ドレン弁

シリンダーに蒸気が入らなくなると、シリンダーはすぐに冷えてしまいます。これは、ボイラーと火室から分離されているためです。そして、シリンダー内の蒸気が凝縮されて、あっという間に水に戻ります。水は蒸気と違って圧縮できないので、シリンダーに十分な量が溜まってピストンで押されると、シリンダーを壊して動力伝達システムの致命的な損傷を引き起こすことがあります。

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