HYDRO ELECTRIFICATION.

Otago Witness, Issue 3017, 10 January 1912, Page 5

HYDRO ELECTRIFICATION.

LAKE COLERIDGE SCHEME. WELLINGTON, January 3. Tenders are to be invited at ones fo* the supply. of machinery for the Lak* Coleridge hydro-electric Scheme, and foi the pipe-line which will convey water from the lake to the turbines. The Government recently called for tenders for th® construction of a tunnel 7100 ft long to convey water from Lake Coleridge through a hill to the Rakaia River, but only one tender was received, and at ths end of this week contractors will be again invited to submit a price for ths work. The tunnel is to have a mean grade of one in 1000, and its top at th® lake end will be 12ft below the mean lak® level. Its internal size is to be Bft by Bft, with a semi-elliptic arch. It is to b® lined throughout with a concrete lining. New Zealand cement being specified. Ths tunnel will convey the lake water into ths outlet works, where it will enter thi pipe-line 2700 ft long leading to the turbines. The pipes are to be of varying thickness, up to five-eighths of an inch, according- to the pressure, which gradually increases as the power-house is approached, a total fall of nearly 500tt from the lake level to the turbine enabling the water to be delivered at a pressure of 2101 bto the square inch. The test pressure for the pipes range up to 4001 b to the square inch. At present only two pipe-lines are specified, but at some future date a third one will be installed, and the tunnel is to be made big enough to cope with the supply then required. Th® initial machinery to be ordered consist® of three Francis reaction turbines of 2150 brake horse-power each, developed at 500 revolutions per minute, and one Pelton impulse turbine, developing 225 horsepower, to be used for driving the exciters. The main turbines will be coupled direct to the generators, which are also to hi ordered at once, and the total capacity of the plant will be 4500 kilowatts, representing 6000 horse-power. The powerhouse and other structural features art designed so as to easily extend the capacity to 12,000 horsepower, when eia generators will be required. Specifications for the power-house are not yefc ready, as the requirements of tha machinery will first have to be settled, but the general plan has been decided. In fact, so far as the electrical engineers’ department is concerned, it has put tha Coleridge scheme into final shape, and it is only necessary now for the machinery contractors to get to work. The tender* will be open for the next three months, and the specified time for delivery at Lyttelton is within 10 months on acceptance. The machinery specified is of th* type in world-wide use, and there are no exclusive features in the design, which would result in restricted tendering, Eight cottages for' the power-house employees are to be constructed immediately, tenders for this work closing on January 31.