Which device primarily indicates the boiler water level?

The device that primarily indicates the boiler water level is the water level gauge. This instrument is specifically designed to provide a visual representation of the water level within the boiler, allowing operators to monitor and maintain the appropriate level of water necessary for safe and efficient operation.

Water level gauges come in various types, such as glass gauges or electronic level sensors, and they are crucial because maintaining the correct water level directly affects the boiler's efficiency and safety. If the water level falls too low, it can lead to overheating and potential damage to the boiler, while too high a water level can result in operational issues and inefficiencies.

In contrast, a pressure gauge is meant to show the pressure within the boiler system, which is important but does not provide information about the water level. A temperature sensor measures the temperature of the water or steam but does not indicate how much water is in the boiler. A flow meter is used to measure the flow rate of water or steam within a system, but again, it does not measure water level directly. Thus, the water level gauge is the key instrument for specifically indicating how much water is present in the boiler.