CHAPTER VIII.

THE TRANSPORTATION, USES AND MODES OF USING NATURAL GAS.

BY EMERSON MCMILLIN.

In the preceding chapters the reader has been told of the geographical locations where natural gas has been found; of the geological horizons that must be pierced to obtain it; of its probable and varied origin; of the reservoirs in which it is stored; of its chemical composition, and of the theories that should probably govern in the location of wells bored for gas, with descriptions and illustrations of rigs, power and tools used in the search for natural gas-the great desideratum of almost every town and city in our land.

Wells may be properly located, the holes successfully drilled, and a flow of gas obtained; but, to be utilized, the gas must be conducted through lines of tubing, from the casing at the well to the burner, fire or furnace, where it is to be consumed. This may be a short or a long distance; if the former, probably but few difficulties will be encountered; if the latter, there are many problems to solve if the work is to be done expeditiously, safely and cheaply.

SYSTEMS OF TRANSPORTATION.

The earliest system of tubing or piping natural gas was that of bored logs. This mode has been practiced in the Kanawha Valley for more than half a century. The logs are usually cut from trees twenty to thirty inches in circumference, and the holes bored from two to four inches in diameter, and from end to end through the center of the log. The sections are cut from six to ten feet long. The end of one log is tapered to a spigot, and driven into the reamed-out end of another log. These conduits answered their purpose quite well in their day, but the high-pressure gas from wells now in use in other parts of the country could not be utilized with a pipe-line made in this manner.

Very efficient gas-pipes for conducting manufactured gas, are made in places in the state of Michigan, by boring out tamarack logs, which are afterwards coated, inside and out, with pitch or asphalt. Twelve or fifteen years ago this class of pipe was a strong competitor of cast-iron pipe for gas-mains. The great reduction in the cost of iron pipe, and the uncertainty attending the probable duration of the wood pipe, have caused the use of the latter to be almost entirely discontinued.

Cast-iron pipes, in sizes above two inches, are used almost exclusively for conveying manufactured gas. This remark applies to the United States, and to most other countries. The French engineers, howeverespecially in Paris-use tubing which is made by coating heavily with hydraulic cement thin sheet-iron, bent to the shape and size desired. This pipe has been used in this country even for heavy-pressure watermains, but the use here has been so limited that an opinion as to its merits cannot be given.

Wrought iron tubing, rolled to the size required, is now being used by a few engineers as mains for conveying manufactured gas.

The first cost is greater than is the cost of cast-iron, and the supposition is that the wrought-pipe will not last so long.

This supposition is probably correct; and yet, with an experience of twenty years, chiefly with cast, but partly with wrought iron gasmains, I have never seen either kind, wrought or cast, removed because of oxidation, except when the conditions of the soil were unusual. Small service-pipes to consumers rust out quickly-in some soils in less than two years-but the iron of the small pipe is very thin, and a little oxidation will go through it.

The iron in the larger pipes is thicker and, when a thin coat of oxide is formed on the outside, it apparently protects the surface from further oxidation. Neither wrought nor cast-pipe conducting gas will oxidize on the inside.

The high-pressure pipes in use in and about the city of Pittsburghthe present center of natural gas utilization-are almost exclusively of wrought-iron. Many miles, however, of larger sizes, ten to twenty-four inches in diameter, of cast-iron pipe have been laid in that city during the last two years. This cast-pipe is not expected to carry a pressure exceeding ten pounds per square inch. By enlarging the area of the cast-pipe, and by properly constructed appliances, to be described further along, the pressure is reduced from 200 pounds, as it sometimes is in the high-pressure wrought-pipe, to ten pounds on entering the cast-pipe.

Much excitement prevailed in and about Pittsburgh during the year following the introduction of natural gas, growing out of the accidents that occurred through defective system of transportation. The escape of the gas-which there possesses no odor-caused houses to be blown up, and many persons to be dangerously injured, and, in some instances, causing loss of life. The dangers became so great that the matter was taken into Court, and an effort made to correct the evil. In the equity proceedings between the city of Pittsburgh and the Fuel Gas Company et al., the Court appointed a Commission of five intelligent persons to make a thorough and exhaustive investigation of the questions involved.

The report of this Commission has been made public, and it imparts much valuable information. The parties giving testimony before the Commission were experts, engineers, pipe-layers, chemists and mechanics, and the testimony given was oftentimes of the most confusing and conflicting character. While there were many questions of detail to be settled by the investigation, there were two principal questions to be determined that transcended all others. First, how high a pressure can be carried in the pipes without endangering life and property; and, second, to how low a pressure may the gas be reduced without increasing its cost beyond the point where a profit, commensurate with the risk of the business, can be made on the money invested.

It was estimated, at the time of the investigation, that about 60,000,000 feet of natural gas was being used in Pittsburgh every twentyfour hours. This equaled 2,500,000 feet every hour.

The consumption, however, would not be regular, and the capacity of the supply-pipes probably had to be equal to a maximum delivery of 5,000,000 feet per hour.

The testimony before the Commission indicated that experts were inclined to believe that, respecting pressure, the old established practice of companies supplying manufactured gas ought to be taken, as a rule, for the government of the natural gas companies. The Commission did not take this view of the question, but advised that a pressure, not exceeding ten pounds per square inch, be allowed in the pipes in the city. The pipes that were laid for transporting natural gas in the city, previous to the report of the Commission, were not laid much, if any, below a depth of three feet. As might have been foreseen, this practice resulted in the winter season-to an almost constant disturbance of the pipes by frost, with enormous leakage and frightful destruction of property, and even loss of life. The apparent necessity for a better and safer system for transporting this dangerous fluid set inventors to work, and scores of plans and devices have been suggested, some possessing merit, but, so far, none seem to entirely meet all phases of the demand. Some governors of great value have been invented. They control the pressure of the gas, preventing its rising above the desired point in the pipes; and if, from any cause, the gas ceases to flow, and the fires or light are extinguished, the gas cannot again pass into the premises without its being turned on by hand. This is probably the most useful invention yet brought out in connection with the question of natural gas supply.

To prevent leakage at joints, many plans have been suggested. The ends of wrought-pipes have been faced, and the threads made long enough, so that the pipes butted together in the middle of the socket, practically making a ground-joint. Another plan was to chamfer the ends of the pipes, and screw them in against a gasket of lead in the center of the socket. Either of these plans would doubtless have given a tight joint, had the temperature of the pipe always remained about the same as when put down; but, at the shallow depth at which the pipes were laid, the joints were failures. Screw-joints, calked with copper wire, also failed for the same reason. Had these joints been made with the pipe at about 40 degrees temperature, and the pipe buried six or seven feet in the earth, it is probable that they would have been practically tight, even at 200 pounds pressure. Pipe should not be laid in long, straight lines, but should form, when down, a slightly wavy line to give room for contraction without destruction of joints. Much of the trouble from leaky joints has been attributed to the variation of the pressure. The registering sheets show this to be constantly varying -generally to but a slight degree, but occasionally the pressure drops down to five pounds, and then suddenly leaps to fifty or sixty pounds per square inch. This change of pressure cannot cause leakage to any great extent, with any of the joints described. The increase of pressure must give an increase of temperature, and that in turn give expansion of the pipes and a consequent tightening of the joints.

To prevent accidents from leakage, various contrivances have been tried. One company in Pittsburgh laid some lines of pipe the usual depth in the ground, and then laid a clay pipe along the top of this pipe, with an occasional outlet leading to and up through a lamp-post, where a light was kept constantly burning-the idea being to have the gas leaking from the iron pipes to follow along in the terra cotta pipe and escape at the lamp-post, and there be consumed. This, of course did not prevent leakage, but prevented accidents from leakage. Opinions differ as to whether this plan is entitled to much confidence, the weight of opinion seeming to be against it. Another plan suggested is that of laying the main below frost, then putting a sleeve over each joint of the main, and this sleeve to be tapped for, say a threequarter-inch pipe, and this pipe to be attached to a two-inch pipe, running parallel to and lying over the main pipe, the upper pipe being buried just under the street pavement. The gas leaking from the joint would enter the sleeve surrounding it, pass up the small pipe into the two-inch, which pipe shall have stop-cocks or valves between the joints, and, by the aid of these valves, the leaky joint can be quickly located. The objects sought to be accomplished are, first, to prevent the escape of gas into cellars, and second, to be able to locate the leaks with rapidity and certainty, with the minimum disturbance of the streets.

Owing to the difference in the composition of the gases, that which is found in the vicinity of Pittsburgh, and also of Findlay, is much more difficult to transport, without leakage, than is that of the oil regions of Pennsylvania. In the first place, its specific gravity is much less, and, second, the absence of oily residuals, which, in the gas-oil regions, aids in closing up the small interstices of the pipes and joints. The specific gravity of the Pittsburgh gas is given as .557; that of Findlay, Ohio, at .585, and that of Bradford, Pennsylvania, as .850-air being 1.000.

MEASUREMENTS OF QUANTITY, ETC.

The extensive use of natural gas at the present time, and the long distances it is being carried, makes the question of a convenient formula for calculating the flow of gases through pipes one of much importance. There is a popular rule in use by gas managers that will occasionally be found convenient to use by those unable to calculate accurately, with the formula in use by engineers, the sizes of pipe required. This general rule is, that

First. The discharge of gas will be doubled when the length of pipe is only one-fourth of any given length.

Second. The discharge of gas will be only one half when the length of pipe is increased four times.

Third. The discharge of gas will be doubled by the application of four times the pressure.

While these rules are good enough when applied to the short distances of lengths of pipe, and to the slight changes of pressure that occur in the distribution of manufactured gas, they have little value when applied to the great variations in length of pipe, and pressure, that are met with in transporting natural gas.

The following formula is in general use for calculating the discharge of gas through mains: