D—4

Tiie major slip adjacent to No. 3 pipe-line continued to show movement, and it was not until the latter part of the year that a removal of the lower part of the slip was commenced. During January, February, and March, the opportunity was taken to completely overhaul No. 3 main machine. This maintenance work had bad to be postponed from the previous year owing to the power situation. In conjunction with this overhaul No. 3 penstock, 3,450 ft. in length and with a diameter varying from 78 in. to 66 in., was sand-blasted and painted internally with coal-tar paint. A roading alongside the penstock had been built to facilitate this work. Extensive alterations were made to the test switches on the control board at the Tuai Power-station. New networks were fitted to Nos. 3 and 5 machine voltage-regulators. The governor-locking solenoid and associated equipment of both Nos. 4 and 5 machines was removed. Satisfactory service was obtained from all machines.

Generating-running times were as follows for the year :

Mangahao Power-station.—The rainfall for the year at No. 1 dam was 110-26 in., compared with 188-74 in. and 198-05 in. in the previous two years. At No. 2 dam the rainfall was 104-29 in., at No. 3 dam 79-55 in., and at the power-house 47-94 in. The annual load factor dropped to 46 per cent, on a maximum load of 21,300 kW. Extensive cleaning and painting of steelwork at all dams was carried out. On 24th November the surge-chamber gates tripped, due to a sustained .overload when Tuai tripped out, and the pipe-lines emptied. All five turbine governors were completely overhauled and the oil renewed. Two more sets of bronze buckets were received. One set was fitted to No. 3 turbine, and this completed the change to new buckets on the three 6,000 kVA. units. The other set is reamed ready for fitting to No. 2 turbine.

Generator-running times were as follows :

A contract has been let for the supply of replacement gates for the by-pass tunnel of No. 1 dam. Negotiations are in hand for a contract for similar gates for No. 2 dam.

11

Generator No. Time oil Load. Time Idle. Time under Repair. Percentage Availability for Service. Honrs. Percentage. Hours. Percentage. Not in j Demand (Hours). In Demand (Hours). 1 Tuai 1 7,061 80-39 1,388 15-80 333 2 96-19 2 7,086 80-67 1,429 16-27 265 4 96-94 3 !! _ !! 5,637 64-17 1,223" 13-92 1,855 69 78-09 Piti'paua 4 5,870 66-83 2,486 28-30 424 4 | 95-13 5 5,840 66-49 2,473 28-15 421 50 94-64 1

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). 1 8,274 94-2 475 5-4 35 99-6 2 8,304 94-5 434 4-9 46 99-4 3 8,168 93-0 396 4-5 220 97-5. 4 8,369 95-3 404 4-6 11 99-9 5 8,363 95-2 413 4-7 8 i 99-9