Flow Rate

Speed of substance movement

Flow rate is the speed which a liquid is moving. In cleaning, ISPE CV Life Cycle states "flow rates through piping should be sufficient to prevent accumulation of residues and ensure full coverage of solutions". The type of flow can be expressed using the Reynolds Number which is equal to the density of the liquid multiplied by the velocity of the liquid and pipe length divided by the viscosity. A Reynolds Number at or over 4,000 is considered turbulent flow which is necessary to induce scrubbing action during cleaning. It is widely accepted that a flow rate of 1.5 m/s is sufficient to achieve turbulent flow if the ratio between the pipe length and diameter is 2 or less.