Compound steam engines

A steam engine in which the expansion of the steam from the boiler pressure to the exhaust pressure is carried out in two stages, necessitating the use of high- pressure and low-pressure cylinders in series. The cranks on the cranshaft are shifted 90°
A ship with a compound engine

Lentz double compound engine.
The Lentz steam engine system consists basically of two classic compound steam engines connected after each other with the crankshafts shifted 90°. This gives a four-cylinder engine with a smooth ride and no starting problems. A ship with a double compound engine.

Compound steam engines with three cylinders have been used, especially as auxiliary engines to produce electricity onboard the steamships. In that case there were three cylinders with the very same diameter, on high pressure cylinder two low pressure cylinders.