Auxiliary Steam Supply and the Electrical Power Plant
In addition to the main steam supply, there were separate steam connections to the pipe supplying steam to all the auxiliary machinery on board the ship. The auxiliary machinery included various pumps, the refrigeration machinery, the electrical plant, the steering engines, steam winches and ash hoists. The auxiliary steam supply came from the five single-ended boilers in BR No. 1, or from two port-side double-ended boilers in BR No. 2 and two starboard-side double-ended boilers in BR No. 4. This auxiliary steam pipe could also be cross connected to the main steam supply lines in the reciprocating engine room, thus receiving steam from any boiler in the ship.
The ship had four main electric dynamos with a capacity of 400 kilowatts each. They produced 100 volts of direct current (DC). These dynamos, and the steam engines that drove them, were situated in a separate watertight compartment located aft of the turbine room. The 580 indicated horsepower steam engines that drove each dynamo were vertical, three-crank, compound engines with one HP and two LP cylinders. They ran at 325 revolutions per minute, and took in steam at 185 psig from two separate steam supply pipes to which they could be cross connected. One pipe was on the port side and was connected to the five single-ended boilers in BR No. 1 and with the two port-side double-ended boilers in BR No. 2. The other supply pipe, on the starboard side, was the auxiliary steam supply that was connected to the five single-ended boilers in BR No. 1, and to the two port-side double-ended boilers in No. 2, and the two starboard-side double-ended boilers in No. 4.
In addition to these, there was a separate steam pipe leading to a pair of emergency dynamo engines situated on a platform 20 feet above the ship’s waterline on D deck on the aft side of the turbine engine room casing. These emergency dynamos produced 30 kilowatts of electric power each at 100 volts DC. These sets supplied power to 500 incandescent lamps fitted throughout all passenger, crew and machinery compartments, at the end of passages, near stairways, and on the Boat deck. There were also change-over switches that enabled 5 arc lamps, 7 cargo and gangway lamps, the ship’s navigation lights, the lights on the navigating bridge (including the wheelhouse and chart rooms), the Marconi apparatus, and 4 electrically-driven boat winches all to be connected up to this emergency circuit if needed. It was the practice to run these emergency dynamos every night after sunset in case of an accident to the main electrical supply during the night.9
Each emergency dynamo was driven at 380 revolutions per minute by a two-crank, compound engine with one HP and one LP cylinders. The emergency steam supply pipe that fed these engines ran along E deck above the watertight bulkheads and was arranged so it can take steam from the double-ended boilers in any of the three boiler rooms No. 2, 3, or 5. As a backup in case of accident to the main steam supply pipes, there was a connection that branched off of this emergency supply pipe to the pumps in the engine room that were connected to the bilges throughout the ship. There was also a cross connection to this pipe so that steam reaching the engine room from any boiler in the ship could be passed up to the emergency dynamos by opening two or three valves.
A schematic of the main and auxiliary steam supply is shown in the diagram below.
