GENERATING POWER

Rotorua Morning Post, Volume 2, Issue 296, 9 August 1932, Page 6

GENERATING POWER

GERMAN SUBMARINE ENGINES PROVIDE ELECTRICITY FOR CHRISTCHURCH. ASSISTING LAKE COLERIDGE. With a continuous roar, the Lyttelton stand-by electric power plant, the engines of which were originally designed as diesel engines for a German submarine, provides power and light for Christchurch in conjunction : with the Lalce Coleridge hydro-electric sch'eme. Though the engines were designed for use in submarines, these parti-

cular ones were never mstalled. A pity, really, for the lettering U182 ST, on cne of them, - has a romantic undersea boat sort of sound about it till you learn that it is probably only a construction number. The engines come in pairs, one of i each pair a right-hand drive, the other j left-hand, built like this for driving ; the two propellers of a twin-screw • boat. j They tower high above you, and a greaser walking round the upper platform looks insignificant. That is not remarkable, for you could almost put | him into any one of the 10 cylinders j of each engine. The monster pistons, j 20 7-8 inches across, move up and ; down that distance, too, and each pis- ! ton and cylinder develops 300 horsepower. 'In the spare parts cupboard at the back of the room are p-iston rings as big as children's hoops, gudgeon pins, several times as thick as the pistons of a large motor car engine, and valve springs several inches across. The top of the engines, which can be seen better from the platform where the greaser is working, are a mass of pipes for oil and water, and for heavy moving parts. Great rocker arms for th'e overhead valve gear, three feet long against the four inches of those in your car, move rhythmically, purposefully, up and down. The cams that operate them are broad ■ as dinner plates, and a great deal thicker. Cooled by Oil. Along one side of each engine runs

the exhaust pipe, big as a city watermain. It is double for cooling water circulates round the actual pipe. The cooling arrangements right through the engines are remarkable. Every part where heat develops is lcept at a reasonable working temperature by

a stream of oil or water. The pistons are cooled by constant-ly-circulating oil, and through the great six-inch wide mushrooms of the exhaust valves water is running all the time, pumped like all the rest of the cooling water, from the sea. B'esides each engine are two metal "bottles," rising from the floor, which contain compressed air. One of them, when a lever on the engine is swung over, pushes air at a pressure of 900 lb to the square inch into the cylinders, setting the engine turning over till it fires. Another, at slightly higher pressure, blasts the fuel oil into the cylinder, where it is ignited by the tremendous pressure tbht develops as the piston comes up. At one end of each engine, too, is a big fuel pump, and there is a bunch of gaugas that tell the pressure of water and oil in every part. There are thermometers, too, to enabffi the engineer on watch to check up on the temperature of the bearing oil, the piston oil, and the cooling water, all of which details are entered periodicaly in a log hook. Immense Generators. Down below the floor level behind the engines is an auxiliary petrol motor which drives a generator, which drives a pump, which sets the oil eirculating through an engine before it is started. Down here also is the auxiliary motor for compressing the air for the bottles. There is a row of four big tanks that hold the fuel, which is pump 3d through coolers to the engines. Up above are separators, just like big cream saparators, in which the fuel oil and lubricating oil are being purified. The fuel of the giant Diesels is about as thick as summer car oil, but darker in colour. It is, of course, these remarkable engines that are the main interest in this plant, but they are only a means to an end, the end being the spinning of the big generators and the consequent supply of electric power. Each generator, partly sunk thongh they all are in wells in the floor, reaches to 10 or 12 feet above the floor level, and each running at the normal 300 revolutions a minute of the engines, to which they are direct-coupffid, turns out about 1300 kilowatts. They are not the generators built for submarines — they were special jobs designed to charge storage batteriis — but Swedish machines built for the engines. An operator sits at a table in front of the long, clean row of switch panels, which have that look of efficiency that only switchboards have. At one end is an instrument known as a synchroscope, which enables the operator to ensure that the current tui-ned out is in step with the Lake Coleridge supply it is supplementing. The moment it gets out of step, lamps on the synchroscope light up, and the approp'riate action can be taken. If an engine speeds up or slows down, its power is automatically cut out. The operator, like the engineer on watch, has to enter particulars of the running of -his part of the plant at intervals. From 7 o'elock in the morning till 3 in the afternoon an engineer, an operator, and a greaser or two are keeping an eye on the plant. at 3 o'clock in the afternoon another watch comes on staying till 11 at night, when the plant shuts down. Because those engines are clattering away, spinning the generators, the level of Lake Coleridge will fall much more slowly now than it has been doing, and the lake will have a chance to refill by February, when the Public Works Department likes to see it overflowing. What one of those people who stepped off the first four ships would have thought if he had been told that a lot of noisy machinery in a shed at his new port 'could affect the level of a lake away back in the mountains, is interesting to imagine.