What is one factor that can cause a false level in the sight glass?

A false level in the sight glass can occur when the sight glass valves are closed. When these valves are shut, the water in the sight glass is not able to move freely, which can prevent it from accurately reflecting the true water level in the boiler. This can lead to misleading readings that do not correspond with the actual amount of water present.

For accurate operation and monitoring, it is vital that the sight glass valves remain open when checking the water level. If they are closed, any visual observation through the glass will not be reliable, leading to potential safety risks or operational inefficiencies due to misinterpretation of water levels.

In contrast, excessive pressure, high water temperature, and incorrect boiler types may affect boiler operation and performance but are not direct causes of false readings in the sight glass itself. Their influence is more indirect and depends on other factors within the system configuration rather than the immediate state of the sight glass valves.