# C251 – API Density Referral 2004

## Description

This calculates the temperature and pressure correction factors of generalised crude oils, refined products and lubricating oils at given temperature and pressure. From these it calculates density of the hydrocarbon liquid.

## References

API MPMS Chapter 11.1 – Temperature and Pressure Volume Correction Factors for Generalized Crude Oils, Refined Products, and Lubricating Oils (ASTM D 1250-04; IP 200/04) (First edition 2004, Addendum 1 2007)

Kelton calculation reference C251

FLOCALC calculation reference F060

KIMS calculation reference K214

## Options

### Solve for

- Density from standard density (Type 1/1M)

This option is chosen if you want to calculate the density from a known standard density. This uses the Type 1 or the Type 1M calculation process, depending on the standard (base) temperature selected, as described in the standard.

- Standard density from density (Type 2/2M)

This option is chosen if you want to calculate the standard density. This uses the Type 2 or the Type 2M calculation process, depending on the standard (base) temperature selected, as described in the standard.

- Density from alternative density (Type 3/3M)

This option is chosen if you want to calculate the density from a density which is not at standard conditions. This uses the Type 3 or the Type 3M calculation process, depending on the standard (base) temperature selected, as described in the standard.

### Commodity Group

- Crude Oil

- Fuel Oils

- Jet Fuels

- Transition Zone

- Gasoline

- Lubricating Oil

- User entered

Select appropriate commodity so that the correct K values are used in the calculation. They are needed to calculate the thermal expansion factor of the liquid. The commodity groups Fuel Oils down to Gasoline are part of the refined products commodity type, for these the K values will change if the density at 60°F moves into that designated for one of the other commodity groups.

If the last option, user entered, is selected then you will have to input the thermal expansion factor at 60°F of the commodity.

### Standard Temperature

- 15°C

- 20°C

- 60°F

Select the temperature at which the standard (base) conditions you are using refer to.

## Constants

Constants as defined by API

Commodity group | K_{0} |
K_{1} |
K_{2} |

Crude oil | 341.0957 | 0 | 0 |

Fuel oils | 103.8720 | 0.2701 | 0 |

Jet fuels | 330.301 | 0 | 0 |

Transition Zone | 1489.067 | 0 | -0.0018684 |

Gasolines | 192.4571 | 0.2438 | 0 |

Lubricating oil | 0 | 0.34878 | 0 |

## Calculation

### Temperature correction factor

The temperature correction factor is calculated using the equation described in C249

### Scaled compressibility factor

The scaled compressibility factor is calculated using the equation described in C250

### Pressure correction factor

The pressure correction factor is calculated using the equation described in C250

### Calculation of standard density

The calculation uses an iterative scheme to refer the input density back to the base density at 60°F, 0 bar gauge. This iterative scheme uses the two calculations above to produce a C_{tl} and C_{pl} between this condition, the required standard conditions and the alternative conditions. It then uses the relevant C_{tl} and C_{pl} to calculate the density at the required standard conditions.

### Calculation of density

If a non-standard density is required then then the same iterative scheme is used to refer the density back to the density at 60°F,0 bar gauge and then the C_{tl} and C_{pl} calculations from C249 and C250 are used to calculate the required non-standard density.