Manual of Petroleum                     Measurement Standards                     Chapter 5-Metering                     S...
COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
Manual of Petroleum                     Measurement Standards                     Chapter 5-Metering                     S...
SPECIAL NOTES                         API publications necessarily address problems of a general nature. With respect to p...
FOREWORD                         This five-part publication consolidates and presents standard calculations for metering  ...
COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
CONTENTS                                                                                                                  ...
CONTENTS                                                                                                            Page  ...
Chapter 5-M ete ring                       Section 3-Measurement                       of Liquid Hydrocarbons by Turbine M...
2                                                        CHAPTER 5-METERING        5.3.2     Field of Application         ...
SECTION 3-MEASUREMENT         OF   LIQUIDHYDROCARBONS TURBINE                                                             ...
4                                                               CHAPTER 5-METERING                                        ...
SECTION 3-MEASUREMENT     OF   LIQUIDHYDROCARBONS TURBINE                                                                 ...
6                                                        CHAPTER 5-METERING        sion chambers, pressure-limiting valves...
SECTION 3-MEASUREMENT      OF   LIQUIDHYDROCARBONS TURBINE                                                                ...
8                                                       CHAPTER 5-METERING        i. Changes in piping, valves, or valve p...
SECTION 3-MEASUREMENT     OF   LIQUIDHYDROCARBONS TURBINE                                                                 ...
10                                                     CHAPTER 5-METERING        proving has shown that meter factor value...
12                                                         CHAPTER 5-METERING             Table A-I-Values       for L and...
SECTION 3-MEASUREMENT      OF   LIQUIDHYDROCARBONS TURBINE                                                                ...
COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
APPENDIX B-SIGNAL                     GENERATION           B.l    Introduction                                            ...
COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
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  1. 1. Manual of Petroleum Measurement Standards Chapter 5-Metering Section 3-Measurement of Liquid Hydrocarbons by Turbine Meters FOURTH EDITION, SEPTEMBER 2000 American Petroleum Institute Helping You Get The Job Done Right?COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  2. 2. COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  3. 3. Manual of Petroleum Measurement Standards Chapter 5-Metering Section 3-Measurement of Liquid Hydrocarbons by Turbine Meters Measurement Coordination FOURTH EDITION, SEPTEMBER 2000 American Petroleum Institute Helping You Get The Job Done Right?COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  4. 4. SPECIAL NOTES API publications necessarily address problems of a general nature. With respect to partic- ular circumstances, local, state, and federal laws and regulations should be reviewed. API is not undertaking to meet the duties of employers, manufacturers, or suppliers to warn and properly train and equip their employees, and others exposed, concerning health and safety risks and precautions, nor undertaking their obligations under local, state, or fed- eral laws. Information concerning safety and health risks and proper precautions with respect to par- ticular materials and conditions should be obtained from the employer, the manufacturer or supplier of that material, or the material safety data sheet. Nothing contained in any API publication is to be construed as granting any right, by implication or otherwise, for the manufacture, sale, or use of any method, apparatus, or prod- uct covered by letters patent. Neither should anything contained in the publication be con- strued as insuring anyone against liability for infringement of letters patent. Generally, API standards are reviewed and revised, r e a m e d , or withdrawn at least every five years. Sometimes a one-time extension of up to two years will be added to this review cycle. This publication will no longer be in effect five years after its publication date as an operative API standard or, where an extension has been granted, upon republication. Status of the publication can be ascertained from API Measurement Coordination [telephone (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. This document was produced under API standardization procedures that ensure appropri- ate notification and participation in the developmental process and is designated as an API standard. Questions concerning the interpretation of the content of this standard or com- ments and questions concerning the procedures under which this standard was developed should be directed in writing to the Standardization Manager, American Petroleum Institute, 1220 L Street, N.W., Washington, D.C. 20005. Requests for permission to reproduce or translate all or any part of the material published herein should also be addressed to the gen- eral manager. API standards are published to facilitate the broad availability of proven, sound engineer- ing and operating practices. These standards are not intended to obviate the need for apply- ing sound engineering judgment regarding when and where these standards should be utilized. The formulation and publication of API standards is not intended in any way to inhibit anyone from using any other practices. Any manufacturer marking equipment or materials in conformance with the marking requirements of an API standard is solely responsible for complying with all the applicable requirements of that standard. API does not represent, warrant, or guarantee that such prod- ucts do in fact conform to the applicable API standard. All rights reserved. No part o this work may be reproduced, stored in a retrieval system, or f transmitted by any means, electronic, mechanical,photocopying, recording, or otherwise, without prior written permission from the publisher: Contact the Publishel; API Publishing Services, 1220 L Street, N. I , T Washington,D. 20005. C. Copyright O 2000 American Petroleum InstituteCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  5. 5. FOREWORD This five-part publication consolidates and presents standard calculations for metering petroleum liquids using turbine or displacement meters. Units of measure in this publication are in International System (SI) and United States Customary (USC) units consistent with North American industry practices. This standard has been developed through the cooperative efforts of many individuals from industry under the sponsorship of the American Petroleum Institute and the Gas Processors Association. API Chapter 5 of the Manual of Petroleum Measurement Standards contains the following sections: Section 1, “General Considerations for Measurement by Meters” Section 2, “Measurement of Liquid Hydrocarbons by Displacement Meters” Section 3 , “Measurement of Liquid Hydrocarbons by Turbine Meters” Section 4, “Accessory Equipment for Liquid Meters” Section 5, “Fidelity and Security of Flow Measurement Pulsed-Data Transmission Systems” 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, warranty, 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 conñict. Suggested revisions are invited and should be submitted to Measurement Coordination, American Petroleum Institute, 1220 L Street, N.W., Washington, D.C. 20005. ... 111COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  6. 6. COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  7. 7. CONTENTS Page 5.3.O INTRODUCTION..................................................... 1 5.3.1 SCOPE.............................................................. 1 5.3.2 FIELD OF APPLICATION ............................................. 2 5.3.3 REFERENCED PUBLICATIONS ....................................... 2 5.3.4 DESIGN CONSIDERATIONS .......................................... 2 5.3.5 SELECTING A METER AND ACCESSORY EQUIPMENT . . . . . . . . . . . . . . . . . . 2 5.3.6 INSTALLATION ..................................................... 3 5.3.6. 1 Flow Conditioning................................................ 3 5.3h.2 Valves .......................................................... 5 5.3h.3 Piping Installation ................................................ 5 5.35.4 Electrical Installations ............................................. 7 5.3.7 METER PERFORMANCE ............................................. 7 Meter Factor .................................................... 7 Causes Of Variations In Meter Factor ................................. 8 Variations In Flow Rate ............................................ 8 Variations In Viscosity ............................................. 8 Variations In Temperature .......................................... 8 Variations In Density .............................................. 8 Variations In Pressure ............................................. 8 5.3.8 OPERATION AND MAINTENANCE .................................... 8 Conditions That Affect Operation .................................... 9 5.33.2 Precautions For Operating Newly Installed Meters ...................... 9 5.33.3 Instructions For Operating Meter Systems ............................. 9 Meter Proving ................................................... 9 Methods Of Controlling Meter Factor ............................... 10 Meter Maintenance .............................................. 10 APPENDIX A FLOW-CONDITIONINGTECHNOLOGY WITHOUT STRAIGHTENINGELEMENTS .............................. 11 APPENDIXB SIGNALGENERATION..................................... 15 APPENDIX C RECOMMENDED PRACTICE FOR PROVING TURBINE METERS AT MANUFACTURERS’ FACILITIES . . . . . . . . . . . . . . . . 17 Figures 1 Names of Typical Turbine Meter Parts ................................... 1 2 Turbine Meter Performance Characteristics ............................... 3 3 Schematic Diagram of Turbine Meter Installations ......................... 4 4 Example of Flow-Conditioning Assembly With Straightening Element . . . . . . . . . 4 5 Effects of Cavitation on Rotor Speed .................................... 6 VCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  8. 8. CONTENTS Page A- 1 Piping Configuration in Which a Concentric Reducer Precedes the Meter Run (K,=0.75) ............................................... 11 A-2 Piping Configuration in Which a Sweeping Elbow Precedes the Meter Run (K,=l.O). ............................................. 12 A-3 Piping Configuration in Which Two Sweeping Elbows Precede the Meter Run (K,=1.25). ............................................ 12 A-4 Piping Configuration in Which Two Sweeping Elbows at Right Angles Precede the Meter Run (K, = 2.0) .......................... 13 A-5 Piping Configuration in Which a Valve Precedes The Meter Run (K, = 2.0). ........................................... 13 Tables A- 1 Values For L And L/d For Figures A- 1 Through A-5. ...................... 12 viCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  9. 9. Chapter 5-M ete ring Section 3-Measurement of Liquid Hydrocarbons by Turbine Meters 5.3.0 Introduction It is recognized that meters other than the types described in this chapter are used to meter liquid hydrocarbons. This API Chapter 5.3 of the Manual o Petroleum Measurement f publication does not endorse or advocate the preferential use Standards is intended to describe methods of obtaining accu- of turbine meters, nor does it intend to restrict the develop- rate measurements and maximum service life when turbine ment of other types of meters. Those who use other types of meters are used to measure liquid hydrocarbons. meters may find sections of this chapter useful. A turbine meter is a flow-measuring device with a rotor that senses the velocity of flowing liquid in a closed conduit (see Figure i). The flowing liquid causes the rotor to move 5.3.1 Scope with a tangential velocity that is proportional to volumetric This section of API MPMS Chapter 5 defines the applica- flow rate. The movement of the rotor can be detected tion criteria for turbine meters and discusses appropriate con- mechanically, optically, or electrically and is registered on a siderations regarding the liquids to be measured; the readout. The actual volume that passes the meter and is regis- installation of a turbine metering system; and the perfor- tered on a readout is determined by proving against a known mance, operation, and maintenance of turbine meters in liq- volume, as discussed in API MPMS Chapter 4. uid-hydrocarbon service. Flow Flow Cantilever Stator Design UpstreamlDownstream Stator Design Notes: 1. Upstream stator. 7. Downstream stator. 2. Upstream stator supports. 8. Downstream stator supports. 3 . Bearings. 9. Meter housing. 4. Shaft. 10. Pickup. 5 . Rotor hub. 11. End corrections. 6. Rotor blade. Figure I-Names of Typical Turbine Meter Parts 1COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  10. 10. 2 CHAPTER 5-METERING 5.3.2 Field of Application e. The installation should ensure appropriate flow condition- ing both upstream and downstream of the meter or meters. The field of application of this section is all segments of f. The installation should comply with all applicable regula- the petroleum industry in which dynamic measurement of liq- tions and codes. uid hydrocarbons is required. This section does not apply to the measurement of two-phase fluids. 5.3.5 Selecting a Meter and Accessory Equipment 5.3.3 Referenced Publications API MPMS Chapter 5.4 provides guidelines for selecting The current editions of the following standards may be the appropriate equipment. In addition, the manufacturer referenced: should be consulted and detailed consideration should be given to the following items: API Manual o Petroleum Measurement Standards f a. The properties of the metered liquids, including viscosity, Chapter 4, “Proving Systems” vapor pressure, toxicity, corrosiveness, and lubricating ability. Chapter 5, “Metering” Toxic and environmentally controlled fluids must receive spe- cial considerationto prevent and control potential leaks or spills. Chapter 5.4, “Instrumentation or Accessory Equipment for Liquid Hydrocarbon Metering Systems” b. The operating flow rates and whether the flow is continu- ous, intermittent, fluctuating, bidirectional, or reversible. Chapter 5.5, “Fidelity and Security of Flow Measure- c. The performance characteristics that are required for the ment Pulsed-Data Transmission Systems” application (see Figure 2). Chapter 7.2, “Dynamic Temperature Determination” d. The class and type of piping connections and materials Chapter 8, “Sampling” and the dunensions of the equipment to be used. Chapter 11, “Physical Properties Data” e. The space required for the meter installation and the prov- Chapter 12, “Calculation of Petroleum Quantities” ing facility. Chapter 12.2, “Calculation of Liquid Petroleum Quanti- f. The range of operating pressures, acceptable pressure ties Measured by Turbine or Displacement losses through the meter, and whether pressure on the liquid Meters” is adequate to prevent vaporization. Chapter 13, “Statistical Aspects of Measuring and g. The operating temperature range and the applicability of Sampling” automatic temperature compensation. Chapter 13.2, “Statistical Methods of Evaluating Meter h. Effects of corrosive contaminants on the meter and the Proving Data” quantity and size of foreign matter, including abrasive parti- Chapter 14.3, “Concentric Square-Edged Orifice Meters” cles, that may be carried in the liquid stream. i. The types of readout and printout devices or systems to be used, signal preamplification (see API MPMS Chapter 5.4), 5.3.4 Design Considerations and the standard units of volume or mass that are required. The design of turbine meter installations should take into j. The method by which a meter in a bank of meters can be account the following considerations: put on or taken off line as the total rate changes and the method by which it can be proved at its normal operating rate. a. The installation should be able to handle the maximum k. The type, method, and frequency of proving (see API and minimum flow rates, the maximum operating pressure, MPMS Chapter 4). and the temperature range and type of liquid to be measured. 1. The method of factoring a meter’s registration. If necessary, the installation should include protective devices m. The need for accessory equipment, such as pulsen, additive that keep the operation of the meter within design limits. injection apparatus, combinators, and devices for predetermin- b. The installation should ensure a maximum, dependable ing quantity. When meter-driven mechanical accessory operating life. Strainers, filters, airhapor eliminators, or other devices are used, caution must be taken to limit the total torque protective devices may be provided upstream of the meter to applied to the metering element (see API MPMS Chapter 5.4). remove solids that could cause premature wear or gases that n. Valves in the meter installation. Valves require special could cause measurement error. consideration since their performance can affect measure- c. The installation should ensure adequate pressure on the ment accuracy. The flow or pressure control valves on the liquid in the metering system at all temperatures so that the main-stream meter run should be capable of smooth opening fluid being measured will be in the liquid state at all times. and closing to prevent shocks and surges. Other valves, par- d. The installation should provide for proving each meter and ticularly those between the meter or meters and the prover should be capable of duplicating normal operating conditions (for example, the stream diversion valves, drains, and vents), at the time of proving. require leakproof shutoff, which may be provided by a doubleCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  11. 11. SECTION 3-MEASUREMENT OF LIQUIDHYDROCARBONS TURBINE BY METERS 3 block-and-bleed valve with telltale bleed or by another simi- FLOW CONDITIONING larly effective method of verifiing shut off integrity. o. Maintenance methods and costs and spare parts that are The performance of turbine meters is affected needed. by liquid swirl and nonuniform velocity profiles that are p. Requirements and suitability for security sealing. induced by upstream and downstream piping configura- q. Power supply requirements for continuous or intermittent tions, valves, pumps, joint misalignment, protruding gas- meter readout (see API MPMS Chapter 5.4). kets, welding projections, or other obstructions. Flow r. The fidelity and security of pulse-data transmission sys- conditioning shall be used to overcome swirl and nonuni- tems (see API MPMS Chapter 5.5). form velocity profiles. Flow conditioning requires the use of sufficient 5.3.6 Installation lengths of straight pipe or a combination of straight pipe and Details for the installation of turbine meters are provided in straightening elements that are inserted in the meter run through Figure 3 is a typical schematic dia- upstream (and sometimes downstream) of the turbine meter gram for a turbine meter system with unidirectional flow. (see Figure 4). - L O i- m c L m i- E - m m Flow range at designated linearity, Application A e! b m O 14 / . I / a m f I 4 Flow range at designated linearity Application B )I e! - S Flow Rate or Reynolds Number Note This figure is illustrative only and should not be construed as representing the likely performance of any given model or size of turbine meter The curve represents the charactenstic performance of a turbine meter under stable operating conditions for flow rates within the manufacturers capacity rating Figure 2-Turbine Meter Performance CharacteristicsCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  12. 12. 4 CHAPTER 5-METERING -4 Meter run - b o 5 o *-@- -Meter bor diameter minimum minimum o o + Flow P Q P Q Notes: 1. Block valve, if required. 6. Straight pipe. 2. Differential pressure device, if required. 7. Pressure measurement device. 3. Filter strainer and/or vapor eliminator 8. Temperature measurement device. (if required) for each meter or whole station. 9. Positive shutoff double block-and-bleed valve. 4. Straightener assembly per Figure 4. 10. Control valve, if required. 5. Turbine meter. 11. Check valve, if required. Note: All sections of line that may be blocked between valves should have provisions for pressure relief (preferably not installed between the meter and the prover). Figure 3-Schematic Diagram of Turbine Meter Installations n Note This figure shows assemblies installed upstream of the meter Downstream of the meter, 5 0 minimum of straight pipe should be used L overall length of straightener assembly (2 100) = A length of upstream plenum (20-30) = B = length of tube of vane-type straightening element (20-30) C = length of downstream plenum (2 5 0 ) 0 = nominal diameter of meter n = number of individual tubes or vanes ( 2 4) d = nominal diameter of individual tubes (B/b 2 10) Figure 4-Example of Flow-Conditioning Assembly With Straightening ElementCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  13. 13. SECTION 3-MEASUREMENT OF LIQUIDHYDROCARBONS TURBINE BY METERS 5 When only straight pipe is used, the liquid shear, All valves, especially spring-loaded or self-clos- or internal friction between the liquid and the pipe wall, shall ing valves, shall be designed so that they will not admit air be sufficient to accomplish the required flow conditioning. when they are subjected to vacuum conditions. Appendix A should be referred to for guidance in applying Valves for intermittent flow control should be fast the technique. Experience has shown that, in many installa- acting and shock free to minimize the adverse effects of start- tions, pipe lengths of 20 meter-bore diameters upstream of ing and stopping liquid movement. the meter and 5 meter-bore diameters downstream of the meter provide effective conditioning. PIPING INSTALLATION A straightening element usually consists of a Figure 3 is a schematic diagram that provides a cluster of tubes, vanes, or equivalent devices that are inserted working basis for the design of a turbine-meter assembly and longitudinally in a section of straight pipe (see Figure 4). its related equipment. Certain items may or may not be Straightening elements effectively assist flow conditioning by required for a particular installation; others may be added if eliminating liquid swirl. Straightening elements may also necessary. consist of a series of perforated plates or wiremesh screens, but these forms normally cause a larger pressure drop than do Turbine meters are normally installed in a hori- tubes or vanes. zontal position. The manufacturer shall be consulted if space limitations dictate a different position. Proper design and construction of the straighten- ing element is important to ensure that swirl is not generated Where the flow range is too great for any one by the straightening element since swirl negates the function meter or its prover, a bank of meters may be installed in paral- of the flow conditioner. The following guidelines are recom- lel. Each meter in the bank shall operate within its minimum mended to avoid the generation of swirl: and maximum flow rates. A means shall be provided to bal- ance flow through each meter. a. The cross-section should be as uniform and symmetrical as possible. Meters shall be installed so that they will not be b. The design and construction should be rugged enough to subjected to undue stress, strain, or vibration. Provision shall resist distortion or movement at high flow rates. be made to minimize meter distortion caused by piping expansion and contraction. c. The general internal construction should be clean and free from welding protrusions and other obstructions. Measurement systems shall be installed so that they will have a maximum, dependable operating life. This Flow-straightening sections shall be used, and requires that, in certain services, protective devices be there shall be ample distance between the meter run and any installed to remove from the liquid abrasives or other pumps, elbows, valves, eccentric reducers, or other fittings entrained particles that could stop the metering mechanism that may induce swirl or a nonuniform velocity profile. or cause premature wear. If strainers, filters, sediment traps, Flanges and gaskets shall be internally aligned, and gaskets settling tanks, water separators, a combination of these shall not protrude into the liquid stream. Meters and the items, or any other suitable devices are required, they shall adjoining straightening section shall be concentrically aligned. be sized and installed to prevent flash vaporization of the liquid before it passes through the meter. Protective devices VALVES may be installed singly or in an interchangeable battery, The valves in a turbine meter installation depending on the importance of continuous service. In ser- require special consideration since their performance can vices where the liquid is clean or the installed meter does affect measurement accuracy. The flow- or pressure-control not require or warrant protection, omission of protective valves on the main stream meter run should be capable of devices may be acceptable. Monitoring devices should be rapid, smooth opening and closing to prevent shocks and installed to determine when the protective device needs to surges. Other valves, particularly those between the meter be cleaned. or meters and the prover (for example, the stream diversion Measurement systems shall be installed and valves, drains, and vents) require leakproof shutoff, which operated so that they provide satisfactory performance within may be provided by a double block-and-bleed valve with the viscosity, pressure, temperature, and flow ranges that will telltale bleed or by another similarly effective method of be encountered. verifiing shut off integrity. Meters shall be adequately protected from pres- If a bypass is permitted around a meter or a bat- sure pulsations and excessive surges and from excessive pres- tery of meters, it shall be provided with a blind or a positive sure caused by thermal expansion of the liquid. This kind of shutoff double block-and-bleed valve with telltale bleed. protection may require the installation of surge tanks, expan-COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  14. 14. 6 CHAPTER 5-METERING sion chambers, pressure-limiting valves, pressure relief In the absence of a manufacturers recommendation, the valves, andíor other protective devices. When pressure relief numerical value of the minimum pressure at the outlet of the valves or pressure-limiting valves are located between the meter may be calculated with the following expression, meter and the prover, a means of detecting spills from the which has been commonly used. The calculated pressure has valves shall be provided. proven to be adequate in most applications, and it may be conservative for some situations. Conditions that contribute to flashing andíor cav- itation of the liquid stream as it passes through the meter shall P,= 2 A p + 1 . 2 5 ~ ~ be avoided through suitable system design and operation of the meter within the flow range specified by the manufacturer. where: This can be avoided by maintaining sufficient pressure within the meter. This may be accomplished by placing a back-pres- P b = minimum back pressure, pounds per square sure valve downstream of the meter to maintain pressure on inch gauge (psig). the meter and the prover above the vapor pressure of the liq- uid. In some operations, the normal system pressure may be Ap = pressure drop through the meter at the maxi- sufficient to prevent flashing andíor cavitation without the use mum operating flow rate for the liquid being measured, pounds per square inch (psi). of a back-pressure valve. Since the meter outlet pressure requirement is based on the fluid conditions and the meter Pe = equilibrium vapor pressure of the liquid at the selection, the meter manufacturer should be consulted for rec- operating temperature, pounds per square inch ommendations on the minimum acceptable operating pres- absolute (psia), (gauge pressure plus atmo- sures for specific applications. spheric pressure). Pulses per unit volume Manufacturers stated maximum flow rate I I Flow rate of volume per unit of time Note: All curves are for example only. Figure &Effects of Cavitation on Rotor SpeedCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  15. 15. SECTION 3-MEASUREMENT OF LIQUIDHYDROCARBONS TURBINE BY METERS 7 For higher vapor pressure liquids, it may be possible to must be restricted to a single direction because of meter reduce the coefficient of 1.25 to some other practical and design, flow in the opposite direction shall be prevented. operable margin. In either case, the recommendations of the A thermometer, or a thermometer well that per- meter manufacturer should be considered (see Figure 5). Dur- mits the use of a temperature-measuring device, shall be ing proving operations, additional back pressure may be installed in or near the inlet or outlet of a meter run so that required to prevent vaporization in the prover. metered stream temperatures can be determined. The device When a flow-limiting device or a restricting ori- shall not be installed upstream within the flow-conditioning fice is required, it should be installed downstream of the sections or downstream closer than the manufacturer’s rec- meter run.An alarm may be desirable to signal a flow rate ommended position. If temperature compensators are used, a that has exceeded the design limits. Flow-limiting or other suitable means of checking the operation of the compensators pressure-reducing devices installed upstream of the meter is required. Refer to API MPMS Chapter 7.2 for additional shall be designed and located to satis6 flow-conditioning and information. meter pressure requirements. To determine meter operating pressure, a gauge, Each meter shall be installed so that neither air recorder, or transmitter of suitable range and accuracy shall be nor vapor can pass through it. If necessary, air and vapor installed near the inlet or outlet of each meter. (See Figure 3.) elimination equipment shall be installed upstream of the meter. The equipment shall be installed as close to the meter ELECTRICAL INSTALLATIONS as is consistent with good practice, but it must not be so close that it creates swirl or a distorted velocity profile at the entry Turbine meters usually include a variety of electrical or to the meter. Any vapors shall be vented in a safe manner. electronic accessories, as discussed in API MPMS Chapter 5.4. The electrical systems shall be designed and installed to Meters and piping shall be installed so that acci- meet the manufacturer’s recommendations and the applicable dental drainage or vaporization of liquid is avoided. The pip- hazardous area classifications and to minimize the possibility ing shall have no unvented high points or pockets where air or of mechanical damage to the components. Since turbine vapor could accumulate and be carried through the meter by meters usually provide electrical signals at a relatively low the added turbulence that results from increased flow rate. power level, care must be taken to avoid signal and noise inter- The installation shall prevent air from being introduced into ference from nearby electrical equipment (see Appendix B). the system through leaky valves, piping, glands of pump shafts, separators, connecting lines, and so forth. 5.3.7 Meter Performance The recommended location for prover connec- Meter performance is defined by how well a metering tions is downstream of the meter run.If it is necessary to system produces, or can be made to produce, accurate locate prover connections upstream of the meter run,it should measurements. be demonstrated that meter performance is not different between proving and normal operation. METER FACTOR Lines from the meter to the prover shall be Meter factors shall be determined by proving the meter installed to minimize the possibility of air or vapor being under conditions of rate, viscosity, temperature, density, and trapped. Manual bleed valves should be installed at high points pressure similar to those that exist during intended operation. so that air can be drawn off before proving. The distance Meter performance curves can be developed from a set of between the meter and its prover shall be minimized. The proving results. The curve in Figure 2 is called a linearity diameter of the connecting lines shall be large enough to pre- curve. vent a significant decrease in flow rate during proving. Flow- The following conditions may affect the meter factor: rate control valves may be required downstream of each meter, particularly in multimeter installations, to keep the proving a. Flow rate. flow rate equal to the normal operating rate for each meter. b. Viscosity of the liquid. Piping shall be designed to prevent the loss or c. Temperature of the liquid. gain of liquid between the meter and the prover during proving. d. Density of the liquid. e. Pressure of the flowing liquid. Special consideration should be given to the f. Cleanliness and lubricating qualities of the liquid. location of each meter, its accessory equipment, and its piping g. Foreign material lodged in the meter or flow-conditioning manifold so that mixing of dissimilar liquids is minimized. element. Most turbine meters will register flow in both h. Changes in mechanical clearances or blade geometry due directions, but seldom with identical meter factors. If flow to wear or damage.COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  16. 16. 8 CHAPTER 5-METERING i. Changes in piping, valves, or valve positions that affect sions of the meter and in the apparent volume measured by fluid profile or swirl. the meter as a result of thermal expansion or contraction of j. Conditions of the prover (see API MPMS Chapter 4). the liquid. The tables and formulas in API MPMS Chapter 11 may be used to calculate the extent of liquid expansion or CAUSES OF VARIATIONS IN METER contraction. For greatest accuracy, the meter should be proved FACTOR in the range of normal operating conditions. Many factors can change the performance of a turbine VARIATIONS IN DENSITY meter. Some factors, such as the entrance of foreign matter into the meter, can be remedied only by eliminating the cause. A change in the density of the metered liquid can result in Other factors, such as the buildup of deposits in the meter, significant differences in meter factor in the lower flow depend on the characteristics of the liquid being measured; ranges, thereby requiring the meter to be proved. these factors must be overcome by properly designing and For liquids with a relative density of approximately 0.7 or operating the meter system. less, consideration must be given to raising the value of the The variables that have the greatest effect on the meter fac- meters minimum flow rate to maintain linearity. The amount tor are flow rate, viscosity, temperature, deposits, or foreign of increase in lower flow rates will vary depending on meter matter. If a meter is proved and operated on liquids with size and type. To establish the minimum flow rate, several inherently identical properties, and operating conditions such provings should be made at different rates until a meter factor as flow rate remain similar, the highest level or accuracy can that yields an acceptable linearity and repeatability can be be anticipated. If there are changes in one or more of the liq- determined. uid properties or in the operating conditions between the proving and the operating cycles, a change in meter factor VARIATIONS IN PRESSURE may result and a new meter factor must be determined. If the pressure of the liquid when it is metered varies from VARIATIONS IN FLOW RATE the pressure that existed during proving, the relative volume of the liquid will change as a result of its compressibility. At the low end of the range of flow rates, the meter factor (The physical dimensions of the meter will also change as a curve may become less linear and less respectable than it is at result of the expansion or contraction of its housing under the medium and higher rates (see Figure 2, Applications A pressure.) The potential for error increases in proportion to and B). If a plot of meter factor versus flow rate has been the difference between the proving and operating conditions. developed for a particular liquid and other variables are con- For greatest accuracy, the meter should be proved at the oper- stant, a meter factor may be selected from the plot for flow ating conditions (see API MPMS Chapters 4 and 12). rates within the meters working range; however, for greatest Volumetric corrections for the pressure effects on liquids accuracy, the meter should be reproved at the new operating with vapor pressures above atmospheric pressure are refer- flow rate. enced to the equilibrium vapor pressure of the liquid at the standard temperature, 60"F, 15"C, or 20"C, rather than to VARIATIONS IN VISCOSITY atmospheric pressure, which is the typical reference for liq- Turbine meters are sensitive to variations in viscosity. uids with measurement temperature vapor pressures below Since the viscosity of liquid hydrocarbons changes with tem- atmospheric pressure. Both the volume of the liquid in the perature, the response of a turbine meter depends on both vis- prover and the registered metered volume are corrected from cosity and temperature. The viscosity of light hydrocarbons the measurement pressure to the equivalent volumes at the such as gasolines essentially remains the same over wide tem- equilibrium vapor pressure at the standard temperature, 60"F, perature changes, and the meter factor remains relatively sta- 15"C, or 20°C. ble. In heavier, more viscous hydrocarbons such as crude oils, This is a two-step calculation that involves correcting both the change in meter factor can be significant because of the measurement volumes to the equivalent volumes at equilib- viscosity changes associated with relatively small tempera- rium vapor pressure at measurement temperature. The vol- ture changes. It is advisable to reprove the meter frequently umes are then corrected to the equivalent volumes at the when the viscosity of the fluid is known to vary under normal equilibrium vapor pressure at the standard temperature, 60"F, operating conditions. 15"C, or 20°C. A detailed discussion of this calculation is included in API MPMS Chapter 12.2. VARIATIONS IN TEMPERATURE In addition to affecting changes in viscosity, significant 5.3.8 Operation and Maintenance variations in the temperature of the liquid can also affect This section covers recommended operating and mainte- meter performance by causing changes in the physical dimen- nance practices for turbine meters. All operating data pertain-COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  17. 17. SECTION 3-MEASUREMENT OF LIQUIDHYDROCARBONS TURBINE BY METERS 9 ing to measurement, including the meter factor control charts, API MPMS that can be used for reference and assistance in should be accessible to interested parties. developing these operating guidelines: a. A standard procedure for meter proving (Chapter 4). CONDITIONS THAT AFFECT OPERATION b. Instructions for operating standby or spare meters. I The overall accuracy of measurement by turbine c. Minimum and maximum meter flow rates and other oper- meter depends on the condition of the meter and its accesso- ating conditions, such as pressure and temperature. ries, the temperature and pressure corrections, the proving d. Instructions for applying pressure and temperature correc- system, the frequency of proving, and the variations, if any, tion factors (Chapter 12.2). between operating and proving conditions. A meter factor e. A procedure for recording and reporting corrected meter obtained for one set of conditions will not necessarily apply volumes and other observed data. to a changed set of conditions. f. A procedure for estimating the volume passed, in the event of meter failure or mismeasurement. Turbine meters should be operated within the g. Instructions in the use of control methods and the action to specified flow range and operating conditions that produce be taken when the meter factor exceeds the established the desired linearity of registration (see Figure 2). They acceptable limits (Chapter 13). should be operated with the equipment recommended by the h. Instructions regarding who should witness meter provings manufacturer and only with liquids whose properties were and repairs. considered in the design of the installation. i. Instructions for reporting breaks in any security seals. If a bi-directional turbine meter is used to mea- j. Instructions in the use of all forms and tables necessary to sure flow in both directions, meter factors shall be obtained record the data that support proving reports and meter tickets. for each direction of flow. The meter factors can be deter- k. Instructions for routine maintenance. mined by a prover that has proper manifolding and the 1. Instructions for taking samples (Chapter 8). required protective equipment and flow conditioning located m. Details of the general policy regarding frequency of meter both upstream and downstream of the meter. proving and reproving when changes in flow rate or other variables affect meter accuracy (Chapters 4 and 5). Failure to remove foreign matter upstream of a n. Procedures for operations that are not included in this list turbine meter and its flow-conditioning system may result in but that may be important in an individual installation. meter damage or mismeasurement. Precautions should be taken to prevent the accumulation of foreign material, such as METER PROVING vegetation, fibrous materials, hydrates, and ice, in the turbine meter run. Each turbine meter installation should contain a permanent prover, connections for a permanent prover, or PRECAUTIONS FOR OPERATING NEWLY connections for a portable prover or master meter. The selec- INSTALLED METERS tion of proving methods shall be acceptable to all parties involved (see API MPMS Chapter 4). When a new meter installation is placed in service, particu- larly on newly installed lines, foreign matter can be carried to The optimum frequency of proving depends on the metering mechanism during the initial passage of liquid. so many operating conditions that it is unwise to establish a Protection should be provided from malfunction or damage fixed time or throughput interval for all conditions. In clean caused by foreign matter, such as slag, debris, welding spat- liquid service at substantially uniform rates and temperatures, ter, thread cuttings, and pipe compound. Following are sug- meter factors tend to vary little, necessitating less frequent gested means for protecting the meter from foreign matter: meter proving. More frequent proving is required with liquids that contain abrasive materials, in liquified petroleum (LP) a. Temporarily replace the meter with a spool. gas service where meter wear may be significant, or in any b. Put a temporary bypass around the meter. service where flow rates andíor viscosities vary substantially. c. Remove the metering element. Likewise, frequent changes in the type of product necessitate d. Install a protective device upstream of the meter. more frequent provings. In seasons of rapid ambient tempera- ture change, meter factors vary accordingly, and proving INSTRUCTIONS FOR OPERATING METER should be more frequent. Studying the meter factor control SYSTEMS chart or other historical performance data that include infor- mation on liquid temperature and flow rate will aid determi- Dehite procedures both for operating metering systems nation of the optimum frequency of proving (see and for calculating measured quantities should be lürnished to personnel at meter stations. Following is a list of items that Provings should be frequent (every tender or these procedures should include, along with chapters of the every day) when a meter is initially installed. After frequentCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  18. 18. 10 CHAPTER 5-METERING proving has shown that meter factor values for any given liq- c. Isolation and diversion valves. uid are being reproduced within narrow limits, the frequency d. Detector switches in the prover and appurtenances of the of proving can be reduced if the factors are under control and tank prover. the overall repeatability of measurement is satisfactory to the e. The displacer in the prover. parties involved. f. Other parts of the meter and meter run. g. Pressure-, temperature-, and density-sensing devices. A meter should always be proved after mainte- h. Pulse counters, preamplifiers, signal transmission system, nance. If the maintenance has shifted the meter factor values, power supply, pickup coils, and all readout devices. the period of relatively frequent proving should be repeated to i. Strainers, filters, air eliminators, water removal equip- set up a new data base by which meter performance can be ment, and flow conditioners. monitored. When the values have stabilized, the frequency of proving can again be reduced. j. The operating conditions of the meter system and the prover, when they differ from design conditions. METHODS OF CONTROLLING METER METER MAINTENANCE FACTOR For maintenance purposes, a distinction should Meter factors can be controlled with a suitable be made between parts of the system that can be checked by statistical control method. API MPMS Chapter 13.2 addresses operating personnel (parts such as pressure gauges and mer- meter measurement control methods and other methods of cury thermometers) and more complex components that may analysis that use historical comparison of meter factor data to require the services of technical personnel. Turbine meters monitor meter performance. and associated equipment can normally be expected to per- Meter factor control charts are plots of successive form well for long periods. Indiscriminate adjustment of the meter factor values along the abscissa at the appropriate ordi- more complex parts and disassembly of equipment are nei- x nate value, with parallel abscissae representing f lo, J? f ther necessary nor recommended. The manufacturer’s stan- 20, a n d x f 30, in whichxis the arithmetic mean or average dard maintenance instructions should be followed. meter factor value and 0 is the standard deviation or other tol- Meters stored for a long period shall be kept erance level criterion (for example, f 0.0025 or f 0.0050). A under cover and shall have protection to minimize corrosion. control chart can be maintained for each turbine meter in each product or grade of crude at a specified rate or range of rates Establishing a dehite schedule for meter main- for which the meter is to be used. tenance is difficult, in terms of both time and throughput, because of the many different sizes, services, and liquids Meter factor control methods can be used to pro- measured. Scheduling repair or inspection of a turbine meter vide a warning of measurement trouble and to show when can best be accomplished by monitoring the meter factor his- and to what extent results may have deviated from accepted tory for each product or grade of crude oil (see API MPMS norms. The methods can be used to detect trouble, but they Chapter 13). Small random changes in meter factor will natu- will not d e h e the nature of the trouble. When trouble is rally occur in normal operation, but if the value of these encountered or suspected, the following components of the changes exceeds the established deviation limits, the cause of measurement system should be systematically checked (not the change should be investigated, and any necessary mainte- necessarily in the following order): nance should be provided. Using deviation limits to deter- a. The liquid and its physical properties. mine acceptable normal variation strikes a balance between b. The moving parts and bearing surfaces of the turbine looking for trouble that does not exist and not looking for meter. trouble that does exist.COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  19. 19. APPENDIX A-FLOW-CONDITIONING TECHNOLOGY WITHOUT STRAIGHTENING ELEMENTS A.l Scope Values of the swirl-velocity ratio, K,, for several piping configura- tions are shown in Figures A-1 through A-5. The data were derived Effective flow conditioning can be obtained by using ade- from API MPMSChapter 14.3. quate lengths of straight pipe upstream and downstream of the meter. Appendix A presents an empirical method for com- A.3 Sample Calculation puting the length of upstream straight pipe required for vari- ous installation configurations and operating conditions. A.3.1 PROBLEM Experience has shown that a nominal length of 20 diame- ters of meter-bore piping upstream of the meter and 5 diame- Determine the length of straight pipe run upstream of a 6- ters of meter-bore piping downstream of the meter provide inch turbine meter for each of the conñgurations shown in effective conditioning in many installations; however, the Figures A- 1 through A-5 under the following conditions: required length of upstream piping should be verified for each Q = 2000 gallons per minute installation, using the method presented in this appendix. This technique does not predict the length of straight pipe required Viscosity (v’) = 1.9 centistokes downstream of the meter. A minimum of 5 diameters of 6 meter-bore piping should be provided downstream of the D = - = 0.5 feet 12 meter unless a different length is supported by the manufac- turer’s recommendations or tests. 263.6Q Reynolds number(R,)= ~ Dv’ A.2 Calculation of Upstream Flow- - (263.6)(2000) Conditioning Length (0:5)(1.9) Based on empirical data, the length of straight pipe required upstream of the meter can be calculated as follows: = (5.55)(105) f = 0.0175 L = (0.35D)(KS/f) Note: The value for f is for R, = (5.55)(105) and a relative roughness of 0.0004 for new steel pipe. The value is taken from L.F. Moody, where “Friction Factors for Pipe Flow,” Transactions o the American Soci- f ety of Mechanical Engineers, November 1944, Vol. 66 p. 671. L = length of upstream meter-bore piping, in feet, D = nominal meter bore, in feet, A.3.2 SOLUTION Ks = swirl-velocity ratio, dimensionless, From Equation A- 1 , f = Darcy-Weisbach friction factor, dimensionless. L = (0.35D)(KS/f) Note: During the 1984-86 review and update of !#I MPMS Chap- L/D = (0.35)(Ks/f) ter 5.3, First Edition, it was discovered that the friction, f , in Equa- tion A-l was incorrectly identified as the Fanning pipe friction factor. The working group determined that the factor is actually the = (0.3 5 K J / ( 0.0 175) Darcy-Weisbach friction factor; the group located the original docu- mentation, implemented the correction, and placed it on file at AFT. = 20K, Meter run I’ ‘I Figure A-I-Piping Configuration in Which a Concentric Reducer Precedes the Meter Run (Ks=0.75) 11COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  20. 20. 12 CHAPTER 5-METERING Table A-I-Values for L and L/D for Figures A-I Equation A-1 is the result of grouping many relatively Through A-5 undehable conditions in the flow stream and should there- fore not be considered a rigorous presentation. However, the Figure L L/D (feet) Ratio simplicity of the equation and its ability to provide answers No. Ks (inches) commensurate with experience suggest that it can be used A- 1 0.75 90 7.5 15 reliably. The real value of Equation A- 1 stems from the defi- A-2 1.o0 120 10.0 20 nition of the fundamental relationship of the swirl-condition- A-3 1.25 150 12.5 25 ing characteristics within a length of straight pipe. A-4 2.00 240 20.0 40 A-5 2.50 300 25.0 50 A.5 Laminar Flow (Special Case) Table A-1 lists values for L and L/D in Figures A-1 through Since llf is a function of Reynolds number R,, Equation A-5 based on L/D = 20K,. Since values of K, are treated as rel- A-2 can be written as follows: ative coefficients in AS, the empirical coefficient K, is assigned a value of 1.O0 to agee with the basic recommendation of 20 LID = (Kla,,!)(Rn)(~s) diameters of straight pipe for the average installation. A.4 Conclusions where: The L/D ratio is inversely proportional to the pipe friction factor and directly proportional to the swirl-velocity ratio. K,,,,,=an empirical factor, Since llfis minimum for conditions of maximum pipe V=velocity of the fluid, roughness for any given Reynolds number in the region of p=density of the fluid, turbulent flow, the best straightening for a minimum length of straight pipe occurs with a pipe of maximum roughness. p=absolute viscosity of the fluid. Meter run 4 b - L c" 4 Figure A-2-Piping Configuration in Which a Sweeping Elbow Precedes the Meter Run (K,=l .O) Meter run I I - 1 t I W I Figure A-3-Piping Configuration in Which Two Sweeping Elbows Precede the Meter Run (K,=l .25)COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  21. 21. SECTION 3-MEASUREMENT OF LIQUIDHYDROCARBONS TURBINE BY METERS 13 Therefore, in the special case of lamina flow, L/D is Report No. 65, Potter Aeronautical Corporation, (Union, New Jer- directly proportional to the velocity, pipe dimeter, and mass sey), January 4,1967. Revision A to the report is dated February 16, 1967, and Revision B is dated February 26, 1967. According to the Of the liquid and to dynamic copies of the correspondence with Mr. November that are now on viscosity. file with the API Measurement Coordination Deuartment. manv Note: The material presented in this appendix is based on Factors individuals, as well as a committee, reviewed this method. The Influencing L/D Ratio for Straight Pipe Flow Straighteners Assoei- was published in 2534 (now Out Of Print) and ated n%th Turbine Flowmeters by M. H. November, Engineering in MpMs Chapter 5.3. Meter run I- 4 YE, L - )I cD ’I I t Figure A-4-Piping Configuration in Which Two Sweeping Elbows at Right Angles Precede the Meter Run (Ks= 2.0) Meter run 4 b L 4 Figure A-&Piping Configuration in Which aValve Precedes the Meter Run (Ks= 2.0)COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
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  23. 23. APPENDIX B-SIGNAL GENERATION B.l Introduction driven by the rotor so that a pulsed signal output is devel- oped. Appendix B supplements and clarifies the information on electrical installation requirements. B.2.4 MAGNETIC REED-SWITCH SYSTEM B.2 Generation of Electrical Signals In a magnetic reed-switch system, the contacts of a reed switch are opened and closed by magnets embedded in the The principal types of devices that produce electrical sig- rotor or in a rotating part of the turbine meter. The switch nals and are used with turbine meters are described in B.2.1 action interrupts a constant input so that a pulsed signal out- through B.2.4. put is produced. B.2.1 INDUCTANCE SYSTEM B.3 Summary In an inductance system, the rotating element of the turbine Of the four systems described, only the inductance and meter employs permanent magnets that may be embedded in variable reluctance systems are true generators, since both the hub or the blade tips or attached to the rotor shaft or to a output frequency and voltage magnitude are proportional to ring driven by the rotor. Regardless of the design, magnetic rotor speed. The photoelectric and magnetic reed-switch sys- flux from a moving magnet induces a voltage in a pickup coil tems both require the application of an external constant volt- that is located near the magnetic field. age that is interrupted by the sensing devices so that a nearly pure, square-wave output results. The frequency of the output B.2.2 VARIABLE RELUCTANCE SYSTEM signal is directly proportional to rotor speed; the voltage mag- In a variable reluctance system, a pickup coil is located on nitude varies only between zero, and the input voltage is not the outside of the turbine meter housing such that the rotor related to rotor speed. blade tips or rotor rim passes near the tip of the pickup coil. A The inductance and variable reluctance systems are low permanent magnet, located in the pickup coil, produces a power level devices because they generate only a few milli- magnetic flux that extends into the housing. When rotation watts of electrical power. This output may be locally ampli- occurs, the paramagnetic blades cause a variation in the mag- fied, and in some instances shaped, at the turbine meter. The netic flux that produces a voltage in the pickup coil. A amplifier output may then be considered a high-level output. rimmed rotor utilizes paramagnetic buttons or slots to cause The photoelectric and reed-switch systems are generally the variation in the magnetic flux. high-level devices because the output level is controlled by the input voltage that they require. Ideally, devices that have B.2.3 PHOTOELECTRIC SYSTEM a high power level are less susceptible to noise problems because of the increased signal-to-noise ratio; however, In a photoelectric system, a beam of light is interrupted each system has dehite frequency limitations that must be by the blades of the rotor or by elements of a member that is considered when one system is weighed against the other. 15COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
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  25. 25. APPENDIX C-RECOMMENDED PRACTICE FOR PROVING TURBINE METERS AT MANUFACTURERS’ FACILITIES The API recommended practice for proving turbine meters Repeatability at each point is to be calculated as follows: at manufacturers’ facilities is as follows: The meter must be tested with the current API 5.3 recom- Maximum K factor - Minimum K factor x 100 mendation for upstream, and downstream flow conditioning Minimum K factor or flow conditioning as specified by the customer. Linearity over the specified range is to be calculated as The meter is to be proved at a minimum of 6 points over follows: the manufacturers’ specified range to include the minimum flow rate, the maximum flow rate and 4 equally spaced points Maximum K factor - Minimum K factor x 100 between the minimum and the maximum flow rates. A mini- Mean K factor mum of 2 runs per point is required. The liquid for proving the meter is to be specified by the manufacturer. Note: The results obtained from proving a turbine meter at the man- ufacturer’s facility should be interperted with caution and it should The data must be calculated as follows: not be assumed that they represent the installed performance of the meter in the field. 17COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
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