As most us know, the triple-screw steamer Titanic, and her sister ship Olympic, were propelled by a combined machinery arrangement consisting of two reciprocating engines and a single Parsons turbine. The reciprocating engines were of the triple-expansion type with one high-pressure cylinder, one intermediate-pressure cylinder, and two low-pressure cylinders. The Parsons turbine, which was fed by exhaust steam from the reciprocating engines, was a low-pressure reaction type. Each reciprocating engine drove one 3-bladed wing propeller of 23½ feet diameter, one on the port side of the vessel, and the other on the starboard side of the vessel. The turbine engine drove a four-bladed propeller of 17 feet diameter located on the ships centerline directly ahead of the rudder. The reciprocating engines were designed for 15,000 indicated horsepower (IHP) each when running at 75 revolutions per minute. The turbine was designed to develop about 16,000 shaft horsepower (SHP) when running at 165 revolutions per minute. At those numbers of revolutions, the ship was expected to make 21 knots.1 Titanic's propelling machinery was registered at 50,000 horsepower. Standard normal full revolutions in service was considered to be 78 revolutions per minute for a speed a little over 22½ knots. When running ahead at 83 revolutions per minute on her reciprocating engines, the entire power plant would develop about 59,000 horsepower, of which 18,000 horsepower would be contributed by the turbine.2 When carrying those number of revolutions, the ship would have made close to 24 knots through the water.
The arrangement of Titanic's propulsion and power generating plant is shown in the diagram below.
The aft most compartment is the turbine engine room that contained the Parsons low-pressure turbine, thrust blocks for the propeller shafts of the reciprocating engines, and the ships two main condensers that turned exhaust steam back into boiler feedwater. Ahead of that compartment was the reciprocating engine room with the two reciprocating engines, the feedwater heaters, the ships refrigeration plant, and other auxiliary equipment. Ahead of the engine rooms were six separate boiler rooms and 11 stokeholds. All of these compartments were separated from each other by transverse watertight bulkheads and protected by automatic drop-down watertight doors.