# C257 – API MPMS/GPA TP-27:2007 Density Referral

## Description

This calculates the density from standard density or vice versa. Calculation of Ctl is done according to the GPA TP-27 standard. Calculation of Cpl is done according to the relevant API MPMS standard.

## References

GPA Technical Publication TP-27, API MPMS 11.2.4 – Temperature Correction for the Volume of NGL and LPG Tables 23E, 24E, 53E, 54E 59E and 60E (2007)

API MPMS Chapter 11.2.2M – Compressibility Factors for Hydrocarbons: 350 to 637 Kilograms per Cubic Metre Density (15°C) and -46°C to 60°C Metering Temperature (1986)

Measurement of Petroleum Measurement Standards Chapter 11.2.1M – Compressibility Factors for Hydrocarbons: 638-1074 Kilograms per Cubic Metre Range (First Edition August 1984)

Kelton calculation reference C257

FLOCALC calculation reference F064

KIMS calculation reference K213

## Options

### Solve For

- Density

- Standard Density

This option is used to specify which type of density the user wants to convert to and from.

### Standard Temperature

- 15°C

- 20°C

- 60°F

This option is used to specify the standard temperature which the calculation is to be based on.

### Precision

- Full Precision

- Rounding

This option is used to specify whether the intermediate values are to be rounded during the calculation as per the standards used.

## Calculation

### Temperature correction factor

The temperature correction factor, C_{tl}, is calculated using the process described in C254

### Pressure correction factor

The pressure correction factor, C_{pl}, is calculated by:

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

F | = | Compressibility |

P | = | Pressure |

P_{e} |
= | Equilibrium Vapour Pressure |

The compressibility, F, is calculated as per the procedures in C220, the method used is dependent on the density of the liquid.

### Standard Density

The standard density is calculated using an iterative calculation that uses the C_{tl} and C_{pl} functions to calculate the standard density.