Triple expansion steam engine

The steam expand in three steps from the boiler pressure to the exhaust pressure using one high-pressure-cylinder, one intermediate-pressure-cylinder and one low-pressure-cylinder. The cranks on the cranshaft are shifted 120°
A ship with triple expansion engines.

Triple expansion engine with exhaust steam turbine.
Schematic diagram of a triple expansion steam engine with a Bauer-Wach exhaust turbine system.
A hydraulic connection between the turbine and the propeller shaft is used to deal with the non-uniformity between the reciprocating engine and the turbine as well as to disengage the turbine at astern running.

Tripel engine with exhaust steam turbine driven steam compressor
The exhaust steam turbine is used to drive a compressor that increases the steam pressure to the intermedate cylinder.

In large steamships the steam engines very large and heavy low-pressure-piston could hardly be lifted by the low pressure steam and it was therefore replaced by two low-pressure-pistons. In that case there were four cylinders, one high- pressure, one intermediate-pressure cylinder and two low-pressure cylinders.
The RMS Titanic had two four-cylinders trippel expansion steam engines, and also a low-pressure exhaust steam turbine.