HOW TO READ THE INDEX
The index of a gas meter looks quite complicated, but it is really a very simple contrivance. The small circle on the top in Fig. 177 is for testing purposes only and need not be considered. The dial of Fig. 177 is shown in Fig. 177A. The first circle, marked 1 thousand, registers 100 feet for each figure, 1000 feet for the entire circle. If the pointer stood on 9 it would mean 900 cubic feet. The second circle registers 1000 for each figure, or 10,000 for the entire circle. When the pointer of the first circle has been around once, it reaches 0 on that circle, but the hand on the second has moved to figure 1, showing 1000 feet used. The process goes on until the pointer of the second circle has traveled around and stands at zero. The pointer on the third circle, however, has moved to 1, indicating 10,000. This explanation shows the general plan of the index. A few minutes study of it will render the index as easy to read as the face of a clock. Of course, the pointers do not always stand exactly on the figures as they move from figure to figure as the gas is used.
Suppose your index stood like this:
Fig. 177A.—Gas-meter dial. It reads 38600 cubic feet.
Take the figure 3 on the 100 thousand circle, the figure 8 on the 10 thousand, and the figure 6 on the 1 thousand, and you have 30,000, 8000, and 600, or 38,600 feet. To ascertain the quantity of gas used in the time elapsing between the readings of the meter, subtract the quantity registered at the previous reading. Thus, if the previous reading was 38,600 feet, and the next reading 40,100 feet, the pointers standing thus:
Fig. 177B.—Gas-meter dial. It reads 40100 cubic feet.
| You have | 40,100 |
| Subtract your last reading | 38,600 and you find |
| ——— | |
| that your bill should be for | 1,500 feet |
When 100,000 feet have been passed, the index is at zero; that is, all the pointers stand at 0, and the registration begins all over again.
Prepayment Meters.
—In many places it is desirable to sell gas in small quantities and to prepay the amount for a given supply of gas. This is accomplished by a meter such as that of Fig. 179. The meter is constructed much the same as the former but provided with a mechanism such that when a coin—usually 25 cents—is deposited, according to the printed directions in the instrument, an amount of gas representing the proportional current rate is allowed to pass the meter. The supply is cut off as soon as the amount paid for is used; when in order to receive more gas, another coin must be deposited as before.
Fig. 179.—The prepayment gas meter.
Gas-service Rules.
—The rules for the regulation of gas service are in many States under the control of a board or commission whose duty it is to form codes prescribing the measurement and sale of all public utilities. The following form, General Order No. 20, State Public Utilities Commission of Illinois, gives an idea of the requirements in that State for the sale of coal gas.
Rule 3. Request Tests.—Each utility furnishing metered service shall make a test of the accuracy of any meter, upon written request by a consumer: Provided, first, that the meter in question has not been tested by the utility or by the commission within 6 months previous to such request; and second, that the consumer will agree to accept the result of the test made by the utility as determining the basis for settling the difference claimed. No charge shall be made to the consumer for any such test. A report, giving the result of every such test, shall be made to the consumer.
Rule 4. Adjustment of Bills for Meter Error.—If on any test of a service meter, either by the utility or by the commission, such meter shall be found to have a percentage of error greater than that allowed in Rule 11 (see below) for gas meters, the following provisions for the adjustment of bills shall be observed.
(a) Fast Meters.—If the meter is faster than allowable, the utility shall refund to the consumer a percentage of the amount of his bills for the 6 months previous to the test or for the time the meter was installed, not exceeding 6 months, corresponding to the percentage of error of the meter. No part of a minimum, service or demand charge need be refunded.
(b) Slow Meters.—If the meter is found not to register or to run slow, the utility may render a bill to the consumer for the estimated consumption during the preceding 6 months, not covered by bills previously rendered, but such action shall be taken only in cases of substantial importance where the utility is not at fault for allowing the incorrect meter to be in service.
Rule 11. Gas-meter Accuracy.—(a) Method of Testing.—All tests to determine the accuracy of registration of a gas service meter shall be made with a suitable meter prover. At least two test runs shall be made on each meter, the results of which shall agree with each other within one-half per cent. (½%).
(c) Allowable Error.—Whenever a meter is tested to determine the accuracy with which it has been registering in service, it may be considered as correct if found not more than two per cent. (2%) in error, and no adjustment of charges shall be entailed unless the error is greater than this amount.
Rule 15. Heating Value.—Each utility furnishing manufactured gas shall supply gas which at any point at least 1 mile from the plant, and tested in the place where it is consumed, shall have a monthly average total heating value of not less than 565 B.t.u. per cubic foot, and at no time shall the total heating value of the gas at such point be less than 530 B.t.u. per cubic foot.
To arrive at the monthly average total heating value, the results of all tests made on any one day shall be averaged and the average of all such daily averages shall be taken as the monthly average.
Rule 8. Railroad Commission of Wisconsin.—Each utility furnishing gas service must supply gas giving a monthly average of not less than 600 B.t.u. total heating value per cubic foot, as referred to standard conditions of temperature and pressure. The minimum heating value shall never fall below 550. The tests to determine the heating value of the gas shall be made anywhere within a 1-mile radius of the center of distribution.
Fig. 180.—Detroit Jewel one-piece, star-shaped burner.
Gas Ranges.
—Gas ranges and all other heaters using gas as a fuel are constructed to utilize the principle of the Bunsen burner. Fig. 180 illustrates the type of burner used in the Jewel gas range. This represents the form adapted to the top burners for all direct-contact cooking or heating. The burners are of different sizes and arranged as they appear in Fig. 181. This picture shows the top of the range as seen from above, looking directly downward. The gas supply pipe and individual valves for each burner are in position as they appear in front of the range.
Fig. 181. Fig. 182.
Fig. 181.—Showing top burners and valve attachment of a gas stove.
Fig. 182.—Section showing arrangement of oven burners and lighter of a gas oven.
In operation, the nozzles of the gas valves stand directly in front of the opening G, in Fig. 180. The stream of gas in passing into the burner induces a flow of air through the opening A. The mixture of gas and air is such as will burn with the characteristic Bunsen flame without smoke.
The oven burners are different in form but the individual flames are the same as those of the top burners. They extend across the oven as shown in Fig. 182. In this the top of the oven is removed and burners as seen are viewed from above.
The top burners are lighted by direct application of a burning match but the oven burners must be lighted by first igniting a special torch or “pilot lighter.” The middle gas valve of Fig. 182 is turned and the torch lighted, then the other valves are opened and the jets are instantly ignited. As soon as they are burning the pilot lighter is extinguished by turning its valve.
The reason for this special lighter is because of the possibility of explosion at the time of lighting. The gas from the jets is mixed with air at the proper proportion to be violently explosive and if by chance the gas should be turned on a sufficient time to fill the oven with this explosive mixture and then lighted, an explosion would be certain, with every possibility of disastrous consequences. All gas ovens should be lighted in a manner similar to that described.
Lighting and Heating with Gasoline.
—The remarkable growth of modern cities, the building of small towns in the west, and the improvement in suburban and rural homes has created a demand for efficient means of illumination in the form of small household lighting plants. The development and improvement in electric lighting has induced an equal, if not greater, improvement in gas lighting. Up to the year 1875, the open-flame gas jet represented the most improved form of city lighting. Then came electricity, which for a time bade fair to supplant all other forms of illumination; but the relative high cost of electric lighting, even with the advantages it afforded, was a stimulus to improvement in less expensive forms of illuminants.
The invention of the incandescent-mantle gas burner enormously increased the opportunities for gas lighting and opened an inviting field of endeavor. In a relatively short time, three distinct types of gasoline lighting plants for household illumination came into common use, with a great number of different systems in each type. As a means of economical illumination the only rival of any consequence to the small gasoline-gas plant of today is acetylene. The dangers attending the use of these agents of illumination have been rapidly eliminated, until today—when intelligently managed—they are fully as safe as any other means of artificial lighting. Gasoline plants are now in common use in cities where competition with all other forms of illumination require excellence in service to hold an established place.
In order that any mechanical appliance may be used with the best results, its principle of operation and mechanism must be thoroughly understood. In the case of gasoline plants, not only familiarity with the mechanism should be acquired but an intimate knowledge of gasoline and its characteristic properties should be gained, that the peculiarities of the plant may be more fully comprehended.
Gasoline
is the first distillate of crude petroleum; that is, in the process of separation, the crude petroleum is distilled from a retort and the condensed vapors at different degrees of temperature form the various grades of gasoline, kerosene, lubricating oil, paraffin, etc. The crude oil is placed in the still and heated; the distillate that first comes from the condenser, at the lowest temperature of the still, is gasoline of a light spiritous nature. As the process of distillation continues, this part of the petroleum is entirely driven off and it is necessary to raise the temperature of the still in order to vaporize an additional portion of the oil. There is no distinct line of separation between the gasoline that first comes from the condenser and that which comes over after the temperature is raised, except that it is less of a spiritous nature and contains more oily matter. As the temperature of the retort is gradually raised, the distillate contains less and less of the spiritous and constantly more of the oily matter.
In order to grade gasoline for the market, the standard adopted was that of relative density. The distillations produced at various temperatures are mixed to produce various densities which form definite grades of gasoline. The Beaumé hydrometer is a scale of relative specific gravities in which the different densities are expressed in degrees. The highest grade of gasoline produced by the first distillation is 90°Bé.; that is, the hydrometer will sink in the gasoline to 90° on the scale. As the temperature of the retort is gradually raised, the distillate becomes heavier and the next commercial grade is 86° gasoline. The 86° gasoline contains a greater proportion of oily matter and a less amount of that of a spiritous nature. The next commercial grade that is produced, as the temperature is raised, is 76° gasoline, a still highly volatile spirit but containing more oil than the last. This process is kept up until there is an amount of oil in the distillate that can no longer be termed gasoline, when kerosene is distilled from the retort.
The following descriptions of gasoline and kerosene by B. L. Smith, State Oil Inspection Chemist of North Dakota, gives a definite idea of their properties and the requirements of the law in their regulation and sale.
“Gasoline is formed by the condensation of vapor that passes off at comparatively low temperatures during the distillation of crude petroleum. It has been common practice among refiners to collect as ‘straight’ gasoline all that distillate having a specific gravity above 60°Bé. At present, the name applies broadly to all the lighter products of petroleum above 50°Bé. in gravity, including products obtained from the ‘casing-head’ gases of oil wells, by methods of compression and cooling, and also the ‘cracked’ gasoline formed by the decomposition of heavier oils when subjected to high temperature and pressure.
“It has been the custom to grade and sell gasoline according to ‘high’ or ‘low’ gravity test. Recent study and investigation has shown that specific gravity in itself is of very little value in determining the quality of a gasoline. It may be taken as an index of other properties, particularly its volatility, if information as to its source and method of production are at hand; but under present market conditions a specific-gravity determination is entirely inadequate. The specific-gravity test alone may give a high rating to a poor gasoline and a low rating to a good one. It has been discarded as a standard of comparison by the U. S. Bureau of Mines. It indicates nothing definite about the quality of a gasoline and in many cases it does not even approximate relative values. Volatility, that is, the ease with which it vaporizes, is the fundamental property that determines the grade, quality, and usefulness of gasoline. The Beaumé test, however, must remain the standard for grading gasolene until a more definite measure is adopted.
“The Oil Inspection Law (1917) for the State of North Dakota, states, that: ‘all gasolines, sold or offered for sale in this State for household use, shall, when one hundred cubic centimeters are subjected to a distillation in a flask—as described for distilling of oil—show not less than three (3) per cent. distilling at one hundred and fifty-eight (158) degrees Fahrenheit, and there shall not be more than six (6) per cent. residue at two hundred and eighty-four (284) degrees Fahrenheit, which shall be known as the chemical test for gasoline sold or offered for sale in this State for domestic purposes.’
“Gasoline for household purposes, as for use in cold-process lighting systems should contain not more than a very slight amount of constituents that do not vaporize readily. It is obvious that a gasoline for cleaning or drying purpose should contain no oily or kerosene distillate. On the other hand, the gasoline for use in a gasoline stove or other generator, where heat is employed in its vaporization, may contain a considerable amount of the less volatile oils. The amount of gasoline sold for household use is in very minor proportion to the immense quantity used for motor purposes.
“No hard and fast line differentiates good motor gasoline from bad. In fact standards of quality seem to be varying with advances in engine design, so that what once was poor gasoline can now be successfully used. Improvement in carburetors seem to be keeping pace with the ever increasing amount of kerosene in the ordinary motor gasoline.
“Gravity test cannot be relied upon as indicating the kerosene content. In the laboratories of the Oil Inspection Department for the State of North Dakota, there have been examined two gasolines of the same gravity, 56.2°Bé. at 60°F., but which contains 31 per cent. and 62 per cent. of kerosene respectively, and their distillation range is quite different. On the other hand, there are other gasolines whose boiling range is nearly parallel and similar, yet whose gravities are 50.2°Bé. and 59.2°Bé. respectively. Also a gasoline and a kerosene having a difference in gravity of but 1°Bé. and a difference of nearly 100°F. in the temperature at which they begin to boil and a difference at 200°F. in the temperature at which all had distilled over. The so-called ‘low’-test gasolines average between 35 per cent. and 40 per cent. kerosene. The chief element of advantage in the so-called ‘high’-test gasolines seems to be that they yield a maximum efficiency over a larger range of engine conditions.
“We have a sample of gasoline sold as ‘high’-test gasoline which contains 29 per cent. of kerosene. Indeed it has a high Beaumé gravity (63.70) compared to the average low-gravity gasolines on the market, and it also contains a large amount (14 per cent.) of very easily volatile constituents. Such a product seems to be a blend of very light ‘casing-head’ stock with kerosene of low boiling range to give the ‘high’ gravity.
“It is desirable that a gasoline should contain a certain percentage of very low-boiling constituents, so that engines may start more readily, especially in unfavorable conditions of weather or climate; but a large proportion would be undesirable because of loss through evaporation and the liability of accidental ignition and explosion. A reasonable amount of light volatile material would probably be about 3½ per cent. Again a reasonably low percentage of the very less volatile constituents is desirable to insure complete vaporization at a not too high temperature, say not more than 10 per cent.; but such a gasoline would be expensive. The producers and refiners claim that the present immense demand necessitates the mixture of low-boiling kerosene constituents with the true gasoline fraction.
“Kerosene.
—The character of this fuel is best understood by comparing it with gasoline, which it in general resembles, except that it is much less volatile. It is obtained from crude petroleum at a temperature just above that (300°F.) at which gasoline passes off. Its chief use is as an illuminant in lamps. It is also increasingly used as a fuel in cooking stoves, small portable heaters, and as a motor fuel for engines and tractors.
“The laws of most States stipulate certain tests which kerosene must meet in order to be approved for general sale. These tests include color, flash point, fire test, sulphur determination, and candlepower tests. The North Dakota Oil Inspection Law (1917) specifies that the color shall be water-white when viewed by transmitted light through a layer of oil 4 inches deep. It shall not give a flash test below 100°F. and shall not have a fire test below 125°F. Such illuminating oils shall not contain water or tar-like matter, nor shall they contain more than a trace of any sulphur compound. The photometric test, when burning under normal conditions, shall not show a fall of more than 25 per cent. in candlepower in a burning test of not less than 6 hours nor more than 8 hours’ duration, consuming 95 per cent. of the oil.
“The flash point of an oil is the lowest temperature at which vapors arising therefrom ignite, without setting fire to the oil itself, when a small test flame is quickly approached near the surface in a test cup and quickly removed.
“The fire test of an oil is the lowest temperature at which the oil itself ignites from its vapors and continues to burn when a test flame is quickly approached near its surface and quickly removed.
“When oils containing sulphur are burned, the sulphur is thrown off in the form of gaseous sulphur compounds. Because of their poisonous nature and their bleaching and disintegrating action on clothing, hangings, wall coverings, etc., it is obvious that to safeguard the health and preserve the furnishings of the home, illuminating oils should contain not more than a trace of sulphur compounds, and that their flash and fire limits should be high enough to insure safety in ordinary use in lamps and stoves.
“The law further specifies as to the boiling limits of kerosene: ‘It shall be the duty of the State Oil Inspector ... to have chemical tests made ... demonstrating whether or no such oils contain more than 4 per cent. residue after being distilled at a temperature of 570°F., and shall not contain more than 6 per cent. of oil distilling at 310°F., when one hundred cubic centimeters of the oil is distilled from a side-neck distilling flask’ of certain specified dimensions.
“This is to insure the kerosene against an excess of easily inflammable material of the gasoline range and thus render it dangerous to the user. In addition it is to insure against an undue proportion of heavy constituent of lubricating oil distillate, which would clog the wick and reduce the efficiency, heating and illuminating value of the oil.”