气缸旋塞

当蒸汽不再进入气缸时，它们会迅速冷却下来。这是因为它们与锅炉和燃烧室分开。汽缸中的蒸汽很快又凝结成水。由于水不可压缩，不像蒸汽，如果足够多的水聚集在汽缸中并被活塞推动，它会破坏汽缸并导致灾难性的动力系统故障。

For this reason there are cylinder cocks. They are operated by a valve from inside the cab, allowing water to be released from the cylinders. As some of the steam from the cylinder is lost while the cylinder cocks are open, acceleration is reduced. Typically, the drivers open cylinder cocks for a few seconds after being stationary for some time.

Cylinders can also fill with water in a process called priming. This is the case of the boiler having too much water, or running the vehicle with the cutoff set in the opposite direction, causing water to overflow into the cylinders.

See also: Mechanical Powertrain Damage, Water Level, Cutoff