Jun,27

API TR 2579-2020 pdf download

API TR 2579-2020 pdf download

API TR 2579-2020 pdf download.Liquid Hydrocarbon Measurement Uncertainty Calculations.
1 Scope This document provides guidelines for the calculation of uncertainty for field stored and transported hydrocarbon liquids. Special emphasis is placed on the measurement uncertainty of crude oils measured at tanks, by lease automatic custody transfer (LACT), and alternative measurement systems. 2 Terms and Definitions For the purposes of this document, the following definitions apply. 2.1 accuracy The closeness of agreement between a measured quantity value and a true quantity value of a measurand. 2.3 calibration A set of operations that establish, under specified conditions, the relationship between the values indicated by a measuring device and the corresponding known values indicated when using a suitable measuring standard. 2.12 metering or measurement system A combination of primary, secondary, and/or tertiary measurement components necessary to determine the flow rate. 2.14 performance The response of a measurement device to influence parameters such as operating conditions, installation effects, and fluid properties. 2.16 uncertainty The range or interval within which the true value is expected to lie with a stated degree of confidence. Describes the range of deviation between a measured value and the true value, expressed as a percentage. For example, a device with an accuracy of 2 % would have an uncertainty of ±2 %. 3 Performance Characteristics and Measurement by Meter Type 3.1 General The primary purpose of a liquid hydrocarbon meter for any application is to measure the flow. The uncertainty of measurement depends on the measurement equipment selected for the application, proper installation of the equipment, the ability to inspect, verify, or calibrate the various measurement system components, and the frequency of those maintenance activities. The performance of the meter may also depend on the piping configuration and compensation for variability of operating pressure, temperature, and fluid composition. 3.2 Uncertainty Requirements General The purpose of this document is to develop the uncertainty representations and example calculations for meters, provers, and associated equipment used on any metering system such as LACT systems, which can be used to address uncertainty requirements. Focus is placed on Coriolis and positive displacement meters since they are the most commonly used on LACT systems to measure crude oil quantities. With the proper understanding of individual system component uncertainties, the overall system uncertainty can be calculated for metering systems in the design phase or already in operation in the field. Specifics of Requirements The sources of uncertainty that are addressed arise from the following. — Meter measurement: — linearity; — thermal and pressure variation; — deviation from meter factor proving conditions. — Fluid properties: — thermal, pressure, and viscosity variation; — profile deviation impact. — Prover: — temperature, pressure variation. — Associated devices: — sediment and water, density. — Calibration: — temperature, pressure, density, viscosity, sediment and water. 4 Uncertainty Development 4.1 General The work by Dahl et al. (2003) [9] was used as basis for the development of this document. Refer to Annex A for examples of the uncertainty calculation procedure. 4.2 Basic Equations General NOTE The basic equations developed in the handbook by Dahl et al. (2003) [9] follow the development from ISO 5168:1978 [7] and ISO/IEC Guide 98-3 [8] .
The uncertainty represented by this term is related to the difference in the meter factors that can be determined over the range of operating conditions for the metering system. It is generally obtained from proving at multiple operating conditions that would represent the largest and smallest meter factors that can be obtained for the metering system. Note that proving at multiple operating conditions and using a mean-average meter factor, scheduling meter factors with flow rate changes, and various forms of linearity compensation will all impact the magnitude of this term.

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