« AnteriorContinuar »
STEAM ENGINES AND PARTS.
The manufacture of steam engines is a large and important industry in the United States, but, owing to the fact that domestic manufacturers are in a position to supply all classes of engines at prices that will ordinarily compete with those of foreign manufacture, the tariff problems are comparatively simple. The imports in 1919 were larger than for any previous year for which records are available, being valued at over $800,000. This amount, however, is no greater than one week's business for one of the large American firms and is negligible as compared with the exports, which run into millions of dollars annually. During 1920 the imports decreased so markedly as to indicate that the 1919 importations were sporadic and the result of abnormal circumstances.
From the tariff viewpoint the manufacture of steam engines may be considered as a highly developed branch of the general machinery industry. They are frequently made in the same plants with other classes of machinery, but designs are well standardized by the different makers and they are made in large quantities under more advanced production methods than those ordinarily in vogue in foreign plants.
Summary table-Steam engines--All other.
Steam engines may be described as prime movers which utilize the heat energy, pressure, or kinetic energy of steam to generate power. Steam locomotives are specially provided for in the tariff in the same paragraph of the 1913 act with steam engines, and these are discussed in a separate Tariff Information Survey. All other classes of steam engines may be considered as grouped under the designation all steam engines" and will be considered in the following discussion.
A great number of different types of steam engines may be distinguished, depending upon the general arrangement of parts, mode of working, and other factors. "A general division may be made between condensing and noncondensing, depending upon whether the steam is exhausted directly into the atmosphere or condensed in a cooling device to form a partial vacuum. Another general division is compound or noncompound, with a further classification of the former into double-, triple-, and quadruple-expansion engines, according to the number of units in which the
the steam is utilized. Single- or double-acting engines are distinguished according to whether the steam acts on one or both ends of a piston. Steam pumps, steam hammers, etc., are nonrotitive. Direct-acting engines are
those in which no lever is interposed between the connecting rod and piston rod, as in the case of a beam engine. Horizontal-, vertical-, or inclined-cylinder engines are obviously classified according to the position of the cylinder, a few vertical cylinder engines being in the invertel-cylinder class. In oscillating cylinder the cylinder moves back and forth on an axis, thereby dispensing with a connecting rod.
In rotary engines there is no piston in the ordinary sense and there is no necessity of converting the usual reciprocating motion into rotary motion. Steam turbines may be considered as a special type of rotary engines, but differ in that they are actuated by the kinetic energy of moving steam rather than by the expansion of steam under pressure. Turbines are also divided into impulse, reaction, and combination reaction and impulse turbines. The various types of reciprocating engines also may be distinguished according to the valve action, of which the Corliss and plain slide valve are the main distinctions, although a relatively recent type is the Unaflow engine, in which the inlet valves are mechanically operated, while the exhaust from both ends of the cylinder goes out through a common port, which is covered or opened by the piston, which is unusually long, in its travel.
The above may serve to indicate some of the more important general classes of steam engines in common use, according to the general construction or method of operation. There are other special types, as, for example, the Pulsometer, a pump in which the steam acts directly in the same cylinder against the liquid that is being pumped. The distinction between high-speed and low-speed engines is also important. Most of these classes, however, may be considered according to the grouping adopted by the Federal Census, which distinguishes only (1) stationary and portable steam engines other than turbines; (2) marine other than turbines; (3) steam turbines; and (4) traction engines. Steam locomotives, as in the tarifl
' act, are taken up separately: The Census classification, which is roughly according to the uses, will be generally used, so far as practicable, in this survey. A further discussion of the uses is unnecessary further than that steam engines are ordinarily the commonest type of prime mover, and in regions in which coal is cheaply obtainable and where water power is lacking they are generally the cheapest source of power. In units
of over about 200 horsepower turbines are generally cheaper in first cost than reciprocating engines and are more efficient.
Internal-combustion engines have displaced steam in many cases, particularly in automobiles and tractors. Heavy oil engines have introduced serious competition with steam engines in certain sections, notably the southwestern part of the United States, where coal is costly and fuel oil is reasonably cheap. Water power when available is a general substitute for steam-generated power. Another element that may be considered of great importance in the steam-engine trade is the modern use of electricity, which eliminates the great number of individual steam plants in factories and works owing to the greater economy of central power houses and the greater flexibility of electric power. The various substitutes for steam engines, however, have rather served to reduce somewhat the expansion in the manufacture and use of steam engines than to displace steam engines from the field of power generation. The number of steam engines produced each year is increasing, but less rapidly than the expansion in the use of power.
Owing to the fact that the United States is the largest user of power in the world, the domestic market for steam engines is greater in this country than in any other part of the world. The industry is a large and important one, the value of the product in 1914 being given by the Federal census as over $30,000,000.
It is doubtless much more at the present time.
Raw materials. The raw materials for the manufacture of steam engines are the same as for other classes of machinery. The most important item is iron and steel, with minor quantities of brass and other finish or bearing metals. Oil cups, cylinder and crank oiling devices, and other accessories may be purchased from special manufacturers or made in the steam-engine factories.
As in other classes of machinery manufacture, the domestic maker can secure his raw materials in sufficient quantity in this country and in this industry the prices of raw materials here and abroad are so nearly the same, under normal conditions, that they need not be considered. The balance of advantage, if any, should be with the American makers in the future as at present.
Equipment.-- The manufacture of a complete steam engine, even in the smaller sizes, calls for a large amount of equipment, including a foundry, machine shops, and forging plant. Such equipment is expensive, but is no more costly per unit in this country than abroad, although owing to the general principle of mechanical methods of production in this country the equipment of American plants per unit of annual product is more extensive than that of foreign plants of similar capacity.
Methods of production.-Steam engines are made in large quantities. The smaller sizes, as produced by any one manufacturer, are made according to standard designs, enabling the adoption of mass production methods. Larger sizes are fairly well standardized, subject to minor changes in design to meet individual conditions. The details of manufacture are similar to those in the manufacture of other classes of machinery. Great precision is required in certain
parts, but no unusual difficulty is found in the production of interchangeable parts, and in this country there is little necessity for further finishing and fitting in the assembly departments of the factories. A large amount of skilled male labor is employed in the operation of the various machine tools, but in the United States the number of operations required to be performed by any one man are relatively few.
Organization.--A considerable proportion of the total output of steam engines comes from firms primarily engaged in the manufacture of other classes of machinery. It is therefore impracticable to attempt to estimate the total amount of capital invested in the industry. Air compressors, pumps, and many other classes of machinery, whether or not designed to be driven by steam power, are frequently manufactured in the same establishment and utilize the same equipment. The larger machinery factories may produce a variety of sizes and types of steam engines. Some of the largest firms manufacture practically a full line of engines for every purpose, although there are also firms which specialize to a considerable degree and devote themselves exclusively to the manufacture of one model.
The Federal Census reports that 809 establishments reported the manufacture of engines in 1914 and of these 243 made steam engines. Doubtless, however, this number includes many establishments in which steam engines are a minor product. A large fraction of the total output comes from some 15 to 20 important firms, several of which operate more than one plant.
Geographical distribution.--Pennsylvania is the leading State in the production of steam engines, furnishing 39.6 per cent of the total horsepower and 33.4 per cent of the total value as reported to the Census in 1914. New York ranked second in point of horsepowers, furnishing 25.2 per cent of the total; but Wisconsin reported a larger value of output, 14.3 per cent of the value as compared with 11.2 per cent reported from New York, although only 11.4 per cent of the total horsepower was manufactured in Wisconsin in that year. The production in various States will be found on page 21, but it will be noted that the above three States furnished over 75 per cent of the horsepower and nearly 60 per cent of the value of the engines produced in 1914. It is interesting to note the extraordinarily high valuation per horsepower of the Michigan product. A large number of small engines were reported from that State, the average being under 20 horsepower and valued at about $42.50 per horsepower as compared with an average value per horsepower for all the engines reported of only $13. The average rating of all the engines produced in the United States in that ear was over 120 horsepower.
Il story of the industry.- Probably the oldest tpe of steam engine is that described by Hero of Alexandria in 130 B. C. This primitive engine, referred to as an aelopile, consisted of a spherical vessel pivoted on a central axis and supplied with steam through one of the pivots. The steam escaped b' means of bent tubes faced tangentially and arranged perpendicularls to the axis. The force of the steam as it blew out into the air revolved the globe. The principle is similar to that of a reaction turbine, although this crude application was practically nothing but a toy. There were practically
no further developments in the application of steam to power generation until the seventeenth century, when attention was directed to this problem. According to the Encyclopedia Britannica, the first commercially successful steam engine was a pumping device patented br Thomas Savery in 1698. This device consisted essentially of a hollow vessel into which steam could be introduced and then condensed by means of a cold water jet. The resulting suction would serve to draw up water from a cistern, filling the vessel
, which could be again emptied by closing the suction connection and admitting steam. Various other developments followed Savery's engine, but it was not until James Watt, an instrument maker of Glasgow, patented his first steam engine in 1769 that anything approaching an economical engine was produced. Watt's studies proved the basis for most of the radical developments in the reciprocating steam engine, although later inventions have resulted in enormous improvements over early engines. A great number of inventors have contributed to this progress, but it is unnecessary even to list the names, as patents are no longer an important factor in the industry and all classes of engines are now being made in the United States. Mention should, however, be made of the steam turbine adopted at first for marine use. These engines, which operate upon different principles from those underlying Watt's chief inventions, were developed independently and along fundamentally different lines by Dr. Gustav de Laval and C. A. Parsons, who produced in the latter part of the nineteenth century the turbines which now bear their names.
In every line of these manufactures various improvements and special designs for certain purposes have been made and patented either by American inventors or foreigners. On account of the large requirements of the United States, as soon as a new design has established a market in this country the right to manufacture it is licensed to some American engine company. One of the most recent examples is the case previously cited of the Unaflow engine, patented by a German (Dr. Stumpf) and for a time imported to some extent into this country. There are now several American companies which manufacture this type in their own plants.
Domestic production and consumption.—The American output of steam engines is largely in excess of domestic requirements and the diversity of domestic products is sufficient to cover all the different classes. Owing to the production of other machinery in the larger works, the total productive capacity of the country has not been fully utilized in the manufacture of steam engines and the output could be increased very largely. There is a marked tendency in the United States toward the adoption of internal-combustion engines for small power units, with a consequent reduction in the demand for small steam units. The demand for large steam plants, however, has been increasing in spite of the large number of heavy oil (Diesel) engine installations.
Domestic exports.—The exports of steam engines are listed by the Department of Commerce under the following designations: (1) Marine. (2) stationary, and (3) traction and caterpillar. Some steam engines, as well as internal-combustion and other engines, are also included under the designation “All other engines," and parts of