Phenomenon:

1. The temperature of superheated steam rises and the exhaust gas temperature rises too. 

2.The control valve is turned up, but the flow of attemperation water reduces or keeps unchanged. 

3. The main steam temperature is difficult to control, in severe case, the superheater is overheated and damaged.  

Causes:

1. The feed water quality has been unqualified for long-term, the spray tube scales internally or the large particles of impurities are mixed in the water. 

2. The quality of superheated steam has been unqualified for long time, the spray tube scales and the spray nozzle holes are blocked.