KARAPIRO HYDRO WORKS

Te Awamutu Courier, Volume 71, Issue 6136, 14 September 1945, Page 7

KARAPIRO HYDRO WORKS

FEATURES OF MAIN DAM AND POWER HOUSE AS IT IS TO-DAY Apart from the continual stream of heavily-laden lorries through the streets of Cambridge, there is nothing to indicate that within a few miles of that town there is an undertaking which is going to play a major part in the rehabilitation of New Zealand. Throughout the war period work has been going ahead steadily on a site of the Waikato River known as Karapiro. During the years of war the engineers in charge were faced with many problems, and although they arc usually called upon to overcome constructional problems, they have had more than their share at Karapiro. The engineers were detailed to construct an electrical generating plant on the Waikato River to be known as the Karapiro Hydro Works. Progress Governed by Manpower The progress in the early stages was governed by manpower and equipment; men were manpowered to Karapiro in small drafts according to their military status; while the majority of equipment came to hand in spasms when transport was available. However, now that hostilities nave ceased rapid strides towards completion can be expected. A few days ago when we visited the works vze were surprised at the progress that had already been made and the activity of the whole works. A.s we passed from one section to another the workmen were all busy with their respective jobs and the extent and magnitude of the undertaking became more obvious. For thoste who have not visited Karapiro for some time the following review should interest them. The carpenters are now busy making .the boxing for the walls of the power-house workshop and the steel reinforcing is being placed in position in readiness for the pouring of concrete. The lilt shaft .is now nearing completion and 90 per cent, of its structure has begn finished. The purpose cf the lift shaft is to give access from the high-level bridge to the powerhouse below. The lift shaft, when completed, will be 204 ft. Sin. above sea level and will be the highest part of the structure on the dam site. At present it is possible to notice the steel reinforcing of the pent-house—-the top of the lift shaft---peering through a multitude of scaffolding. When this pent-house is completed everything will be in readiness for the installation of the lift, which is being supplied by Waygood-Otis, England, .a firm specialising in lift manufacturing. * . .The boxing and reinforcing steel is in progress of construction for the high-level bridge spanning the spillway. At present under the boxing of the high-level bridge it is possible to see the concrete peers that will carry the bridge over the spillway. The peers are of a stream-lined nature to minimise the obstruction of the flow of water over the spillway. The stairway running from the top of. the syphons to the high-level bridge is about 40 per cent, completed. This stairway is. an alternative means of reaching the power-house, other than the lift in the lift shaft from the high-level bridge. Inside the lift shaft provision has been made to carry the control cables from the power-house to the outdoor station, via a covered-in duct in the centre of the 12ft. roadway across the dam. Work on the syphon, which had been abandoned for some time owing to the carpenters being urgently rei quired in other portions of the works, i is now about to be re-commenced to | complete the syphon flumes. i The unloading bay walls in the, ! power-house are being pushed ahead !as speedily as possible to enable the early erection of one of the 100-ton I electric cranes. The unloading bay ! i-s 100 ft. above sea level. The remaining walls of the power house are almost concreted up to crane-beam level. In this unloading bay workmen are busy erecting 50ft. steel trusses to carry the form work for concreting of the power-house roof. Some of these trusses are already in position at the unloading-bay end. Each span is 50ft- Jong, 6ft. deep and weighs a ton; consisting of angles of structural steel with welded joints. About 20 of these trusses will be placed in position to carry the form work for th& concreting of the roof of the power-house. Locking down on the main foundations of the nower-house the first thing that strikes an outsider goingover the works is the enormous generator beds in the floor of the power-house. Tin re are three of them over which will be mounted the three turbines. The foundations are completed and a start has been made to lower into position the four segments of the “speed ring” for No. 1 machine. The .magnitude of the structure can readily be gained when it is realised that each segment of the speed ringweighs approximately 11 tons, and as the cranes cannot be used at this stage a special ramp has been erected. The ramp is of structural steel and it is now possible to slide each segment along it into position. This is actually a start of the installation of the permanent machinery; which in itself is a major problem that will take from six to nine months to complete. The administrative offices in the power-house are now ready for internal finishing*. Tn this section provisi n has been made for a visitors’ lounge and is also ready for interior finishing; workmen were busy placing the steel window frames into position when we viewed the works. The control room, or intelligence department, is also well advanced and is ready for final finishings. In this loom there will be an enormous amount of electrical installations required which will necessitate many hours of skilled and scientific labour before it is finally completedBelow the control is the cable basement, 83ft. above sea level, which is also nearing completion. In this room special care has had to be taken to guard against any seepage of water during high floods and water-proofing has played a prominent part in the construction and finishing of this room. One Unit First As the installation of units, or tur•bines, takes a considerable time, work is being concentrated on one unit so

that power will be available as early as possible. It will be possible for power to be generated as soon as the No. 1 turbine is completed and the two remaining ones will then be started. The power-house is so constructed that with one unit generating electricity i workmen can still be assembling machinery for . the two remaining units. Internal welding of the penstock pipes in their final position is well under way. The welders inside the 21ft. diameter pipes move about by making use of a portable scaffold, resembling a drilling carriage as used in tunnelling. In the power-house provision has been made for an auxiliary unit and it is now ready for the installation of the machinery. This auxiliary unit will develop 10,000 k.w. and the output will probably be used for local consumption.. The draught tube is complete and ready for the machinOn the Maungatautari side of the dam the outdoor station building is now finished and about 10 per cent, of the work on the concrete towers has been done. Concreting of the intake section has new reached the top level of the steel lining and form-work, prefabricated at the works factory, is now being placed into position at a point where the 21ft. diameter transitions into a rectangle 18ft. by 24ft. This section of the v.-.’i-ks gi'.\.’S visilm’;.an idea of the precision engineeringundertaken at the Karapiro works. '.ln another portion of the works a unit was drilling holes at 3ft. centres down 100 ft. to rock along the slab in front of the spillway section. These holes are being grouted to make the rock surrounding the spillway foundation thoroughly sound and watertight, as a precautionary measure to any possible rock’seepage. Radial Cableway Probably one of the greatest labour saving pieces of machinery operated at Karapiro at the present time is the radial cableway. This cableway works on principles similar to the one at Shasta Dam, in California, but, of course, is on a smaller scale. The .headmast is 90ft. high and weighs 15 tons. The tailmast runs on four bogeys, each wheel being double-flanged. The- tailniast s on a rail track at a speed of Ift. per second; the tail is weighted down with 28 concrete blocks, each block weighing five tons. The span of the cableway is 920 ft.; the main cable is 81 inches in circumference. Loads across the cable travel up to 720 ft. per minute and can be hoisted or lowered at the rate of 180 feet per minute. This cableway is used mainly for placing concrete in the arch. It transports three cubic yards in, a bucket, the total weight being about seven tons. Al! operations are controlled by the operator in the winch-house who carries out instructions received by a “walkie-talkie.” As the cableway is so extensive and passes cut of view of the man in the winch-house, he receives his instructions by ear-phones from an observer across the span and is referred to as a “walkie-talkie.” The motor used is 135 h.p. and the winch is fitted with a Westinghouse air break.