This paper reviews the recent numerical and experimental investigations on improving the efficiency of Clean-In-Place procedures thus saving operation energy. The paper covers the fouling of equipment surfaces, the concept of CIP and its operation practices, the physical factors controlling the efficiency of CIP procedures with a special attention being paid to the hydrodynamic force of the cleaning fluids. The studies show that CIP efficiency dependents on many factors, such as the type of soil to be removed, the cleaning time, the temperature of cleaning agent, and the favourable hydrodynamic force of the moving liquid. Among the hydrodynamic factors, the wall shear stress and its fluctuation rate reported to be the dominating factor for cleaning straight circular pipes. Whilst for cleaning of more complex geometries and areas difficult to clean, the controlling factor may also include the flow pattern, flow exchange, flow turbulence, and the property of the recirculation zone.