API MPMS 11.2.5 2020 (2023) PDF

Full title and description

API MPMS Chapter 11.2.5 — "A Simplified Vapor Pressure Correlation for Commercial NGLs" (Second Edition, December 1, 2020; amended by Errata 1, October 1, 2023). The document provides a simplified, table-driven correlation and algorithmic procedures for estimating equilibrium vapor pressures of commercial natural gas liquids (NGLs) from commonly measured properties (for example, relative density and process temperature), intended to support volume and pressure-correction calculations in custody transfer and process measurement contexts.

Abstract

This chapter of the API Manual of Petroleum Measurement Standards defines a practical correlation (with “new” and “modified” calculation methods) and associated coefficient tables that allow measurement and operations personnel to estimate vapor pressure for a range of commercial NGLs when full compositional data are not available. The correlation is intended to be accurate enough for most measurement-correction and engineering uses while remaining computationally simple to implement in measurement systems and software.

General information

• Status: Active (current edition with Errata 1 issued).
• Publication date: Second Edition — December 1, 2020; Errata 1 — October 1, 2023.
• Publisher: American Petroleum Institute (API).
• ICS / categories: 75.160 (Fuels) — Petroleum and related technologies.
• Edition / version: 2nd Edition (Dec 2020); incorporating Errata 1 (Oct 1, 2023).
• Number of pages: 33 (standard text plus errata document adjunct pages where applicable).

Key bibliographic facts above are taken from API/M PMS listings and the published errata notice for MPMS 11.2.5.

Scope

Provides a simplified vapor-pressure correlation and implementation guidance for commercial natural gas liquids (NGLs). The standard is applicable where vapor pressure must be estimated from limited field measurements (not full compositional analyses) to support pressure-correction factors, volume calculations, or safety/process limits. It supersedes earlier revisions of the MPMS 11.2 series (including earlier TP-15 implementations) and is written for typical NGL product families within the specified density and temperature ranges described in the text.

Key topics and requirements

• Definition and purpose of a simplified vapor-pressure correlation for commercial NGLs.
• Two calculation approaches: the “new” method and a “modified” method (the modified may require a reference vapor pressure input at 100°F).
• Tabulated coefficient sets (Table 1 style) keyed to relative density ranges (γ60 or similar) used to form the correlation coefficients A and B.
• Specified input parameters and units (relative density at 60°F, process temperature, optional P100 for modified method) and formulae for converting those inputs to an estimated equilibrium vapor pressure.
• Limits of applicability, recommended uses (measurement corrections and engineering estimates), and cautions where compositional methods or direct measurement are preferred.

Typical use and users

Applied by custody-transfer measurement engineers, pipeline and terminal operators, process engineers, laboratory personnel, and software vendors who implement MPMS-based measurement corrections. Typical uses include estimating vapor pressure to compute pressure-correction factors, safety/operating limit checks, and where composition data are unavailable or impractical for routine operations.

Related standards

Part of API MPMS Chapter 11 (Physical Properties Data) and related to other MPMS parts addressing physical properties and compressibility (for example, MPMS 11.1 and the 11.2.x series). It replaces or supersedes earlier MPMS/GPA implementations such as the earlier MPMS 11.2.2A / GPA TP-15 correlation documents and should be used in conjunction with other MPMS measurement and volume-correction chapters as appropriate.

Keywords

vapor pressure, NGL, natural gas liquids, MPMS 11.2.5, API MPMS, vapor-pressure correlation, relative density, P100, custody transfer, measurement correction.

FAQ

Q: What is this standard?

A: API MPMS Chapter 11.2.5 is an API Manual of Petroleum Measurement Standards chapter titled "A Simplified Vapor Pressure Correlation for Commercial NGLs" that provides table-driven correlations and calculation methods to estimate equilibrium vapor pressure for commercial natural gas liquids when detailed compositional data are not available.

Q: What does it cover?

A: It covers the correlation equations (new and modified methods), coefficient tables keyed to relative density ranges, required input variables (e.g., relative density at 60°F, process temperature, optional P100), implementation notes, and limits of applicability for NGL measurement and correction purposes.

Q: Who typically uses it?

A: Measurement and process engineers, laboratory analysts, terminal and pipeline operators, and software/system vendors who need a practical vapor-pressure estimate for volume/pressure corrections or operational checks when compositionally based methods are unavailable.

Q: Is it current or superseded?

A: The second edition was published December 1, 2020, and has an Errata 1 issued October 1, 2023; the 2020 edition with the 2023 errata is the current published text (it supersedes earlier revisions). Users should implement the errata corrections where applicable.

Q: Is it part of a series?

A: Yes — it is part of API MPMS Chapter 11 (Physical Properties Data) and relates to other parts in the 11.2 subseries that cover compressibility, temperature corrections, and related physical-property correlations for hydrocarbons.

Q: What are the key keywords?

A: Vapor pressure, NGL, correlation, relative density, custody transfer, MPMS 11.2.5, API, P100, measurement correction.