High-Pressure System in London.
A private corporation in the British metropolis has laid a system of mains in the streets which furnish high pressure, the volume being supplied by the regular city mains. The principles of the plan arc reported as follows:
“The London Hydraulic Power company began operations in 1887. It now has 160 miles of mains laid in the streets throughout the closely built-up parts of the city on both sides of the river. It supplies hydraulic power for elevators and general power-purposes, and there are over 6,000 such connections to its mains. Turbines are extensively used in connection with this service, and are economically and successfully employed for various purposes where continuously running machinery is required. The power is also used for running automatic pumping machinery and automatic ejectors for keeping the many basements, which are lower than the sewers, free from water. The system is in direct competition with electricity for power-purposes, and, in a number of cases, provides the waterpower to turn turbines directly connected with dynamos in isolated electric lighting plants. The water is taken from the Thames, the Regent’s canal and wells, and is filtered before passing into the mains. There are four pumping stations. The water is pumped into accumulators loaded to a pressure of 750 lb. per sq. in.—producing the same effect as a reservoir at an elevation of 1,700 ft. The company states that there is an average pressure of 700 lb. day and night all the year round. The street mains are mostly 6-in., there being some 7-in. in the more important centres. They are of extra heavy cast iron pipe with thick flanges. The system is partly gridironed and liberally provided with valves, so that, in case of a break, the section affected is made as small as possible. For fire protection purposes, this system is used in connection with the public water supply. Branches of both mains are brought into the plant to he served, and both connected to a device known as an Ellington injector. In this device, a small stream from the Power company’s main at a very high velocity is directed into the system with a much larger volume of the sluggish city water. To make the high-pressure supply automatic and at the same time keep the very high pressure off the system, an automatic device is installed, which will keep anv desired pressure on the system, hut, when sprinklers operate, will open the valves, allowing full pressure. The device will also close the valves again, if the flow of water is stopped. A special hydrant is used with this system, having the large connection for the low-pressure water, the small connection for the high-pressure water and the ejector, and a eontroling valve for each, all compactly arranged. It is simple and as easily handled as the ordinary hvdrant. There is another very ingenious device installed to prevent the water from the company’s mains from flowing back into the city mains. It is called a ‘water-lock.’ and consists of two peculiar check valves, with an automatic reliefvalve. which discharges to the atmosphere, if the pressure between the checks raises above the pressure in the town mains. A system of this sort could hardly he said to take the place of the high pressure water systems which have been installed in this country, and. of course, its use for fire service only, would hardly support such a service. This system, however, can be arranged to give a high-pressure fire service which can be easily controled and regulated as to pressures, for the reason that the pressure on any hydrant can he regulated varying the size of the orifices in the ejector. Two hydrants off the same main, at the same location, can be arranged to give two other different pressures by the same method. It is stated that the system of the London Hydraulic Power company is not unique: but that the other installations are only small ones and exist in several small towns in Great Britain.”