水位

操作蒸汽機車 時，保持鍋爐 中適當的水位至關重要。觀察「鍋爐水位計」並調整水位至最適當的高度。水位應隨時維持在水位計中可見處，此範圍通常是鍋爐完整高度的 75% 至 85% 之間。

If water rises above the limit, there are two potential dangers - there is less room for steam to be generated in, and water can overflow into the cylinders , potentially causing them to break .

If water falls under the limit, the boiler can explode and cause catastrophic damage . If the firebox is sufficiently hot and its top surface, known as crown sheet, protrudes above the water level, it can soften from high temperatures and pressure, and lead to the boiler explosion, destroying the entire vehicle.

In an emergency attempt to save the engine from exploding, immediately feed water and dump coal from the firebox.

To feed water to the boiler from storage , there's an injector . To dump water from the boiler there's a blowdown valve. Both controls are usually found in a vehicle's cab .

水位會受溫度影響。當水溫上升，縱使未對鍋爐注水，水位也會因熱漲冷縮升高。

水位也受坡度影響。若機車正在下坡，水位計所顯示的水位將低於實際水量，上坡時則高於實際水量。