# C104 – API Volumetric Flow Rate of Natural Gas at Standard Conditions (Factors Approach Method) 1992

## Description

This calculates the volumetric flow rate of natural gas at standard conditions using the ‘Factors Approach’ method outlined in the MPMS Chapter 14.3.3 Appendix 3-B.

## References

FLOCALC Calculation reference F034

Kelton calculation reference C024

Kelton calculation reference C104

Manual of Petroleum Measurement Standards Chapter 14 – Natural Gas Fluids Measurement, Section 3 – Concentric, Square-Edged Orifice Meters, Part 3 – Natural Gas Applications, Appendix 3-B – Factors Approach (Third Edition 1992; Reprinted 2009)

## Calculations

Calculation as documented in standard

### Volumetric Flow Rate

The volumetric flow rate is calculated from:

Where | ||
---|---|---|

F_{c} |
= | Orifice calculation factor |

F_{gr} |
= | Real gas relative density factor |

F_{n} |
= | Numeric conversion factor |

F_{pb} |
= | Base pressure factor |

F_{pv} |
= | Supercompressibility factor |

F_{sl} |
= | Orifice slope factor |

F_{tb} |
= | Base temperature factor |

F_{tf} |
= | Flowing temperature factor |

Y_{1} |
= | Expansion factor |

P_{f1} |
= | Upstream pressure in psi |

h_{w} |
= | Orifice differential pressure in inH_{2}O (60°F) |

C’ | = | Composite flow factor |

### Orifice Calculation Factor

The numeric conversion factor, F_{c}, is calculated from:

Where | ||
---|---|---|

D | = | Pipe diameter at flowing temperature in inches |

β | = | Orifice diameter ratio |

Re_{D} |
= | Reynolds number of pipe flow |

### Real Gas Relative Density Factor

The real gas relative density factor, F_{gr}, is calculated from:

Where | ||
---|---|---|

G_{r} |
= | Real gas relative density |

### Numeric Conversion Factor

The numeric conversion factor, F_{n}, is calculated from:

Where | ||
---|---|---|

d | = | Orifice bore diameter at flowing temperature in inches |

β | = | Orifice diameter ratio |

### Base Pressure Factor

The base pressure factor, F_{pb}, is calculated from:

Where | ||
---|---|---|

P_{b} |
= | Base pressure in psi |

### Supercompressibility Factor

The supercompressibility factor, F_{pv}, is calculated from:

Where | ||
---|---|---|

Z_{b} |
= | Base supercompressibility factor |

Z_{f1} |
= | Line supercompressibility factor |

### Slope Factor

The slope factor, F_{sl}, is calculated from:

Where | ||
---|---|---|

β | = | Orifice diameter ratio |

Re_{D} |
= | Reynolds number of pipe flow |

### Base Temperature Factor

The base temperature factor, F_{tb}, is calculated from:

Where | ||
---|---|---|

T_{b} |
= | Base temperature in °R |

### Flowing Temperature Factor

The flowing temperature factor, F_{tf}, is calculated from:

Where | ||
---|---|---|

T_{f} |
= | Flowing temperature in °R |