Pakistan Nandipur 425/525 MW CCPP situated at Nandipur near Gujranwala in the Punjab province of Pakistan. Due to the high calcium hardness and alkalinity of circulation cooling water (deep-well water), the condenser tubes` scaling problem had seriously affected its output and efficiency. The thickness of scale reached 0.4~1.0mm, meanwhile the terminal temperature difference of condenser was down to around 14℃ low. In order to break this limit, the condenser chemical cleaning work was implemented in September to October 2018. Sulfamic acid and proper inhibitor, with a Chinese patented cleaning method was adopted to this work. The scale analysis report indicates that the main component of scale is calcium and magnesium carbonate type. During the construction process, a large amount of black and oily components were found in the scale. It was considered that during the HFO operation period, a large amount of ash and other oily dirt were deposited as scale. Heavily scaling situation makes chemical cleaning work more challenging.