D—4

Penrose. —The three Diesel engines were completely dismantled for inspection by the Inspector of Machinery. A magnetic test by the Department of Scientific and Industrial Eesearch of a suspected hair crack in No. 1 engine crankshaft produced a negative result. All crankshafts were passed as fit for service. Huntly. —The Mines Department completed dismantling the plant in September and transferred it to the west coast of the South Island. Arapuni and Karapiro. —Lake Taupo Control: The rainfall in the Lake Taupo area for the year was 70-34 in., compared with 66-17 in. for 1947-48. The level of Lake Taupo at the beginning of the year was 1,172-75 ft. which rose to 1,176-74 ft, early in December, and only fell to 1,175-45 ft. by the 31st March, 1949. Arapuni: A new stator for No. 8 generator arrived in July and was put into service in December. No. 6 generator has been shut down since 17th February, to replace the temporary 25,000 b.h.p. turbine runner by a new 30,000 b.h.p. runner that was originally ordered for this machine in June, 1939. The cast-iron downstream bend pipes of Nos. 7 and 8 bypass butterfly valves were replaced by new mild-steel bend pipes on account of erosion and cavitation. Karapiro : Turbine efficiency tests were carried out on No. 1 generating-unit in November. A chlorinating plant for the village water-supply was installed in January. Cables were laid for the village reticulation and street-lighting, and supply to the village was changed over from a temporary 50/11 kV. bank to the 110/11 kV. bank in January. The Cambridge Electric-power Board metering was changed over from Leamington to Karapiro on Ist January.

Generator-running times were, as follows :

— (a) Shut down on 6th and 7th April for maintenance work on the 6kVA. pendulum-drive generator(6) Fault on D.C. cable of 6 kVA. pendulum-drive generator, Bth March. (c) Shut down on 17th February to replace a temporary turbine runner by the permanent runner. (d) Shut down on 19th October for repairs to mam butterfly valve bypass. (<?) Shut down from Ist November to 31st December to install a new stator and winding, and from3rd to 17th February to fit a new sealing-hose to the main butterfly valve. (/) Shut down from 9th February to 9th March for examination. (g) Shut down from 14th to 28th March for examination. (A) Running-times are taken from 2nd June, 1948. Waikaremoana. —The main lake-level improved rapidly, reaching a maximum level of 2,007-2 ft. early in December, the hydraulic position thus comparing more than favourably with the previous year. Annual rainfall of 101-3 in. showed a definite increase over the 1947-48 total of 86-1 in.

10

Time on Load. Time Idle. Time under Repair. Percentage Availability for Service. Generator No. Hours. Percentage. Hours. Percentage. Not in Demand (Hours). In Demand (Hours). Arapuni 1 7,660 87-44 1,100 12-56 100-00 2 7,585 86-59 1,130 12-90 41{a) 4(6) 99-49 3 7,633 87-13 1,127 12-87 100-00 4 7,741 88-37 1,019 11-63 100-00 5 7,051 80-49 1,709 19-51 100-00 6 6,160 70-32 1,592 18-17 1,008 (c) 88-49 7 6,978 79-66 1,753 20-01 29 (d) 99-67 8 5,538 63-22 1,424 16-26 1,798 (e) 79-48 Karapiro 1 6,474 73-90 1,497 17-09 789 (/) 90-99 2 7,391 84-37 1,038 11-85 331 (g) 96-22 3 .. .. 6,397 87-97 875 12-03 100-00(ft>