in price, the question of the available supply of coal will become of paramount importance. The most promising source appears to be the Alaskan coal fields, which are