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A hydraulic power network is a system of interconnected pipes carrying pressurized liquid used to transmit mechanical power from a power source, like a pump, to hydraulic equipment like lifts or motors. The system is analogous to an electrical grid transmitting power from a generating station to end-users. Only a few hydraulic power transmission networks are still in use; modern hydraulic equipment has a pump built into the machine. In the late 19th century, a hydraulic network might have been used in a factory, with a central steam engine or water turbine driving a pump and a system of high-pressure pipes transmitting power to various machines. The idea of a public hydraulic power network was suggested by Joseph Bramah in a patent obtained in 1812. William Armstrong began installing systems in England from the 1840s, using low-pressure water, but a breakthrough occurred in 1850 with the introduction of the hydraulic accumulator, which allowed much higher pressures to be used. The first public network, supplying many companies, was constructed in Kingston upon Hull, England. The Hull Hydraulic Power Company began operation in 1877, with Edward B. Ellington as its engineer. Ellington was involved in most of the British networks, and some further afield. Public networks were constructed in Britain at London, Liverpool, Birmingham, Manchester and Glasgow. There were similar networks in Antwerp, Melbourne, Sydney, Buenos Aires and Geneva. All of the public networks had ceased to operate by the mid-1970s, but Bristol Harbour still has an operational system, with an accumulator situated outside the main pumphouse, enabling its operation to be easily visualised. ==History== Joseph Bramah, an inventor and locksmith living in London, registered a patent at the London Patent Office on 29 April 1812, which was principally about a provision of a public water supply network, but included a secondary concept for the provision of a high-pressure water main, which would enable workshops to operate machinery. The high-pressure water would be applied "to a variety of other useful purposes, to which the same has never before been so applied." Major components of the system were a ring main, into which a number of pumping stations would pump the water, with pressure being regulated by several air vessels or loaded pistons. Pressure relief valves would protect the system, which he believed could deliver water at a pressure of "a great plurality of atmospheres", and in concept, this was how later hydraulic power systems worked. In Newcastle upon Tyne, a solicitor called William Armstrong, who had been experimenting with water-powered machines, was working for a firm of solicitors who were appointed to act on behalf of the Whittle Dene Water Company. The water company had been set up to supply Newcastle with drinking water, and Armstrong was appointed secretary at the first meeting of shareholders. Soon afterwards, he wrote to Newcastle Town Council, suggesting that the cranes on the quay should be converted to hydraulic power. He was required to carry out the work at his own expense, but would be rewarded if the conversion was a success. It was, and he set up the Newcastle Cranage Company, which received an order for the conversion of the other four cranes. Further work followed, with the engineer from Liverpool Docks visiting Newcastle and being impressed by a demonstration of the crane's versatility, given by the crane driver John Thorburn, known locally as "Hydraulic Jack". While the Newcastle system ran on water from the public water supply, the crane installed by Armstrong at Burntisland was not located where such an option was possible, and so he built a tower, with a water tank at the top, which was filled by a steam engine. At Elswick in Glasgow, charges by the Corporation Water Department for the water used persuaded the owners that the use of a steam-powered crane would be cheaper. Bramah's concept of "loaded pistons" was introduced in 1850, when the first hydraulic accumulator was installed as part of a scheme for cranes for the Manchester, Sheffield and Lincolnshire Railway. A scheme for cranes at Paddington the following year specified an accumulator with a piston and a stroke of , which enabled pressures of to be achieved. Compared to the of the Newcastle scheme, this increased pressure significantly reduced the volumes of water used. Cranes were not the only application, and hydraulic operation of the dock gates at Swansea reduced the operating time from 15 to two minutes, and the number of men required to operate them from twelve to four. Each of these schemes was for a single customer, and the application of hydraulic power more generally required a new model. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hydraulic power network」の詳細全文を読む スポンサード リンク
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