1. The channels to superheater and reheater have noise of leaking or exploding.
2. The combustion is not stable, the pressure of boiler hearth chamber becomes less or positive. Flue gas or steam come from the gas duct where are not sealed closely.
3. The steam pressure drops, the main steam temperature changes and the unit load decreases/
4. The flow of water supply is abnormally greater than steam flow.
5. The difference of flue gas temperature at both sides is increased and the temperature at leakage side is lower.
6. When the induced draft fan is automatically operating, the current is increased.
7. The fuel gas is pushed by the leaking steam toward one side, the local tube bundle may be superheated, the local flue gas pressure is in negative and the flue gas temperature difference between the left and right sides is increased.