Gas-Liquid Leak provides quick and accurate estimates of leak-rates of Natural Gas, Crude Oil or Water from piping and tanks/vessels given hole-size (or seal-leak) with given operating pressure and temperature, assuming the leak is to the atmosphere.
The Gas-Liquid Leak app is provided as a tool for use in oil and gas pipelines, pipes or vessels/tanks or offshore oil and gas installations. The app gives quick and accurate estimates of leak rates of gas, oil and water from piping and equipment cracks, holes, seals directly on your iPhone without having to run simulations on a computer.

For natural gas the assumption is that the pressure difference across the leak-point (hole) is large enough to cause critical flow across the hole. Flow-rate is calculated based on restriction orifice correlations, i.e., sonic velocity exists at the leak-point orifice and further decrease in the upstream and downstream pressures ill not change the leak-rate. 

For liquids, critical (choked) flow occurs when a cavitation barrier exists across the leak-point (hole) and the downstream pressure (atmospheric) is below the liquid vapor pressure. At this point the liquid will start to flash into bubbles of vapor. For crude oil below about 35 degree and water, the vapor pressure will normally be less than atmospheric pressure. Therefore, in this app, if vapor pressure is found to be lower than atmospheric pressure, the flow-rate is calculated based on control valve pressure drop calculations as defined in the documentation of the app (download from URL).

The app also lets the user select US-Customary or SI-Metric units.