NEW FERRY STEAMER

Hokitika Guardian, 21 October 1931, Page 2

NEW FERRY STEAMER

ADVENT OF THE RANGATIRA. AN ALL-ELECTRIC SHIP. Special interest attaches to the arrival in New Zealand of the Union Company’s turbo-electric steamer Rargatira, which arrived at Port Chalmers direct from the Civile last week, and which will enter on her maiden run in the ferry service on November 4.

Built at by V;ck-c-rs-Armstrong Ltd., who also loiistrn-U-d the turbo-electric liners Stratlii.aver and Strathliaird for the P. and 0. Compnin, tin* Rangatira is a twinscrew ship with two funnels, a raked stem, a cruiser stern and two masts. Her principal dimensions are: Length, b.p*., 100 ft.; breadth, moulded, qSii depth, moulded to upper deck. 29it.; and load draught, 17ft. She has five decks, of which the upper one is continuous all lore and alt. In gross tonnage she ranks seventh among the Union Company’s passenger ships. Sh> is considerably larger than tile Waliiro. and the Maori, and- as the following comparative table shows she has the same breadth as the Alakura, though that ship is 50ft. longer and measures nearly 2000 tons more- —

The Rangatira has accommodation for about 720 first-class passengers, there being cabin accommodation for COO. the remainder, in 1 h busy season, being provided ;or in up*-n northing. A total of 236 secomi-eias:- passengers is carried, 17(1 in cabins and 66 in open berthing. Tin* crew numbers about 112. The public rooms are spacious,, and ventilated on the well-known Theijomotank system. Provision re made for the carriage of a certain amount of cargo, including large* spaces for motor-cars in the ’tween decks, where there are also a certain number of horse stalls. The cargo holds are connected to the weather deck by means of trunked hatchways and are served by steel derricks and electric winches. The whole of the deck gear is electrical, a windlass and a capstan being fitted forward and twin electrio capstans aft for mooring purposes. The steering gear is of electric-hydraulic type, with telemotor control from the bridge, and a how rudder for manoeuvring purposes has also electric-hydrau-lic control.

Floating Power Station. The propelling machinery of the Rangatira is of special interest. Steam is generated in six high-pressure wat-er-tube boilers, and leaves the stopvalves at the high pressure of 4001 b. to the square inch, superheated to 725 deg. Falir. The total generator surface of the boilers is about 27,600 sq, ft, while the superheater surface is about; 9000 sq. ft., the total qrai of the tubular air-heaters being approximate, ly 27,648 sq, ft. The boilers burn ofl only under the forced draught air duct system. The boilers supply steam to two turbine-driven alternators, which in turn supply electric current to two double unit synchronous electric motors direct connected to tlie propeller shafts. The turbo-alternators are compact, and each unit “sits” on its own condenser, the- two condensers being of Weir's regenerative type hav. ing a total cooling surface of 13.500 .sq. it.; the capacity of the condensers is sufficient to maintain a vacuum of 28jin. of mercury with a sea temperature of 70 deg. Falir. The turbo-alter. nators have a maximum rating of 5120 kw., 3080 revolutions per minute, 3150 volts, 3-phase. The two electric propelling motors ar© in a separate space abaft the turboalternator compartments. These are dou-ble-unit, synchronous machines, each rated 6500 shaft horse-power, at 220 revolutions per minute. Special isolators are provided 011 the forward end of the control cubicle to enable each alternator to be electrically connected to its respective propeller motor, or either of the alternators to be connected to both propeller motors. The ship has a maximum speed of 21 j knots with both turbo-alternators running. but is required to do the majority of her service at 17 knots, which can easily bo accomplished with one only of the ti'L° in operation. If, howeve: !■ - *« lata on schedule or on cei l ■ > of the year when she has to n, >’ double 11111 in 24 hours, the higher speed is necessary, and both turbo-alternsftors come into use.

There are three control levers for each propeller—these being of manganoes bronze, each having four blades cast solid with the. boss —a direction lever, a field lever, and a turbine speed control lever. They are all mechanically interlocked. The whole of i 1V control cubicle is mista'-oqvnof. I and with the special keys incorrect | switching is impossible. Electricity : s I used for the whole of the auxiliary purposes, including lighting and cooking, and for this purpose there are three d.c. turbogenerators, each of j 350 kw. capacity, supplying current at 22a volts. It is to lie noted that al-. though the majority of the auxiliaries ! are electrically driven, the main feed, pumps are of the turbo type, and thoj stand-by . food pumps are steam-driven direct-acting. Surface feed heaters are fitted for raising the temperature of, the feed water, comprising one lowpressure, one intermediate-pressure, and one high-pressure heater, the

heating steam being taken from the auxiliary exhaust system and bled at, suitable pressure from the main turbines. In all, 13 pumps are electrically driven.

Length Tons (b.p.) Breadth gross feet feet Jhuigntirn ... (U52 400 58 Wall i mi . 4456 375 52.2 Maori . 34 S8 300.5 47.2 Makura 450 57.7 Maiuigamn . .. 7527 430.8 55,7 Maraina . 04.97 420.3 53.2