1、Manual of PetroleumMeasurement StandardsChapter 6Metering AssembliesSection 6Pipeline Metering SystemsSECOND EDITION, MAY 1991REAFFIRMED, JANUARY 2012Manual of PetroleumMeasurement StandardsChapter 6Metering AssembliesSection 6Pipeline Metering SystemsMeasurement CoordinationSECOND EDITION, MAY 1991
2、REAFFIRMED, JANUARY 2012SPECIAL NOTES 1. API PUBLICATIONS NECESSARILY ADDRESS PROBLEMS OF A GENERAL NATURE. WITH RESPECT TO PARTICULAR CIRCUMSTANCES, LOCAL, STATE, AND FEDERAL LAWS AND REGULATIONS SHOULD BE REVIEWED. 2. API IS NOT UNDERTAKING TO MEET THE DUTIES OF EMPLOYERS, MANUFACTURERS, OR SUPPLI
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6、E YEARS. SOMETIMES A REVIEW CYCLE. THIS PUBLICATION WILL NO LONGER BE IN EFFECT AS AN OPERATIVE API STANDARD FIVE YEARS AFTER ITS PUBLICATION DATE OR, WHERE AN EXTENSION HAS BEEN GRANTED, UPON REPUBLICATION. THE STATUS OF THE PUBLICATION CAN BE ASCERTAINED FROM THE API AUTHORING DEPARTMENT (TELEPHON
7、E 202 682-8000). A CATALOG OF API PUBLICATIONS AND MATERIALS IS PUBLISHED ANNUALLY AND UPDATED QUARTERLY BY API, 1220 L STREET, N.W., WASHINGTON, D.C. 20005. ONE-TIME EXTENSION OF UP TO TWO YEARS WILL BE ADDED TO THIS Copyright 1991 American Petroleum Institute FOREWORD This publication provides gui
8、delines for selecting the types and sizes of meters for use on pipelines. API publications may be used by anyone desiring to do so. Every effort has been made by the Institute to assure the accuracy and reliability of the data contained in them; however, the Institute makes no representation, warran
9、ty, or guarantee in connection with this publication and hereby expressly disclaims any liability or responsibility for loss or damage resulting from its use or for the violation of any federal, state, or municipal regulation with which this publication may conflict. Suggested revisions are invited
10、and should be submitted to the director of the Measure- ment Coordination Department, American Petroleum Institute, 1220 L Street, N.W., Washington, D.C. 20005. iii CONTENTS Page SECTION however, special additional precautions may be required. 6.6.2 Scope This chapter provides guidelines for selecti
11、ng the type and size of meter(s) to be used to measure pipeline movements. Types of accessories and instruments that may be desirable are specified, and the relative advantages and disadvantages of the methods of proving meters by tank prover, by conven- tional pipe prover, by small volume prover, a
12、nd by master meter are discussed. This chapter also includes discussions on obtaining the best operating results from a pipeline-meter station. 6.6.3 Field of Application The information provided in this chapter may be applied to the following systems: a. Gathering systems from production facilities
13、 to a main crude oil storage or pipeline system. b. Crude oil pipelines. c. Refined product pipelines. d. Liquefied petroleum gas (LPG) pipelines. 6.6.4 Referenced Publications Manual of Petroleum Measurement Standards Chapter KProving Systems” Chapter 4.3, Small-Volume Provers” Chapter 5-“Metering”
14、 Chapter 5.1, “General Considerations for Measurement by Meters” Chapter 5.2, “Measurement of Liquid Hydrocarbons by Displacement Meter” Chapter 5.3, “Measurement of Liquid Hydrocarbons by Turbine Meters” Chapter 5.4, “Accessory Equipment for Liq- uid Meters” Chapter 5.5, “Fidelity and Security of F
15、low Measurement Pulsed-Data Transmission Systems” Chapter 8-“Sampling” Chapter 12.2, “Calculation of Liquid Petroleum Quantities Measured by Turbine or Displacement Meters” Chapter 13.2, “Statistical Evaluation of Meter Proving Data” (under development) 6.6.5 Meter Station Design As defined in this
16、publication, a metering station on a pipeline system is one where custody transfer measurement takes place through one or more meters. When a pipeline- metering system is designed, the objective is to obtain op- timum measurement accuracy for custody transfers regardless of the volume handled. The m
17、easurement accuracy of the system depends on meters, provers, valves, and other equipment selected for that measurement system. Other considerations for a meter station design include providing for future expansion and upgrades, accessibility of the equipment for maintenance, and accuracy verificati
18、on. Chapters 4 and 5 of this manual should be consulted for further requirements common to all proving and metering systems. 6.6.5.1 METER SELECTION Although displacement meters (see Chapter 5.2) and tur- bine meters (see Chapter 5.3) are the most commonly used meters in pipeline applications, other
19、 types of meters are not excluded if they serve the intended purpose. Many of the aspects of the metering functions are con- sidered at length in other parts of this manual. Please refer to the following chapters for more information. Meter selection is discussed in Chapter 5.1. In general, turbine
20、meters are preferred for high-flow rate and low- viscosity applications. In high-pressure applications, capital 1 2 CHAPTER 6-METERING ASSEMBLIES and installation costs ofturbine meters may be less. However, in crude oil service viscosity, wax content or the presence of fibrous material may limit th
21、e use of turbine meters. When the relative merits of displacement and turbine meters are evaluated, both maintenance and operating costs should be considered. Maintenance costs for displacement meters may be significant when liquids with poor lubricity or abrasive characteristics are handled. Turbin
22、e meter maintenance costs are usually low, but maintenance of adequate back-pressure to ensure accuracy may result in higher power costs. Before selecting a meter, the designer must know or have a good estimate of the following: a. The range of physical and chemical characteristics of the liquid in:
23、 1. Viscosity, lubricity, and pour-point. 2. Density (API gravity). 3. Corrosive, abrasive, fibrous, wax, or other foreign material. 4. Vapor pressure. b. The range of flow rates and pressures. c. The range of liquid temperature and ambient temperatures that will be encountered. d. The duration of o
24、peration (continuous or intermittent). e. The location of the meter station and whether its control is to be local or remote, attended or unattended. 6.6.5.1.1 Viscosity The-linearity of a displacement meter improves as the viscosity of the fluid being metered increases. This improve- ment is a resu
25、lt of decreased slippage in the meter. (See Chapter 5.2.) Turbine meters generally perform with a broader linear range in lower viscosities. (See Chapter 5.3.) Turbine meters would normally be selected for use with low-viscosity refined products, such as propane, gasoline, diesel oil, and so on, bec
26、ause of their longer service life, greater rangeability, and equal or better accuracy than a displacement meter on these types of products. (See Chapter 5.1.) 6.6.5.1.2 Density The rating of a displacement meter is generally not af- fected by the density of the liquid that it must measure. In instal
27、lations where turbine meters are used, the linear range of the meter tends to shift with density. (See Chapter 5.3.) In general, a turbine meters normal flow range shifts to a higher range as density decreases. Conversely, for higher density liquids, the pressure drop across the meter increases more
28、 rapidly as flow rate increases. 6.6.5.1.3 Corrosive, Abrasive, and Foreign Materials Abrasive solids, acid or alkaline chemicals, and some salts are typical foreign materials in a petroleum liquid that can harm a meter and its operation. If displacement meters are intended for use with liquids cont
29、aining relatively large amounts of abrasive or corrosive materials, the manufacturer should be consulted about the materials used for meter construction. In general, a limited amount of fine abrasives and cor- rosive contaminants have less effect on the life and perfor- mance of a turbine meter beca
30、use solids in suspension continue to flow uninterrupted through the meter. Corrosive contaminants do not affect, to any marked degree, typical stainless steel turbine meters. On the other hand, displace- ment meters are more affected by fine abrasives because of the close clearances of the moving pa
31、rts and because the standard materials of construction can be affected by reactive chemicals. Conversely, fibrous materials, weeds, and wax, which are sometimes present in crude oils, have little effect on displacement meters. However, these contaminants tend to become lodged on rotor blades and str
32、aightening sections of turbine meters and affect their operation. 6.6.5.1.4 Vapor Pressure The vapor pressure of the liquid to be metered is a factor in determining the pressure rating required for the meter and the meter manifold. Vapor pressure also has a bearing on the type of pressure control eq
33、uipment and valves needed to maintain a liquid phase and accurate measurement. 6.6.5.1.5 Flow Rate The selected meters shall have the capacity to handle the minimum and maximum expected pipeline flow rate. Dis- placement meters are normally selected for continuous opera- tion at about 75 percent of
34、the manufacturers nameplate capacity, if the liquid has reasonable lubricity. The capacity of displacement meters is reduced to as low as 40 percent of nameplate capacity for liquids with poor lubricity, such as butane or propane. Turbine meters may be operated at full nameplate capacity and beyond,
35、 but because pressure drop increases with flow rate, power costs may be a factor in choosing the most suitable size of meter. Optimum accuracy may require displacement meters to be operated at rates above 20 percent of maximum nameplate capacity. Turbine meters, depending on fluid characteristics, m
36、ay require operation at rates above 40 percent of maximum nameplate capacity for optimum accuracy. 6.6.5.1.6 Temperature When pipelines generally operate in moderate ambienl SECTION therefore, greater meter capacity may be required to satisfy a given flow rate. As the density of a liquid decreases,
37、the entire linear portion of the performance curve moves toward the higher flow rates; that is, a liquid with a density of around 0.5 may effectively have the meter over- ranged by a factor of 1.5 times its maximum nameplate capacity with no appreciable increase in pressure loss. Because the perform
38、ance of turbine meters tends to im- prove with increased size, caution should be exercised before smaller sizes are selected, especially for crude oil service. Thus, a simple formula to determine the number of meters required for a specific application cannot be given. Manufac- turers should be cons
39、ulted for particular applications. 4 CHAPTER not all options shown in the schematics may be required, and options not shown may still be required. 6.6.6 Meter Station Operation This publication is intended to assist the designer of a pipeline-meter station to select and install the equipment appropr
40、iate to the needs of its proposed operation. Chapters 4 and 5 contain much information that applies to pipeline- meter station design, selection, and installation, and these chapters also contain most of the information affecting their operation and maintenance. The operator of a pipeline-meter stat
41、ion, therefore, know- ing the type of liquids involved, the type and size of meters and proving systems provided, and the range of values of the principal variable-rate, viscosity, temperature pressure, and density-should review those parts of Chapter 5 that deal with meter performance, operation, a
42、nd maintenance, bearing in mind the considerations described in 6.6.7. 6.6.7 Meter Performance Meter performance is a general expression and is used to indicate how satisfactorily a meter can continuously measure the actual volume of liquid passing through it. It is most often shown as a characteris
43、tic or performance curve, which is a plot of meter factor versus rate. Because a meter factor is applied to the indicated volume in all pipeline-metering sys- tems involving liquid hydrocarbons, the usefulness of the characteristic curve lies in its ability to show by how much a meter factor will ch
44、ange with a given change in rate. In- dividual curves should be made for each product or grade of crude oil. Meter performance can also be plotted as meter factor versus any operating parameter, that is, viscosity, tempera- ture, and so forth. However, when the liquid properties change significantly
45、 (for example, when a new batch or tender is to be measured), a new meter factor should be developed by re-proving. The most common presentation of meter performance is a plot of meter factor versus rate at stable operating conditions. Meter proving should be done frequently if maximum accuracy is e
46、ssential. 6.6.7.1 NET STANDARD VOLUMES The custody transfer measurement of hydrocarbon liquids is performed to obtain a quantity definition that is the basis for commercial transactions. This quantity is most often expressed as a net standard volume. Net standard volumes are volumes corrected for me
47、ter factor, for the effects of tempera- ture and pressure on both the liquid and the steel of the prover used to determine the meter factor, and for sediment and water content, if applicable. The standard methods for calculating a provers base volume, a meter factor, and a measurement ticket are det
48、ailed SECTION &PIPELINE METERING SYSTEMS 7 To storage ( 10 Mainline i. Pressure-reducing valve-manual or automatic, 6. Check valve, if required. 7. Control valve, if required. 2. Filter, strainer and/or vapor eliminator 8. Positive shut-off, double block and bleed valves. 9. Flow control valve, if r
49、equired. 3. Displacement meter. 4. Temperature measurement device. 5. Pressure measurement device. if required. (if required) for each meter or whole station. 10. Block valve, if required. 11. Differential pressure device, i required. 12. Sampler, proportional to flow. Note: This simplified diagram indicates primary components for typical stations but is not intended to indicate preferred locations. All sections of the line that may be blocked between valves should have provisions for pres- sure relief (preferably not to be instailed between the meter and the prover). Fig
