In industrial circulatory cooling water monitoring systems

the fouling criteron ΔA is widely adopted for monitoring the fouling situation

but it is discovered that the phenomenon of ΔA0 is often appeared in production and in the laboratory

this phenomenon may mislead to make judgement and decision

brings along hinden troubles into safe and economic operation of the enterprise.The causes leading to appearance of said error ΔA have been analysed

it is believed that the measurement of chlorine ion and alkalinity has affected the error of ΔA

the solving measures given are as follows:(1)adopting the data obrained from gravimetric method to replace the method of calculating ΔA using chloride ion concentration;(2)in the field

adopting the limit carbonate hardness method or installing on-line fouling thermal resistance monitoring instrument to instead the method of calculating ΔA.