Where should the midpoint of the water-gauge glass be positioned?

The midpoint of the water-gauge glass should be positioned at the normal boiler water level because this placement provides the most accurate representation of the water level within the boiler. The normal water level indicates where the system is meant to operate under standard conditions, ensuring safety and efficiency.

By placing the gauge at this level, operators can easily monitor the boiler's performance and identify any deviations that may indicate issues, such as low water levels which could lead to overheating or damage to the boiler. If the gauge were positioned above the normal level, it might suggest a higher water level than is actually present, leading to potentially dangerous situations. Conversely, placing it below the normal water level would not provide an accurate reflection of the operational status of the boiler, making it difficult to maintain safe and consistent operations. Thus, the location of the water-gauge glass at the normal boiler water level is critical for effective monitoring and management of boiler safety.