AN ALL-ELECTRIC SHIP

Dominion, Volume 22, Issue 105, 28 January 1929, Page 12

AN ALL-ELECTRIC SHIP

NEW OIL TANKER BRUNSWICK DUE AT WELLINGTON TO-MORROW A REMARKABLE VESSEL A wonderful ship, the largest of her special type in the world and the first that has visited the Southern Hemisphere, will arrive at Wellington to-morrow morning. The vessel is the Atlantic Union Company’s Diesel-electric oil tanker Brunswick, which is carrying the largest cargo of petrol that has ever come to New Zealand in one bottom. Her arrival marks an epoch in the shipping history of the Dominion, which, during the last two or three years, has been associated in its overseas trade with some of the most noteworthy developments in naval architecture and marine engineering.

The Brunswick is different from any other ship (hat lias visited Wellington, not only in appearance, but in other more important respects. The vessel is a true “all-electric” ship in that she is not only propelled by electric power but the whole of her engine-room auxiliaries and her deck machinery are elebt rically driven. Steam finds no place in her internal economy save for a small vertical boiler working at 251 b. pressure per square inch, and supplying steam only for heating purposes. At sea it uses the exhaust gases from two of the Diesel engines and in port steam is raised by an oil-fuel burner. In appearance the Brunswick differs from the ordinary oil-tanker by having her navigating bridge and the whole of her living accommodation right aft. The only deck erections consist of a topgallant forecastle 40 feet in length used for cargo and stores and a poop 103 feet long for housing the crew and -galley, with houses above the poop for the officers and engineers surmounted by the navigating bridge. The ship has no funnel, the only uptakes being that of the auxiliary heating boiler nnd the four exhaust pipes and silencing heads from tlie Diesel engines. From the break of the poop to the forecastle head the main deck stretches in a wide expanse for 350 feet. Notable Clyde Production. The Brunswick, which was built last year bn the Clyde by Scott’s Shipbuilding and Engineering Co.. Ltd.. Greenock, is one of nine Diesel-eler-trie tankers owned by the Atlantic Oil Shinning Company of Pbiladelnhia. and is the first ship of her type built in Britain. She was constructed on the Tsherwood system of longitudinal framing to the requirements of “Lloyd’s Register” for the highest class. Her principal characteristics are: — Length (between perpendiculars) 469 feet Breadth 63 feet Depth (inould?cl 36ft.. 9in, Load draught 26l't. 6in. Deadweight capacity 13,210 tons Load displacement 17.680 tons Gross registered tonnage .. 8.947 tons Designed speed 11 knots Up-to-date Oil-Tanker. For the carriage of bulk motor spirit the' vessel lias ten pairs of main and summer tanks, and these and all the piping in connection therewith have been specially arranged for . the carriage of light oils. A 12-inch main pipe on deck is provided for filling and discharging the cargo oil, there being four filling or discharging positions, and each having two 6-ineh hose connections. Inside the tanks there is a 10-incli main line on the port and another on the starboard side,.for the main tanks, and 6-ineh main pipes on the port and on the starboard side for the

summer tanks. These main pipes extend throughout the cargo tanks. The main pump room is situated just forward of tlie engine-room, and the pumping installation comprises three cargo pumps, each capable of discharging 81,000 gallons of oil per hour. The pumps are of the rotary type, and are driven through gearing by 80 B.H.P. electric motors situated in the engine-room. A small electrically-driven bilge pump is also fitted in the main pump-room, the motor being in the engine-room. Ejectors are fitted to the ventilators to expel gases from the pump-room if necessary. All the deck machinery, ineluding the windless, capstans, and winches, are electrically-driven. The steering gear comprises a Hele-Shaw motor-driven pump operating in conjunction with a pair of opposed hydraulic rams. The control of the gear from the bridge is electrical, and can be operated either by a .small hand-wheel on the main motor bridge controller or automatically by the gyro, pilot. In addition, mechanical control is fitted on the upper deck just above the gear, and powerful hand gear is arranged near to this position, thus providing against a total breakdown of the power gear.

A distinctive feature of the hull equipment is the Sperry standard .Mark VIII. gyro compass equipment, complete with a steering and bearing repeater, as well as a course-recorder. In addition, a Sperry two-unit type of gyro pilot is fitted. As already indicated, the gyro pilot provides a method of controlling the steering gear. The top cap of the bridge unit of the pilot also contains the control, for the main propelling machinery, as in this vessel the motors are controlled from the bridge .when the ship is maoenvring. Other items in the vessel’s outfit are a Sperry helm-angle equipment and two 18-inch incandescent searchlights, with pilot-house mounting. .The accommodation for the officers.and crew is of the highest order, the crew being quartered in rooms arranged for two men. Effective steam-heating arrangements have been installed in tlie accommodation. For the preservation of the ship’s provisions, refrigerating plant of the ammonia type is fitted on the main deck over the engine-room. This • machinery operates in conjunction with two cold-storage rooms and a common handling room, arranged on the deck above. An ice-making tank is also installed. The Diesel Engines. AH the electric power is generated by four Diesel engines direct-coupled, to the B.T.H. main generators and auxiliary generators, arranged athwartships. The engines, which are of the Carels-Ingersoll-Rand type, built under license in Belgium by Messrs. Carel-Bros., of‘Ghent. They are, six-cylinder, four-stroke cycle, trunk-

piston. airless-injection, heavy-oil engines, each developing 750 brake horsepower at 225 revolutions per minute. The cylinders, which are cast separately, are 194 inches in diameter with a piston stroke of 24 inches, 'he cast-iron pistons are uncooled, and sea-water cooling of the main jackets and cylinder heads is used. The principal features of interest are the employment of two diametrically opposed fuel valves per cylinder, of the automatic type, these valves being placed on the fore and aft centre line of the engine, and spraying into the centre of the combustion chamber: fuel is fed to these valves by a single fuel pump operating at three times engine speed in conjunction with a mechanical distributor. Another interesting feature of the design is the employment of eccentrics for valve operation, the eccentric shaft being totally enclosed in the base chamber and running in oil. Tlie six-throw crankshaft of each engine is a solid steel forging. The Electric Generators.

Each of the four Diesel engines is direct-coupled direct-coupled to a 600 k.w, 2400 amp., 250 volts at no load generator. Each engine also drives an auxiliary generator of 75 k.w„ 250 volts, which is arranged in tandem with the main generator. These auxiliary generators supply power for the ship's auxiliaries and also for the excitation of the main generators and the propelling motor. Tlie main generators are electrically coupled in series; and. although all four are in operation at full power, three, two. or only one set may be used for reduced power, the combined voltages being WOO, 750, 500, and 250, according lo the number of sets on the v --elling circuits. ■» The Propelling Motor.

The main propelling motor is rated at 2800 shaft horse-power at 95 revolutions per minute. It comprises two units, each complete with a separate magnet frame, armature, and commutator, the two armatures being electrically connected in series and mounted on a common shaft which is supported between two pedestal bearings. As the propelling motor consists virtually of two motors in series, it is possible to develop power for about three-quarter speed with only one-half of the motor in commission. AU the propelling generator and motor fields are separately excited from one of the auxiliary generators. Starting, stopping, and reversing of the propelling motor are effected entirely by varying the excitation of the main generators or generator, as the case may be. The control arrangements are sueh that the main propellin" circuits are never interrupted, and all regulating nnd reversing are carried out by varying the field circuits only. Provision is made, however, for isolating any of the generating units as may be desired. The control is carried out by means of a lever attached to a small controller fixed to the front of a sheet-steel panel carrying the necessary instruments. This lever is moved by the operator to either side of a central stop point., so that, when manoeuvring, all that lias to be done is to move the lever on the bridge of the vessel to the speed point required, either ahead or astern.

The actual varying of the propelling generator fields during mameuvring is effected by means of a reversing poteniometar rheostat common to each generator field.'circuit; the rheostat being operated through gearing by a small electric motor. Movement of the bridge control lever merely switches this small motor into circuit, and by means of follow-up gear tlie small motor switches itself out and stops when it has moved tlie field rheostat to a position where a field strength is obtained on the generators corresponding: to the speed point where the lever is at rest on the controller. In addition, a special type of overload current relay fin the main circuit is arranged so that, should the operator attempt to accelerate or decelerate too quickly and so cause un excessive power current to flow in the ■system, the relay interrupts the supply to the small rheostat motor; and, although the bridge lever may be operated quickly, the varying of the generator field strength is only carried out when’the relay again completes the supply circuit to the small motor. This allows the cap-

thin, to carry out orders in the. quickest possible manner and safeguards the equipment against careless handling. Control Equipment. Main circuit-breakers, or main powerinterrupting devices, are not provided in the propelling circuit, as it is considered preferable on plants of this description to leave the stressing of ‘the equipment under abnormal conditions entirely at the discretion of- the engineer on watch. As this propelling motor is of a size which is equal in capacity to the generating plant, it is not so liable to prolonged overloads. Normally, the propelling system is connected through a circuit-breaker and current-limiting resistance to the ship’s structure at the point between the two motor armatures; but should an accidental earth occur on any part of the main, circuit sufficient to open this.circuitbreaker, a loud ringing bell in the engineroom gives audible warning. Another feature of the equipment is the simple manner in which a generating set Can be put into or taken out of service without entailing a stoppage of the propelling motor. Even if the set which it is desired to shut down is supplying the excitation, the operator at the control panel can, by means of a convenient handwheel, transfer the excitation to another auxiliary generator without leaving his post. Each propelling generator is provided with a protected type of switch panel carrying four operating handles and suit-, able interlocking gear, which enable a generator to be put in the propelling circuit or taken out without damage by careless switching. These panels'also allow any one of the propelling generators to he used for the auxiliary load. In the event of failure of the excitation supply voltage, the main potentiometer rheostat returns automatically to the “stop” point, reclcses the field contactors, resets the overload relay (if tripped), and returns automatically to the previous setting (according to the position of the bridge controller) as soon as voltage is resumed. To provide against such a contingency as failure of the small rheostat motor when the vessel is being manoeuvred iu narrow waters, a handwheel mounted ou the motor panel enables the potentiometer rheostat to be manually operated. This handwheel is normally disengaged from the rheostat operating shaft, but is always ready for instant engagement should the propeller speed fail to respond .to a movement of the bridge control lever, and,when engaged, it automatically cuts the small rheostat motor out of circuit. The bridge control lever is so arranged as to > allow a complete full-power reversal to be carried out in about, eight seconds. The effort required to do this manually is too great to allow it to be done in this period, and the handwheel is geared so, that it ean be operated conveniently through a full-power reversal in about thirty seconds.

When bringing the propeller to rest prior to a reversal in its direction of.rotation, the power returned to the electrical system due to the action of the water causing the propeller to keep ro- . fating in a forward direction (and consequently to drive the propelling motor as a generator) is dissipated in “motoring” the propelling generators. A feature of the electrical installation of the ship is the main switchboard, which has an overall length of 30 feet, and consists of eleven panels. The four main generators are connected in series: and “set-up” switches on the main switchboard enable one. two, three; or four generators to be used. When it is desired to run at reduced speed it is more economical to shut down one, two, or three engines, according to the speed required. The auxiliary generators or exciters are self-excited, and are'used to supply excitation to the propelling motor and main generators and to run the auxiliary plant. They .are not “paralleled,” but each supplies an independent circuit. Any three can be used for these purposes, at the same time, the fourth being a standby.

Auxiliary Machinery.

All the engine-room auxiliaries are electrically driven. The total horse-power of the auxiliary motors is 550, and the sizes of the individual motors range from one to eighty horse-power. All the motor starters are mounted on two auxiliary panels, the motors generally being controlled by push buttons arranged in convenient positions! The auxiliaries fitted in the engineroom are comparatively few in number and of small dimensions. All the pumps are of the centrifugal or rotary type. Three pumps, two of which are required for full power, are provided for the cool-ing-water supply to the inain engines. One of the pumps has a motor of larger power than the others, to enable it' to be Used as a fire pump. For supplying steam for heating the accommodation, a vertical inultitubular boiler, having a heating surface of 630 square feet, is installed. The working pressure of this boiler is 251 b. per square inch.

An Ingersoll-Rand two-cylinder auxiliary Diesel generator is provided for lighting and auxiliary-power purposes in port, the generator being of 35 kw. output. The Starting air pressure is 2501 b. per square inch for both the main and auxiliary engines, and two air-storage reservoirs are installed for the main engines and two small reservoirs for the auxiliary engine. Two Ingersoll-Rand motor-driven air-compres-sors supply the reservoirs, and a small hand-operated compressor is provided, for charging auxiliary - engine reservoirs should no air be available and all engines stopped. The air-storage capacity and the air compressors are very small compared with the usual marine Diesel installation where manoeuvring of the main engines is necessary.

Electrically-driven pumps are provided for bilge and ballast, sanitary, freshwater, and boiler-feed duties. Each main engine has a separate, oil-fuel supply tank; and two rotary oil-fuel transfer pumps are fitted. A de Laval centrifugal purifier is provided in connection’ with the main and auxiliary engine lubricat-ing-oil systems, as well as a similar machine in connection with the fuel-oil system. An engineers’ workship is arranged on the main deck over the engineroom. Successful Trials. ‘ On the trials of the Brunswick, which were carried out on August 29, the mean speed attained on four runs on the measured mile was 11.48 knots, or nearly half a knot in excess of the designed speed, the vessel’s total displacement being .17,250 tons. The Diesel engines and the electric-transmitting gear worked with the utmost smoothness. The arrangements for navigating the vessel wholly from the bridge proved highly satisfactory. The navigating officer himself operated the switches which controlled the propelling machinery, and the steering was by the Sperry gyro compass and gyro pilot, so that the staff in the engineroom were all standby men, and no quartermaster was required.

The Brunswick will remain at Wellington for two days and then go on to Auckland to complete discharge. It is understood that the ship-will trade regularly to New Zealand.