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Jan 13, 2024

Column: Initial steam engine designs intended for mining

May 13, 2023 When Thomas Savery received a British patent for his steam engine

May 13, 2023

When Thomas Savery received a British patent for his steam engine in 1689, it was not entirely his invention. According to many historians, Savery based his design on an earlier idea of Edward Somerset, Second Marquee of Worcester. According to the Royal Collection Trust, Somerset's idea, which he called a "water-commanding engine, was a precursor of the steam engine. The Trust states it was a hydraulic engine constructed from the barrel of a cannon and Worcester hoped that it could be used in farming to speed up irrigation.

Savery designed his engine, not for irrigation, but for pumping water out of a mine in Cornwall.

There is an irony in that Savery's engine, which he designed for mines, was not used for pumping out mines, but his steam pump was useful for supplying water to estates and country houses, it found no interest among mine owners, states the American Physical Society, in its July, 2018, Vol. 27, Number 7 edition of APS News. The article, "July 2, 1698: Thomas Savery Patents an Early Steam Engine,"

The online scholarly magazine, Economic Historian's July 31, 2022 article, "Steam Engine," states that Savery's engine was intended to use fire to pump water out of mines. It worked by filling a tank with steam and then subsequently isolating the tank from the steam source. When the temperature in the steam-filled tank dropped due to isolation, the steam condensed, creating a vacuum in the tank. The vacuum was formed by the difference in volume between the liquid and gaseous phases of water. Water from the mines rushed in to fill the vacuum, and although the vacuum system was successful, it could only work efficiently at shallow depths. The water drawn into the tank was then expelled or forced higher up to 80 feet using steam pressure.

The engine had several flaws, states APS News. It was not efficient for lifting water, partly because the technology did not yet exist to machine tightly sealed joints. All the parts were made from brass, copper, and bronze, pieced together from casts or molded parts and then soldered or riveted together. The imperfect sealing meant the engines were prone to exploding. It also consumed too much fuel to make it economically viable for mining applications.

Thomas Newcomen was a blacksmith (ironmonger), Savery hired to forge his own engine. NPS states Savery allowed Newcomen to forge a copy of the machine for his own backyard research. In 1712, Newcomen built his own steam engine based on Savery's design, but Newcomen's atmospheric steam engine was far superior to Savery's, says NPS. Newcomen's engine showed vastly improved performance, significant mechanical differences, had no need for steam pressure, and used a vacuum differently.

The Newcomen engine utilized a piston working within an open topped cylinder, states the National Museums Scotland, which houses an original Newcomen engine. The piston was connected by chains to a rocking beam. At the other end, the beam was connected to the pumps in the mine by a rod. On the up stroke, the cylinder is filled with steam from the boiler and then cold water is injected into the cylinder to change the steam back to water and create a vacuum (when water turns to steam it expands 1,500 times, so a contained volume of steam, if condensed back to water, will create a vacuum). The vacuum then pulled the piston down and, via the rocking beam, raised the plunger in the water pump.

The use of a rocker beam in Newcomen's engine was how the engine later became referred to as a beam engine.

As the Economic Historian points out, the Newcomen engine's major flaw was that it consumed excessive steam to reheat the piston during each heating and cooling stroke. for the time, however, it was the best design available.

The next development — and it was major — came from an instrument maker from Scotland named James Watt. Watt did not invent a steam engine; he had invented a steam condenser. He studied one of Newcomen's engines that he had been asked to repair, saw its flaws and improved them, using his own invention. It revolutionized steam application.

When the steam in Newcomen's engine was condensed back into water, it cooled the cylinder as well. Because the cylinder constantly needed to be reheated, it used excessive amounts of coal.

While testing his newly repaired steam engine, states authors, Nicholas Hatch in his scholarly article, "James Watt's Steam Engine and the Start of the Industrial Revolution," (posted on the StMU Research Scholars website) Watt realized that more than a quarter of the steam created by the engine was being released and wasted, causing it to be inefficient when used in the work field.

Eventually, one of Watt's patented inventions, the condenser, would eliminate this inefficiency.

Ben Russell, in his Jan. 2019 Science Museum article, "James Watt and the Separate Condenser," stated: The separate condenser resolved the engine's fundamental problem, that for maximum fuel economy the steam cylinder had to stay as hot as possible, while for maximum thermal efficiency it should be cooled once per working cycle.

By condensing the steam in a separate condenser kept permanently cool, both fuel economy and efficient use of heat were maximized, states Russell. Steam engines with Watt's condenser burned two-thirds less coal, making them capable of working not just on mines but in factories, mills, workshops, and anywhere else that needed power. Russell states that Watts’ 1769 condenser patent is now regarded as one of the most significant patents ever granted in the UK.

Not only was the engine popular with mining, it was quickly realized that it could be applied to other uses as well. By 1800, there were over 500 Watt engines in factories and mines throughout Great Britain, including Cornwall.

Cornish immigrant miners and engineers imported Cornish and British technology to the Lake Superior copper region starting in the mid-19th century. The Mining Magazine, in 1853, in discussing the Cliff Mine, near Keweenaw Point, stated:

"The work of pumping the mine, and of raising the ore and rock, is performed by a steam engine, while another large lever-beam engine, of upright form and of great power, performs the stamp work. The stamps at this mine carry twenty-four heads, and are the most perfect and efficient upon Lake Superior."

The same publication, in 1856, published the annual report of the National Mining Company's agent, in which was proposed modifying the operation of a Cornish beam engine:

"It is almost beyond doubt that with a 40-inch cylinder and 12 feet stroke, which is simply a Cornish engine turned upside down, the cylinder resting on a strong sole plate over the mouth of the shaft, and the piston-rod attached direct to a forcing set-pump rods. The air pump is small in diameter, with the same length of stroke as the engine, thus doing away with the ponderous beam, paralleled motion, and heavy masonry of the cylinder pedestal, lever wall, and engine house, and obtaining any desirable length of stroke by merely adding to the length of the cylinder and piston-rod, thereby increasing the efficiency of the pumps, and making smaller ones do the same work."

The report went on to describe, in very technical terms, the vacuum system employed in the operation of the engine. When simplified to "layman" terms, the agent was describing the application of slide valves.

In Cornwall, the drive to improve the efficiency of steam engines was constant, because the engines were necessary to keeping water out of the depths of mines. But, because of the high cost of coal, which was purchased from collieries in Wales, and shipped by sea, the efficiency of engines had to be improved to be economical.

The mines in the Lake Superior district faced the same problem, because the Michigan copper mines purchased their coal primarily from Pennsylvania, which also required long-distance shipping.

Next week, we will continue our talk on the impact steam power had on the Lake Superior mines, and their similar challenges shared with the mines in Cornwall.

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