The S.S. "Otaki." A Promising Experiment.

Progress, Volume IV, Issue 5, 1 March 1909, Page 164

The S.S. "Otaki." A Promising Experiment.

Our illustrations show the arrangement of the machinery in the engine room of the s.s. "Otaki, " the New Zealand Shipping Co.'s great cargo carrier, which reached Auckland, from London, in January. This is her maiden voyage, and the fact is of especial interest because the "Otaki" is somewhat of an experiment, being the first ship in the world to be fitted with engines combining the reciprocating and the turbine principles. In addition to twin-screw triple expansion reciprocating engines made by Messrs Denny, of Dumbarton, and having cylinders of 24^in., 39in., and 58in. by 39in. stroke, she has a low pressure turbine of the Parsons ' type located between the reciprocating engines, and operated by the exhaust from the low pressure cylinders.

The experiment has succeeded, and the erecting engineer (Mr. Evans) who is acting as Chief Engineer of the "Otaki" during her maiden voyage, expressed his complete satisfaction with the result. "I am perfectly convinced that this combination is going to be a big success," he says. "There is a big future before it." To drive the " Otaki V turbine, steam is utilised, which in ordinary reciprocating engines leaves the low pressure cylinder and

goes direct to the condenser. In the "Otaki" this exhaust passes through the turbine on its way to the condenser, thus effecting a great saving of power. In the case of ordinary engines the exhaust from the low pressure cylinder is somewhere between 5 and 81bs. above atmospheric pressure. In the "Otaki," in order to take advantage of this low pressure, the blades of the turbine are very large, ranging, in five grades, from 4%in. to 13in. in length. The diameter of the rotor is 7ft. 6in., and it makes from 160 to 180 revolutions per minute under ordinary sea-going conditions.

During the voyage out, the turbine averaged 160 revolutions per minute. There are several novel features in the construction of the turbine, but precise information concerning them is not at present to be made public. Our drawings are, however, drawn to scale, and are interesting as showing very clearly the general arrangement of the engine room. The other machinery with which the new steamer is fitted is also most up-to-date, one of the main features being a "contra flow" condenser invented by Mr. Morrison, well known in connection with Morrisons furnace. In this condenser there are three sets of tubes in three separate compartments, and the steam flows from one compartment to another, and comes in contact with each set of tubes in succession, the water being withdrawn from the bottom of each compartment. The object of the invention is to allow the water of condensation to be immediately withdrawn from the condenser instead of as hitherto falling from one tube to the other and remaining for some time in the apparatus, thereby impairing the cooling surface of the tubes and reducing the effect of the condenser. With this new condenser, with the barometer at 30, the very high vacuum of 29% inches is obtained, which shows what a very effective apparatus it is. A refrigerating plant fitted by Messrs. Haslam, has all the latest improvements in the brine and dry air systems. The "Otaki" is 464 feet long, 60 feet beam, and on her trials, with 5,000 tons of cargo, she averaged 15.2 knots, a big speed for a cargo carrier.