Improvements to the steam engine were some of the most important technologies of the Industrial Revolution, although steam did not replace water power in importance in Britain until after the Industrial Revolution. From Englishman Thomas Newcomen's atmospheric engine, of 1712, through major developments by Scottish inventor and mechanical engineer James Watt, the steam engine began to be used in many industrial settings, not just in mining, where the first engines had been used to pump water from deep workings. Early mills had run successfully with water power, but by using a steam engine a factory could be located anywhere, not just close to a water source. Water power varied with the seasons and was not always available.

In 1776 Watt formed an engine-building and engineering partnership with manufacturer Matthew Boulton. The partnership of Boulton & Watt became one of the most important businesses of the Industrial Revolution and served as a kind of creative technical centre for much of the British economy. The partners solved technical problems and spread the solutions to other companies. Similar firms did the same thing in other industries and were especially important in the machine tool industry. These interactions between companies were important because they reduced the amount of research time and expense that each business had to spend working with its own resources. The technological advances of the Industrial Revolution happened more quickly because firms often shared information, which they then could use to create new techniques or products. The development of the stationary steam engine was a very important early element of the Industrial Revolution. However, it should be remembered that for most of the period of the Industrial Revolution, the majority of industries still relied on wind and water power as well as horse and man-power for driving small machines.

Thomas Savery's steam pump

The industrial use of steam power started with Thomas Savery in 1698. He constructed and patented in London the first engine, which he called the "Miner's Friend" since he intended it to pump water from mines. Early versions used a soldered copper boiler which burst easily at low steam pressures. Later versions with iron boiler were capable of raising water about 46 meters (150 feet). The Savery engine had no moving parts other than hand-operated valves. The steam once admitted into the cylinder was first condensed by an external cold water spray, thus creating a partial vacuum which drew water up through a pipe from a lower level; then valves were opened and closed and a fresh charge of steam applied directly on to the surface of the water now in the cylinder, forcing it up an outlet pipe discharging at higher level. The engine was used as a low-lift water pump in a few mines and numerous water works, but it was not a success since it was limited in pumping height and prone to boiler explosions.

Thomas Newcomen's steam engine

The first practical mechanical steam engine was introduced by Thomas Newcomen in 1712. Newcomen apparently conceived his machine independently of Savery, but as the latter had taken out a wide-ranging patent, Newcomen and his associates were obliged to come to an arrangement with him, marketing the engine until 1733 under a joint patent.Hulse, David H: The Early Development of the Steam Engine; TEE Publishing, Leamington Spa, UK, 1999 Newcomen's engine appears to have been based on Papin's experiments carried out 30 years earlier, and employed a piston and cylinder, one end of which was open to the atmosphere above the piston. Steam just above atmospheric pressure (all that the boiler could stand) was introduced into the lower half of the cylinder beneath the piston during the gravity-induced upstroke; the steam was then condensed by a jet of cold water injected into the steam space to produce a partial vacuum; the pressure differential between the atmosphere and the vacuum on either side of the piston displaced it downwards into the cylinder, raising the opposite end of a rocking beam to which was attached a gang of gravity-actuated reciprocating force pumps housed in the mineshaft. The engine's downward power stroke raised the pump, priming it and preparing the pumping stroke. At first the phases were controlled by hand, but within ten years an escapement mechanism had been devised worked by of a vertical plug tree suspended from the rocking beam which rendered the engine self-acting.

A number of Newcomen engines were successfully put to use in Britain for draining hitherto unworkable deep mines, with the engine on the surface; these were large machines, requiring a lot of capital to build, and produced about 5 hp. They were extremely inefficient by modern standards, but when located where coal was cheap at pit heads, opened up a great expansion in coal mining by allowing mines to go deeper. Despite their disadvantages, Newcomen engines were reliable and easy to maintain and continued to be used in the coalfields until the early decades of the nineteenth century. By 1729, when Newcomen died, his engines had spread to France, Germany, Austria, Hungary and Sweden. A total of 110 are known to have been built by 1733 when the joint patent expired, of which 14 were abroad. In the 1770s, the engineer John Smeaton built some very large examples and introduced a number of improvements. A total of 1,454 engines had been built by 1800.

James Watt's steam engines

A fundamental change in working principles was brought about by James Watt. With the close collaboration of Matthew Boulton, by 1778 he had succeeded in perfecting his steam engine which incorporated a series of radical improvements; notably, the use of a steam jacket around the cylinder to keep it at the temperature of the steam and, most importantly, a steam condenser chamber separate from the piston chamber. These improvements increased engine efficiency by a factor of about five, saving 75% on coal costs.

The Newcomen engine could not, at the time, be easily adapted to drive a rotating wheel, although Wasborough and Pickard did succeed in doing so in about 1780. However, by 1783 the more economical Watt steam engine had been fully developed into a double-acting rotative type with a centrifugal governor, parallel motion and flywheel, which meant that it could be used to directly drive the rotary machinery of a factory or mill. Both of Watt's basic engine types were commercially very successful.

By 1800, the firm Boulton & Watt had constructed 496 engines, with 164 driving reciprocating pumps, 24 serving blast furnaces, and 308 powering mill machinery; most of the engines generated from 5 to 10 hp. An estimate of the total power that could be produced by all these engines was about 11,200 hp. This was still only a fraction of the total power-generating capacity in Britain by waterwheels (120,000 hp) and by windmills (15,000 hp); however, water and wind power were seasonably variable. Newcomen and other steam engines generated at the same time about 24,000 hp.

Development after Watt

The development of machine tools, such as the lathe, planing and shaping machines powered by these engines, enabled all the metal parts of the engines to be easily and accurately cut and in turn made it possible to build larger and more powerful engines.

In the early 19th century, after the expiration of the Boulton & Watt patent in 1800, the steam engine underwent great increases in power due to the use of higher-pressure steam, which Watt had always avoided because of the danger of exploding boilers, which were in a very primitive state of development.James Watt Monopolist

Until about 1800, the most common pattern of steam engine was the beam engine, built as an integral part of a stone or brick engine-house, but soon various patterns of self-contained portative engines (readily removable, but not on wheels) were developed, such as the table engine. Further decrease in size due to use of higher pressure came towards the end of the 18th century when Cornish engineer Richard Trevithick, and American engineer Oliver Evans, independently began to construct higher-pressure (about ) engines that exhausted into the atmosphere, although Arthur Wolf working at the Meux Brewery in London was already experimenting with higher-pressure steam in his efforts to save coal. This allowed an engine and boiler to be combined into a single unit compact and light enough to be used on mobile road and rail locomotives and steam boats.

Trevithick was a man of versatile talents, and his activities were not confined to small applications. Trevithick developed his large Cornish boiler with an internal flue from about 1812. These were also employed when upgrading a number of Watt pumping engines; by this time Arthur Wolf had already produced high-pressure engines whilst working at Meux Brewery, in his efforts to improve efficiency, thus saving coal, as he had been trained by Joseph Bramah in the art of quality control, which resulted in him becoming chief engineer at Harveys of Hayle in Cornwall, by far the largest and leading manufacturer of steam engines in the world.

The Cornish engine was developed in the 1810s for pumping mines in Cornwall. It was the result of using the exhaust of a high-pressure engine to power a condensing engine. The Cornish engine was notable for its relatively high efficiency.

The Corliss Engine

The last major improvement to the steam engine was the Corliss engine. Named after its inventor, George Henry Corliss, this stationary steam engine was introduced to the world in 1849. The engine boasted a number of desired features, including fuel efficiency (lowering cost of fuel by a third or more), low maintenance costs, 30% higher rate of power production, high thermal efficiency, and the ability to operate under light, heavy, or varying loads while maintaining high velocity and constant speed. While the engine was loosely based on existing steam engines, keeping the simple piston-flywheel design, the majority of these features were brought about by the engine's unique valves and valve gears. Unlike most engines employed during the era that used mainly slide-valve gears, Corliss created his own system that used a wrist plate to control a number of different valves. Each cylinder was equipped with four valves, with exhaust and inlet valves at both ends of the cylinder. Through a precisely tuned series of events opening and closing these valves, steam is admitted and released at a precise rate, allowing for linear piston motion. This provided the engine's most notable feature, the automatic variable cut-off mechanism. This mechanism is what allowed the engine to maintain a set speed in response to varying loads without losing efficiency, stalling, or being damaged. Using a series of cam gears, which could adjust valve timing (essentially acting as a throttle), the engine's speed and horsepower was adjusted. This proved extremely useful for most of the engine's applications. In the textile industry, it allowed for production at much higher speeds while lowering the likelihood that threads would break. In metallurgy, the extreme and abrupt variations of load experienced in rolling mills were also countered by the technology. These examples demonstrate that the Corliss engine was able to lead to much higher rates of production, while preventing costly damages to machinery and materials. It was referred to as “the most perfect regulation of speed.”