The temperature difference between the saturation temperature under the  condenser pressure and the cooler water inlet of the condenser is called terminal temperature difference. For a certain condenser, its terminal temperature difference is related with the condenser cooling water inlet temperature, condenser steam load per unit area, the surface cleanliness of the condenser copper pipe, the air amount leaking within the condenser and the velocity of the cooling water in the tube. A clean condenser, at a certain temperature of circulating water and circulating water volume and under the unit steam load, will have a certain terminal temperature difference value index, the general terminal difference value index is that when the circulation water amount increases, the cooling water outlet temperature will be much lower, and the terminal temperature difference will be bigger,  and vice versa; The greater the unit steam load is , the greater the terminal temperature difference is,  and vice versa. In actual operation, if the terminal temperature difference value is much higher than the terminal temperature difference index value, which means that the copper tube surface of the condenser is too dirty, causing thermal conditions deteriorating. Reasons of Terminal Temperature Difference Increased
1. The condenser copper pipe water side or steam side are scaling.
2. Air leaks in condenser steam side.
3. The cooling water pipe is plugged.
4. The cooling water amount is increasing.