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  • 1. Manual of Petroleum Measurement Standards Chapter 6-Metering Assemblies Section 1-Lease Automatic Custody Transfer (LACT) Systems SECOND EDITION, MAY 1991 American Petroleum Institute 1220 L Street, Northwest Washington, D.C. 20005 1’ 1COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 2. A P I M P M S * b - L 91 W 0732290 0076202 2 m Manual of Petroleum Measurement Standards Chapter 6-Metering Assemblies Section I-Lease Automatic Custody Transfer (LACT) Systems Measurement Coordination Department SECOND EDITION, MAY 1991 American Petroleum InstituteCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 3. A P I MPMS*beL 91 m 0732290 0096203 4 m SPECIAL 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. APIISNOTUNDERTAKING TOMEETTHE 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 UNDERTAKINGTHEIR OBLIGA- TIONS UNDER LOCAL,STATE, OR FEDERAL LAWS. 3. INFORMATION CONCERNING SAFETY AND HEALTH RISKS AND PROPER PRECAUTIONS WITH RESPECT TO PARTICULAR MATERIALS AND CONDI- TIONS SHOULD BE OBTAINED FROMTHE EMPLOYER, THE MANUFACTURER OR SUPPLIER OF THAT MATERIAL, OR THE MATERIAL SAFETY DATA SHEET. 4. NOTHING CONTAINEDIN ANY APIPUBLICATIONIS TO BE CONSTRUEDAS GRANTINGANYRIGHT,BYIMPLICATION OROTHERWISE,FORTHE MANUFACTURE, SALE, OR USE OF ANY METHOD, APPARATUS, OR PRODUCT COVERED BY LETTERS PATENT. NEITHER SHOULD ANYTHING CONTAINED IN THE PUBLICATION BE CONSTRUED AS INSURING ANYONE AGAINST LIABILITY FOR INFRINGEMENT OF LETTERS PATENT. 5. GENERALLY, API STANDARDS ARE REVIEWED AND REVISED, R E M - FIRMED, OR WITHDRAWN AT LEAST EVERY FIVE YEARS.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 AS AN OPERATIVE API STANDARDFIVE YEARS AFTER ITS PUBLICATION DATE OR, WHERE AN EXTENSION HAS BEEN GRANTED, UPON REPUBLICATION. THE STATUS OF THEPUBLICATIONCANBE ASCERTAINED FROM THE API AUTHORING DEPARTMENT (TELEPHONE 202 682-8000). A CATALOG OF API PUBLICATIONS AND MATERIALS IS PUBLISHED ANNUALLY AND UPDATED QUARTERLY BYAPI, 1220 L STREET, N.W., WASHINGTON, D.C. 20005. Copyright@ 1991 American Petroleum InstituteCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 4. A P I MPMS*bmL 91 m 0732290 009bZOLI b m FOREWORD This publication covers the design, installation, calibration, and operation of lease automatic custody transfer &ACT) 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 anyfederal, state, or municipal regulation with which this publication may conflict. Suggested revisions are invited 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. iiiCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 5. ............. ............... m m CONTENTS Page SECTION 1-LEASE AUTOMATIC CUSTODY TRANSFER (LACT) SYSTEMS 6.1.1 Introduction ...................................................... 1 6.1.1.1 Compliance ................................................... 1 .. 6 1 1.2 Future Developments ........................................... 1 6.1.2 Scope ............................................................ 1 6.1.3 Field of Application ................................................ 1 6.1.4 Referenced Publications ............................................. 1 6.1.5 Requirements for All LACT Systems ................................... 1 . 6.1.5 1 Sampling ..................................................... 2 6.1S.2 Maintaining Allowables ......................................... 2 6.1S . 3 Monitoring Quality ............................................. 3 6.1.6 Displacement and Turbine Meter LACT Systems ......................... 3 6.1.6.1 Installation .................................................... 3 6.1.6.2 Specific Requirements .......................................... 3 6.1.6.3 Facilities and Procedures for Proving Displacement and Turbine Meters ............................................. 3 6.1.6.4 Displacement and Turbine Meter System Operation ...................5 6.1.6.5 Nonmerchantable Oil Interruption ................................. 5 Figure 1-Typical Displacement or Turbine Meter LACT Unit Schematic Diagram ........................................ 4 VCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 6. API M P M S * b - L 91 m 0732290 009b206 T m Chapter 6”Metering Assemblies SECTION I-LEASE AUTOMATIC CUSTODY TRANSFER (LACT) SYSTEMS 6.1 -1 Introduction of the metering function of a LACT unit are considered at length in other parts this manual and are referenced of This publication has been prepared as a guide for the in 6.1.4. design, installation, calibration, and operation of a leaseauto- matic custody transfer (LACT) system. 6.1.3 Field of Application A LACT system is an arrangement of equipment designed for the unattended custody transfer of liquid hydrocarbons The field of application of this publication is the unat- from producing leases to the transporting carrier. The system tended and automatic measurement by meter of hydrocarbon must determine net volume and quality, provide for fail-safe liquids produced in the field and transferred to a pipeline in and tamperproof operation, and meet requirements of ac- either a scheduled or a nonscheduled operation. curacy and dependabilityas agreed to by mutually concerned Note: The information contained in Chapter 6.7 should also be con- parties, such as the producer,the transporter, the royalty sidered when measuring viscous fluids by meter. owner, and federal, state, and municipal regulatory bodies. 6.1.4ReferencedPublications Many of the aspects of the metering function are discussed 6 1.I . COMPLIANCE . I at length in other parts of this manual. Please refer to the Compliancewith the provisions of this standard may result following chapters for more information. in an approach to accuracy or may establish safeguards that API are not necessary under all conditions. When not required, Manual of Petroleum Measurement Standards those portions of this standard not considered applicable may Chapter 4”’Proving Systems” be disregarded with the mutual agreement of all parties con- Chapter5.1, “General Considerations for cerned. The compulsory verb form “shall,” while not neces- Measurement by Meters” sarily binding for all conditions, has beenusedwhen a Chapter 5.2, “Measurement of Liquid deviation from the standard is likely to adversely affect the Hydrocarbons by Displacement Meters” satisfactory operation of a system that is designed for op- Chapter 5.3, “Measurement of Liquid timum operation under typical producing conditions. Hydrocarbons by Turbine Meters” Chapter 6.7, “Metering Viscous Hydrocar- 6 1.I .2 FUTURE DEVELOPMENTS . bons” Although this standard presents the concurrence of the Chapter 7-“Temperature Determination” industry on system requirements for lease automatic custody Chapter 8-“Sampling” transfer, it is not intended in any way to restrict future Chapter 8.2, “Automatic Sampling of developments. Equipment now exists in thedesign or field- Petroleum and Petroleum Products” proving stages that may further improve the art of lease Chapter 9-“Density Determination” automatic custody transfer. The industry encourages such Chapter 10”‘Sediment and Water” developments, and when concerned parties mutually agree Chapter12.2,“CalculationofLiquid to use such systems or components, every effort should be Petroleum Quantities Measured by Turbine made to expedite their use and standardization. or Displacement Meters’’ Spec 11N Specljìcation for Lease Automatic Custody 6.1.2 Scope Transfer (LACT)Equipment This publication describes the metering function of a 6.1.5 Requirements for All LACT LAC“ unit and is intended to complement API Specification Systems 11N,Specification for Lease Automatic Custody Transfer (LACT) Equipment. LACT equipment includes a meter The requirements for all LACT systems are as follows: (either displacementor turbine),a proving system (either a. When hydrocarbon liquids are measured and trans- fixed or portable), devices for determining temperature ferred, the fluid should be stable to permit subsequent and pressure and for sampling the liquid, and means a storage during transportation without abnormal evapora- of determining nonmerchantable oil. Many of the aspects tion losses. 1COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 7. A P I MPMSa6.L 91 I0732290 0096207 L 2 CHAPTER 6"METERING ASSEMBLIES b. During custody transfer, provisions shall be made for components shall be unlocked or unsealed only after prior determining net standard volume, (See Chapter 12.2.) notice to and consent of the parties concerned. c. Temperature measurements, recordings, or corrections m. System malfunctions shall be anticipated, and applicable to volumetric measurement shall be made in ac- deliveries that could occur during such periods shall be cordance with Chapter 7. estimated. This requirement may be metby independent d. Temperature and pressure measurements (either recorded gross fluid delivery-recording systems, that is, by using or indicated) shall be taken, and corrections applicable to a dual-head meter and temperature recorder, by using a volumetricmeasurements shall be made in accordance with meter in series, or by recording temperature or pressure Chapter 12.2. The method of performing temperature com- or otherinstrumentsthatindicateperiods of flow. In pensationis a matter of negotiationbutshouldbe installationswheresuchapparatusisnotused,prior accomplished by use of volume-weighted temperature- agreement should be established for calculating or es- averaging devices or temperature compensators for op- timating procedures that will be followed in instances of timum accuracy. measurement system malfunction. e. A representativesample of transferred oil for determining n. Sediment and water content and density (API gravity) density (API gravity), sediment and water content, and any measurements shall be made from composite samples ob- other physical properties required shall be obtained. (See tained byautomatic samplers of acceptable design. Samplers Chapter 8, Chapter 9, and Chapter 10.) shall be installed in accordance with Chapter 8.2. f. The merchantability of hydrocarbon liquids should be established when they are transferred; that is, when the liquids are within a specified density (API gravity) range, 6.1.5.1 SAMPLING do not contain more than a specified sediment and water In most cases, accounting for a crude oil run is determined percentage, are at an acceptable temperature, and are of on the basis of net standard volume, which includes correc- an acceptable Reid vaporpressure.Ameansshall be tions for meter factor, temperature, pressure, and sediment provided to stop the flow oil to the carriers system and of and water content. Therefore, the composite sample accumu- to the sampling system if the oil becomes unmerchant- lated in a run period and any portion used for the determina- able. tion ofdensity (API gravity) and sediment and water content g. A means shouldbe provided to control flow rates, periods must represent all crude oil delivered during that run period. of flow, and net quantities of oil delivered into the carriers When density (API gravity) and sediment and water content system. are based ona sample from the composite sample of the run, h. A means shall be provided to stop the flow of oil into the the procedures used must ensure that this secondary sample carriers system at or before completion of delivery of the leases assigned allowable capacity. is representative of the composite sample. (See Chapter 8 for additional details.) The sampling should be proportioned to i. The control and recording system shall include fail-safe the flow rate through the meter. componentsto prevent mismeasurementor hazardousoperat- ing conditions in the event of a power or system functional failure of any of the systems components required for the 6.1.5.2 MAINTAININGALLOWABLES LACT. j. All components of the system that require periodic When regulatory agencies apply production allowables, calibration and/or inspection should be accessible for runs from the LACT system shall conform to but shall not inspection by all parties involved in the custody transfer exceed these allowances. Automatic means shall be used to transaction. Adjustment, repair, or replacement will be accomplish this requirement. The system must be fail-safe, performed by those responsible for the operation of the tamperproof, and sealed so that neither the producer nor the system. The designof the system shall providea means carrier can change the arrangement without the consent for readily detecting leakage throughout the system, for andlor knowledge of the other party. example,double-blockandbleed-typevalves,sight System devices must be capable of being pre-set and verified drains, or pressure instruments. for a predetermined volume that will approach but not exceed k. The piping system shall not have connections or bypasses theleaseallowable.Whenthepredetermined volume has that wouldpermit liquids to be transferred without measure- been reached, the arrangement used must prevent any ment and shall be designed or equipped so that a reverse flow further movementof oil from lease untilit is the manually of liquid through the measuring device cannot occur. reset. The arrangement must be adjustable so that chan- 1. A means shall be provided to lock or seal components that gesinproductionallowablesareaccommodated. affect control or indicate measurement of quantity or quality. Registers and counters should be readily visible so that Unless this requirement has been specifically waived, such oil deliveries can be checked at any time.COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 8. API M P M S * b - L 91 m 0732290 O096208 3 I I-LEASE AUTOMATIC SECTION CUSTODY TRANSFER(LACT) SYSTEMS 3 6.1 5.3 MONITORING QUALITY producer or the carrier may require the installation of a dielectricorcapacitanceinstrument,more commonly Means shall be provided to prevent water-contaminated referred to as a water monitor. This monitor will automat- oil orslugs of water from enteringa carrier’s system.The ically stop or divert flow before liquid is delivered to the parties shall agree on the maximum permissible sediment meter when the carrier’s specifications are not met. The water and water content of the crude oil. One such satisfactory monitor shall be located upstream from the meter and shall automatic device which detects wateris an instrument that be in operation at all times during delivery. The carrier shall measures capacitance (dielectric constant of theliquid specify the maximum water setting of the instrument. stream). This device shouldbe installed in a vertical riser Meters shall be operated within the manufacturer’srecom- in the piping before themeter and should be used to actuate mended flow rates and at a rate as near as possible to the rate controls so that water-contaminated oil is not deliveredto at the time of the meter proving when the meter factor was the pipeline. A time-delay element may be incorporated obtained. A back-pressure control valve is necessary to main- into the monitor system. tain a constantflow rate and pressureindependent of downstream conditions. Meters shall not be subjected to 6.1.6 Displacement and Turbine Meter pressure pulsations, flow rate surges and shall not be sub- LACT Systems jected to shock pressures caused by quick-closing valves. Practical methods for obtaining accurate measurements of When temperature compensators with density selectors are lease oil runs, using either a displacement or a turbine meter, used, they shall be adjusted for the density (API gravity) of with equipment arranged to meet the requirements defined in the metered liquids. When temperature variations result in this chapter are outlined in 6.1.6.1 through 6.1.6.5.(See mismeasurement, temperature stabilization and monitoring Chapters 5.1,5.2, and 5.3 for details on meter selection.) may be required. The carrier may require that a pressure surge and/or suction tank be installed upstream from the LACT system to ensure that fluid-packed line conditions lead to the 6.1.6.1 INSTALLATION meterandtoprotectthe meter from flow rate surges. LACT systems that use meters shall be designed in accord- “Weathering” the crude oil, expansion chambers, and other ance with applicable industry codes or standards. Each item such requirements may be required by the carrier to prevent essential to quantity and quality control shall be located so unstable metering conditions. that it will consistently perform its function. When system pressure requires the use of the oil compres- Figure 1is a schematic flow diagram showing the principal sibility factor and pressure may not remain constant, flow componentsof a meter-equippedL A U unit. All items shown weighted pressure-averaging devices or pressure recorders may be used in an installation, but if certain components are may be required. (See Chapter 12.2 for computing Cpl.) not required for the integrity of quantity and quality control, When required by operating conditions that change suffi- they maybe omitted. ciently to alter the meter factor beyond acceptable limits, such as temperature variations the associated viscosity and 6.1.6.2 SPECIFICREQUIREMENTS changes, the oil temperature shall maintained reasonab- be ly constant and shall be approximately the same as the The design and function of a LACT system are matters of proving temperature. negotiation. These negotiations determine which of the re- quirements are applicable. However, when the quantity or 6.1.6.3 FACILITIES AND PROCEDURES FOR quality measurement or control depends on compliance with PROVING DISPLACEMENT AND the requirement, the specific conditions detailed in 6.1.1.1 TURBINE METERS shall apply. LACT systems that use meters shall maintain fluid pres- Proving procedures for each LACT location should be sure throughout the measurement system in excess of the agreed to by the parties concerned. (See Chapter 4 ) Copies . product bubble-point pressure by an amount sufficient to of the agreement should be furnished to both the operating prevent the formation of vapor. If vapor is introduced into the personnel and proving personnel. Such procedures should measurement system, the measurement will be inaccurate. include: When vapor removers are specified, they shall be sized for a. A step-by-step method to befollowed at the location. releasing vapor to the atmosphere or to a suitable vapor b. A procedure for checking valves for leakage before and recovery system at rates equal to or greater than the normal during the proving operation. flow rates of the liquid. Vapor outlet lines from removers shall c. A preliminary inspection or operation of the proving comply with safety standards. When the design of storage equipment. facilities ensures fluid-packed line conditions leading to the d. The locations and specifications of seals to be inspected meter, vapor removers may not be required. Either the at time of proving.COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 9. ~~ API MPMS8b.L 91 m 0732290 009b209 5 m 4 &METERING CHAPTER ASSEMBLIES to Delivew Prover system I To wet oil storage or I dehydration I facility 1. Chargingpump and motor 10. Back-pressurevalve 2. Sampler Note:Locatethe back-pressure valveupstream of 3. Samplecontainer and circulationpump the prover loop for tank provers. 4. Strainer 11. Power panel a. Integral aidgas eliminator(optlonal) 12. Control equlpment (for example, watermonitor, b.Separatealr/gaseliminator(optional) allowablecounter, and shufdown system) 5. Watermonitor probe 13. Recirculation (optional) pump Note:Themonitorchassis may be mounted 14. Checkvalve withtheelectrical córitrol system 15. Double-block and bleed-valve ordirectly on themonitorprobe. 16. Pressuremeasurement device 6. Divertervalve 17. Temperature measurement device 7. Wet oil back-pressurevalve(optional) 18. Level control-start 8. Custodytransfermeter and accessories 19. Level control-stop 9. Block valve 20. Low level control (optional) LACT units but is not in- Note: This simplified diagram indicates primary components necessary typical for tended to indicate preferred locations. Figure I-Typical Displacement or Turbine Meter LACT Unit Schematic DiagramCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 10. API M P M S * b * L 7 1 m 0732270 009b2LO L m i-LEASE AUTOMATIC SECTION CUSTODY (LACT) SYSTEMS TRANSFER 5 e. The notification and witnessing required when seals are 6.1.6.4.1 Case A-Normal Delivery to a Gravity broken for maintenance purposes. Flow Pipeline in Nonscheduled f. Thelocation, type, scale division, and methodsforreading Operation the thermometers used in the proving process. a. When the liquid level in the delivery tank reaches the g. The location, type, scale division, and methods of reading normal high working level, the charge pump starts and the pressure instruments used in proving. control valve opens to the pipeline, admitting flow through h. The specifications of a proving run, such as: the meter. l . The number of times the prover tank should be filled. b. When the valve reaches its open-to-pipeline position, the 2, Specifying the number ofruns for a pipe prover. automatic sampler begins sampling as soon as themeter starts 3. Defining a minimum time and/or volume if the turning. master-meter method is used. c. Under normal conditions, delivery to the pipeline con- i. The repeatability criteria for runs to be usedand the tinues until the liquid level reaches the normal low-level number of runs to beaveraged to obtain a new meter factor. position. j. The normal period between required meter provings. The d. The back-pressure valve then closes the pipeline outlet, period between provings may be established either on a the charge pump stops, and the automatic sampler stops throughput or on an elapsed-time basis. This period may be sampling when the meter stops turning. amended based on individual location meter performance records. 6.1.6.4.2 Case B-Normal Delivery to a Pres- k. The normal date and time of provings or thenotice to be surized Pipeline in Nonscheduled given to witnessing parties when a proving schedule is estab- Operation lished. 1. The witnessing required for provings. a. When the liquid level in the delivery tank reaches the m. The standard of consistency desired between meter fac- normal high working level, the charge pump starts and the tors obtained from consecutive provings. control valve opens to the pipeline, admitting flow through n, The procedure to be followed when the desired consisten- the meter. cy is not obtained, either in the results of consecutive runs b. When the valve reaches its open-to-pipeline position, the during an attemptedproving or in meter factors obtained from pipeline shipping pump starts and the automatic sampler consecutive provings. begins sampling as soon as the meter starts turning. o. The frequency of inspection or the frequency and method c. Under normal conditions, delivery to the pipeline con- of recalibrationor calibration verification of the basic proving tinues until the liquid level reaches the normal low-level device. position. p. The content for the forms to beused record meter-prov- to d. The charge pump stops, the back-pressure valve closes the ing data, complete with sample calculations and references to pipeline outlet, and the pipeline shipping pump is shut down. tables used for correction factors and conversions. 6.1.6.4.3 Case C-Normal Delivery to a Pipeline The proving record for each meter shall be kept on f i e for in Scheduled Operation at least the same period as the meter tickets to which it applies or fora period mutually agreed to by the parties concerned. Somepipelinesystemsareoperatedon a schedule At least one copy of each official proving record should be whereby it is desirable to admit oil only during a certain supplied to each party concerned. interval. For this arrangement, the operation sequence shall be the same as for nonscheduled delivery (6.1.6.4.1 and 6.1.6.4 DISPLACEMENT AND TURBINE METER 6.1.6.4.2) except that a time-intervalcontroller shall be added SYSTEM OPERATION to the circuit that overrides the normal high working level control. The operation of a meter system will vary depending on the characteristics of the liquid, the design of the installation, 6.1.6.5NONMERCHANTABLEOILINTERRUPTION the type of pipeline facility connection, and the operating schedule of the pipeline. To be successful, a system must In each of the three cases, the following procedures shall satisfy the requirements of the producer and the carrier. be followed: Before an installation is completed, operating sequences a. After delivery to the pipeline has begun, if nonmerchant- should be checked to ensure that the requirements of a l l able oil flows continuouslypast the watermonitor for a interested parties have been met. The following cases are predetermined time interval, the charge pump is automat- typical, and the items to be checked are suggested as guides ically stopped unless the pump is required to circulate oil for for system studies. treatment.COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 11. API MPMS*b.L 91 m 0732290 0096233 3 m 6 ASSEMBLIES &METERING CHAPTER b. The valve closes, stopping flow to the pipeline. d. The controls lock out the transfer of oil to the pipeline until c. The automatic sampler remains energized in of inad- the nonmerchantable oil has been treated to meet specifica- vertent flow throughthe meter. tions. The LACT unit can be designed to restart automatically after a period of recirculation.COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 12. Order No. 852-30121COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 13. A P I MPMS*b.L 91 m 0 7 3 2 2 9 0 0096213 7 m American Petroleum Institute 1220 L Street, NorthwestCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services