Compressed air

Front matter

OFFICE

OF THE

Sup'g-Abch't

Preface

THE literature on the commercial uses of compressed air, especially in its application to the mechanic arts, has not kept pace with the growing importance of the subject, having been confined, in the main, to occasional papers presented to engineering societies, and to special articles appearing at intervals in the various technical journals of this and foreign countries, or in the still more fugitive form of trade circulars; but even these, fragmentary publications at best, cover scarcely more than the past two decades.

The thermodynamic treatment of air under compression, its transmission and expansion, have been ably worked out by careful experimenters and communicated to scientific societies by competent writers ; these articles, valuable in themselves, have not met the requirements of the modern engineer, whose immediate necessities demand a more complete gathering of the widely distributed data relating to this subject, as well as a better classification of the known properties of the atmosphere. This want has long been apparent to the author by reason of many years' experience in answering constantly recurring inquiries relating to compressed air, and to its direct application to the commercial needs of the day. The fund of information acquired and carefully preserved by the author during the many I. years of his editorial work is now brought into compact form and in a single volume for ready reference. That this has been no light task will be apparent from even a casual perusal of the present work.

The progressive advancement in experimental research ex-

8 PREFACE.

tends in two opposite directions : the partial vacuum incident to the ordinary operations of an air pump or the condensation of ^vatery vapor has been extended by other methods to the highly attenuated results obtained in the manufacture of incandescent lamps; while, on the other hand, compression has extended through its various stages until, and in connection with a very low temperature, the final product, liquid air, has been made commercially available. Many of the difficulties in regard to the expression of mathematical details and thermodynamic formulas have arisen in consequence of this progressive advancement ; so also, the knowledge of the atmospheric relation to other elements is yet in a progressive state ; the practical application of compressed air for doing mechanical work is of so recent date that the design and construction of any of the most useful machines operated by compressed air rest upon empirical rather than scientific formulas. It is one of the objects of the present volume to make available the ascertained facts of experimental research in atmospheric phenomena, and, so far as possible, the fundamental basis upon w^hich such ascertained facts securely rest.

To limit the consideration of the properties of air when simply compressed above the ordinary pressure of the atmosphere was believed to be wanting in scope to make the treatment of the subject complete ; this work includes, therefore, a consideration of the properties of air below atmospheric pressure, for the reason that we are surrounded by an atmosphere compressed by gravity, but it is used in the arts in many ways much below atmospheric pressure, even approaching the zero condition of a vacuum, so that, remote as the connection appears, this subject of partial pressures below the atmosphere properly belongs to a treatise on compressed air.

The wide range of manufacturing interests in which compressed air plays an important or even a subordinate part is such that special machines for its production and utilization .are as numerous as the diversified industries of our day ; this

PREFACE. 9

condition has suggested the large number of illustrations employed to place before the reader the salient features of only the latest and best designs. These designs include portable machines, together with a large number of individual and special tools designed for and greatly contributing to the lessening of manual labor, as well as tending to increase the output of useful work.

The development of the caisson method in submarine work for engineering structures has become very general ; requiring not only special appliances, but introducing problems in hygiene which do not ordinarily occur in engineering practice ; the sensations and physical effect of varying air pressures and temperatures upon workmen engaged in labor of this kind belong essentially to the subject-matter of this work, and have been included.

Within the past few years an important and useful commercial effect has been obtained by the use of compressed air and its subsequent expansion in the production of temperatures suited to refrigerating purposes ; such machines are in use on warships and other vessels in which, for one reason or another, the use of ammonia gas is either objectionable or prohibitive.

The author, recognizing the economic value of such machines, has given considerable space to the consideration of the physical and thermodynamic problems connected therewith. There are many interesting problems in this connection which lie beyond the domain of commercial refrigeration, in which, by the production of temperatures far below the Fahrenheit zero and approaching the absolute zero, the critical temperature of air is passed and its physical condition changed from a gaseous to a liquid, and thence to a solid state; as this subject has been fully treated in a recent volume on Liquid Air, it has therefore been given but limited space in this work.

Among the available sources of information employed by the writer have been tho various standard treatises on thermodynamics, including Weisbach, Rankine, Roentgen and Dubois, lO PREFACE.

Thurston, De Volson, Wood, and others ; free use has been made of articles on compressed air and its appliances which have appeared in the Scientific Ainerican from time to time ; acknowledgment is also due to the leading technical journals of this country and of Europe ; while the writer w^ould be wanting in appreciation and gratitude if he failed to suitably acknowledge the action of his friend Mr. William L. Saunders, editor and proprietor of the journal Compressed Air, who, with characteristic liberality, tendered the entire valuable contents and illustrations of this journal to the use of the author in the preparation of this volume. Gardner D. Hiscox.

New York, November, iqoi.

CHAPTER I. PAGE CHAPTER n

Physical PRorERTiEs of Air, 29

CHAPTER HI.

Air in Motion and its Force, 41

CHAPTER IV.

Air Pressures Below Atmospheric Pressure, 49

CHAPTER V.

The Flow of Air under Pressure from Orifices into the Atmosphere, 89

CHAPTER VI.

The Power of the Wind, 97

CHAPTER VII.

Isothermal Compression and Expansion of Air, 113

CHAPTER VIII.

Thermodynamics, 119

CHAPTER IX.

Adiabatic Compression and Expansion 133

CHAPTER X.

The Compressed-Air Indicator Card 153

CHAPTER XI.

Actual Work of the Compressor, 163

CHAPTER XII.

Multi-Stage Air Compression, 175

CHAPTER XIII.

The Expansion of Compressed Air and the Work of the Motor, . 195

CHAPTER XIV.

Transmission of Power p.v Compressed Air, 211

CHAPTER XV.

Compressed Air Reheating and its Work 223

CHAPTER XVI.

The Co.mpressed-Air Motor, 241

Xn CONTENTS.

CHAPTER XVII. PAGE

Efficiency of Air Compressors at High Altitudes, 255

CHAPTER XVIII.

Air Compressors (Descriptive), 269

CHAPTER XIX.

Air Compressors — Continued, 291

CHAPTER XX.

Air Compressors — Continued 337

CHAPTER XXI.

Air Compressors — Continued 367

CHAPTER XXII.

Compressed Air in Mining and Quarrving, 415

CHAPTER XXIII.

Pneumatic Tools — The Pneumatic Hammer and its Work, . . . 445

CHAPTER XXIV.

Pneumatic Tools — Continued, 497

CHAPTER XXV.

Air as Applied to Pyrometrv, 553

CHAPTER XXVI.

Compressed Air in Railway Service, 571

CHAPTER XXVII.

Pneumatic Work, 611

CHAPTER XXVIII.

Pneumatic Work — Continued 627

CHAPTER XXIX.

Pneumatic Work — Continued, 661

CHAPTER XXX.

The Pneumatic System of Tube Transmission, 673

CHAPTER XXXI.

Compressed Air in Warfare 693

CHAPTER XXXII.

Compressed Air Work, 709

CHAPTER XXXIII.

Refrigeration, . ' 745

CHAPTER XXXIV.

The Hygiene of Compressed Air 773

CHAPTER XXXV.

Liquid Air, its Properties and Uses, 785

CHAPTER XXXVI.

List of Patents from 1875 to July, 190 r, 803

OFFICE

OF THE

Sup'G. Arch't.

Chacpter I. \ TREASURY

DEPT.

HISTORICAL.

The use of air in its lower condition of compression for power and for mechanical purposes has been known from the earliest ages, and antedates any knowledge we possess of the use of steam by many generations.

The reduction of metals from their ores and the forging of iron and steel brought the forge and the blast furnace, with the use of air under pressure, into existence as mechanical appliances more than two thousand years before the Christian Era.

The evidences of the use of the air blast under compression are plainly seen depicted on the sculptured walls of the structures of the oldest civilization, and are made still more manifest in its endurated paintings and in the legends of the early historians.

The first inception of air power, as gathered from the example of the w^inds, seems to have been less progressive in its uses than other of the mechanical arts ; for, while it formed one of the vital elements in producing the metals, the inventive instinct in handicraft seems also to have been instilled in the early workers of metals in creating the tools that by the ancient genius of art worked out the models of beauty that are our examples of to-day.

The old methods of compressed-air production seem to have taken on a crude and nearly stationary form for at least two thousand years before, and for more than a thousand years after, the Christian Era, and in some parts of the world may be seen in operation to this day.

In China, India, Burmah, Borneo, Africa, and Madagascar the primitive methods of compressing air are still in use : the air treading bags, the wooden cylinder and piston, and the Chinese wind-box are the common devices for producing the air blast.

The only further progress that appears on record in regard to the production of compressed air and its uses for power purposes has been handed down in fragmentary history, and mostly contained in the pneumatics of Heron of Alexandria.

From the descriptions extant, he seems to have been the first to invent or to describe the pressure air pump or compressor for pressures greater than the forge blast, and to have applied it in the famous fountain attributed to him. Notwithstanding the alleged ignorance of the ancients respecting the physical properties of the atmosphere, there are circumstances related in history which seem to indicate the reverse ; for Diogenes of Apollonia reasoned on its condensation and rarefaction.

The description of the fire engine of the Egyptians, as given in Heron's " Spiritalia," shows very plainly that the use of air compression and its elasticity in the air chamber of a hydraulic pump were well understood in the second century before the Christian Era.

The devices of the Egyptian priesthood for exciting the wonder and awe of the people, possessed as they were of the suj^erstitions and proclivities of that age, were no doubt derived from a general knowledge of many of the physical laws of the elements possessed by the ruling and priestly classes.

They understood the nature of the expansion and contraction of air by heat and cold, of which the vocal statue on the plain of Thebes was an example.

Th.^ movement of the statue of Serapis and the altar tricks of the Pharaonic priesthood are other examples of the designed antics, due to the use of compressed air and the vapor of water.

Had it not been for the written work of Heron, the "Spiritalia," we should never have suspected that at'r was made to perform so important a part in ancient frauds, nor that its compression and expansion had been employed to raise liquids.

Notwithstanding the high opinion which history gives us of the historical and philosophical knowledge of the old Egyptian priesthood, we should hardly have surmised that they had the art of applying this subtle fluid so ingeniously. They seem, however, to have searched all nature for devices ; and to have become familiar with many of the principles upon which the most valuable of our arts and mechanics are based.

The condensing air pump or compressor must have been used in charging the ivind guns of Ctesibius of Alexandria, about 120 B.C., as described by Vitruvius. The properties exhibited by a partial vacuum must have been well known from five hundred to one thousand years before the Christian Era, as illustrated in the use of the siphon and the atmospheric watering-pots of the early Egyptians, though the principle of the perfect vacuum is undoubtedly due to Torricelli, by his production of the mercurial vacuum, about 1643 a.d.

The air-pressure bellows, in its many forms, seems to have been confined to a stated use, that of forcing a fire, from the earliest times, when a slight advance was made in air pressure to operate the devices and toys used in priestly incantations, followed by its application in the propulsion of projectiles by Ctesibius.

Then its principles slumbered in its low-pressure use for more than a thousand years, when the arrow discharged under air pressure by Ctesibius finally developed into the pneumatic gun of Marin in France, which was presented to Henry IV. in 1600. A more perfect compressed-air gun was brought out by Guter at Nuremberg in 1656, which had attached to the stock, in musket form, all the appliances for charging and discharging by air compression. But little further progress was made in this line until near the middle of the nineteenth century, when compressed-air guns took a wide range of design; their most useful and effective outcome being the pneumatic guns of Zalinski and others.

While the mechanic arts slumbered through the dark ages in Europe, the Chinese seem to have improved the aboriginal piston blower by a more perfect action and finish, in an instrument styled by them the "wind-box."

The water trombe, or tromp, for compressing air by a fall of water in a tube, used for blowing forges and other purposes,, was known to Heron, and was mentioned by Pliny in his. " Natural History."

In improved form the tromp has held its place for two^ thousand years, and is in use at the present day in Europe and the Orient.

The principle of Heron's pneumatic fountain for raising water was carried out on a large and useful scale in the pneumatic pumping engine at the mines of Chemnitz, in Hungary,, erected by M. Hoell in 1755; there was probably first illustrated the refrigerating power of air when expanded from great pressure. In the lower chamber of this apparatus the discharge of air and its expansion with water produced hail or pellets of ice. At first this machine required personal attention in its manipulation, but in 1796 it was made automatic.

The use of compressed air for submarine work was no doubt well known in the earliest ages, being almost coeval with the dawn of commerce.

Aristotle (350 B.C.) describes a kettle in which divers supplied themselves with fresh air under water. The legend of the descension of Alexander the Great to the bottom of the sea in a vessel called a colympia, with a glass window in it, is no doubt an allusion to the use of the diving-bell. It was employed in Phoenicia in the year 320 B.C., and the use of glass was well known then.

Nothing further appears on record in regard to submarine work with a bell for more than fifteen hundred years, when mention of its use in vSpain in 1538 is met with. Bacon describes it (1620) as a macliine used to assist persons laboring tinder water upon wrecks, affording a reservoir of air into which they could enter to take breath.

From this time on for a hundred years the diving-bell was largely used in Europe in recovering wreckage and treasure ; in 171 5 Dr. Halley made the first contrivance for supplying the diving-bell with fresh air by lowering air-filled barrels and discharging the air under the bell, letting out the foul air at the top through a cock ; or of allowing of completely filling the space with air that was made unavailable heretofore by the compression of the air in the bell.

Dr. Halley suggested the present system of submarine armor by using a cap or portable helmet connected with a tube leading to the surface, through which fresh air was forced to the helmet for the needs of the diver. Smeaton and Brunei, from 1779 on, improved on the use of the diving-bell, making its operation continuous by a fresh supply of compressed air through tubes from pumps.

The submarine armor continued to be improved along the lines of its present form for deep-sea work, in which depths of 148 feet have been attained, involving work under an air pressure of 65 pounds per square inch for several hours. It has been claimed that a depth of 200 feet has been reached without serious results from the great pressure due to that depth.

The compressed-air and vacuum pump was greatly improved by Otto Van Guericke about 1650, and it has been claimed as his invention.

Savary increased the pressure of air for blast furnaces by the use of more substantial blowers, in the latter part of the seventeenth century.

Denys Papin was the first to propose and make, in 1653, an actual trial of the transmission of power to a distance by compressed air. His early ideas being finally developed into more practicable shape, they resulted in his recommending the use of water power for compressing air and forcing it to a distance for useful w^ork, thus foreshadowing the now common practice of the long transmission and distribution of air through mines for the operation of machinery.

His system of an air pump driven by a water wheel, operating on air and water chambers at a distance, was in the right direction, but failed in its practical operation by the elasticity of the air, which he had intended to use as a long piston in transmitting power from an air-working piston to a distant water piston.

It was the fertile and mechanical brain of Papin that first conceived the idea of the pneumatic tube for transmitting parcels by air pressure, thus antedating by more than two hundred years our pneumatic-tube postal and package service, and thus early opening the way for future advancement in the use of compressed air.

Experiments were made in Wales in these early years to utilize water power for compressing air and transmitting it long distances for operating blast furnaces.

In 1757, Wilkinson, in England, patented a method of compressing air by the use of a column of water, effecting his -object by means of a series of chambers or water compressors, used one after another, so as to keep up a regular pressure ; thus, in a crude way, preceding by a hundred years the water compressor of Sommeiller at the Mont Cenis tunnel.

Many vague descriptions of apparatus for the use of compressed air in the mechanic arts and for its compression are found in the English patents during the eighteenth century; but either their practical applications were never realized or else no record was made of their operation.

The application of compressed air to practical uses and its transmission for power purposes seem to have commenced an era of advancement in the last years of the eighteenth century.

Professor St. Clair, of the Edinburgh University, in 1785^ proposed attaching air bags to sunken vessels beneath the surface of the water and inflating them by air pumps; followed by its practical use for raising vessels, for which many patents have been issued in Europe and the United States for various modifications of this device. Its most successful trials were made in 1864 in raising a steamer sunk in Lake Boden, and in raising the vessels sunk at Sebastopol during the Crimean War.

From that time on many patents have been issued for various devices for raising vessels by inflating floats by air pressure, and for compressing air and its use in diving-bells and submarine armor.

Medhurst, a Danish engineer in England, in 1799 compressed air to 15 atmospheres (210 pounds), stored and transmitted it to a motor in a mine ; he patented a pneumatic system for conveying persons and parcels in tubes in 18 10, followed by publications during a period of several years on tubular transmission by compressed air. There is no record of the practical working of the many schemes of this fertile genius.

Compressed air for driving vehicles seems to have had its birth with the beginning of the nineteenth century in a patent to Medhurst, in England, August 2, 1800, for means for propelling carriages by compressed air from a reservoir.

Compressed air for tramway cars appears to have received an impulse in Wright's English patent, April, 1828; he also proposed the use of iron cylinders beneath the cars, with an additional cylinder for heating the air by a small furnace, to increase its expansive force before entering the working cylinder and to mingle steam generated by the same furnace with the hot air.

The air brake seems to have first taken shape at this time in Wright's patent with an eccentric on a wheel shaft, connected w^ith a piston, which was to be operated as a brake on downgrades by pumping air into the air chambers; but it was not until 1869 that air brakes began to take a practical form under the patents of Westinghouse.

In 1828, Bompass, in England, patented and built a compressed-air locomotive.

Parsey, in 1847, built and ran a vehicle in which an intermediate reservoir was provided for reducing and equalizing the air pressure to the cylinders. Baron von Rathlen built and ran a vehicle with compressed air in England in 1848, attaining a speed of 12 miles per hour on the best roads of that day; he also suggested an increased pressure to 750 pounds per square inch as desirable for road and locomotive power, and advised compound compression and intercooling.

The earliest known appliance for making ice by the expansion of compressed air was invented and put into actual practice by Dr. John Gorrie, of New Orleans, La., in 1850, to whom a patent was issued in 185 1. The system of cold-room storage by the expansion of compressed air has since been greatly enlarged on the lines originated by Dr. Gorrie, and is in use in the meat and fruit transport service.

Vallance again agitated the subject of tube transmission in England, in 18 18 and on, and proposed a cast-iron tube system for passengers and parcels ; followed by others with feeble efforts to establish the pneumatic tube system from about 1824; and again by William Mann with English patents in 1824.

It was not until about 1865 that practical success was achieved by the Parcel Dispatch Company of London; since then the use of this system for parcel and postal transmission has been greatly developed in Europe and in the United States.

The first compound compression of air was probably suggested in the patent to William Mann in 1829, for what was then called stage pumping, — i.e., the use of two or more cylinders with intercooling; which was then properly claimed not only to effect great economy in compressing air, but also to decrease the machinery strain and to admit of lighter construction of the compressor.

In 1830 and on, Clegg and Pinkus, in England, agitated the system of a slotted tube and travelling piston with a vacuum or air pressure, with connections to an outside carriage. Experiments were carried on through several years without success, although trials were made with short lines of slotted air tubes in England and Ireland.

In 1830, Thilorier compressed gases to high pressures in stages, for which he received a medal from the French Academy.

The air-plunger pump for producing fire by compressed air was a family adjunct before friction matches came into use, in the home of the writer's father, who, in 1833, employed an apparatus made by himself, consisting of a cast-iron barrel weighing several pounds, with a bore three-eighths of an inch in diameter, like a cannon without the vent. A steel piston, about eight inches long, was accurately and tightly fitted, but moved rather easily when lubricated. The end of the piston had a small cavity for receiving a piece of punk ; the handle was provided with a stop or shoulder to prevent the plunger from striking the bottom in its sudden movement. The weight of the barrel, pushed by hand, acted by its momentum to complete the final pressure of, probably, eight hundred or more pounds per square inch, with an instantaneous evolution of temperature to a red heat, which fired the punk. A quick withdrawal of the plunger and the touch of a sulphur match completed the operation of generating a fire.

Following the agitation of the slotted-tube system of Clegg and Pinkus, in 1830, the subject was revived by Count Fontainemoreau, in 1844, and trials were made with unsatisfactory results.

The parcel-tube transmission system was again brought to the surface in England about i860. A thirty-inch tube, a quarter of a mile in length, was constructed at Battersea, and afterward removed to London and used for conveying the mail between district offices.

This was followed in 1864 by a larger and longer line in London.

The trials of Mr. A. E. Beach in New York, in 1867, with an eight-foot subway tinder Broadway for the propulsion of passenger cars by air pressure, seemed a step in the right direction, and failed only from apathy in financial circles.

The pneumatic-tube system simply slumbered for a time, and was then developed into its most useful work; at the present time it is largely in use for interpostal and telegraphic-office connections throughout Europe and the United States. The store cash system, in its intricate detail, promptness, and accuracy, is a modern wonder.

Compressed air for machine-driving, crane-hoisting, and other mechanical purposes was agitated in England in 1840 and on, with patents on detail plants for the transmission of compressed air from a central station to distant hoisting engines in warehouses and on docks. Ericsson, in 1858, compressed air by the power of caloric engines, for operating hoisting-engines in warehouses in New York, followed by a practical system for running sewing-machines in large numbers from a central station by the transmission of compressed air to small motors on the machines.

Compressed air for high working pressures, generated by hydraulic pressure and the use of waterfalls, was an improvement on the antiquated methods by the use of the trompe.

The direct pressure system was brought into use by Sommeiller at the Mont Cenis tunnel in 1872, and did good work at that time ; but as it required as much water to compress the air as was equal to the amount of free air compressed, the system was applicable only in favorable localities, and has now dropped out of use. Many patents have since been issued on direct-acting hydraulic air compressors, but the principle is not economical in practice, and we know of no compressors of this class in use at the present time.

The trompe system has been greatly improved and extended for high pressure, with a large flow of water with moderate head, by making a deep pit with an air chamber at the bottom and returning the water to the foot-fall as in an inverted siphon. This was first demonstrated in experiments by Mr. J. P. Fizell, of Boston, in 1877, and patented in 1878. It has been finally put in practical operation by Mr. C. H. Taylor in large instalments of hydraulic plants at Magog, near Montreal, and at Ainsworth, British Columbia.

Both plants have proved a success, and the utilization of water power for compression of air and its transmission for all power purposes is thereby assured.

The vertical excavated shafts may not be needed where steep slopes, or chasms, or mountain sides are available. The moving water will carry air down a slope as well as by vertical shaft, and the return pipe only follows the same line back, so that the friction due to the additional length of flow line is the only loss in effiicency.

Compressed air for street railways was continually agitated by newspapers and promoters during the middle of the nineteenth century. But little practical progress was made, much of the difficulties and obstructions being due probably to the distrust of the moneyed interest of schemes that had no practical and reliable tests and trials.

In 1862 the writer made plans for a light car street-railway system with compressed-air storage under the seats and on top of the car, with the engine under the platform, so that the passenger accommodation was not interfered with. The air pressure of two hundred and fifty pounds was to be supplied from station storage tanks and a compressor on the line. The plans did not meet with financial encouragement, and proved to be premature. The horse was not yet ready to go. Another generation was needed to bring compressed-air power for railways to a financial acceptance.

Further progress was made about 1873 in the intercooling of the compressing air in the cylinders by water jets or sprays, in the compressors at the St. Gothard tunnel. This led to still further improvements and economics in the construction of air-compressing machines ; until at the present day there seems to be nothing but change of detail in construction — that may not always result in improvement.

The introduction of compressed-air-hauling locomotives in the St. Gothard tunnel was a successful turn in favor of compressed air for railway work, and seemed to stimulate efforts in that direction ; it was soon followed by the Mekarski and Beaumont compressed-air railway systems in Europe, with increased air pressure and better appliances for economical compression and motor use. Compressed-air locomotives for mine haulage continued to improve in constructive details, and are now largely in use in the United States. For mining purposes compressed-air appliances have been steadily perfected, until at the present day there seems to be little room left for greater improvement except changes in detail, if such can be really called improvement.