NORCRAFT

Gas leak rates are based on the assumption that the pressure difference across the leak-point (hole) is large enough to cause critical flow across the leak-point. Flow-rate is calculated based on restriction orifice correlations. This means that sonic velocity exists at the orifice throat, and further decrease in the downstream pressure does not increase mass flow rate. Flow-rate calculated is only correct if upstream and downstream pressures remain constant. In a blow-down situation the flowrate drops significantly due to reduction in upstream pressure until pressures equalize across the leak-point. In this case, the app only calculates the initial flowrate.