UP TO SCHEDULE.

Putaruru Press, Volume VII, Issue 276, 21 February 1929, Page 5

UP TO SCHEDULE.

ARAPUNI WORKS. * Important Statement. A most interesting trip around the ■ Arapuni hydro-electric works was made on Saturday last by the members of the Parliamentary party -which toured the Putaruru district. The party was conducted by Mr. T. ■C. V. Rabone, engineer-in-charge, who took great pains to explain every detail of the huge undertaking. Commencing on the high knob overlooking the dam, the party was given a bird’s eye view of works, after which each portion was visited in turn.

Interesting particulars given by Mr. Rabone, including several important and authoritative statements in regard to the powerhouse site, are as follow: Diversion Tunnel. The water pressure against the *dam wall is approximately 100,000 tons. The gates of the diversion tunnel are still available for use and can be lifted in two minutes. The leakage in the tunnel amounts to one cubic foot per second (cusec)* and is just the saturation natural to any tunnel. There has been no inin the flow. When the tunnel gates were first there was a ‘ ~ little river ” about four inches deep. The water pressure on each gate amounts to 1000 tons, and as no gate made fits close enough to withstand such pressure a natural and expected spray resulted. This has been decreased to practically nothing. As steel gates will not last for »ever and it is impossible to get down •to repair them the tunnel will later ie plugged with concrete. Powerhouse Site. The Public Works Department had little difficulty in laying the foundations on the site of the powerhouse. * The coffer dam erected by the contractors was useless for the purpose. It consisted of a bank of loose rubble which had been excavated from the site. As this was not compact the water poured through. Later hteel joists were rammed down in an •effort to cope with the water but they were not driven deep enough and to have been any good should have been driven a further 35 feet. The was that the water simply went to a lower level and poured underneath. The steel joists were not driven down to the foundations.

Nature of Country. The country on which the powerhouse is built is volcanic ash consolidated under pressure and presents little difficulty. Its crushing strength is 70 to 100 tons per square foot. The fact* that it has upheld the great rhyolite cliff above it testifies to its strength. Here Mr. W. E. Parry, M.P., an experienced miner, said the country was what was known as “ woolly ” and was good country to work.

Power in June. 1

rj% The department was well up to timetable, and the first turbine would be supplying power in June next, the second turbine in the spring 'and the third in the summer. The position was well in hand. Some four million cubic yards of spoil had been removed by the great flow of water which was turned down the spillway. Had the contractors kept up to schedule and carried out the work as they should have done there would have been no trouble below the spillway weir, as the water would have been controlled and sent the penstock tunnels to the turtles, as it was intended in the specifications of the job. The waters rush over the falls below the spillway weir at the rate of 60 miles per hour, the final drop being 100 feet. Minute observations are made at many points every day, and it appeared that the river was fast settling down to its Original bed. The cut in the Wietete fiats was about 60 feet deep and the river was cutting into its old bed at the rate of about three inches per month. . Controlling the Station. • Contrary to general belief, the waters will not rush down the penstocks to the turbines when Arapuni is working, at a tremendous rate. The speed down the penstocks will be feet per second, and the water will leave the outlet tunnel devoid of its energy a’- a s P eed of only 4,5 feet per Contrary to general expecta- " the turbine outlets will be ccv- ‘ --ed with 15 feet of water. i’ith all the turbines in operation thlw will be no rushing torrent down in Next Column)

the old river bed either, but just a sluggish flow. When the first machine is in operation the water will flow down the river bed at only one foot per second.

The weight of a turbine and generator complete is 400 tons, the spinning part of the generator alone being 110 tons. The total height of a turbine is 40 feet.

From the power-house to the stepup station on the cliff top the electric power will flow on 11,000 volt cables* which are much thicker than the main transmission lines. The power is then “ stepped-up ” ten times, and is delivered to Auckland and other parts on much thinner 110,000 volt lines.

The engineer-in-charge of the power station, will, when the station is in operation, operate all plant by what is known as remote control. In a huge room in the power-house fitted something like a ship’s bridge he will be able to tell at a glance the condition of any part of the plant from a huge indicator board. Numerous switches connect with power-wires which control everything at Arapuni, even to the tunnel gates at the damsite. There are speaking-tubes and a telephone exchange, and though the operator cannot see any part of the works, he can tell at a glance exactly how things are. The indicator boards are finished with beautiful grey Italian marble, and the room will be finished in white with indirect lighting. The control-house is also connected — T4 -h Waikaremoana and Auckland. 1 ” ’-]<* whole control is automatic and I should the engineer fall asleep, or be I incapacitated, a wonderful fool-proof relay board would automatically shut | the power off any particular line if 1 danger threatened.