PART XV Metering Systems SECTION 2 GUIDE TO GAS METERING SYSTEMS

Transcription

1 THE INSTITUTE OF PETROLEUM PETROLEUM MEASUREMENT MANUAL PART XV Metering Systems SECTION 2 GUIDE TO GAS METERING SYSTEMS

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3 THE INSTITUTE OF PETROLEUM PETROLEUM MEASUREMENT MANUAL PART XV Metering Systems SECTION 2 GUIDE TO GAS METERING SYSTEMS March 2002 Published by The Institute of Petroleum, London A charitable company limited by guarantee

4 Copyright 2002 by The Institute of Petroleum, London: A charitable company limited by guarantee. Registered No , England All rights reserved No part of this book may be reproduced by any means, or transmitted or translated into a machine language without the written permission of the publisher. ISBN Published by The Institute of Petroleum Further copies can be obtained from Portland Press Ltd. Commerce Way, Whitehall Industrial Estate, Colchester CO2 8HP, UK. Tel: +44 (0) sales@portlandpress.com

5 CONTENTS Foreword... vii Page Acknowledgements... Introduction... viii ix 1 Definitions and symbols Quantitative and qualitative measurements Measurement conditions Flow measurement Uncertainty and accuracy Symbols Applications - General requirements Basic design considerations Gas acceptability criteria Performance and calibration Choice of primary device Mass, volume and density measurement Service considerations System design Design criteria Piping configurations and valving Secondary instrumentation Safety Orifice meters General principles Flow equations Meter design Installation v

6 Contents Cont... Page 5 Other meters Turbine meters Displacement meters Vortex meters Ultrasonic meters Sonic nozzles Some other meters Calibration and proving General Off-site calibration In-service proving Tracer methods Secondary instrumentation Differential pressure transmitters (DPTs) Temperature measurement Pressure measurement Density measurement Continuous measurement of density The ptz method Measurement of relative density Installation of line density transducers Redundancy in density measurement Equipment for composition and quality measurement Gas sampling Measurement of composition Measurement of calorific value Measurement of Wobbe index Measurement of hydrocarbon dewpoint Measurement of water dewpoint Measurement of contaminants Flow computation and display Flow computers Calculation of gas quantities Calculation of gas properties Simple flow computers Commissioning and maintenance Testing and commissioning Commissioning Inspection and maintenance Table 1- Main features of primary devices Figures References Annexes vi

7 FOREWORD Measurement accuracy is essential in the sale, purchase and handling of petroleum products. It avoids disputes between buyer and seller and provides control over losses. Accurate measurement involves the use of standard equipment and procedures. The Petroleum Measurement Committee of the Institute of Petroleum is responsible for the production and maintenance of standards and guides covering the various aspects of static and dynamic measurement of petroleum. These are issued as separate Parts and Sections of the Institute s Petroleum Measurement Manual, which was first published in Membership of the IP working panels includes experts from the oil industry, equipment manufacturers, cargo surveyors and government authorities. Liaison is maintained where appropriate with parallel working groups of the Committee on Petroleum Measurement of the American Petroleum Institute, and is extended as necessary to embrace other organizations concerned with quantitative measurement in other countries and in other industries. Users are invited to send comments, suggestions, or details of experience with this issue to: The Technical Manager, Standards Institute of Petroleum 61 New Cavendish Street London W1G 7AR United Kingdom The Petroleum Measurement Manual is widely used by the petroleum industry and has received recognition in many countries by consumers and the authorities. In order to promote their wide adoption internationally, it is the policy to submit selected standards through the British Standards Institution to Technical Committee 28 - Petroleum Products and Lubricants - of the International Organization for Standardization (ISO) as potential International Standards. A full list of Parts and Sections of the Petroleum Measurement Manual (PMM) is available on request from the Institute of Petroleum. Note: The IP Petroleum Measurement Manual is recommended for general adoption but must be read and interpreted in conjunction with weights and measures, safety and other regulations in force in a particular country in which it is to be applied. Such regulatory requirements shall have precedence over corresponding clauses in the Manual. The Institute disclaims responsibility for any personal injury, or loss or damage to property howsoever caused, arising from the use or abuse of any Part or Section of the Manual. Attention is also drawn to the fact that some of the equipment mentioned in the Manual is protected by patents throughout the world. The mention of any proprietary information in this Guide does not imply its endorsement by the IP for any particular application; neither does omission imply rejection. vii

8 ACKNOWLEDGEMENTS The following members of the IP Petroleum Measurement Committee and of its Sub-Committees and Panels have been associated with the production of the revision of this section of the Petroleum Measurement Manual: M D H Bayliss J H R Phipps Measurement Innovation Ltd. Institute of Petroleum (Editorial) viii

9 INTRODUCTION This section of the Petroleum Measurement Manual covers the specification, design, installation and operation of metering stations for high accuracy measurement of the bulk flow of gases in pipelines and process plants. It was first published in 1991, this revision being updated to incorporate new technology and latest standards. The types of metering equipment described are intended for the measurement of natural hydrocarbon gases for the purposes of sales, custody transfer, taxation or the allocation of production in a multi-user pipeline. Such systems will be referred to in this guide as fiscal metering systems, implying a standard of accuracy that is the highest reasonably attainable in practice, bearing in mind the balance between cost and accuracy. Compliance with this guide and the relevant standards to which it refers should assist approval, where appropriate, by the UK Government and other regulatory authorities but it does not guarantee or imply such approval. It is hoped that this guide will also be of use in the design and specification of metering systems that are not required to meet fiscal standards of accuracy such as those used for plant operational purposes, equipment performance monitoring, etc. Gas metering technology, at the time of revision of this guide, is at a state where the orifice meter is still in wide use for fiscal gas measurement. There is a large amount of data in the form of internationally accepted standards on the performance and construction of this type of meter. Other meter types are also in operation for fiscal measurement that can offer a similar standard of accuracy, or that have specific advantages suitable for particular purposes. In particular, multi-path ultrasonic meters are rapidly gaining acceptance as high accuracy devices. Whilst this guide deals with the orifice meter in greater detail than other types of meter, this does not imply that other types of meter, such as the turbine meter, ultrasonic or vortex meter, etc., are less suitable. The choice of meter for each metering application should be made on the basis of suitability for purpose, taking account of the performance of the meters offered by individual manufacturers and the developments that are continuing in measurement technology. It must be emphasized that this guide is not intended to replace any of the national or international standards covering the detailed aspects of meter installation and design. The guide instead gives an overall picture of the metering system and an introduction to its component parts with references to the appropriate standards, from which further details can be obtained. ix