What are two devices commonly used on a boiler to determine water level?

The correct choice identifies two essential devices used in boiler systems to measure water level: sight glasses and try cocks.

Sight glasses are transparent tubes attached to the boiler that provide a direct visual indication of the water level inside. This allows operators to easily observe whether the water level is within the safe operating range. They typically operate under the principle of communicating vessels, where the water level in the sight glass mirrors the water level in the boiler.

Try cocks serve as small valves positioned at various levels on the boiler, allowing operators to manually check the water level by releasing a small amount of water. By operating the try cock, personnel can determine if the water reaches the corresponding level indicated by the valve. This practice is important for maintenance and safety, ensuring that the water level is adequate to prevent overheating and damage to the boiler.

Other devices mentioned, such as pressure gauges, thermometers, float switches, and flow meters, are involved in measuring different parameters in a boiler system but do not provide a direct measurement of the water level like sight glasses and try cocks do. Level sensors and alarms may also contribute to monitoring water levels but are typically used in more advanced systems rather than traditional steam boilers. Thus, the combination of sight glasses and try cocks