D—4

B. OPERATION AND MAINTENANCE 1. Power-stations King's Wharf. —The station ran for the whole year except for two weeks in May. All boilers were surveyed. A new turbine rotor was fitted to No. 10 machine, and a new superheater was fitted to No. 15 boiler. Fuel was mainly of indifferent quality which gave rise to many problems in firing and caused a good deal of grit nuisance. Penrose. —This Diesel station was not on load except for testing purposes until March, when it commenced running for two shifts a day. Arapuni and Karapiro.—Arapuni: No. 2 generator went out of service on 6th January, 1950, for a major overhaul. Air-coolers have been installed for an enclosed air-cooling system. No. 6.generator was fitted with a new 35,000 b.h.p. turbine runner in April, and a new 24,000 kVA. stator in December. No. 2 auxiliary generating-set was given a complete overhaul. Over two-thirds of the 924 fiashboards on the main and extension spillway weirs were renewed. Chlorinating equipment for the village watersupply was installed in July. Karapiro : No. 3 generating-unit was shut down on several occasions in May, June, and July to inspect and repair a cracked blade on the 42,000 b.h.p. Kaplan type turbine. A new blade was fitted in July.

Generator-running times were :

Waikaremoana. —The lake-level reached 2009-9 ft. in August, 1949, and fell steadily to 1997-4 ft. at 31st March. In August, during heavy rains, a slip carried away a chain of the ground supporting the Mangaone Stream deviation pipes, and substantial slips occurred on various roads. Operation and control of Tuai Nos. 1, 2, and 3 headgates were changed over from D.C. to A.C. The interior of No. 1 pipe-line was sand-blasted and painted, extra manholes being fitted in the lower half. Manholes were also installed in No. 2 pipe-line. No. 1 generator and governor and No. 5 generator were completely overhauled. Alterations to bearings were made on Nos. 4, 6, and 7 machines to provide better oil usage. Bucholz relays and open-type 11 kY. terminals were fitted on two of the 11 /110 kV. transformers.

15

Generator No. Time on Load. Time Idle. Time under Repair. Percentage Availability for Service. Hours. Percentage. Hours. Percentage. Not in Demand (Hours). In Demand (Hours). Arajpuni 1 7,773 88-73 895 10-22 92 98-95 2 6,042 68-97 750 8-56 1,968 77-53 3 7,882 89-98 817 9-33 61 99-31 4 7,834" 89-43 810 9-25 ■ 57 59 98-68 5 7,608 86-85 872 9-95 280 96-80 6 6,683 76-29 723 8-25 1,354 84-54 7 7,532 85-98 931 10-63 297 96-61 8 7,766 88-65 905 10-33 83 6 98-98 Karapiro 1 7,130 81-39 1,582 18-06 I 48 99-45 2 7,157 81-70 1,585 18-09 18 99-79 3 .. .! 6,141 70-10 1,457 16-63 1,162 86-73