2.5.3 Propulsion system and control

The propulsion system consisted of four medium-speed diesel engines, connected in pairs to two propeller shafts via gear boxes. The engines were four-stroke turbo-charged engines with eight cylinders and a maximum continuous output of 4 400 kW each. They were designed to operate on heavy fuel oil. Maximum continuous operating revolutions of the engines were 600 rpm which corresponded to 188 rpm of the propellers.

Each propeller shaft carried one controllable-pitch propeller with a diameter of 4.0 m. The port-side propeller rotated clockwise and the starboard side one counter-clockwise.

The pitch control of the propellers was hydraulic, separate for each propeller. The control was effected electrically be power selector levers on the main control console on the bridge, on the bridge wings and in the engine control room. The control signal from the power selector affected the engine revolutions as well as the propeller pitch via an electro-hydraulic "combinator". Revolutions and pitch both increased at increasing power settings up to about 70% output, when the maximum continuous engine revolutions, i.e. 800 rpm were reached. After that, the output could be further increased to 90% by increasing the propeller pitch only while the revolutions of the engines remained at 600 rpm.

All the normal indicators, alarms and control devices were on the bridge and in the engine control room. The installation qualified for unmanned machinery space at sea in accordance with the classification requirements, but actual operation was at all times conducted with the engine control room manned by one engineer and one motorman.

The total fuel oil tank capacity was 940 m³ of heavy fuel oil and 291 m³ of marine diesel oil. Bunkering for a complete round trip was always done in Stockholm.