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  • 1. API MPMS*b-5 93 m 0732290 O096234 9 m Manual of Petroleum Measurement Standards Chapter 6-Metering Assemblies Section 5-Metering Systems for Loading and Unloading MarineBulk Carriers SECOND EDITION, MAY 1991 American Petroleum Institute 1220 L Street, Northwest Washington, D.C. 20005 41’COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 2. API MPMS*b-5 71 m 0732290 009b2115 O 1 m Manual of Petroleum Measurement Standards Chapter 6-Metering Assemblies Section 5-Metering Systems for Loading and Unloading MarineBulk Carriers Measurement Coordination Department SECOND EDITION, MAY 1991 American Petroleum InstituteCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 3. A P I MPMS*b.S 91 H 0732290 O096236 2 H SPECIAL NOTES 1. API PUBLICATIONS NECESSARILY ADDRESS PROBLEMS OF A GENERAL NATURE. WITH RESPECT TO PARTICULAR CIRCUMSTANCES,LOCAL, STATE, AND FEDERAL LAWS ANDREGULATIONS 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 UNDERTAKING THEIR OBLIGA- TIONS UNDER LOCAL, STATE, OR FEDERAL, LAWS. 3. INFORMATION CONCERNING SAFETY AND HEALTH RISKS AND PROPER PRECAUTIONSWITH RESPECT TO PARTICULAR MATERIALS ANDCONDI- TIONS SHOULD BE OBTAINED FROM THE EMPLOYER, THE MANUFACTURER OR SUPPLIER OF THAT MATERIAL, OR THE MATERIAL SAFETY DATA SHEET. 4. NOTHING CONTAINEDIN ANY API PUBLICATIONIS TOBE CONSTRUED AS GRANTING ANYRIGHT,BYIMPLICATIONOROTHERWISE,FORTHE MANUFACTURE, SALE, OR USE OF ANY METHOD, APPARATUS, OR PRODUCT COVERED BY LETTERS PATENT. NEITHER SHOULD ANYTHING CONTAINED INTHE PUBLICATION BE CONSTRUED AS INSURING ANYONE AGAINST LIABILITY FOR INFRINGEMENTOF LEmERS PATENT. 5. GENERALLY, API STANDARDS ARE REVIEWED AND REVISED, REAF- FIRMED, OR WITHDRAWN AT LEAST EVERY FIVE YEARS.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 STANDARD FIVE YEARS AFTER ITS PUBLICATION DATE OR, WHERE AN EXTENSION HAS BEEN GRANTED, UPON REPUBLICATION. THE STATUS OF THEPUBLICATIONCANBEASCERTAINEDFROM THE API AUTHORING DEPARTMENT (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. Copyright@ 1991 American Petroleum InstituteCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 4. ~____ A P I MPMS*b-5 73 m 0732290 O076237 4 m FOREWORD This publication deals with the operation and special arrangements of meters, provers, manifolding, instruments, and accessory equipment used for measurement during loading and unloading of marine bulk carriers. 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 thispublication 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. API MPMS*b-5 91 W 0732290 0096218 b CONTENTS Page SECTION 5”ETERIJVG SYSTEMS FOR LOADING AND UNLOADING MARINE BULK CARRIERS 6.5.1 Introduction ....................................................... 1 6.5.2 Scope and Field of Application ...................................... -1 6.5.3Referenced Publications ............................................. 1 6.5.4 Meter Facility Design ............................................... 1 6.5.5 Equipment Selection ............................................... 1 6.5.5.1 TypeofMeter ................................................ 1 6.5.5.2Meter Sizing .................................................. 4 6.5.5.3 MeterProver ................................................. 4 6.5.5.4 Strainers ..................................................... 4 6.5.5.5AirIGas Eliminators ........................................... -4 6.5.5.6 Flow Control and Back-Pressure .................................. 4 6.5.5.7Valves ....................................................... 4 6.5.5.8 Instrumentation ............................................... 4 6.5.5.9 Sampler ..................................................... 5 6.5.6 Transfer of Liquid Hydrocarbons toand from Marine Bulk Carriers ..........5 6.5.6.1 GeneralOperatingConditions .................................... 5 6.5.6.2 Loading ..................................................... 5 6.5.6.3Unloading .................................................... 5 6.5.7 PreventiveMaintenance ............................................. 5 6.5.7.1 Meters ....................................................... 5 6.5.7.2 MeterAccessories ............................................. 5 6.5.7.3 Prover ....................................................... 5 6.5.7.4 Valves ....................................................... 5 6.5.7.5 ReadoutPrintoutEquipment ..................................... 6 6.5.7.6Meter Records ................................................ 6 6.5.7.7 Personnel Qualifications ........................................ 6 6.5.7.8 Lubrication ................................................... 6 6.5.7.9 Strainer Screens and Filters ...................................... 6 Figures 1“Schematic Arrangement of a Loading Marine BulkCarrier Meter Station With Three Meters a Prover ............................ and 2 2Schematic Arrangement ofan Unloading Marine Bulk Carrier Meter Station With Three Meters aProver ............................ and 3 VCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 6. API MPMSUb.5 91 m 0732290 009b219 B m Chapter 6-Metering Assemblies SECTION 5-METERING SYSTEMS FOR LOADING AND UNLOADING MARINE BULK CARRIERS 6.5.1 Introduction Chapter 12-“Calculation of Petroleum Quantities” This section describes equipment and provides operational guidelines for metering crude oil and other liquid hydrocar- 6.5.4 Meter Facility Design bons in the loading and unloading of marine bulk carriers. Metering offers several advantages over tank gauging, in- This discussion is limited to marine bulk carrier loading cludingminimumvesselturnaroundtime,increased and unloading meter station design. Chapters 5.2 and 5.3 reliability and accuracy, traceable field standards (provers), should be consulted for design requirements common to all automated printing of tickets, and safety. metering systems. Metering stations are usually dedicated to either loading 6.5.2 Scope and Field of Application or unloading and are frequently used for custody transfer accounting. To expedite the efficient transfer of fluid from This publication deals with the operation and special ar- tankage to carrier or vice versa, the meter, or aremote readout, rangements of meters, provers, manifolding, instrumentation, should be located near the docking facility to facilitate and accessory equipment used to measure the loading and monitoring by the ship’s personnel. unloading of marine bulk carriers. Pressure surges that may develop in lines between tankage The information provided this publication is applicableto in and the carrier can have a detrimentaleffect on any equipment shore-to-carrierand carrier-to-shore measurement of crude oils that is hydraulically associated with the line. To avoid abnor- and refined products. These procedures are not intended tomal pressure surges during normal operation of the system, apply to hydrocarbons that require specialized measurement and han- factors such as fluid velocity, density, line length, and valve dling equipment, such liquefied natural (LNG). as gas closure time must be considered when the system is designed. Applicable carriers may range from river barges to ocean- Other factors that may have an adverse effect on accurate going ultralarge crude carriers (ULCCs). Measuring equip- fluid measurementinclude product contamination and air/gas mentwill,accordingly,rangefromsmallmetering entrapment in portions of the lines or manifolds. installations that use bare essentials to very large, sophisti- Figure 1 illustrates a typical metering facility for carrier cated metering installations that incorporate optimal equip- loading. Figure 2 shows an unloading arrangement. ment that speed operations and ensure optimum measurement accuracy in vessels that handle large volumes. 6.5.5 EquipmentSelection 6.5.3 ReferencedPublications 6.5.5.1 TYPE OF METER Thispublication refers only to displacement meters Many aspects of the metering function are discussed at described in Chapter 5.2 and turbine meters described in length in other parts of this manual. Please refer to the Chapter 5.3. However, any type of meter meeting the require- following chapters for more information. ments of repeatability and accuracy over the required flow API range may be considered. Meter repeatability and linearity Manual of Petroleum Measurement Standards tolerances depend on the fluids being handled and the equip- Chapter 4”‘Proving Systems” ment agreed on by custody transfer parties. Chapter 5.1, “General Considerations for Factors to be considered when selecting meters for a Measurement by Meters” facility include (see Chapter 5.1): Chapter 5.2, “Measurement of Liquid a. Fluid properties (for example, viscosity and relative den- Hydrocarbons by Displacement Meters” sity). Chapter 5.3, “Measurement of Liquid b. Maximum and minimum flow rates. Hydrocarbons by Turbine Meters” c. Repeatability and linearity requirements. Chapter 5.4, “Accessory Equipment for Liq- d. Fluid temperature expected. uid Meters” e. Maximum working pressure. Chapter 8.2, “AutomaticSampling of f. Meter-driven accessories. Petroleum and Petroleum Products” g. Provisions for meter and prover system maintenance. 1COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 7. A P I MPMSwb.5 91 m 0732290 009b220 4 m 2 CHAPTER 6-METERING ASSEMBLIES l. Pressure-reducingvalve 1 . Loadingarm 3 2. Aidgasseparator(ifrequired) 14. Remotemeterreadout 3. Air/gasrelease (if required) 1 . Sampler(automatic)proportionalto 5 flow 4. Throttlevalve,air/gassensed (if required) 1 . Watermonitor (if required) 6 5 Isolationvalve . 1 . Thermowell (TW) 7 6. Strainer 7 Meter . 8. Pressuremeasurementdevice 9. Temperaturemeasurementdevice 10. Flow controlvalve 11. Double-blockandbleed-valves 12. Prover Note: This simplified diagram indicates but primary components for typical stations is notintended to indicate preferred locations. Figure I-Schematic Arrangement o a Loading Marine Bulk Carrier Meter f a Station With Three Meters andProverCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 8. API MPMS*b-5 91 m 0732290 009b221 b m SECTION 5"METERING SYSTEMS FOR LOADING UNLOADING MARINE CARRIERS AND BULK 3 u 8 6 """ " J " " "" Q 2 -I I 13 I I I 16 - 1. Unloadingarm 13. Temperaturemeasurementdevice 2. Remotemeterreadout 14. Flowcontrolvalve 3 Checkvalve . 15. Double-blockandbleed-vaives 4. Watermonitor(ifrequired) 16. Prover 5 Sightglass . 17. Sampler(automatic),proportionaltoflow 6 Aidgasseparator . 18. Thermoweil 0 7 Aidgasvent . 8 Throttlevalve,airsenses . 9. Isolationvalve IO. Strainer 11. Meter 12. Pressuremeasurementdevice Note: This simplified diagram indicatesprimary components for typical stations but is not intended fo indicate preferred locations. Figure 2-Schematic Arrangement of an Unloading Marine Bulk Carrier Meter Station With Three Meters and a ProverCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 9. li A P I MPMS*b.5 91 m 0732290 0 0 9 6 2 2 2 B m 4 CHAPTER &METERINGASSEMBLIESI h. Environmentalconditions. facilities discussed above, a start-up screen of fine mesh is i. Space limitations. frequently used in early operation procedures, 6.5.5.2 METERSIZING 6.5.5.5 AIWGASELIMINATORS While it is possible to handle the total throughput of a Aidgas must be removed from the fluid upstream from the facility through only one or two large meters, it is generally meter and meter prover for accurate measurement. Shore-to- preferable to use multiple small meters mounted in parallel. carrier loading does not generally present a severe air problem This arrangement allows for closing-off one or more meters because tankage, manifolds, and lines are normally kept full during low-flow,topping-off,or strippingoperationsto main- of fluid; thus, only low-capacity aidgas elimination equip- tain the desired flow range through each meter. In addition, ment may be required. Carrier unloading presents a different operations are less disrupted when flow is diverted for prov- situation because air is introduced each time load-arm con- ing or the meter is isolated for maintenance. nections are made to the carrier. Air may also be introduced during a vessels stripping operations. 6.5.5.3 METERPROVER Aidgas eliminators at carrier unloading meter installations Because meter performance is subject to change as flow must be large enough so that the rate of flow can be reduced rate changes, as fluid characteristicschange, or as meters age to allow gas-fluid separation. Adequate vent capacity and and wear, a meter factor must be determined. A meter prover control valves must be provided to slow the flow temporarily is essential for determining the meter factor. The meter factor as the liquid in the eliminator drops to a predetermined level, is then multiplied by the indicated volume to give a true The performance of &/gas eliminators is adversely affected volume. by increases in velocity and viscosity. The eliminator vessel Provers may be of the conventional pipe, small-volume, should also be equipped with armored liquid level sight tank, or master-metertype, Conventional pipe provers gauges so that the level can be determined before and after (bidirectional and unidirectional types) are commonly used the unloading operation. for all flow capacities. Tank provers or master meters may be used when volumesare relatively low, when initial cost is a 6.5.5.6 FLOW CONTROL AND BACK-PRESSURE factor, or when operating efficiency and accuracy have a low priority. Unlike conventional pipe provers, small-volume The need for controlling flow through each meter depends provers and master meters, tank provers, because of their on several factors, including the size of the facility, flow filling and emptying operation, cause flow through the meter demand, compartment stripping and topping, and proving. stations to fluctuate during proving. In addition, tank provers Flow should be controlled so that meters are protected against are poorly adapted for use on marine bulk carriers because of excessive speed, operated within the manufacturers recom- the relative slowness of their proving cycles. However, tank mended range, and proved at their normal flow rate. provers are suitable for operations on small vessels, such as Adequate back-pressure must be maintained at all meters barges. When space is limited, a small-volume prover using and meter provers on high-vapor pressure fluids. Flow control pulse interpolation techniques may be considered. and back-pressure can be maintained by local or remote Numerous factors affect prover selection and sizing. Refer manual or automatic valves operated by controllers or control to Chapter 4 for complete information on prover charac- systems. teristics, design criteria, operation, and maintenance. 6.5.5.7 VALVES 6.5.5.4 STRAINERS High-integrity, double-block and bleed-type valves are Strainers are generally installed upstream from all meter- required at all prover and meter isolation points to verify the ing equipment, including proving -connections, to protect valve seal and to prevent leaks. (See Figures 1 and 2.) equipment from foreign debris. Whenstrainers are selected, particle size entrapment,pressure drop, strainer basket access 6.5.5.8 INSTRUMENTATION and removal, and the effect of debris retention on pressure drop must be considered. Pressure gauges are sometimes Instrumentation required at a measurement facility may installed across the strainer to evaluate the condition and vary from relatively simple meter totalizers, with or without performance of the strainer. remote reading pressure gauges and thermometers, to quite When filtration is required to remove finer material, such complex elements used in fully automated facilities that often as iron oxide or other abrasive materials, a separate, large- incorporate current computer technologies. In general, the capacity filtration unit is generally installed adjacent to, but higher level of automation and control is designed to comply not as part of, the meter bank. In addition to the permanent with specific requirements for a particular measurement COPYRIGHT American Petroleum Institute Licensed by Information Handling Services
  • 10. API MPMS*b.5 91 m 0732290 009b223 T m SECTION 5"METERING SYSTEMS FOR AND BULK LOADING UNLOADING MARINE CARRIERS 5 facility. Refer to Chapter 5.4 for information on standardized 6.5.6.2 LOADING meter accessory equipment common throughout the industry. Uniform loading meter flow rate should be maintained by proper management of compartment filling. Periods of low 6.5.5.9 SAMPLER flow should be minimized to the extent practical during For crude oil measurement, automatic, flow-proportional compartment topping off because the meter factor may not be line samplers are recommended as an integral part of the applicable in the low flow range. If meters are mounted in measurement system. The sampler takes a representative parallel, one or more meters can be closed off during the sample of the fluid metered for quantitative and qualitative topping-off operation so that the remaining meter or meters analyses. The sampler should not be located between the may operate at near-normal flow rates. meter and meter prover. (See Figures 1 and 2.) If the meter station is remote from the unloading arm, the sampler should 6.5.6.3 UNLOADING be located at the unloading arm to ensure a representative sample for the marine bulk carrier. Mixing devices may be A uniform discharge flow rate should be maintained used if required. (Refer to Chapter 8, Section 2.) during unloading operations by proper management of com- partment stripping. Low-flow removal rates should be mini- mized to the extent practical during compartment stripping. 6.5.6 Transfer of Liquid Hydrocarbons If meters are mounted in parallel, one ormore meters can be to and from Marine Bulk Carriers closed off during the stripping operation, because the meter factor may not be applicable in the low-flow range. 6.5.6.1GENERALOPERATINGCONDITIONS Smooth meter station operation depends on proper proce- 6.5.7 PreventiveMaintenance dures and the need to exercise reasonable caution. Significant areas of concern to ensure smooth operations are listed below. 6.5.7.1 METERS a. Start-up procedures should be performed at low-flow levels and should be closely monitored. Meter-proving records can be beneficial in a preventive b. Ar should not be introduced into the systems. i maintenance program. Excessive meter factor drift on a given c. If air is inadvertently introduced into the system, it should product indicates abnormal wear. Accurate information will be purged at a point upstream from the meter@). permit maintenance to be scheduled at a convenient time. d. Flow should be maintained within the manufacturers New meter factors must be determined when adjustments are recommended ranges for the equipment selected. made or maintenance is performed on meters. Meter factor e. Stable flow and pressure conditions are necessary for control charts or other meter performance records should be maintained to assist in monitoring meter performance. meter accuracy. f. Provisions shall be made to correct for line-fill between the custody point and the meter location. 6.5.7.2METERACCESSORIES g. Adequate back-pressure should be maintained in the meter installation. Meter accessories, such as automatic temperature com- h. Provisions shall be made to account for hydrocarbon pensators or gravityselectors, temperature, or pressure between the meters and the carrier or, in unloading, between devices associated with measurement, should have periodic the carrier and the meters. performance checks and should be recalibrated as required. , i. Sources of back-up measurement data that could be used in the event of equipment malfunctionor failure of procedures 6.5.7.3 PROVER should be considered. j. Double-block and bleed-valves should be checked at each The meter-prover system should be periodically full operation. recalibrated as required and checked to ensure that all as- k. The integrity of the totalizer and/or the meter gear-train sociated equipment is in good working order and that no should be verified by comparing the totalizer volume with the deficiencies exist that might affect results. prover counter. 6.5.7.4 VALVES For additional information pertaining to the selection, installation, operation, and maintenance of meters see Chap- Double-block and bleed-valves should be maintained ters 5.1,5.2, and 5.3. and/or repaired if evidence of leakage is found.COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 11. , A P I MPMS*b.S 91 m 0732290 009b224 1 m 6 ASSEMBLIES &METERING CHAPTERI 6.5.7.5READOUT/PRINTOUTEQUIPMENT 6.5.7.8 LUBRICATION Meter readout and printout equipment should be perî- All miscellaneous components requiring lubrication for odically inspected, checked, and calibrated to ensure that all proper operation, such as valves, should be periodically lubri- components are operating properly. cated, repacked, or otherwise repaired as appropriate for the specific item. 6.5.7.6 METERRECORDS 6.5.7.9 STRAINER SCREENS AND FILTERS Individual meter records should be maintained to verify that prescribed tests and maintenance have been performed Strainer screens or filters should be cleaned at prescribed periodically and to schedule preventive maintenance. intervals or when pressure differentials become excessive. Any strainer screens or filters showing signs of excessive 615.7.7 PERSONNELQUALIFICATIONS wear, bulges, or apparent deterioration should be replaced with new elements of the proper size for the particular service. All maintenance should be performed with approved Disposable filters should be replaced when they reach their equipment and by authorized, qualified personnel who have maximum recommended differential operating pressure. A been properly trained or otherwise qualified to perform the means should be provided to indicate the pressure differential required tests, adjustments, or repairs. across the strainer. COPYRIGHT American Petroleum Institute Licensed by Information Handling Services
  • 12. A P I MPMS*b-5 91 m 0732290 0096225 3 m Order No. 852-30125COPYRIGHT American Petroleum InstituteLicensed by Information Handling Services
  • 13. API MPMS*h.5 91 E 0732270 0 0 9 b 2 2 h 5 m American PetroleumInstitute 1220 L Street, NorthwestCOPYRIGHT American Petroleum InstituteLicensed by Information Handling Services