Power: Hydraulic Water Pressure Engines

Transcription

1 Power: Hydraulic Water Pressure Engines Extract taken from Burt, R A Short History of British Metal Mining Technology in the Eighteenth and Nineteenth Centuries. De Archæologische Pers Nederland Their development Greater and more lasting success with the efficient use of water power was achieved with the hydraulic or 'water pressure' engine, which employed not the weight of water in a bucket but the pressure of water on a piston, permitting much faster rates of operation. The hydraulic engine was a development of the cylinder and piston principle evolved in the steam engine, with the piston being moved by water pressure rather than atmospheric or steam pressure. The earliest models were almost identical in design to atmospheric engines and were single-acting devices with the piston moving on a work stroke in only one direction and being returned by a counterpoise weight. Later development, however, saw the construction of double-acting engines with the piston being powered in both directions. Most engines were installed underground on an adit so that water could be brought down a shaft and exhausted in the adit. The height of the column of water, the 'head1, was varied according to its volume but was usually 150 feet or more depending on the pressure required. In the 1860s Sir William Armstrong, the well-known mining and mechanical engineer, conducted experiments at Blackett level in Northumberland to develop a hydraulic 'accumulator' to allow water pressure engines to operate without a large head of water. Acting rather like a compressed air receiver, the accumulator consisted of a cylinder into which water was pressed by a series of waterwheel powered force pumps, and from which water could be piped with a pressure equal to a column 1,200 to 1,400 feet high. This not only increased freedom in location of the water pressure engines, both below and above ground, but also enabled machinery scattered over a large area to be worked from a single power source. Like many advances in mining techniques the credit for inventing hydraulic

2 machinery was not British, but German and Hungarian. The first reliable engine was constructed at the Oberharz in Germany in 1748, and by the late 1760s similar devices had been installed at Schemnitz in Hungary an Freiberg in Saxony. Nevertheless, British engineers were quick to adopt and further improve the efficiency of the machines. William Westgarth, agent for the Blackett/Beaumont enterprise in the North Pennines, installed the first British engine at a mine in the Coalcleugh area in 1765 and in 1768 John Smeaton, who himself became interested in hydraulic engine design, reported that there were four engines operating in the same district. Distribution in Britain During the last quarter of the eighteenth century several more machines were installed in the Aliendale and Nent Head districts of Northumberland and Cumberland. They proved their usefulness and reliability so convincingly that from the early nineteenth century they began to be installed in all major mining districts of. England and Wales, often in direct competition with the then usual sources of water power and steam power. In Derbyshire, for example, where steam power had by then been in common use for nearly a century, Richard Trevithick installed a hydraulic engine of his own improved design in 1803 to pump water up to sough level at Aiport mines. Presenting no large running costs and operating almost continuously and trouble free for 47 years, the engine proved such a success that by the 1840s five or six similar engines had been installed to further assist working below adit level in the now newly formed Aiport Mining Company. By the mid-century hydraulic engines had also been tried in Cornwall, Cardiganshire, Flintshire, Swaledale in Yorkshire, the Lake district and the Leadhiils district of Scotland. The hydraulic winding engine erected at the Fairchance mine in Cardiganshire in 1785 was one of the first to be installed in a mining district outside of the North Pennines. However, like several other engines erected in the district from the mideighteenth century, it proved a failure and was removed in No further engines of this type were installed in the district, the greater majority of mines continuing to rely on the more conventional forms of water power. During the hundred years f rom the first introduction of hydraulic engines, their power and efficiency were improved by a long line of engineers,

3 such as John Smeaton, Richard Trevithick, Thomas Dean, William Fairburn, William Armstrong, and John Darlington. Most of these men came to hydraulics with considerable experience in stearn engineering and through them there was a major interchange of ideas and experience between the two sectors on such matters as valve design and the use and regulation of high pressures. Trevithick's pioneering work with high pressure steam, for example, may well have been influenced by his experience with water pressure engines which he designed and installed in Derbyshire and at the Druid Copper Mines, lllogan near Redruth. As a result of this interaction and numerous improvements in the design and construction of machinery, by 1842 Darlington was able to install an engine at the Alport mines using a 132 feet column of water exerting a force of more than 50 tons on a 50 inch diameter piston. At maximum capacity it could operate at 5 1/2 strokes a minute, generating 168 net hp and raising 6,000 gallons of water a minute from a depth of 138 feet. Darlington, who had care of the machine as engineer to the Alport Company from 1840 to 1850, estimated that it never cost more than 12 a year to operate and it worked for six years without interruption. In 1851, when the Alport mines closed, Darlington became the manager of Minera mine in Denbigshire and installed a similar engine there in Together with other engines built for mines operated by John Taylor and Sons in Wales, they proved so successful that the adventurers at Talargoch in Flintshire also decided to install hydraulic machinery in direct competition with stearn power. Indeed, hydraulic engines, with their continuing improvement in design and efficiency, continued to be installed and operated at competitive costs well into the 'electrical age' at the end of the nineteenth century. For example, a double-acting horizontal winding engine and a double-acting vertical pumping engine were installed in the Sir Francis Level in Swaledale in 1879 and can still be seen in situ as they were abandoned in Similarly, in 1881 a powerful hydraulic engine was installed at the Laxey mines in the Isle of Man to operate a 200 fathom man-engine; a function which it continued to perform efficiently into the twentieth century. Pros and cons of the hydraulic engine Hydraulic engines had many advantages over other sources of power. They were considerably more efficient than waterwheels and often generated more power than steam engines of a similar size. Even the

4 early and relatively simple engine erected by Trevithick at the Alport mines, only capable of making three strokes a minute, developed more than twice as much power from its 25 inch cylinder as a 63 inch cylinder Boulton and Watt engine then working on the Dolcoath mine in Cornwall. The strong and robust design of hydraulic engines, necessitated by the high pressure used in the machinery, and the low level of corrosive or choking substances in their 'fuel' tended to reduce maintenance costs and interruptions to working to a minumum, with many machines operating continuously and trouble free for many years. Similarly, the operating costs of the machinery were negligible, amounting only to the cost of ensuring a steady supply of water and! operators could avoid the costs of purchasing and transporting large quantities of coal as well as the high royalties sometimes due to patent holders like Boulton and Watt. However, hydraulic engines had three important drawbacks. Firstly, like all forms of water powered machinery, they were subject to interruptions caused by winter frosts and summer droughts. The large water requirements of some engines meant that long dry summers posed particularly serious problems. At the Alport mines in Derbyshire, for example, the two engines operating in the 1820s required 2,000 gallons of water per minute to cope with a flow of up to 6,000 gallons per minute to the mine. This requirement was larger than the entire flow of the river Bradford, the major water supply for the engines, and during several long droughts, flooding caused the deeper workings of the mine to be permanently abandoned. Secondly, the massive construction of the machines made them costly to build and install. The two engines on the Sir Francis Level, for example, cost 4,500 to buy and install compared to an estimated 3,000 for a single Cornish steam engine of equal capacity for both winding and pumping. These high purchase costs must have largely offset the advantages which robust construction gave in terms of low maintenance costs. Thirdly, since hydraulic machinery-lifted less water than it consumed over the same height, it could only be used effectively where an adit was available for the underground discharge of the water used to power the machine. Trevithick's engine at Aiport, for example, used 416 gallons of water to lift 280 gallons from eight fathoms below adit level. These engines were therefore less flexible and often less convenient than alternative sources of water or steam power. Notwithstanding these problems, many mine owners were convinced that they were outweighed by the advantages of the engines and the installation of hydraulic machinery reached its high point around the mid-

5 nineteenth century, with some districts, like the North Pennines, becoming entirely dependent on water power. During the third quarter of the century, however, further improvements in steam technology and major reductions in coal transport costs following on the extension of the railway systems, gradually reduced the advantages of hydraulic machines over steam engines and by the 1880s many districts were turning away from water power. In 1881, for example, there were said to be no operational engines in Derbyshire and in 1887 Robert Hunt, in his comprehensive survey of British mining, made no mention of working hydraulic engines anywhere in the country, although there were still some operating in several districts.