水位

Maintaining a proper water level in the boiler is critical. This is done by observing the water gauge and adjusting the amount of water in the tank accordingly. The water level should be visible on the water gauge at all times. This range typically shows between 75% and 85% of the boiler height, which is the intended range of operation. Blowdown valve is used to dump water from the boiler, while the injector is used to add more. Having the water level above the gauge leaves less than optimal room for steam to generate in and may overflow to the cylinders, potentially causing major damage. Having the water level below the gauge can be even more catastrophic. If the firebox is sufficiently hot and its top surface (known as “crown sheet”) protrudes above the water level, it can melt, causing the pressurized boiler to explode.

水位也取决于等级。如果机车正在下坡，水平面将低于平坦表面，反之亦然。在紧急情况下，防止爆炸的方法之一是用排污阀、鼓风机甚至汽缸旋塞从锅炉中排放蒸汽。

Water level is also grade dependent and subject to sloshing. If a locomotive is going downhill the level will appear lower than on a flat surface, and vice versa.

In case of low water level emergency, one of the last resort actions to prevent explosion is to wide open the injector to add more water and immediately dump coals from the firebox in hopes to lower its temperature, before the crown sheet melts.