Estimating the leakage flow rate allows the designer to understand the amount of fluid being lost from the system since the leakage of certain fluids, such as hazardous chemicals which can pose safety risks to personnel and the surrounding environment. Hence, quantifying the leakage flow rate can help in the mitigation of those hazardous impacts.
For the liquid discharge, the density remains constant during the discharge, then the mechanical energy balance which is derived from the Open System Steady-State Energy Balance can be used to determine the discharge rate model.
How to ensure the leakage liquid will not flash
Flashing will be considered only for the liquids stored under the pressure above their normal boiling point.
Example: The boiling point of n-Hexane and propane are 68.72oC (155.73oF) and -42oC (-43.73oF) respectively at atmospheric pressure. If stored pressure 600 psia, 100oF leakage occurs, the n-Hexane is still in the liquid form but propane will flash to two-phase form.
Pipe leakage calculation formula
If the leakage size 10mm. occurs on the 10inch pipe (25.4mm), the calculated r/d is 0.394, the kf of entering the hole is 0.24 and kf of exiting the hole is 1.
When apply flow coefficient (CD) term
The following are suggested of the discharge coefficient (CD)
- Sharp-edged orifice and Reynold number > 30,000: CD = 0.61
- Short section of pipe attached to a vessel and L/D ratio > 3: CD = 0.81
- Conservative approach: CD = 1
PROcess Safety TASK 