氣缸旋塞

因為氣缸與鍋爐和火箱有段距離，當氣缸中不再有蒸汽注入時會迅速冷卻。氣缸中的蒸汽會很快地凝結成水，而由於水不像蒸汽能被壓縮，當足夠的水聚集在氣缸中並被活塞推動時，它會使氣缸受損並導致災難性的動力系統損壞。

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