When the water in a boiler is foaming, how will the water level appear in the gauge glass?

When the water in a boiler is foaming, the appearance of the water level in the gauge glass will be erratic. This foaming occurs when steam bubbles are formed in the water due to overheating or impurities. As these bubbles rise and burst, they cause fluctuations in the water level, leading to an unstable reading in the gauge glass.

An erratic reading indicates that the water is not at a steady state, which can be dangerous as it might give misleading information about the actual water level in the boiler, potentially leading to unsafe operating conditions. It's crucial for operators to understand this behavior in order to manage the boiler's functions safely and effectively.