TABLE V. FOR DETERMINING THE TEMPERATURE OF FLOWING GAS FROM THE TEMPERATURE OBSERVED ON THE ENCASED THERMOMETER, AS IN FIG. 6. Observed pressure Observed temperature given by the encased thermometer. 30°. 50°. 80°. 120°. 160°. 200°. 240°. 280°. 320°. 360°. 400°. Table V is for use when the encased thermometer 13 used for determining the temperature of flowing gas through the well-mouth. In most cases this observation may not be required, as this temperature can be approximated by observing the well. When ice forms arouu nd the well-pipe the temperature will be not far from 32° F, probably, though this observation shou'd be taken not immediately at a discharg ing-mouth, but some feet below. The practice of opening a cock for gas to flow out from a high pressure, in which jet to insert the thermometer, will not answer by any means, for two reasons: 1st, because of the great cooling of gas with sudden expansion, and 2d, because the striking of gas particles against the thermometer bulb will have the effect to heat it, thus affecting the thermometer readings by two very considerable causes of error. The thermometer may be introduced in the well-tube into the gas itself below the mouth for a tolerably close approximation to truth, but even the second cause named above will to some slight degree at least affect the thermometer. Probably the most practical way for closely approximating the temperature of flow, by other observations than the encased thermometer, would be by submerging the thermometer bulb in a puddle of water lying on the bare well-pipe below the mouth. To do this, get some moist clay and form a dam of it against the pipe large enough to receive the water, with one side of the pool of water against the pipe for vertical pipes, or the bottom of the pool on the pipe in horizontal pipes. In this pool or puddle of water place the thermometer bulb and allow it to stand some minutes before observing. Thus the water will take very nearly the temperature of the pipe, and also the thermometer bulb. In this case the temperature of the wellpipe is assumed to be the same as that of the flowing gas. But the encased thermometer is the only scientifically correct means for determining the temperature of the flowing gas at the well-mouth. EXAMPLES. The following examples are worked out to illustrate the use of the tables: Then by calculation with the formulas direct, we obtain v = 1453.9 feet per second, and V. day = 11,180,000 cubic feet per day, as obtained without the use of the tables. By Table II we obtain for the same example, the observed pressure being p1 - P2 = 10 lbs. V. day = 9,428,000 cubic feet. Then to correct this for the specific gravity 0.45, the temperature of flowing gas 40° Fahr., and the temperature of storage of 50°, we obtain from Table IV the multiplier .188, additive, giving for the result sought: V. day = 9,428,000 + 9,428,000 × .188 =11,200,500 cubic feet per day, which differs from the calculation above by only 5th, an error of less than a fifth of one per cent. 2d example. Observed pressure p1 - p2 = 25 lbs. Pitot tube. v = 1542.3 feet per second. V. day = 27,231,000 cubic feet per day. By table II observed pressure being 25 lbs., V. day = 30,425,500 cubic feet, and from table IV we obtain the multiplier.102 subtractive, and finally the corrected value of V. day = 27,322,000 cubic feet per day, which is in error only a third of one per cent. 3d example. The Karg well, Findlay, O. : Observed pressure P1-P2 = 15. by Pitot tube. By table II, V. day = 11,107,500 for a temperature of storage at 32°. Correction for temperature of storage at 50°, table IV is .0366 × 11,107,500 additive = 406,534, which added, gives V. day = 11,514,034 cubic feet per day. This figure is less than the previously published figures, one reason being the fact that the figure 12 million, by calcula tion, was for a temperature of storage of 60°. 4th example. The Briggs well, Findlay, O. : P2 = 6.5 lbs. by Pitot tube. By table II, V. day = 2,510,700 cubic feet found by interpolating between 1,959,400 for a 2-inch mouth, and 3,062,000 for a 24 inch mouth. By table IV the correction multiplier is 0366, found by interpolating for 32° between the value under 30° and 35°. The correction is then 91,891 cubic feet, and the corrected value V. day = 2,602,591 cubic By table II, V. day = 871,658 cubic feet, found by interpolating under d = 3 inches between observed pressures of 3 and 4 inches; also, by interpolating likewise under d = 31⁄2 inches, and then interpolating between the quantities thus obtained for the diameter 3 inches. Then by table IV the multiplier is .0366, giving a correction + 31,903, and the final results for a storage temperature of 50°, of V. day = 903,561 cubic feet per day. II. PIPING OF GAS. The recent rapidly increasing demand for natural gas at points comparatively remote from the gas well districts has led to the piping of gas to such great distances as to render a knowledge of the capacity of long pipes for conducting gas a necessity. It has been stated that the quantities of gas transferred in these long pipes considerably exceeds the amount determined by the ordinary formulas for calculating gas-flow in pipes. The difficulty of obtaining accurate results on the flow has probably delayed definite knowledge on this important subject, the chief difficulty consisting of close determination of either the quantity of gas or of velocity. Probably the simplest way for reasonable accuracy is to determine the velocity directly by means of a Pitot tube placed in the stream of gas as it flows in the pipe, as suggested over a year ago, and stated under "applications" in this chapter. Last spring, in accordance with this, some experiments were made with a Pitot tube placed in a pipe-line leading into Fostoria, by which velocities were determined in a 6-inch pipe under a fall of pressure of from one-third of a pound per square inch per mile, up to two pounds per mile, giving about thirty results for the coefficient of friction of natural gas in pipes. Two important facts were discovered from these results. First, the extraordinarily low value of the coefficient; and, second, that the smaller the fall of pressure per mile in the pipe, the lower the coefficient, while for a greater drop in pressure per mile, of say, eight or ten pounds per square inch, the coefficient approaches the usually accepted value. For these experiments a portion of pipe-line, three miles long and six inches in diameter, was selected, at each end of which was placed an accurate pressure-gauge reading to single pounds and estimated to quarters, and a Pitot tube for measuring velocity. The gauges were carefully compared after the experiments by placing them both in common on a pressure apparatus, and reading them simultaneously. Corrections were made according to index errors thus determined. The Pitot tube apparatus at one end was identically the same as that used at the other end of the three-mile length of the pipe-line experimented on. Each of these consisted of two tubes, about 1 inch diameter, inclosed inside a 14-inch piece of inch gas-pipe, and plugged, so as to prevent gas from passing through, except in the two small pipes. The small pipes reached out about one inch distance at one end and were dressed square and beveled out to a sharp edge. One of these ends was bent to a right angle to form the Pitot tube-mouth proper, while the other was left straight for a "side outlet," so that, when the containing tube of this combined arrangement was inserted at right angles into the pipe-line main, the bent end could be presented square toward the current, while the straight end would serve as side outlet, as for the two openings in fig. 5, at A and B, respectively. Then, by properly directing the bent end, the stream of gas in the pipe would drive direct and square against it, while the straight end would receive the current square across, and be uninfluenced by the velocity of gas, and thus the straight end be influenced by only the statical pressure, while the bent end would be influenced by the statical pressure plus a pressure due to the velocity of the stream of gas, and by which excess the velocity was determined. The other end of this combination of tubes had a U-shaped water-manometer attached to the small tubes, one branch of the manometer to one, and the other branch to the other small pipe. In this way the statical pressure at one mouth in the stream of gas is balanced by the statical pressure at the other mouth, leaving to be read off from the manometer only the column of water which is due to the velocity of the current. The containing tube, as above described, was made smooth outside and fitted to run through a packing joint so that the Pitot tube-mouth could be put to any point in the diameter of the main pipe of the pipe-line. To mount this Pitot tube apparatus in serviceable connection with the pipe-main, a cock was tapped into the main, through the plug of which cock the mouth end of the Pitot apparatus could be passed into the stream of gas. To the outer end of this cock was screwed a larger |