Purgeurs de cylindres

Cylinders are steam engine components that house pistons that propel the vehicle. Typically, there are two cylinders in the front of the vehicle, one on each side. They are alternately fed steam from the steam chest , with every full rotation of the driving wheels, in the amount set with the cutoff .

Steam in cylinders pushes the pistons inside, mechanically linked to the driving wheels, propelling the vehicle. The used steam is then expelled through a blastpipe, where it mixes with smoke from the firebox in the smokebox, and together they are exhausted to the atmosphere through a chimney.

Lorsque la vapeur n'est plus admise dans les cylindres, ceux-ci refroidissent rapidement, car ils sont séparés de la chaudière et du foyer. La vapeur dans les cylindres se condense ainsi en eau assez rapidement. Comme celle-ci n'est pas compressible, contrairement à la vapeur, si une quantité suffisante s'accumule dans les cylindres et est poussée par un piston, elle peut briser les fonds de cylindres et provoquer une avarie de la transmission.

To prevent this, steam engines come equipped with cylinder cocks. They are usually operated by a lever from inside the cab , and allow water to be expelled from the cylinders. However, since steam escapes through the cocks too, they should only remain open for a short time, typically just a few seconds, when the vehicle begins moving from a standstill.

Cylinders can also fill with water if the boiler is overfilled , or from running the vehicle with the cutoff set in the opposite direction.