1、Manual of PetroleumMeasurement StandardsChapter 16Measurement of Hydrocarbon Fluids By Weight or MassSection 2Mass Measurement of Liquid Hydrocarbons in Vertical Cylindrical Storage Tanks By Hydrostatic Tank GaugingFIRST EDITION, NOVEMBER 1994REAFFIRMED, MARCH 2012Manual of PetroleumMeasurement Stan
2、dardsChapter 16Measurement of Hydrocarbon Fluids By Weight or MassSection 2Mass Measurement of Liquid Hydrocarbons in Vertical Cylindrical Storage Tanks By Hydrostatic Tank GaugingMeasurement CoordinationFIRST EDITION, NOVEMBER 1994REAFFIRMED, MARCH 2012SPECIAL NOTES1. API PUBLICATIONS NECESSARILY A
3、DDRESS PROBLEMS OF A GENERALNATURE. WITH RESPECT TO PARTICULAR CIRCUMSTANCES, LOCAL, STATE,AND FEDERAL LAWS AND REGULATIONS SHOULD BE REVIEWED.2. API IS NOT UNDERTAKING TO MEET THE DUTIES OF EMPLOYERS, MANU-FACTURERS, OR SUPPLIERS TO WARN AND PROPERLY TRAIN AND EQUIPTHEIR EMPLOYEES, AND OTHERS EXPOS
4、ED, CONCERNING HEALTH ANDSAFETY RISKS AND PRECAUTIONS, NOR UNDERTAKING THEIR OBLIGATIONSUNDER LOCAL, STATE, OR FEDERAL LAWS.3. INFORMATION CONCERNING SAFETY AND HEALTH RISKS AND PROPERPRECAUTIONS WITH RESPECT TO PARTICULAR MATERIALS AND CONDI-TIONS SHOULD BE OBTAINED FROM THE EMPLOYER, THE MANUFACTU
5、REROR SUPPLIER OF THAT MATERIAL, OR THE MATERIAL SAFETY DATA SHEET.4. NOTHING CONTAINED IN ANY API PUBLICATION IS TO BE CONSTRUED ASGRANTING ANY RIGHT, BY IMPLICATION OR OTHERWISE, FOR THE MANU-FACTURE, SALE, OR USE OF ANY METHOD, APPARATUS, OR PRODUCTCOVERED BY LETTERS PATENT. NEITHER SHOULD ANYTHI
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7、WCYCLE. THIS PUBLICATION WILL NO LONGER BE IN EFFECT FIVE YEARSAFTER 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 THE APIAUTHORING DEPARTMENT TELEPHONE (202) 682-8000. A CATALOG OF APIPU
8、BLICATIONS AND MATERIALS IS PUBLISHED ANNUALLY AND UPDATEDQUARTERLY BY API, 1220 L STREET, N.W., WASHINGTON, D.C. 20005.Copyright 1994 American Petroleum InstituteiiiFOREWORDThis publication covers standard practice for mass measurement of liquid hydrocarbonsin vertical cylindrical storage tanks by
9、hydrostatic tank gauging systems that use pressuresensors with one port open to the atmosphere. This standard is based entirely on ISO 11223-1, Petroleum and liquid petroleum products- Direct static measurements - Contents of vertical storage tanks, Part 1 - Mass measure-ment by hydrostatic tank gau
10、ging. International standard ISO 11223-1 was prepared by theTechnical Committee ISO/TC 28, Petroleum products and lubricants, Subcommittee 3,Static petroleum measurement.Changes have been made to use American spelling and vocabulary, to provide customaryunits in addition to SI units, and to provide
11、API instead of ISO reference publications.Appendices A and B are required.Appendices C and D are for information only.API publications may be used by anyone desiring to do so. Every effort has been madeby the Institute to assure the accuracy and reliability of the data contained in them; however,the
12、 Institute makes no representation, warranty, or guarantee in connection with this publication and hereby expressly disclaims any liability or responsibility for loss or damageresulting from its use or for the violation of any federal, state, or municipal regulation withwhich this publication may co
13、nflict.Suggested revisions are invited and should be submitted to Measurement Coordination,Exploration and Production Department, American Petroleum Institute, 1220 L Street,N.W., Washington, D.C. 20005.vCONTENTSPageSECTION 2MASS MEASUREMENT OF LIQUID HYDROCARBONS IN VERTICAL CYLINDRICAL STORAGE TAN
14、KS BY HYDROSTATIC TANK GAUGING1 Scope 12 Introduction 13 Required Referenced Publications . 14 Definitions15 System Description 26 Installation 47 Maintenance . 78 Safety 9APPENDIX A (required)Calculations Overview . 11APPENDIX B (required)Second Order Influences. 15APPENDIX C (information)Terminolo
15、gy 17APPENDIX D (information)Illustrative Example 19Figures1HTG System Functional Diagram. 3A-1Measurement Parameters and VariablesFixed Roof Tank 12A-2Measurement Parameters and VariablesFloating Roof Tank 12Tables1HTG Stored Parameters 4A-1Units Table for HTG Equations 11A-2Example of Inventory Ac
16、curacies. 141 ScopeThis standard provides guidance on the installation,commissioning, maintenance, validation, and calibration ofhydrostatic tank gauging systems for the direct measurementof static mass in petroleum storage tanks.This standard is applicable to hydrostatic tank gaugingsystems that us
17、e pressure sensors with one port open to theatmosphere.This standard is applicable to the use of hydrostatic tankgauging on vertical cylindrical atmospheric storage tankswith either fixed or floating roofs.This standard is not applicable to the use of hydrostatictank gauging on pressurized tanks.Saf
18、ety and material compatibility precautions should betaken when using HTG equipment. Manufacturers recom-mendations on the use and installation of the equipmentshould be followed. Users should comply with all applicablecodes and regulations, API standards, and the National Elec-tric Code.2 Introducti
19、onHydrostatic tank gauging is a method for the determina-tion of total static mass of liquid petroleum and petroleumproducts in vertical cylindrical storage tanks.HTG uses high precision stable pressure sensors mountedat specific locations on the tank shell.Total static mass is derived from the meas
20、ured pressuresand the tank capacity table. Other variables, such as level,observed and standard volumes, and observed and referencedensities, can be calculated from the product type andtemperature using the established industry standards forinventory calculations.The term mass is used to indicate ma
21、ss in vacuum (truemass).In the petroleum industry, it is not uncommon to useapparent mass (in air) for commercial transactions.3 Required Referenced PublicationsThe following standards contain provisions that, throughreference in the text, constitute provisions in this standard.APIManual of Petroleu
22、m Measurement Standards (MPMS)Chapter 1, VocabularyChapter 2.2A, Calibration of Upright Cylin-drical TanksChapter 2.2B, Calibration of Upright Cylin-drical Tanks Using the Optical ReferenceLine MethodChapter 3.1A, Standard Practice for ManualGauging of Petroleum and Petroleum Prod-ucts in Stationary
23、 TanksChapter 3.1B, Standard Practice for LevelMeasurement of Liquid Hydrocarbons inStationary Tanks by Automatic TankGaugingChapter 7.1, Static Temperature Determina-tion Using Mercury-in-Glass Tank Ther-mometersChapter 7.3, Static Temperature Determina-tion Using Portable Electronic Thermome-tersC
24、hapter 7.4, Static Temperature Determina-tion Using Fixed Automatic Tank Thermome-tersChapter 8.1, Manual Sampling of Petroleumand Petroleum ProductsChapter 9.1, Hydrometer Test Method forDensity, Relative Density (Specific Gravity),or API Gravity of Crude Petroleum andLiquid Petroleum ProductsChapt
25、er 9.2, Pressure Hydrometer TestMethod for Density or Relative DensityChapter 11.1, Volume Correction FactorsChapter 15, Guidelines for Use of theInternational System of Units (SI) in thePetroleum and Allied IndustriesRP 500 Recommended Practice for Classification ofLocations for Electrical Installa
26、tions atPetroleum FacilitiesRP 2001 Protection Against Ignition Arising Out ofStatic, Lightning, and Stray Currents4 DefinitionsFor the purpose of this standard, the following definitionsapply:4.1 ambient air density: The density of air at the tankside on which the pressure sensors are mounted.4.2 a
27、mbient air temperature: The representativetemperature of the ambient air at the tank side on which thehydrostatic tank gauging (HTG) pressure sensors aremounted.Chapter 16Measurement of Hydrocarbon Fluids by Weight or MassSECTION 2MASS MEASUREMENT OF LIQUID HYDROCARBONS IN VERTICALCYLINDRICAL STORAG
28、E TANKS BY HYDROSTATIC TANK GAUGING12CHAPTER 16MEASUREMENT OF HYDROCARBON FLUIDS BY WEIGHT OR MASS4.3 critical zone height: The upper limit of the criticalzone; the level at which one or more of the floating roof orfloating cover legs first touch the tank bottom.4.4 critical zone: The level range th
29、rough which thefloating roof or floating cover is partially supported by its legs.4.5 floating roof mass: The manually entered value ofthe floating roof mass inclusive of any mass load on the roof.4.6 free water level: The level of any water and sedimentthat exist as separate phases from the product
30、 and lie beneaththe product.4.7 gauge pressure sensor: A sensor that uses theambient atmospheric air pressure as the pressure reference.4.8 head mass: The total measured mass between theHTG bottom sensor and the top of the tank.4.9 head space: The space inside the tank, above thebottom HTG sensor. P
31、roduct and in-tank vapor are present inthe head space.4.10 heel space: The space inside the tank, below thebottom HTG sensor.4.11 HTG reference point: A stable reference point fromwhich the HTG sensor positions are measured.4.12 hydrostatic tank gauging: A method of directmeasurement of liquid mass
32、in a storage tank based onmeasuring static pressures caused by the liquid head abovethe pressure sensor.4.13 innage volume: The observed volume of product,sediment, and water calculated from the innage level and thetank capacity table.4.14 in-tank vapor density: The density of the gas orvapor (mixtu
33、re) in the ullage space at the observed condi-tions (product temperature and pressure).4.15 pin height: The lower limit of the critical zone; thelevel at which the floating roof or floating cover rests fullyon its legs.4.16 pressure sensor effective center: The point onthe sensor from which the hydr
34、ostatic pressure head ismeasured.4.17 product heel mass: The mass of product below thebottom HTG sensor.4.18 product heel volume: The observed volume ofproduct below the bottom HTG sensor, calculated bysubtracting the water volume from the total heel volume.4.19 product mass: The sum of the head mas
35、s and theproduct heel mass reduced by the floating roof mass (ifapplicable) and the vapor mass.4.20 product temperature: The temperature of the tankliquid in the region where the HTG measurements areperformed.4.21 reference density: The density at the referencetemperature.4.22 reference temperature:
36、 The temperature to whichreference density and standard volumes are referred.4.23 tank average cross sectional area: The averagecross sectional area between the elevation of the bottomHTG sensor and the innage level over which the hydrostaticpressures are integrated in order to obtain the mass.4.24
37、tank lip: The tank bottom plate on the outside of thetank shell.4.25 total heel volume: The observed volume below thebottom HTG sensor, calculated from the bottom sensorelevation and the tank capacity table corrected for observedtemperature.4.26 ullage pressure: The absolute pressure of the gas(air
38、or vapor) inside the tank, above the product.4.27 ullage volume: The observed volume of thevapor/air mixture in the ullage space, calculated as the differ-ence between the total tank volume and the innage volume.4.28 vapor relative density: The ratio of molecularmass of vapor (mixture) to that of ai
39、r (mixture).4.29 water volume: The observed volume of free sedi-ment and water, calculated from the free water level and thetank capacity table.5 System Description5.1 GENERALAn HTG system is a tank inventory static mass measuringsystem. It uses pressure and temperature inputs and theparameters of t
40、he tank and of the stored liquid to computethe mass of the tank contents and other variables asdescribed in Table A-1. See Figure 1.5.2 SENSORS5.2.1 Pressure SensorsThe HTG system consists of up to three pressure sensorsmounted on the tank shell. Additionally, temperature sensorscan be included to m
41、easure the temperature of the tankcontents (T) and of the ambient air (Ta). An ambient air pres-sure sensor (Pa) may be installed for high accuracy measure-ments.Sensor P1 is installed at or near the tank bottom.Sensor P2 is the middle pressure sensor and is requiredfor the calculation of density an
42、d levels. If the productdensity is known, the HTG can operate without P2. In theabsence of P2, the density should be manually entered.Sensor P2, if installed, should be at a fixed vertical distanceabove sensor P1.SECTION 2MASS MEASUREMENT OF LIQUID HYDROCARBONS IN VERTICAL CYLINDRICAL STORAGE TANKS
43、3Sensor P3 is the tank ullage space pressure sensor. P3 isnot required on floating roof tanks. If the tank is freelyvented, the HTG can operate without P3. P3 is normallyinstalled on the tank roof.5.2.2 Temperature SensorsThe following are the reasons for measuring the producttemperature:a. Calculat
44、ion of the volumetric expansion of the tank shell.b. Calculation of the reference density from observed density(used in HTG systems that calculate level and density as wellas mass).If the reference density is known and P2 is not used, thetemperature sensor may still be required for the observeddensi
45、ty calculations.The following are the reasons for measuring ambienttemperature:a. Calculation of ambient air density.b. Calculation of the volumetric expansion of the tank shell.c. Correction for thermal expansion of the P1 and P1P2 tie-bars.5.2.3 System ConfigurationThe configurations vary dependin
46、g on the application.Some of the more common variations are as follows:a. Known liquid density: P2 is normally used for the tankliquid density measurement. It is not required if the averageliquid density is known.b. Known ullage pressure: P3 is not required for thosetanks that are vented to atmosphe
47、re (ullage gauge pressureequals zero). This includes all floating roof tanks and allfixed roof tanks that are freely vented or that have gauginghatches that are not sealed. Note that tank ullage pressure onatmospheric fixed roof tanks may differ slightly from atmo-spheric pressure during transfers t
48、o and from the tank. Sinceinventory measurements are not taken during a transfer,errors due to this effect are not significant. If the ullage pres-sure is known, P3 can be entered as a constant and the P3sensor omitted on non-vented tanks.c. Known tank liquid temperature: Tank liquid andambient temp
49、eratures are used to correct the shell thermalexpansion. The tank liquid temperature sensor is not required636363636363638750548863 63874677734763 635572 6364636364 63517663647663 63864788646463 63638639647263 637864 636364 63636464646463 636363636364 636364 636364 636364 636364 636364 636364 636364 636364 636364 636364 63646463636464646464646464646464101646464646464646464646463636464646464646464646464101646464646464646464646463636464646464646464646464101646464646463 636364 63647263 6463 636364 6364 6463 636364 6364 6463 636364 6364 6463
