Henry Petroski. American Scientist. Volume 84, Issue 1. January 1996.
The elements of the steam engine were known to the Greeks. Ctesibius of Alexandria is credited with inventing, more than 2,100 years ago, the piston and cylinder, which he put to use pumping water, and his compatriot Hero harnessed steam power to produce mechanical motion, albeit mainly to drive toys and other devices of amusement. Although the evolution of the modem steam engine is commonly reckoned from the early-18th-century work of Thomas Newcomen, that is at best an oversimplification. Like all achievements in engineering, Newcomen’s engine was built on important technological developments that were achieved over many years in many different locations. In the case of the steam engine, events in the 17th century in particular laid some important groundwork and foreshadowed some ominous developments in the 19th and 20th centuries.
Salomon de Caus was a French-born engineer whose early-17th-century activity ranged from tutoring the Prince of Wales to landscaping the gardens of Heidelberg Castle. Among other things, he developed a scheme whereby steam produced in a spherical vessel could force jets of water to considerable heights in ornamental fountains. Just after mid-century, the German Otto von Guericke demonstrated the power of a vacuum created within a 20-inch-diameter cylinder fitted with a piston: The efforts of 50 men could not prevent the piston from being sucked in. Years later, von Guericke conducted his more famous demonstration, in which teams of horses were unsuccessful in pulling apart two hollow hemispheres from which the air had been evacuated. At about the same time, a British inventor, Edward Somerset, the Marquis of Worcester, devised a water pump, known as his “water commanding engine,” which created a partial vacuum to raise water as high as 40 feet.
Toward the end of the 17th century, just before fleeing religious persecution in France, Denis Papin served briefly in Paris as a research assistant to the Dutchman Christian Huygens. There, Papin observed some of Huygens’s experiments with a gunpowder-fired engine, a forerunner of the internal combustion concept, which Papin later pursued until he came to employ steam as a less dangerous source of energy. His engine used a fire under a closed cylinder to heat water to steam, which drove a piston. The fire was then removed to allow the steam to condense, thereby creating a vacuum that caused the piston to return to its original position. In 1698, the British mining engineer Thomas Savery patented a steam pump that could raise water as high as 50 feet by the partial vacuum created when steam was condensed in closed boilers. However, because many mines were much deeper, Savery’s “miner’s friend” came to be used more for supplying water to the top floors of London buildings. Among the drawbacks of the device were the limitations of relying on atmospheric pressure and the danger of boiler explosions because of the use of steam under high pressure.
Thomas Newcomen built on this experience developed in the 17th century, noting not only the features that worked but also those that were detriments to lifting water from deep mines. The scheme he devised required steam at little more than atmospheric pressure to raise a piston, water to condense the steam inside the cylinder, and atmospheric pressure to lower the piston into the evacuated cylinder and thus complete the cycle. Recognizing the superiority of Newcomen’s engine, Savery allowed the use of his patent covering all water-raising devices that employed “the impellant force of fire,” in exchange for partnership in the new engine. Savery’s heirs thus controlled its commercial exploitation and received royalties, whereas Newcomen died relatively unknown and far from wealthy.
Although Newcomen’s atmospheric engine was effective in raising water from mines, to the point of being credited with revitalizing the mining industry in north-central England, it also had its own shortcomings and limitations. Chief among these was its inefficient use of energy, for the entire cylinder was alternately heated and cooled to generate and condense the steam during each cycle. Some critics estimated the wastage to be in excess of 90 percent of the fuel consumed. Others used hyperbole: “It takes an iron mine to build a Newcomen engine and a coal mine to keep it going.” Scottish-born James Watt addressed this problem in the late 18th century by developing a condensing unit separate from the cylinder proper. By this means, the cylinder could be kept at a relatively constant temperature, and thus energy was not wasted in heating it anew each cycle. Watt’s earliest engines consumed only about half the fuel required previously to do the same amount of work.
Beyond Lifting Water
Late 18th-century steam engines were restricted mainly to use as pumps, however, because they provided only on the downward stroke of the piston a lifting force through a flexible chain pulled upward via a rocker beam. This limitation of a purely unidirectional vertical motion did not allow the ready application of the Newcomen engine to driving factory machinery, which required a continuous rotary motion, like that produced by a water wheel. To address this failing, Watt devised the double-acting cylinder, in which steam alternately admitted and released from two sides of an enclosed piston drives it both ways. On the other side of the engine’s rocking beam, Watt replaced a flexible chain with rigid linkages and gearing that converted reciprocal motion to rotary. This made the steam engine attractive to the British cotton industry, which was then the main user of automatic machinery. Thus freed of reliance on water power, manufacturers could and did build larger factories located nearer to sources of raw materials and labor, such as in and around port cities.
Steam engines thus evolved from curiosities to shapers of industry and society without benefit of the engineering science of thermodynamics. Indeed, it was efforts to improve the poor five-percent thermal efficiency of Watt’s steam engine that drove the French mechanical engineer Nicolas Leonardo Sadi Carnot’s theoretical studies. Thermodynamics had little impact on steam-engine design until well into the 19th century, but this is not to say that technological advances had to wait for the engineering science of thermodynamics to mature.
In developing the steam engine, Watt benefited from his partnership with Matthew Boulton, whose state-of-the-art ironworks employed highly skilled workmen operating top quality machinery. It was Boulton’s entrepreneurial sense of a market for rotary power that led him to insist that Watt develop that aspect of the engine. With Boulton handling the financial end of the partnership, a research-and-development operation could be supported in which Watt pursued further improvements, as well as other inventions, such as a centrifugal governor and an indicator device to record engine power output, thereby also providing a means for calculating royalties that were owed to the patent holders. To compare different engines, Watt devised the term “horsepower,” which he determined to be 33,000 foot pounds per minute, the rate, he calculated, at which a brewery horse could do work. Boulton successfully petitioned Parliament to extend Watt’s original 1769 patent for a separate condenser to the end of the century. Thus, rather than struggling just to recover their investment before the original patent would have expired in 1783, Watt and Boulton realized considerable financial gain.
Progress Begets Hazard
Although Watt’s machines were designed to operate at about 7 pounds per square inch above atmospheric pressure, steam engines were dangerous because far greater pressures could build up in their boilers. Indeed, Papin’s invention of a pressure valve and Watt’s fly-ball governor were designed to keep the machines from running out of control. In time, increasing capabilities to manufacture mechanical devices with tighter tolerances and more leak-proof boilers made it possible for steam engines to operate under greater and greater pressure. No matter what safety devices were designed to limit speed and prevent over-pressure in these machines, some steam-engine operators were inclined to tie down pressure-relief valves or otherwise override safety controls.
By the middle of the 19th century, when the use of steam engines was widespread not only as a source of stationary power for factories but also, thanks to the likes of Robert Fulton and Richard Trevithick, as a source of motive power for steamboats and railroad locomotives, boilers were pressurized to several times atmospheric, and explosions had come to be commonplace. Steamboat captains especially were prone to drive their power plants at higher-than-prudent pressures in order to achieve greater speeds. As early as 1824, there were calls for restrictive federal legislation in the U.S. The Franklin Institute, founded in Philadelphia that same year, came to devote much space in its journal to the subject of boiler explosions. By the early 1830s, government funds were granted to the institute for an experimental apparatus to test boilers, and by the middle of the decade its report helped lead to the introduction of federal legislation, which was passed in 1838. This required independent boiler inspectors, but it specified no inspection criteria and was ultimately ineffective in reducing steamboat explosions to any significant degree. Continuing incidents finally caused Congress to create, in 1852, a Joint Regulatory Agency. This federal control did lead to a diminishing of deaths from steamboat accidents, but the stationary steam engines operating in factories remained unregulated.
As has often been the case with a technology that has ceased to be novel, steam power had come to be taken somewhat for granted, and its potential dangers were largely ignored or at least minimized. Although boilers were exploding in factories and on waterways everywhere, one incident in Hartford, Connecticut, in 1854 aroused more than the usual interest. On March 2 a boiler in the engine room of the Fales and Gray Car Works exploded, killing nine people immediately, with 12 more dying of their injuries and 50 others being left seriously hurt. There was an inquiry, but it was to be 10 years before Connecticut had a boiler-inspection law.
A more significant outcome of the Fales and Gray incident was the initiative of several Hartford businessmen associated with the use of steam power to organize in 1857 a group known as the Polytechnic Club, which supported the rational study of the properties of steam and the causes of boiler explosions. The Polytechnic Club did not accept prevailing superstitions and theories that explosions were caused by such things as acts of God, a demon in the boiler or the violent recombination of the hydrogen and oxygen into which the steam had broken down. Rather, they concluded logically that an explosion happened when steam pressure exceeded the ability of the boiler to contain it. Such a situation could be remedied by the use of reliable materials, sound designs, and regular inspections to identify and correct weaknesses and deterioration in existing boilers. There was already in England the Association for the Prevention of Steam Boiler Explosions and the Boiler Insurance and Steam Power Company, the latter of which not only inspected boilers but also insured their owners and operators against losses and claims. The Polytechnic Club was well on its way to instituting similar practices in America when the Civil War caused it to disband.
In 1865 another significant boiler explosion took place. This one was on the Mississippi steamboat Sultana, which was overloaded with about 2,200 passengers, most of them Union soldiers recently freed after the Confederate surrender at Appomattox. The death toll, variously estimated at between 1,200 and 1,500 people, made this then the worst marine disaster in U.S. history. The Sultana incident reawakened discussion among some Polytechnic Club members, who formed the Hartford Steam Boiler Inspection and Insurance Company and incorporated it in 1866. Before long, the company was offering services to manufacturers, including supervising the selection of materials for, and the construction and installation of, steam boilers. It also created an engineering department to help its policyholders with boiler design. Municipal and state authorities began to accept the company’s inspections in lieu of their own.
The Origins of ASME
Boiler explosions continued, however, and this blemish on advancing technology was among the concerns of a group of engineers who met in 1880 to form a new organization, the American Society of Mechanical Engineers (ASME). Other concerns of the founders of ASME were the establishment “with scientific precision” of standards for threads on nuts and bolts and of procedures for testing the strength of iron and steel.
A code of practice entitled “Standard Method for Steam Boiler Trials” was fomulated by ASME as early as 1884, and papers and reports began to be published that provided background material for writing a comprehensive boiler code. In the meantime, no state codes were being created for stationary boilers, even though each year several hundred of them were exploding nationwide. Among the reasons legislators in New England, at least, had not acted was their belief that the Hartford Steam Boiler organization had virtually eliminated the dangers. The situation changed in 1905, however, when a boiler explosion in a Brockton, Massachusetts, shoe factory caused 58 deaths, 117 injuries and a quarter of a million dollars in property damage.
Another explosion the following year, in Lynn, Massachusetts, made the matter of steam boilers a highly visible political issue. Massachusetts soon passed rules regulating steam boilers, and this provided impetus to ASME members to accelerate their efforts to produce a boiler code that was promulgated by the engineering profession rather than the government. The first ASME Boiler Code, a 148-page document, carried a publication date of 1914 but was not formally approved until 1915. In essence, it represented a unique joint venture of a professional society and an insurance company.
By the time civilian nuclear power was being promoted at mid-century, the ASME Boiler and Pressure Vessel Code had become well established, and it was natural to extend it to include the components of nuclear-power plants. Now the code takes up three feet of bookshelf, and ASME’s monthly magazine, Mechanical Engineering, carries announcements of code-committee meetings and drafts of documents available for public comment, as well as queries and responses regarding the interpretation of the code.
From its inception, the creation, expansion and maintenance of the Boiler and Pressure Vessel Code, which by 1970 attracted some 14,000 inquiries annually, relied largely on the volunteer efforts of society committee members, which presented a potential for conflict of interest. In response to critics who doubted that employees of the manufacturers could serve on such committees and fairly regulate the industry to which they owed their livelihood, society leaders pointed out that professional engineering standards dictated that individuals rise above selfish interests for the common good. However, a situation that developed in the 1970s cast a long shadow over such assertions.
In 1972, ASME received a letter requesting interpretation of the code with regard to boiler feed-water indicating devices. What made the letter remarkable was that it was drafted by the chairman and vice chairman of the ASME subcommittee on heating boilers, who were, respectively, the vice president of the Hartford Steam Boiler Inspection and Insurance Company and the vice president for research of McDonnell & Miller, a company that dominated the U.S. market for heating-boiler safety controls. The subcommittee’s response, which was written by the chairman, was subsequently claimed to have been used by McDonnell & Miller salesmen to discredit the feed-water indicating device of a small competing manufacturer, the Hydrolevel Corporation. When Hydrolevel complained to ASME, a response came from the same subcommittee on heating boilers, which by then was chaired by the McDonnell & Miller vice president.
The matter was the subject of an article in The Wall Street Journal, and in 1975 hearings were held before the U.S. Senate Subcommittee on Antitrust and Monopoly. Hydrolevel sued ASME, Hartford Steam Boiler and McDonnell & Miller’s parent organization, the International Telephone & Telegraph Company. The last two defendants settled out of court in 1978, but an unrepentant ASME fought the charges that it had conspired against Hydrolevel in violation of federal antitrust laws. ASME lost, and in 1979 a U.S. District Court ruled that the society was guilty and assessed damages of almost $7.5 million, a large amount but somewhat less than the annual income from the sale of codes and standards publications. The appeal went all the way to the U.S. Supreme Court, which ruled against ASME in 1982.
The Hydrolevel case is an anomaly in the 80-year history of the ASME Boiler and Pressure Vessel Code, to which so much is owed for the safety of modern steam and related power plants. This was demonstrated very dramatically in the 1979 loss-of-coolant accident at the Three Mile Island nuclear-power plant, which was designed and constructed according to the code. For all the mechanical and human failures involved in that accident, it did not result in a catastrophe of the kind too often experienced in 19th-century factories and steamboats—or worse. Today’s steam boilers, out of sight and mind in the bowels of public and work places, work silently, efficiently and without incident. Boilers and pressure vessels across the country, whether employed to provide electric power for the grid, central heating in our great institutions or hot water in our homes, are the steady and reliable workhorses of which so many of the pioneers of steam power dreamed.