Abstract: Water hammer often occurs in tubular heater after running a certain time due to tube scaling. Process flow of this kind of heater is field investigated and scale sample and water sample are taken. Scale sample is analyzed with X-ray and chemical methods. Results show that the composition of these scales is composed of carbonate primarily, corrosion products and organic grease secondly. Proneness experiment of medium scaling with water sample is launched by special water analysis software and scaling probability of the water sample is predicted theoretically based on Davis-Stiff saturation index method and Ryznar stabilization index method, and the results between the experiment and the prediction are well fitted. The phenomenon of water hammer in tubular heater is revealed: due to the high temperature, CO₂ in water is released, which makes system's pressure lowered, pH value rose and solubility of CaCO₃ declined. In the last, calcium salt is separated out and deposited. According to the analysis results, corresponding physical and/or chemical methods are presented in order to reduce or eliminate the phenomena of water hammer during operating tubular heater.