API MPMS 126.96.36.199 2013 pdf download.Manual of Petroleum Measurement Standards Chapter 188.8.131.52 Ethylene Density.
1 Scope This standard identifies an equation of state (EOS) suitable for use in custody transfer measurement of pure ethylene (>99 %) in the gaseous, liquid, and super critical phases. Given flowing temperature and pressure, an EOS is capable of calculating density and other thermodynamic properties used to calculate mass and volumetric flow of ethylene to custody transfer accuracy. All accuracy and uncertainty statements in this standard are limited to the EOS results and do not include the uncertainty added by the primary and secondary measuring equipment. 2 Normative References The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IUPAC-88 1 , Ethylene (Ethene), International Thermodynamic Tables of the Fluid State, Volume 10 (1988) 3 Terms and Definitions For the purposes of this document, the following definitions apply. 3.1 critical region Thermodynamic state of a fluid in which phase boundaries cease to exist. NOTE In the case of ethylene, a vapour-liquid critical region exists. Density determination is extremely sensitive in the critical region, as minor changes in flowing pressure can bring about significant changes in density for a given temperature. 3.2 equation of state EOS Thermodynamic equation describing the state of matter under a given set of physical conditions. NOTE An EOS provides a mathematical relationship between two or more state functions associated with the material, such as its temperature or pressure. 4 Ethylene Equations of State 4.1 General This standard provides a reference for an ethylene EOS: — IUPAC-88, part of the Ethylene, International Thermodynamic Tables of the Fluid State, Volume 10 (1988) publication. IUPAC-88 is a publication that incorporates the work carried out by Jahangiri et al.  on ethylene.
5 Implementation Procedures To properly implement an ethylene EOS, the user should follow the implementation procedures in the IUPAC-88 publication. Through mathematical manipulation it is possible to derive a form in terms of density, pressure and temperature. However, it is recognized that tolerances for solutions and validation procedures are not provided in the publication itself. To maintain industry consistency, a technical report will be issued separate of this standard providing guidance on how to perform the calculations. Ultimately though, the end use for an ethylene EOS will determine the procedures of implementation. In some custody transfer applications, programming support could be required to implement the proper code for each EOS. In other custody transfer applications, the EOS could already be in a compiled form and available for use. An example of this would be the use of an ethylene EOS in flow computing applications to determine mass flow rate. Example and auxiliary calculations are presented in the individual publication IUPAC-88.
The purpose of this standard is to provide an equation of state that can be used to obtain an accurate determination of ethylene density. Other thermodynamic properties can be calculated using the equation of state, but this standard is primarily concerned with the determination of ethylene density. Temperature and pressure can have significant effects on the accurate determination of ethylene density, and as a result, the means for temperature and pressure determination have to be assessed appropriately for these applications. The previous edition of this standard, published in 1974, was in the form of a measurement manual and was not confined to calculating the physical properties of ethylene. The previous edition included orifice and turbine metering calculations, as well as data that were not in agreement with the current API Manual of Petroleum Measurement Standards (MPMS) that cover these metering devices. The original density lookup tables were based on FORTRAN code originally published in the mid-1960s as API 2565 Subroutine Ethyl. This Second Edition of API MPMS Chapter 184.108.40.206 is intended to replace the 30+ year old equations with references to more modern equations of state, limited to the physical properties of ethylene. Typically, ethylene equations of state are used in custody transfer metering applications. Such is the case with modern flow computers, which have various options for selecting which equation of state is utilized in determining flowing ethylene density.