Annex A - Examples of Shore Tank and Marine Vessel Tank Calculations

Transcription

1 API Manual of Petroleum Measurement Standards Chapter 12 - Calculation of Petroleum Quantities Section 1 - Calculation of Static Petroleum Quantities Part 1 - Upright Cylindrical Tanks and Marine Vessels Third Edition, xx/xxxx EI HM1 Part 1 Foreword This two-part publication presents standard calculation procedures for static petroleum liquids. The two parts consist of the following: Part 1 - Upright Cylindrical Tanks and Marine Vessels - 10/2001 Part 2 - Calculation Procedure for Tank Cars 5/2003 This standard has been developed through the cooperative efforts of many individuals from industry under the sponsorship of the American Petroleum Institute and the Energy Institute. Suggested revisions to this publication are invited and should be submitted to the Measurement Coordinator, Exp Contents Section 1 - Calculation of Static Petroleum Quantities Part 1 - Upright Cylindrical Tanks and Marine Vessels 0 Introduction 1 Scope 2 References 3 Definitions 3.1 General 3.2 Abbreviations 4 Interrelationship between Chapter 12 and Chapter Hierarchy of Accuracies 6 Rounding and Discrimination 6.1 Data Level 6.2 Rounding of Numbers 6.3 Discrimination 7 Observed Data (Input, Direct, or Primary) 8 Calculated Data (Indirect or Secondary) 9 Calculation of Gross Observed Volume (GOV) 9.1 Shore Tanks Total Observed Volume (TOV) Adjustment for the Presence of Free Water (FW) and Tank Bottom Sediments Correction for the Effect of Temperature on the Steel Shell of the Tank (CTSh) Floating Roof Adjustments and Corrections (FRA) & (FRC) 9.2 Marine Vessel s Tanks Total Observed Volume (TOV) Trim Correction List Correction Combining Trim and List Corrections Free Water Volume (FW) 10 Calculation of Gross Standard Volume (GSV) and Total Calculated Volume (TCV) - Shore Tanks and Marine Vessel s Tanks 10.1 Gross Standard Volume (GSV) 10.2 Correction for the Effect of Temperature on a Liquid (CTPL) or Volume Correction Factor (VCF) 10.3 Total Calculated Volume (TCV)

2 11 Calculation of Net Standard Volume (NSV) 11.1 Calculation of the Correction for Sediment and Water (CSW) 11.2 Calculation of the Volume of Sediment and Water (S&W) 12 Calculation of Mass (Weight in Vacuum) and Weight (Weight in Air) 12.1 Introduction 12.2 Calculation Methods Volume at Standard Temperature to Mass/Weight Volume at Observed Temperature to Mass/Weight Calculation of Gross Standard Weight and Net Standard Weight Calculation of Gross Standard Mass and Net Standard Mass 12.3 Converting Between Mass and Weight 13 Direct Mass Measurement 14 Calculation Sequence 14.1 General 14.2 Volume at Standard Temperature to Mass/Weight Calculation Procedure 14.3 Volume at Observed Temperature to Mass/Weight Calculation Procedure 15 Calculation of Transferred Volumes for Custody Transfer 15.1 General 15.2 Small Lease Tanks Transferred Volume Calculation Procedure for Lease Tanks 15.3 Volumetric Shrinkage 16 Miscellaneous 16.1 Precautions When Using an Automatic Sampler 16.2 Interrelation of Units Annex A - Examples of Shore Tank and Marine Vessel Tank Calculations A1 Custody Transfer Flow Chart Shore Tank(s) with Automatic Sampler A2 Custody Transfer Flow Chart - Shore Tank(s) with Individual Tank Samples A3 Shore Tank Calculation Using Volume At Standard Temperature To Mass/Weight Calculation Procedure A4 Marine Vessel Tank Calculation Using Volume at Standard Temperature To Mass/Weight Calculation Procedure A5 Shore Tank Calculation of Volume at 15ºC and Weight of p-xylene using ASTM D1555M A6 Shore Tank Calculation of Volume at 15ºC, Mass and Weight of MTBE using API MPMS Chapter 11.1/Adjunct to ASTM D1250/Adjunct to IP 200, Table 54C A7 Shore Tank Calculation of the Weight of Benzene Using Density Correction Coefficients Annex B - Example of Shell Temperature Correction Factors for Expansion and contraction of Upright Cylindrical Steel Tanks Due to Temperature B1 Shell Temperature Correction Factors for Expansion and Contraction of Upright Cylindrical Steel Tanks Due to Temperature B2 Application of Shell Temperature Correction Table B-1 - Correction Factors for Effect of Temperature on the Tank Shell Reference Temp 60ºF Table B-2 - C Adjustment Calculations: Methods 1 and 2 C1 Example when roof calculation is calculated into the tank capacity table C2 Example when roof adjustment is not calculated in the tank capacity table Figures 1 -Method to Calculate Vessel s List Using Amidships Draft Readings Tables 1 - Significant Digits

3 2 - Observed Data 3 - Calculated Data 4 - Generalized Crude Oils API Correction to 60ºF 5 - Mass to Weight Density Corrections 6 - Excerpt from API MPMS Chapter 11.1/Adjunct to ASTM D1250/Adjunct to IP 200, Table 5A. B-1 - Correction Factors for Effect of Temperature on the Tank Shell Reference Temp 60ºF B-2 - Correction Factors for Effect of Temperature on the Tank Shell Reference Temp 15ºC B-3 - Linear Therm API Chapter 12 - Calculation of Petroleum Quantities Section 1 - Calculation of Static Petroleum Quantities Part 1 - Upright Cylindrical Tanks and Marine Vessels EI HM1 Part 1 0 Introduction These procedures are intended to encourage a uniform approach to volumetric and mass calculation of crude oil, petroleum products, and petrochemicals when contained in tanks. This publication will also address 1 Scope This standard is intended to guide the user through the steps necessary to calculate static liquid quantities, at atmospheric conditions, in upright, cylindrical tanks and marine tank vessels. The standard defines The standard also specifies equations that allow the values of some correction factors to be computed. Fundame so forth) regardless of whether the information is gathered automatically or manually. This standard does not address the calculation of clingage, non-liquid material, small quantities (such as onboar 2 References The following documents are referenced throughout this standard: API Manual of Petroleum Measurement Standards (MPMS) Chapter 1, Vocabulary Chapter 2, Tank Calibration Chapter 3, Tank Gauging Chapter 7, Temperature Determination Chapter 8, Sampling Chapter 9, Density Determination Chapter 10, Sediment and Water Chapter 11, Physical Properties Data Chapter 15, Guidelines for the Use of International System of Units (SI) in the Petroleum and Allied Industries Chapter 16, Measurement of Hydrocarbon Fluids by Weight or Mass Chapter 17, Marine Measurement Chapter 18, Custody Transfer ASTM1 Adjunct to D1250 Temperature and Pressure Volume Correction Factors for Generalized Crude Oils, Refined Products, and Lubricating Oils D1555 Hydrocarbons and Cyclohexane D4311 Test Method for Calculation of Volume and Weight of Industrial Aromatic Practice for Determining Asphalt Corrections to a Base Temperature 1 American Society for Testing and Materials, 100 Bar Harbor Drive, West Conshohocken, PA 19428, USA. IP2 Adjunct to IP 200 Temperature and Pressure Volume Correction Factors for Generalized Crude Oils, Refined Products, and Lubricating Oils 3 Definitions 3.1 GENERAL The definition of those terms relative to this document can be found in other API or associated documents, as fo General Terms - API MPMS Chapter 1 Marine Terms - API MPMS Chapter 17.1 (17.1.3)

4 Units of Measure and Interrelation API MPMS Chapter 11.5 International System (SI) Units - API MPMS Chapter ABBREVIATIONS AND DEFINITIONS The designation of corrections and correction factors by abbreviations rather than words is recommended to abb coefficient of thermal expansion per degree Cs The amount by which the density of a material changes, per degree, due to a change in temperature correction for sediment and water. CSW Corrects a volume, usually at standard temperature, for the effects of suspended sediment and water correction for the temperature and pressure of the liquid CTPL Corrects a volume at an observed temperature & pressure to an equivalent volume at base temperature and pre API MPMS standards) correction for the temperature of the liquid CTL Compensates for the effect of temperature on a liquid correction for the pressure of the liquid CPL Compensates for the effect of pressure on a liquid. 2 Energy Institute, formerly the Institute of Petroleum, 61 New Cavendish Street, London W1G 7AR, UK correction for temperature of the shell CTSh The correction factor for the effect of the temperature, both ambient and liquid, on the shell of the tank density Mass per unit volume; i.e. the mass of a substance divided by its volume. When reporting density, the unit used or lbs per gallon at 60ºF floating roof adjustment FRA A secondary correction or adjustment for any difference between the reference density and the observed density floating roof correction FRC The correction made to offset the effect of the displacement of the floating roof, when no correction has been bu free water FW The water present in a container that is not suspended in the liquid hydrocarbon. A free water quantity deduction gross observed volume

5 GOV The total volume of all petroleum liquids and sediment and water, excluding free water, at observed temperature gross standard volume GSV The total volume of all petroleum liquids and sediment and water, excluding free water, corrected by the appropri ### gross standard mass GSM The mass of the GSV quantity. ### gross standard weight GSW The weight of the GSV quantity. ### mass The technical description of mass exists in API MPMS Chapter 11.5; however, within this document it refers to weight in vacuum. ### net standard volume NSV The total volume of all petroleum liquids, excluding sediment and water and free water, corrected by the appropr ### net standard mass NSM The mass of the NSV quantity. ### net standard weight NSW The weight of the NSV quantity. ### tank shell reference temperature TShREF The tank shell temperature used to calculate volumes in the preparation of a tank capacity table; frequently 60 F, or 15 C, although other temperatures are used. ### total calculated volume TCV The total volume of all petroleum liquids and sediment and water corrected by the appropriate volume correction ### total observed volume TOV Total measurement volume of all petroleum liquids, sediment and water, free water, and bottom sediments at obs ### temperature of the tank shell TSh Observed temperature of the metal (usually steel) shell of the tank. ###

6 volume correction factor VCF This is the same as CTL and under atmospheric conditions is also the same as CTPL, making these three symb ### weight The technical description of weight exists in API MPMS Chapter 11.5; however, within this document it refers to weight in air. 4 Interrelationship between Chapter 12 and Chapter 11.1 Currently, the Manual of Petroleum Measurement Standards is organized into Chapters covering general measu API MPMS Ch is the primary standard for the determination of the temperature (CTL), pressure (CPL), and API MPMS Ch. 12 is the primary standard for the calculation of volume quantities. It determines the discrimination levels (rounding) required for each input variable and correction factor in a specific volume calcula NOTE: The terms RHOb, APIb, RDb, and Fp, are not used in this document. RHO refers to density, API refers to API Gravity and RD refers to relative density. Subscript b refers to base conditions. The standard or base condition is a defined combination of temperature and pressure at which liquid vo standard and base are used interchangeably. Accepted standard temperatures are 60 F, 15 C and 20 C. Accepted standard pressures are zero gauge pressure (for non-volatile liquids at the standard temperature) or the liquid s vapor pressure at the standard temperature (for volatile liquids). Fp is called the "compressibility coefficient" or "scaled compressibility factor (units of 1/psi)". For additional information on thes 5 Hierarchy of Accuracies A hierarchy of accuracies applies in petroleum measurement. At the top are the standards calibrated by a National Metrology Institute (NMI) such as the National Institute of Standards and Technology (NIST) in the To expect equal or less uncertainty in a lower level of the hierarchy than exists in a higher level is unrealistic. The 6 Rounding and Discrimination 6.1 DATA LEVEL In many cases the number of decimal places that are to be used is influenced by the source of the data itself. For example, if a vessel s capacity tables are calibrated to the nearest whole barrel, than all subseque Table 1 - Significant Digits Units Liters Gallons No. of Decimals, xxx.0, xxx.xx Units API 60ºF CTPL No. of Decimals xxx.x x.xxxxxa Barrels Cubic meters, xxx.xx, xxx.xxx Density lbs/gal Density kg/m3 xx.xxx xxxx.x Pounds, xxx.0 Density kg/litre x.xxxx Kilograms, xxx.0 Density correction coefficient x.xxxxx Short tons, xxx.xxx Relative density x.xxxx Metric tons, xxx.xxx S & W % xx.xxx Long tons, xxx.xxx CSW x.xxxxx Temperature ºF xxx.x xxx.xa Temperature ºC TSh ºC / ºF (See Section 9.1.3) xxx.0 CTSh x.xxxxx Note a Not applicable if the implementation guidelines ( Grandfather Clause ) from API MPMS Chapter have been invoked. For those invoking the Grandfather Clause, the following note, from API MPMS four decimal digits above and below standard temperature in addition to limiting table entry discrimination to 0.5º 6.2 ROUNDING OF NUMBERS When a number is to be rounded to a specific number of decimals, it shall always be rounded off in one step to the number of figures that are to be recorded and shall not be rounded in two or more steps of succe

7 6.3 DISCRIMINATION The rounding and discrimination requirements set forth in this section may be applied to verify compliance with the calculation procedures of this standard. The data in Table 1 should not be used to construe Where used to verify conformance to calculation procedures, the accounting hardware that displays or prints res 10 digits or better. In certain situations, such as with on-line real time calculations that are required by process m 7 Observed Data (Input, Direct, or Primary) The input or observed data in Table 2 must be gathered as a first step in the calculation process. This document does not address how these data are obtained. That information is found in the referenced publication Table 2 - Observed Data Shore Tanks Marine Vessel s Tanks Recorded reference gauge heighta Average liquid temperature ºF or ºC After draft reading List Recorded reference gauge heighta Observed reference Average liquid temperature ºF or ºC Observed a These data points do not have any direct impact on the calculation process. However, they can impact the calc 8 Calculated Data (Indirect or Secondary) The data points presented in Table 3 are necessary for the calculation process and are calculated or extracted using the input data from the previous section. Table 3 - Calculated Data Shore Tanks Marine Vessel s Tanks standard temperature Vessel s trim Floating roof adjustment or correction standard temperature Tank shell temperatur Free water volume Free water volume Gross observed volume Gross observed volume Correction for temperature of liquid Correction for temperature of liquid Gross standard volume Gross standard volume Sediment and water (volume or factor) Sediment and water (volume or factor) Net standard vol Mass or weight (See Section 12) Mass or weight (See Section 12) 9 Calculation of Gross Observed Volume (GOV) The calculation process for shore tanks and marine tank vessels only differs up to the point of calculating gross observed volume (GOV). From this point on, the calculations are the same. Refer to Annex A for examples of shore tank and marine vessel tank calculations. 9.1 SHORE TANKS To calculate the GOV for shore tanks, deduct any free water (FW) from the total observed volume (TOV) and multiply the result by the tank shell temperature correction (CTSh); then, apply the floating roof adjust GOV = [(TOV - FW) x CTSh] FRA Total Observed Volume (TOV) The TOV is obtained from the shore tank s capacity table and is entered with the observed innage or ullage Adjustment for the Presence of Free Water (FW) and Tank Bottom Sediments and bottom sediments, if any, before and after each product movement into or out of a tank so that the appropriate corrections can be made. This adjustment (FW) will always be in the form of a volumetric deduction Correction for the Effect of Temperature on the Steel Shell of the Tank (CTSh) Any tank, when subjected to a change in temperature, will change its volume accordingly. Assuming that they have been calibrated in accordance with API MPMS Chapter 2, upright cylindrical tanks have capacity tables based on a specific tank shell temperature. If the observed tank shell temperature differs from the

8 Storage tanks differ from test measures in size and wall thickness. Differences also occur because the tanks can Cross-sectional area correction, CTSh = 1 + 2άΔT + ά2δt2 Where: ά = Linear coefficient of expansion of the tank shell material [see note 4] ΔT = Tank Shell Temperature (TSh) Tank Shell Reference Temperature (TShREF) Note 1: Tank Shell Reference Temperature (TShREF) is the tank shell temperature for which the capacity table volumes were calculated to; typically 60 F, 15 C and 20 C, although other temperatures are used. Note 2: Note 3: The Tank Shell Reference Temperature (TShREF) is usually stated on the capacity table. If this is not th When calculating ΔT it is important to maintain the arithmetic sign as this value can be positive or negative and must be applied as such in the CTSh formula. Note 4: See Table B3 in Annex B for linear expansion coefficients of various metals For non-insulated metal tanks, the temperature of the shell may be computed as follows (refer to Annex B): TSh = [(7 x TL) + Ta ] 8 Where: TL = liquid temperature. Ta = ambient temperature. Note: Ambient air temperature surrounding a storage tank can vary widely. For practical operational purposes the recommended methods of taking this temperature are: A temperature device carried by the measurement technician into the tank area when gauging tanks. Take at least one temperature reading in a shaded area. If more than one temperature is taken, a Shaded external thermometers permanently mounted in the tank farm area. Local on-site weather stations. All on site temperature devices, used to record ambient air temperature for the calculation of tank shell correction factors during custody transfer shall have their accuracy of plus or minus two degrees Fahrenhei Where the uncertainty of the ambient air temperature is plus or ± 5ºF (± 2.5ºC), the effect on calculating the tank shell correction factor is 1 in 100,000. Temperature readings are to be taken 3 feet [1 meter] from any obstructions or the ground. Additionally, allow sufficient time for temperature readings to stabilize For insulated metal tanks, the temperature of the shell may be taken as closely approximating the adjacent liquid temperature, in which case, TSh = TL The third dimension needed to generate volume - height - is a function of gauging and should be considered separately. The volumes reflected on tank tables are derived from area multiplied by incremental heig The shell temperature correction factor is to be applied to volumes obtained from capacity tables that are at standard conditions and are unrelated to the corrections designed to account for volume expansion an The application of a CTSh does not apply in the following circumstances To lease tanks and other such small tanks of 5,000 bbls (795 m3)or less Marine vessels Floating Roof Adjustments and Corrections (FRC & FRA) There are two types of floating roofs internal and external; however, the calculation process to determine the floating roof adjustment or correction is the same for both types of roofs. The determination of the ethod is used when a correction for the roof has been g a reference density. A secondary correction (or adjustment) must therefore be calculated for any difference between the reference density and the observed density at tank temperature. This correction can be positive or negative. b. Floating Roof Correction (FRC) In this situation the tank capacity table has not been adjusted for

9 the roof; therefore a volume, equivalent to the entire weight of the roof, must be calculated and applied as a corr Examples of floating roof adjustment and correction calculations can be found in Annex C Note: No floating roof correction will be accurate if the liquid level falls inside the floating roof s critical zone regardless of table style. While the results can be displayed they should not be used for custody transfer. Note: If a significant amount of water, ice, or snow is present on a floating roof, it should either be removed or its weight estimated and calculated into the roof correction. Note: Roof corrections are not applicable for volumes below the critical zone. 9.2 MARINE VESSEL S TANKS To calculate the GOV for marine vessel s tanks, deduct the FW volume from the TOV. GOV = TOV - FW In the event of a volumetric trim or list correction as per Item a, the calculation is as follows: GOV = (TOV ± trim or list correction) - FW (see note) Note: Refer to Total Observed Volume (TOV) The TOV is obtained from the vessel s capacity tables, which are entered with one of the following: a. The observed ullage or innage, if the trim and/or list corrections are a volumetric adjustment. The amount of trim and/or list correction will need to be applied to the TOV quantity to arrive at a trim and/or list corre b. The trim and/or list corrected ullage or innage. c. The observed ullage or innage and the vessel s trim. Some capacity tables show varying TOV values for the Trim Correction The trim correction is applied to compensate for the change in liquid level due to the longitudinal plane of the vessel not being horizontal. Subtract the forward draft reading from the after draft reading. If the trim is positive (that is, the after draft reading a. The trim correction is found in the vessel s calibration tables and is usually a correction to the observed innage/ullage. However, it can be a volumetric adjustment to the TOV. b. Trim corrections can be either positive or negative. The trim correction table will state how this correction is to c. If trim corrections are not available, it may be possible to calculate this value. Refer to API MPMS Chapter 2.8A, Section List Correction List correction is applied to compensate for the change in liquid level due to the vertical plane of the vessel not being perpendicular to the horizontal. A vessel s list is usually read from its inclinometer. However, if s a. List corrections are applied in the same manner as are trim corrections. b. List corrections can be either positive or negative. The list correction table will state how this correction is to b c. If list corrections are not available, it may be possible to calculate this value. Refer to API MPMS Chapter 2.8A, Section Insert Figure 1 - Method to Calculate Vessel s List Using Amidships Draft Readings (This is the same as is in the current Edition and will not be changed for this edition) Combining Trim and List Corrections Caution must be exercised when applying trim and list corrections collectively. In many cases these corrections are only applicable when the other condition does not exist. For information on the calculation proced Free Water Volume (FW) FW volume is obtained from the vessel tank capacity tables, which are entered with the FW innage or ullage. As with any liquid in a marine vessel s tank, FW is subject to the effects of trim and list, and the previously formula for calculating whether or not a wedge condition exists, the application of wedge tables/formulae, and th 10 Calculation of Gross Standard Volume (GSV) and Total Calculated Volume (TCV) - Shore Tanks and Marine Vessel s Tanks 10.1 GROSS STANDARD VOLUME (GSV) The GSV is calculated by multiplying the GOV by the correction for the effect of temperature and

10 pressure on the liquid (or the volume correction factor). GSV = GOV x CTPL 10.2 CORRECTION FOR THE EFFECT OF TEMPERATURE AND PRESSURE ON A LIQUID (CTPL) or VOLUME CORRECTION FACTOR (VCF) If a quantity of oil is subjected to a change in temperature, its volume will increase as the temperature rises or decrease as the temperature falls. The volume change is proportional to the thermal coefficient of expan These correction factors can be obtained from API MPMS Chapter 11.1, the Adjunct to ASTM D1250, or the Adjunct to IP 200. These computer programs or tables are entered with the observed average temperature Table 4 - CTPL Factors Table Product Temp Entry 6A Generalized crude oil ºF API 60ºF 6B Generalized products ºF API 60ºF 6C Individual & special applications ºF Thermal expansion coefficient 6D Generalized lubricating oils ºF API 60ºF 24A Generalized crude oil ºF Relative 60/60ºF 24B Generalized products ºF Relative 60/60ºF 24C Individual & special applications ºF Thermal expansion coefficient 54A Generalized crude oil ºC 15ºC 54B Generalized products ºC 15ºC 54C Individual & special applications ºC Thermal expansion coefficient 54D Generalized lubricating oils ºC 15ºC 60A Generalized crude oil ºC 20ºC 60B Generalized products ºC 20ºC 60C Individual & special applications ºC Thermal expansion coefficient 60D Generalized lubricating oils ºC 20ºC ASTM D4311 Asphalt to 60ºF, Table 1 ºF API 60ºF, Table A or B ASTM D4311 Asph Additionally, ASTM D1555 and D1555M (Metric edition), which tabulates CTL (VCF) for various aromatic hydrocarbons. Many products, especially petrochemicals, may have specific volume correction factor tables, developed by the manufacturer. These are usually in the form of product specific tables of CTL (VCF), showing t The use of these tables should be by mutual agreement of all parties concerned TOTAL CALCULATED VOLUME (TCV) Total calculated volume (TCV) is determined by adding the Gross Standard Volume (GSV) to the Free Water (FW) TCV = GSV + FW 11 Calculation of Net Standard Volume (NSV) 11.1 NET STANDARD VOLUME (NSV) To calculate NSV, multiply the GSV by the CSW. NSV = GSV x CSW This, can be expanded to: NSV = GSV x [(100 S&W %) 100] 11.2 CALCULATION OF THE CORRECTION FOR SEDIMENT AND WATER (CSW) To calculate the CSW value, the percentage of S&W must be known. Deduct the S&W percentage value from 100, thus determining the NSV as a percentage of the GSV, divide this by 100, and multiply the GSV CSW = (100 - S&W %) 100 On multiple tank shipments, NSV can be calculated on a tank-by-tank basis if the individual S&W values are known. However, it can be calculated on a grade or parcel basis if the S&W was analyzed on an appr NOTE: Crude oil and some liquid petroleum products contain sediment and water suspended or entrained throughout

11 that fluid. The quantity of sediment and water is determined by laboratory analysis of a representative sample and is express 11.3 CALCULATION OF THE VOLUME OF SEDIMENT AND WATER (S&Wvol) It is frequently necessary to calculate the actual volumetric value of S&W. This can be achieved by subtracting the net standard volume (NSV) from the Gross Standard Volume (GSV). S&WVOL = GSV - NSV 12 Calculation of Mass (Weight in Vacuum) and Weight (Weight in Air) 12.1 INTRODUCTION While the terms mass and weight have there own definitions within the scientific community, when referred to in this document, mass will refer to weight in vacuum (vacuo) and weight will refer to weight in air. If th The routines, however, for calculating mass and weight are the same, they just use different factors CALCULATION METHODS There are two common methods utilized to calculate mass and/or weight, both of which are capable of calculating either of them Volume at Standard Temperature to Mass/Weight Method This method corrects the volume at the observed temperature to the volume at the standard temperature by applying a CTPL or CTL (VCF) after which the weight/mass is obtained by multiplying the standa Volume at Observed Temperature to Mass/Weight This method adjusts the density at standard temperature to its density at observed temperature by use of a thermal expansion coefficient per degree, then, multiplying it by the volume at observed temperature to obtain Calculation of Gross Standard Weight and Net Standard Weight Gross Standard Weight (GSW) and Net Standard Weight (NSW) are calculated by multiplying the GSV or NSV by the appropriate density in air. NSW = NSV x Density in air GSW = GSV x Density in air Calculation of Gross Standard Mass and Net Standard Mass Gross Standard Mass (GSM) and Net Standard Mass NSM are calculated by multiplying the GSV or NSV by the appropriate density in vacuum. NSM = NSV x Density in vacuum GSM = GSV x Density in vacuum 12.3 CONVERTING BETWEEN MASS AND WEIGHT As the difference is equal to the weight of the volume of air displaced by the object being weighed, high density materials will displace less air than low density materials; therefore, the difference between weight in air a Table 5 Mass to Weight Density Corrections Density Range (kg/m3) Less than ,663.5 Greater than 1,6635 = D15 ### Density Correction (kg/m3) The majority of petroleum based materials are in the density range of to kg/m3, therefore, the most c correction is added. s for mass to weight calculations and vice versa is convenient and quick, especially for field applications, API MPMS Chapter specifies a formula for making The following equation expresses the relationship between Density in Vacuum in kg/m3 at 15 C and Density in Air at 15 C in kg/m3 15 in kg/m3 Where: D 15

12 = Density in Air D15 = Density in Vacuum In the event of a dispute or when greater discrimination is required than is provided for by Table 5, the formula specified in API MPMS Chapter shall be used. 13 Direct Mass Measurement drostatic tank gauges, determine mass by measuring liquid head rather than liquid level. The calculation algorithms used by these methods may include corrections fo these corrections should not be duplicated. For calculation procedures, refer to API MPMS Chapter Calculation Sequence 14.1 GENERAL nstruct the user in the procedures and techniques necessary to obtain all the observed information that will be needed in order to calculate a net volume. It is the u subroutines. Any deduction that is inappropriate for a particular application will be a zero deduction, and any correction that is inappropriate will be held at The calculation routine will be the same VOLUME AT STANDARD TEMPERATURE TO MASS/WEIGHT CALCULATION PROCEDURE The calculation sequence follows that of the preceding sections. The flow is as follows (see Figures A- 1 and A-2): TOV GOV GSV NSV NSW or TOV GOV GSV NSV NSM a. With the liquid level or gauge, enter the capacity table and record the TOV, as recorded in the table. b. Subtract any gauged FW volumes. The FW volume is obtained by entering the capacity table with the gauge c. Apply the CTSh to arrive at the GOV. d. Correct this quantity for any applicable FRA or FRC. e. Correct the GOV to standard temperature. This is done by multiplying the GOV by the CTPL to arrive at the G f. Adjust for any measured amount of S&W. This is done by multiplying GSV by the CSW. g. If net standard w h. If net standard mass [NSM] is required, multiply the result from Item f. the density in vacuum The mathematical formulae for the various required values can be expressed as follows: GSV = {[(TOV - FW) x CTSh] FRA} x CTPL GSW = {[(TOV - FW) x CTSh] FRA} x CTPL x Density (in air or vacuum as required) NSV = {[(TOV - FW) x CTSh] FRA} x CTPL x CSW NSW = {[(TOV - FW) x CTSh] FRA} x CTPL x CSW x Density (in air or vacuum as required) Chain calculations must be performed. Only the final result in the calculation is to be rounded. If it is necessary to report any intermediate values, the figure should be rounded as required in Section 5; however, the 14.3 VOLUME AT OBSERVED TEMPERATURE TO MASS/WEIGHT CALCULATION PROCEDURE The calculation sequence follows that of the preceding sections. TOV GOV Mass or Weight a. With the liquid level or gauge, enter the capacity table and record the TOV, as recorded in the table. b. Subtract any gauged FW volumes. The FW volume is obtained by entering the capacity table with the gauge c. Apply the CTSh to arrive at the GOV. d. Correct this quantity for any applicable FRA or FRC. e. Correct the GOV to mass or weight. This is done by multiplying the GOV by the density in air at observed tem NOTE: This method is not normally used on crude oils or other materials where net standard volume [NSV] or net standard weight [NSW] is required. Should this be required, the density at standard temperature should be applied to the mas The mathematical formulae for the various required values can be expressed as follows: GOV = {[(TOV - FW) x CTSh] FRA} Mass or Weight = {[(TOV - FW) x CTSh] FRA} x Density at Observed Temperature (in air or vacuum as required)

13 Density at standard temperature is converted to density at observed temperature as follows: ( Cs) t s t Where: ρt = density at measured temperature ρs = density at standard temperature = difference in temperature (standard - measured) t Cs = coefficient of thermal expansion per degree Chain calculations must be performed. Only the final result in the calculation is to be rounded. If it is necessary to report any intermediate values, the figure should be rounded as required in Section 6; however, the 15 Calculation of Transferred Volumes for Custody Transfer 15.1 GENERAL The calculation routines specified in this document are specific to the quantity of material in a tank whose contents are not in motion. The calculation of transferred volumes for custody transfer typically involves performi calculated from each tank s opening and closing measurements, and then additional calculations to NSV and mass or weight are made collectively to this quantity. Alternatively, the individual opening and closing reading 15.2 SMALL LEASE TANKS Lease tanks differ from storage tanks not only in size but in gauging procedure. Therefore, it is necessary to establish unique calculation procedures for lease tanks. This procedure is applicable to lease tanks and should not be applied Transferred Volume Calculation Procedure for Lease Tanks The following are the procedures for calculating transferred volumes for lease tanks: a. With the liquid level or gauge, enter the capacity table and record the TOV for the opening gauge. b. Correct for the temperature of the oil. This is done by multiplying the answer from Item a. by the CTPL, arriving at the GSV, and rounding appropriately. c. With the liquid level or gauge, enter the capacity table and record the TOV for the closing gauge. d. Correct for the temperature of the product. This is done by multiplying the answer from Item c. by the CTPL, arriving at the GSV, and rounding appropriately. e. Subtract the closing GSV from the opening GSV. f. The last correction shall be to adjust for any measured amount of S&W. This is done by multiplying the GSV obtained from Item e. by the CSW and rounding appropriately VOLUMETRIC SHRINKAGE Volumetric shrinkage occurs when light hydrocarbons are mixed with much heavier hydrocarbons. The tables and calculation routines are specified in API MPMS Chapter It is not normal practice to include these quantities in custody transfer calculations as the volumes lost are not available again, except throu Note: Mass or weight is not affected by volumetric shrinkage. 16 Miscellaneous 16.1 PRECAUTIONS WHEN USING AN AUTOMATIC SAMPLER When automatic sampling systems are employed for product transfer, tanks with varying densities (crude oil systems, for example) will need to accumulate base data differently than for transfers that do not includ a. At the beginning of the transfer, there is nothing in the sampler and therefore nothing on which to base opening measurements. b. After the transfer, the incoming product has been blended with whatever was in the tank. In order for the CTP c. The tank s FW level must be left the same on the closing report as on the opening report. All deducted water v d. S&W are usually only deducted on crude oil cargoes. Petroleum products are not usually corrected for S&W u 16.2 INTERRELATION OF UNITS

14 It is frequently necessary to convert from one type of unit to another using a conversion factor. These conversion factors are found in API MPMS Chapter 11.5 of which there are three subchapters: Chapter Conversions of API Gravity at 60 F Chapter Conversions for Relative Density (60/60 F) Chapter Conversions for Density in vacuum at 15 C These three standards replace the Density/Weight/Volume Intraconversion tables formerly located in API MPMS Chapter 11.1, Volumes XI/XII. There are separate conversion factors for mass and weight, depending upon which one is required. Due to the complexity of these interrelations there is frequently more than one way of performing these conversions and this standard does not attempt to define any specific routines for converting from one unit to an Conversion units that are exact by definition are to be considered primary and shall be used whenever possible Conversion processes shall not produce a result that contradicts an exact by definition value The use of multiple conversion factors should be avoided if possible. If this cannot be avoided the process that u NNEX A E VESSEL TANK CALCULATIONS (NORMATIVE) Example A-1 Custody Transfer Flow Chart Shore Tanks with Automatic Sampler OPENING GAUGE CLOSING GAUGE TOTAL RVED VOLUME Minus Free Water tiply by CTSh g Roof Adjustment or Correction TOV DEL/REC TOTAL RVED VOLUME Minus Free Water tiply by CTSh g Roof Adjustment or Correction Notes: 1. For multiple tank movements add each tank s delivered or received GSV and proceed as shown. 2. Facilities that apply the vessel s free water to the transferred quantity shall apply this immediately prior to the CSW correction 3. Tank free water (FW) on opening and closing must remain constant. GROSS RVED VOLUME GOV DEL/REC GROSS RVED VOLUME tiply by CTPL (VCF) tiply by CTPL (VCF) GROSS DARD VOLUME GROSS DARD VOLUME OTAL GSV ERY or RECEPT by Density in Air y Density in Vacuum GROSS STANDARD WEIGHT GROSS STANDARD MASS Multiply by Correction for Sediment & Water (CSW) OTAL NSV

15 ERY or RECEPT by Density in Air y Density in Vacuum NET STANDARD WEIGHT NET STANDARD MASS Example A-2 Custody Transfer Flow Chart Share Tank(s) with Individual Tank Samples ank Calculation CLOSING GAUGE Note: For multiple tank movements add each tank s delivered or TOTAL RVED VOLUME Minus Free Water TOV DEL/REC TOTAL RVED VOLUME Minus Free Water received quantity as appropriate Multiply by CTSh Multiply by CTSh r Minus Floating Adjustment or Correction r Minus Floating Adjustment or Correction GROSS RVED VOLUME GOV DEL/REC GROSS RVED VOLUME tiply by CTPL (VCF) tiply by CTPL (VCF) GROSS DARD VOLUME GSV DEL/REC GROSS DARD VOLUME Multiply by Correction for Sediment & Water (CSW) Multiply by Correction for Sediment & Water (CSW) NET DARD VOLUME NSV DEL/REC NET DARD VOLUME Density in Air Density in Vacuum Density in Air Density in Vacuum

16 NET DARD WEIGHT NSW DEL/REC NET DARD WEIGHT NET NDARD MASS NSM DEL/REC NET NDARD MASS ample A-3 ank Calculation Using o Mass or Weight Calculation Procedure Analytical and Observed Data Liquid level gauge /4 Free water gauge /4 API 60ºF 33.7 (rounded from 33.69) Liquid temperature ºF 88.3 Ambient temperature ºF 71.5 Temperature of tank shell ºF (TSh) 86.0 (rounded from 86.2) Sediment and water percent 0.12% Calculation Calculated or Derived Data Symbol Reported Unit Barrels or Long Tons Running Calculation (Not Reported) Total observed volume1 Free water Gross observed volume2 Correction for temperature of shell Floating roof adjustment Gross observed volume Correction for temperature of Liquid (Table 6A) Gross standard volume Correction for sediment and water4 TOV1 FW GOV , CTSh , FRA , CTPL GSV CSW , , , , , , , Net standard volume NSV 428, , Density in air (Long tons per bbl) (API MPMS Chapter ) Net standard weight (long tons) NSW 57, , Alternate Calculation from Net Standard Volume if Net Standard Mass is required: Density in vacuum (Long tons per bbl) (API MPMS Chapter ) Net standard mass (long tons) NSM 57, , NOTES: 1 Quantity from the tank capacity table using the liquid level gauge to enter the table. For this example, it is assumed that any 2 Gross observed volume, uncorrected for the temperature of the tank shell and floating roof adjustment. 3 As displayed on a 12-digit calculator. Actual discrimination is determined by the calculating capacity of the calculation hardw 4 Refer to 11.3 to calculate the volumetric value for sediment and water. ample A-4 el Tank Calculation Using o Mass or Weight Calculation Procedure

17 Analytical and Observed Data Liquid level gauge (ullage) /4 Free water gauge (ullage) /4 API 60ºF 27.1 (rounded from 27.14) Liquid temperature ºF 91.1 Sediment and water percent 0.17% Forward draft After draft 3 Calculation Calculated or Derived Data Symbol Reported Unit Barrels or Running ulation orted) Total observed volume1 Trim correction (volumetric)2 TOV1 Trim2 35, , Total observed volume TOV 34, , Free water (by wedge) Gross observed volume FW GOV , , Correction for temperature of liquid Gross standard volume CTPL GSV (Table 6A) 34, , Correction for sediment and water4 CSW Net standard volume NSV 34, , Density in air (Long tons per bbl) (API MPMS Chapter ) Net standard weight (long tons) NSW 4, , Alternate Calculation from Net Standard Volume if Net Standard Mass is required: Density in vacuum (Long tons per bbl) (API MPMS Chapter ) Net standard mass (long tons) NSM 4, , NOTES: 1 Quantity from the vessel s tank capacity table using the liquid level ullage gauge to enter the table. 2 Not all trim (or list) corrections are volumetric. Many are linear adjustments that are made to the observed ullage. In this cas 3 As displayed on a 12-digit calculator. Actual discrimination is determined by the calculating capacity of the calculation hardw 4 The volumetric value for sediment and water is determined by subtracting the net standard volume from the gross standard Example A-5 Shore Tank Calculation of Volume at 15ºC and Weight of p-xylene using ASTM D1555M Analytical and Observed Data Liquid level gauge 4606 mm Free water gauge 10 mm Density at 15ºC kg/l (air) kg/l Liquid temperatur Temperature of tank shell ºC (TSh) 22.0ºC (rounded from 21.8 ºC) Calculation Calculated or Derived Data Symbol Reported Unit Litres / kg Running Calculation (Not Reported) 3 Total observed volume1 Free water Gross observed volume2 Correction for temperature of shell Floating roof adjustment Gross observed volume Correction for temperature of Liquid (Table ASTM D1555) Gross standard volume at 15ºC TOV1 FW GOV CTSh FRA [VCF] CTPL GSV

18 Density in air at 15ºC kg/l Weight NOTES: 1 Quantity from the tank capacity table using the liquid level gauge to enter the table. For this example, it is assumed that any correction to the gauge, due to expansion or contraction of the tape itself, has already been made. This issue is not 2 Gross observed volume, uncorrected for the temperature of the tank shell and floating roof adjustment. 3 As displayed on a 12-digit calculator. Actual discrimination is determined by the calculating capacity of the calculation hardw Example A-6 Shore Tank Calculation of Volume at 15ºC, Mass and Weight of MTBE using API MPMS Chapter 11.1/Adjunct to ASTM D1250/Adjunct to IP 200, Table 54C Analytical and Observed Data Liquid level gauge 5810 mm Free water gauge None Found Coefficient of thermal expansion alpha per ºC Density in air at 15ºC kg/l Liquid temperature ºC 22.5ºC Ambient temperature ºC 12.0ºC Temperature of tank shell ºC (TSh) 21.0ºC (rounded from 21.1 ºC) Calculation Calculated or Derived Data Symbol Reported Unit Litres / kg Running Calculation (Not Reported) Total observed volume1 Correction for temperature of shell TOV1 CTSh Floating roof adjustment FRA Gross observed volume Correction for temperature of [VCF] Liquid CTPL (API MPMS Chapter 11.1, Table 54C)2 Gross standard volume at 15ºC GSV Density at 15ºC kg/l (air) Weight (in air) For Conversion to Mass (weight in vacuum) Density at 15ºC kg/l (air) Density adjustment (From Table 5 in Section 12.3) Density at 15ºC kg/l (vacuum) Gross standard volume at 15ºC GSV Density at 15ºC kg/l (vacuum) Mass (weight in vacuum) Notes: 1 Quantity from the tank capacity table using the liquid level gauge to enter the table. For this example, it is assum 2 MTBE has a special application table, which is a function of the API MPMS Chapter 11.1/Adjunct to ASTM D12 3 As displayed on a 12-digit calculator. Actual discrimination is determined by the calculating capacity of the calcu ExampleA-7 on of the Weight of Benzene Using Expansion per Degree (Cs). The Density at standard temperature is converted to Density at Measured temperature, which is then applied to the measured volume to give mass or weight, as appropriate. Analytical and Observed Data

19 Liquid level gauge 5810 mm Free water gauge None Found Density at 15ºC Ambient temperature ºC 12.0ºC Temperature of tank shell ºC (TSh) 21.0ºC (rounded from 20.8ºC) Calculation Calculated or Derived Data Symbol Reported Unit Litres / kg Running Calculation (Not Reported) Total observed volume1 Correction for temperature of shell Floating roof adjustment Gross observed volume Density at Obs. Temp. 22.5ºC kg/l (air) Weight (in air) Density at 15ºC, kg/l (air) Liters at 15ºC t Where: ( Cs) TOV1 CTSh FRA s t Note: 1 Quantity from the tank capacity table using the liquid level gauge to ρt = density at measured temperature ρs = density at standard temperature = difference in temperature (standard - measured) t Cs = coefficient of thermal expansion per degree Density at 15ºC kg/l (air) Expansion coefficient kg/l per ºC ρt = ([ ] * ) = (-7.5 * ) = = enter the table. For this example, it is assumed that any correction to the gauge, due to expansion or contraction of the tape itself, has already been not addressed in this standard. The user should refer to the tape manufacturer s instructions for specific details. 2 As displayed on a 12-digit calculator. Actual discrimination is determined by the calculating capacity of the calculation hardware. NNEX B NTRACTION OF UPRIGHT CYLINDRICAL STEEL TANKS DUE TO TEMPERATURE (NORMATIVE) For mild steel tanks with a linear coefficient of expansion of / F, use Table B1. For temperatures

20 outside the range of this table or for other coefficients expansion, use the formula in This table is applicable to tanks whose capacity tables were calculated at a reference tank shell temperature of 60 F. For tanks with capacity tables calculated at a reference tank shell temperature other than 6 B.1 Shell Temperature Correction Factors for Expansion and Contraction of Upright Cylindrical Steel Tanks Due to Temperature B.1.1 Tanks undergo expansion or contraction due to variations in ambient and product temperatures. Such expansion or contraction in tank volume may be computed once the tank shell temperature is determined. B.1.2 For tanks that are insulated, the tank shell temperature (TSh) is assumed to be the same as the temperature of the product (TL) stored within the tank (that is, TSh = TL). For tanks that are not insulated, the she TSh = [(7 x TL) + TA] / 8 Where TL = liquid product temperature TA = ambient air temperature B.1.3 Once the shell temperature is determined, the shell temperature correction factor (CTSh) is computed using the following equation: CTSh = 1 + 2άΔT + ά2δt2 Where: ά = Linear coefficient of expansion of the tank shell material ΔT = Tank Shell Temperature (TSh) Tank Shell Reference Temperature (TShREF) B.2 Application of Shell Temperature Correction Case 1: Capacity table at tank shell reference temperature (TShREF) of 60 F, of mild steel, noninsulated construction with a linear coefficient of expansion of / F. - Volume at a given level (tank shell reference temperature [TShREF] 60 F) = 100,000 bbls. - Ambient Temperature = 70 F. - Product Temperature = 155 F. - Compute capacity table volume reflecting above conditions. Solution: a. Calculate shell temperature (TSh) at 155 F product temperature: TSh = [(7 x TL) + TA] / 8 TSh = [(7 x 155) + 70] / 8 TSh = 144 F (rounded to nearest 1 F) b. Compute ΔT ΔT = Tank Shell Temperature (TSh) Tank Shell Reference Temperature (TShREF) ΔT = ΔT = 84 c. Compute the shell temperature correction factor (CTSh) for 144 F CTSh = 1 + 2άΔT + ά2δt2 ΔT = Tank Shell Temperature (TSh) - Tank Shell Reference Temperature (TShREF) CTSh = 1 + (2 x x CTSh = 1 + ( x 84) + ( x 7056) CTSh = CTSh = (rounded to five decimal places) d. Compute the correct volume: V = Volume at TSh 60 F x CTSh FOR 144 F V = 100,000 bbls x V = 100,104 bbls. Case 2: Capacity table already corrected for a tank shell temperature of 185 F, on a mild steel noninsulated tank [see note below]. - Volume at a given level (tank shell reference temperature [TShREF] 185 F) = 100,000 bbls.