conditions, part of these vapors are condensed and then precipitated in the form of a liquid, and will give trouble in choking up the line, and the water may freeze, closing the line entirely. The gasoline will soften and decompose the rubbers in the couplers. This is due to the solvent action of the gasoline on the rubber, and the immediate effect will be to cause the joints to leak, thereby greatly increasing the leakage loss. The general tendency of natural gas is to become wetter as the well becomes older, and, therefore, natural gas from a new well that may be so dry as not to yield any gasoline at all, may yield gasoline in commercial quantities after the well has been in use for several years. The removal of the gasoline and water vapor car ried by natural gas is 2. Gasoline vapor exists in such a form that practically none of it ever can be delivered to the ultimate con sumer. 3. The condensed gasoline vapors will injure the rubber in the cou plers and in this way increase the leakage of the transmission line. 4. The condensed water vapor will freeze, causing interruption of service, or disturbed and fluctuating pressure conditions. 5. The removal of water and gasoline by blowing the drips results in a large waste of natural gas. 6. The drying of the gas tends to stabilize the gas service by decreasing line troubles. Similar conclusions have been presented by the United States Geological Survey, on pages 645 and 646, in Natural Gas Statistics for 1916, and in Bulletin No. 120, page 11, of the United States Bureau of Mines. FIG. 10. TYPICAL NATURAL GAS TRANSMISSION LINE PRESSURE CONDITIONS. PRINCIPLES OF NATURAL GAS TRANSMISSION. TRANSMISSION IS MORE THAN MERE TRANSPORTATION. Continuity of service from the gas sand-usually one-half mile or more below the earth's surface-through the gas main as a continuous conduit connecting the gas sand and the consumer's fixtures, many miles away, is a cardinal feature of the delivery of natural gas. The general custom of the natural gas business has been to refer to the taking of natural gas from the gas sand to the consumer as transportation. However, the word transmission more correctly expresses the actual operation. Transmission from the roots, trans across, and mitto-to send, emphasizes the fundamental ideas of "to send through" and "to send" and where interstate lines are involved, to "send across" such lines. The fundamental idea "to send" is especially relevant, because the gas is always sent through the line by virtue of its own expansive force, as explained on page 101, and never pulled through by anything ahead, while transportation from the roots, trans= across, and porto=to carry, suggests fundamentally transference only. That is, you transmit through, but transport over. Transmit, for "to send," fixes the attention immediately on the intervening agency and relates to the service, while transport relates to the commodity, although both imply delivery. WHY NATURAL GAS IS COMPRESSED. Natural gas is compressed merely to expedite transmission-for the same reason that makes it necessary to compress cotton, hay, or straw, for shipment. The first feature is to contract the volume, and secondly, to secure enough pressure range between the intake and discharge of the transmission line to secure a large enough pressure drop to force the gas through the line. The broad public interest in an effective and continuous service and a future generation's equity in a conserved future supply makes it the duty of the gas-producing company: 1. To conserve the supply of gas in every way possible. By conservation is meant not merely saving, but using in the most effective manner. This means that it is the duty of the gas companywhen it can be done without financial loss-to remove every foot of gas from the ground that can be obtained. 2. Every appliance known to the art ought to be used to bring about the most economical mining of the gas, and most effective method of transmission and distribution. A normal characteristic of every gas field is that its rock pressure declines each year as the gas is removed from the ground, as shown in graphical form in figures 3 and 4. This means that as the fields grow older it is necessary for the gas company to increase the rapidly declining pressure by mechanical means. HOW NATURAL GAS IS COMPRESSED. This is accomplished by a compressor which is merely a mechanical device to squeeze the gas together into a small volume, thereby increasing its pressure. The specific effect of gas compression is evident from the following: If we take 1,000 cubic feet of gas at 4 ounces gage pressure and increase the gage pressure to 300 pounds, the volume will be contracted to 46 cubic feet. STATUS OF GAS COMPRESSOR ART. The art of natural gas compression is now over 29 years old and has grown at practically the same rate as the increase in domestic natural gas consumers. There are now over 220 natural gas compressor stations in North America, aggregating approximately 350,000 horse power of compressor capacity and compressing about 90 per cent of all the natural gas used. The age and magnitude of the art make it evident that the use of gas compressors is a recognized integral part and universal custom of the natural gas business. 66 66 GAS COMPRESSING' AND GAS PUMPING." These terms, unfortunately, are almost universally used synonymously to describe the contraction of volume of gas by compressing it with a machine known as a gas compressor. Much misunderstanding has arisen because the term pumping station has come into general use in speaking of gas compressor stations. This is wrong, for the reason that the term pumping signifies the action of lifting alone, or lifting combined with force. In the case of natural gas transmission the work is one of pure compression, since the gas is delivered to the gas compressors under an initial pressure considerably higher than the atmospheric pressure, on account of the natural rock pressure forcing the gas out from the wells into and through the intake lines to the compressors. ROCK PRESSURE DECLINE LOWERS COMPRESSOR CAPACITY. As the rock pressures of the gas wells decline, the pressures that have been maintained on the intake side of the gas compressors are also lowered. This has the immediate effect of lowering the capacity of the compressing station. The output of a typical compressor operating against a discharge pressure of 300 pounds gage is as follows, for the respective intake SIZE AND COST OF LINES NECESSARY WITHOUT COMPRESSORS. From an engineering viewpoint it would be possible to take the gas to market without compressors, by simply building a great number of large size lines. However, the number and cost of lines neces sary to do this would be so great as to make the plan prohibitive from a financial viewpoint. That is, the gas compression method is the economical way of handling the problem. The natural gas compressor performs a similar function to the step-up transformer for an electrical transmission line. NO HEAT LOSS IN NATURAL GAS COMPRESSION. Contrary to a widespread popular opinion, the compression of natural gas does not decrease its heating value. While a certain amount of gas is used to drive the compressors, this does not in any way affect the heating value of the gas passing through the compressors. On account of the mechanical work performed on the gas as it flows through the compressors the gas becomes quite warm, and to protect the rubbers in the main lines, is cooled just beyond the compressor discharge before it goes into the main line transmission system. This, however, pertains merely to the temperature of the gas itself, and in no way affects its heating value. NOT FEASIBLE TO MAKE NATURAL GAS MAIN LINES COMMON CARRIERS. The natural gas main lines form the connecting link between the mining operations in the natural gas field and the public utility service in the city distributing plants. A number of attempts have been made by large consumers, owning natural gas in the field, to have the main transmission lines made common carriers so that they could be compelled to haul the large consumer's gas to market. The converting of main lines into common carriers is not only not feasible from an operating viewpoint, but the idea could be based only on distinctly local and selfish interests, and would ignore entirely the domestic consumers' interest. That is, this plan would greatly injure service to the over 2,000,000 domestic natural gas consumers in the United States, because it is not generally appreciated that: 1. There is a clear distinction between the duties of a common carrier or railroad, and the duties of a public utility. (a) The terms "railroad," "common carrier," and "public utility" are frequently confused. A railroad is a common carrier that undertakes for hire to transport persons or goods, or both, from place to place, for all persons indifferently. The fundamental duty of a railroad or common carrier being indifference as to who shall be served, and an equal readiness to serve all who apply in the order of their application. On the other hand a property becomes a public utility only when dedicated to a public use. (b) Even though legislative enactments would be passed declaring natural gas lines public transportation agencies—that is, common carriers they could not be enforced because such legislation would be in direct conflict with well-known economic and engineering |