At what level must the gauge glass be installed in relation to the normal boiler water level?

The gauge glass must be installed at the midpoint of the normal boiler water level to provide an accurate reading of the water level within the boiler. This positioning ensures that the water level visible in the gauge glass reflects the actual water level in the boiler, allowing operators to monitor it effectively.

Placing the gauge glass at the midpoint is essential because it provides a clear and reliable reference point. If the gauge glass were placed higher, it might give a false impression of a safe water level during operations when it might not actually be indicative of the boiler's current condition, risking overheating and potential damage. Conversely, if installed lower, it may not show the correct water level when the boiler is under pressure, leading to the same risks.

This positioning also aligns with safety standards and best practices in maintaining the boiler's operational efficiency and safety, as operators rely on accurate level readings to prevent conditions such as low water level situations.