Api mpms 19 1 2012 (american petroleum institute)

19 1 e4 covers fm Manual of Petroleum Measurement Standards Chapter 19 1 Evaporative Loss From Fixed Roof Tanks FOURTH EDITION, OCTOBER 2012 Manual of Petroleum Measurement Standards Chapter 19 1 Evap[.]

Manual of Petroleum

Measurement Standards

Chapter 19.1

Evaporative Loss From Fixed-Roof Tanks

FOURTH EDITION, OCTOBER 2012

Manual of Petroleum

Measurement Standards Chapter 19.1

Evaporative Loss From Fixed-Roof Tanks Measurement Coordination

FOURTH EDITION, OCTOBER 2012

API publications are published to facilitate the broad availability of proven, sound engineering and operatingpractices These publications are not intended to obviate the need for applying sound engineering judgmentregarding when and where these publications should be utilized The formulation and publication of API publications

is not intended in any way to inhibit anyone from using any other practices

Any manufacturer marking equipment or materials in conformance with the marking requirements of an API standard

is solely responsible for complying with all the applicable requirements of that standard API does not represent,warrant, or guarantee that such products do in fact conform to the applicable API standard

Users of this standard should not rely exclusively on the information contained in this document Sound business,scientific, engineering, and safety judgment should be used in employing the information contained herein

All rights reserved No part of this work may be reproduced, translated, stored in a retrieval system, or transmitted by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the publisher Contact the

Publisher, API Publishing Services, 1220 L Street, NW, Washington, DC 20005.

Copyright © 2012 American Petroleum Institute

Nothing contained in any API publication is to be construed as granting any right, by implication or otherwise, for themanufacture, sale, or use of any method, apparatus, or product covered by letters patent Neither should anythingcontained in the publication be construed as insuring anyone against liability for infringement of letters patent.Shall: As used in a standard, “shall” denotes a minimum requirement in order to conform to the specification

Should: As used in a standard, “should” denotes a recommendation or that which is advised but not required in order

to conform to the specification

This document was produced under API standardization procedures that ensure appropriate notification andparticipation in the developmental process and is designated as an API standard Questions concerning theinterpretation of the content of this publication or comments and questions concerning the procedures under whichthis publication was developed should be directed in writing to the Director of Standards, American PetroleumInstitute, 1220 L Street, NW, Washington, DC 20005 Requests for permission to reproduce or translate all or any part

of the material published herein should also be addressed to the director

Generally, API standards are reviewed and revised, reaffirmed, or withdrawn at least every five years A one-timeextension of up to two years may be added to this review cycle Status of the publication can be ascertained from theAPI Standards Department, telephone (202) 682-8000 A catalog of API publications and materials is publishedannually by API, 1220 L Street, NW, Washington, DC 20005

Suggested revisions are invited and should be submitted to the Standards Department, API, 1220 L Street, NW,Washington, DC 20005, standards@api.org

iii

Summary of Changes to API MPMS Chapters 19.1, 19.2 and 19.4

The third edition of API Manual of Petroleum Measurement Standards (MPMS) Chapter 19.4 was published following

a revision that was carried out concurrently with revisions to Chapter 19.1, published as the fourth edition, andChapter 19.2, published as the third edition Primary changes are:

1) Consolidation of common material in Chapter 19.4 Material that had previously been included in both Chapters

19.1 and 19.2 has been moved to Chapter 19.4 Chapter 19.4, which was previously Recommended Practice for

Speciation of Evaporative Losses, now has the title Evaporative Loss Reference Information and Speciation Methodology This Chapter had already contained reference information on the properties of chemicals and

typical petroleum liquids, and this information has now been removed from Chapters 19.1 and 19.2 In addition,meteorological data have been moved from Chapters 19.1 and 19.2 to Chapter 19.4 In the revised documents:a) Meteorological data are found in Chapter 19.4,

b) Calculation of storage tank temperatures is found in Chapters 19.1 and 19.2 (in that fixed-roof tanks involvecalculation of the vapor space temperature in order to determine vapor density, whereas this step is notinvolved in estimating emissions from floating-roof tanks), and

c) Calculation of true vapor pressure is found in Chapter 19.4 (in that this is now calculated in the same mannerfor both fixed- and floating-roof tanks)

2) Reconciliation of nomenclature Chapters 19.1 and 19.2 previously had different nomenclature for the samevariables These revisions adopt a common set of symbols for both chapters

3) Reorganization of the formats In addition to common material having been removed from Chapters 19.1 and 19.2,the remaining text has been edited to remove unnecessarily verbose or repetitive language The summary tableswere deemed redundant, and have been deleted

4) Appendices Appendices have been redesignated as annexes

5) SI units An annex has been added to each chapter to address SI units

Chapter 19.1, fourth edition

In addition to common reference material being deleted from Chapter 19.1, the following changes have been made:1) Reference to API Technical Reports References to API TR 2568 (cleaning storage tanks) and API TR 2569(closed vent IFRTs) have been added

2) Terminology The following terminology has been revised:

a) “Standing storage loss” has been changed to “standing loss.”

b) “Solar insolation” has been changed to “insolation.”

3) Effective Throughput An expression has been added for the sum of changes in liquid level, designated ΣH Q, forcalculating effective throughput

4) Normal operating pressure An expression has been added for calculating the normal operating pressure, as theaverage of the maximum and minimum vent settings

5) Vapor density from vapor space temperature The temperature used in the calculation of vapor density has beenchanged from the liquid surface temperature to the vapor space temperature, and an equation has been added fordetermining the vapor space temperature

v

Page

1 Scope 1

2 Normative References 1

3 Symbols 2

4 Procedure for Estimating Loss 3

4.1 General 3

4.2 Standing Loss L S 3

4.3 Working Loss L W 9

5 Example 11

5.1 Parameters 11

5.2 Solution 11

6 Equipment Descriptions 13

6.1 General 13

6.2 Fixed-Roof Tanks 14

6.3 Roof Fittings 14

6.4 Insulation 15

6.5 Outside Surfaces of the Tank 16

7 Loss Mechanisms 16

7.1 General 16

7.2 Standing Loss 16

7.3 Working Loss 17

8 Development of Estimation Methods 18

8.1 General 18

8.2 Standing Loss 19

8.3 Working Loss 23

Annex A (informative) SI units 25

Bibliography 26

Figures 1 Fixed-Roof Tank Geometry 5

2 Typical Fixed-Roof Tank 14

vii

fixed-Types of fixed-roof tanks and roof fittings described are for information only

The equations estimate average annual losses from uninsulated fixed-roof tanks for various liquid stocks, stock vapor pressures, tank sizes, meteorological conditions, and operating conditions

The following special cases are addressed:

a) Horizontal tanks

b) Higher volatility stocks (true vapor pressure greater than 0.1 psia)

c) Vent settings higher than 0.03 psia (0.5 oz/in2)

The estimation may be improved by using detailed field information, including climatic data and operational data for the appropriate time period

The equations are not intended to be used in the following applications:

a) To estimate losses from unstable or boiling stocks or from petroleum liquids or petrochemicals for which the vapor pressure is not known or cannot readily be predicted (to calculate emissions from tanks that contain material at or above their boiling point or the point at which material starts to flash, the API model E&P Tank (API Publication 4697) can be used)

b) To estimate losses from fixed-roof tanks which have an internal floating roof API MPMS Ch 19.2[4] and API TR 2569[13] address these

c) To estimate losses from fixed-roof tanks which have either roof or shell insulation

d) To estimate losses from cleaning fixed-roof tanks API TR 2568[12] addresses this

The estimation procedures were developed to provide estimates of typical losses from fixed-roof tanks that are properly maintained and in normal working condition Losses from poorly maintained tanks may be greater Because the loss equations are based on equipment conditions that represent a large population of tanks, a loss estimate for a group of fixed-roof tanks may be more representative than a loss estimate for an individual tank

Evaporative loss considerations are not the only criteria for equipment selection Many other factors not addressed in this standard, such as tank operation, maintenance, and safety, are important in designing and selecting tank equipment for a given application

2 Normative References

The following referenced documents are indispensable for the application of this document For dated references, only the edition cited applies For undated references, the latest edition of the referenced document (including any amendments) applies

API Manual of Petroleum Measurement Standards (MPMS) Chapter 19.4, Recommended Practice for

Speciation of Evaporative Losses, 3rd Edition, 2012

2 APIMPMSC HAPTER 19.1

3 Symbols

H RO roof outage (or shell height equivalent to the volume under the roof) ft Eq 6a through 6f

I daily total insolation on a horizontal surface Btu/(ft2 day) 19.4 Table 1

P BN breather vent minimum pressure setting (negative if a vacuum setting) psig user

P BX breather vent maximum pressure setting (always positive) psig user

P VA stock true vapor pressure at the daily average liquid surface temperature psia 4.2.4

P VN stock true vapor pressure at the daily minimum liquid surface temperature psia 4.2.5b)

P VX stock true vapor pressure at the daily maximum liquid surface temperature psia 4.2.5b)

V Q stock throughput associated with increasing the liquid level in the tank ft 3 /yr Eq 22a, 22b

E VAPORATIVE L OSS F ROM F IXED -R OOF T ANKS 3

NOTE 1 "19.4" refers to API MPMS Ch 19.4, 3rd Edition

NOTE 2 The term "average" refers to average over the period (i.e year) being considered

Abbreviations for units

bbl barrels

Btu British thermal units

ft feet

psia pounds per square inch absolute

psig pounds per square inch gauge

4.2.1 Aboveground and Underground Tanks

a) For aboveground tanks, the standing loss L S(lb/yr) is:

where

D, H VO , K S , K E , and W V are determined in 4.2.2 through 4.2.6, respectively;

The constant 365 has units of days/yr

b) For underground tanks, assume no standing loss occurs (L S = 0) because the insulating nature of the earth

limits the diurnal temperature change

4.2.2 Tank Diameter D

The tank diameter D (ft) is:

a) For vertical tanks,

where D V is the cylindrical diameter of a vertical tank (ft)

(3b) where

L H is the end-to-end length of a horizontal tank (ft);

D H is the cylindrical diameter of a horizontal tank (ft)

4.2.3 Vapor Space Outage H VO

The vapor space outage H VO (ft), the height of a cylinder of diameter D whose volume equals the vapor

space volume of a fixed-roof tank, is:

a) For vertical tanks (see Figure 1):

where

H S is the tank shell height (ft);

H L is the average liquid height (ft);

where

H LX is maximum liquid height (ft);

H LN is minimum liquid height (ft) (height of remaining heel when emptied)

H RO is the roof outage (ft), the shell height equivalent to the volume contained under the roof

(this assumes the roof slope is 3/4 in on 12 in.)

(this assumes the roof radius equals the tank diameter)

b) For horizontal tanks:

where D H is the cylindrical diameter of a horizontal tank (ft)

E VAPORATIVE L OSS F ROM F IXED -R OOF T ANKS 5

Figure 1 — Fixed-Roof Tank Geometry

4.2.4 Vented Vapor Saturation Factor K S

The vented vapor saturation factor K S (dimensionless) accounts for the degree of stock vapor saturation in

the vented vapor:

where

H VO is determined in 4.2.3;

The constant 0.053 has units of 1/(psia-ft)

P VA is the stock true vapor pressure (psia) at the average liquid surface temperature T LA

(use API MPMS Ch 19.4, 3rd Edition, Section 4.2 to determine vapor pressure P V at a given

T MAX is the daily maximum ambient temperature (°F), obtained from

meteorological records or from historical averages given in API MPMS Ch 19.4, 3rd

Edition, Table 1

T MIN is the daily minimum ambient temperature (°F), obtained from

meteorological records or from historical averages given in API MPMS Ch 19.4, 3rd

Edition, Table 1

The constant 0.0079 has units of °R ft2 day/Btu

T B is the liquid bulk temperature (°R), preferably obtained from tank records

6 APIMPMSC HAPTER 19.1

The equation below for estimating liquid bulk temperature is based on the assumption that the product is in

thermal equilibrium The time required for the liquid bulk to achieve thermal equilibrium with ambient

conditions, however, would result in the stock typically not being in thermal equilibrium for much of the

storage period Therefore, it is highly preferable to use measured values for the liquid bulk temperature If

measured values are unavailable, T B may be estimated as:

The constants 6 and 1 have units of °R

When possible, meteorological data for the tank site should be used If site-specific data are not available,

meteorological data from the nearest weather station may be used Data for selected U.S locations are

listed in API MPMS Ch 19.4, 3rd Edition, Table 1

Alternatively, if sufficient data are available, API MPMS Ch 19.4, 3rd Edition, Appendix I may be used for a

slight improvement in the estimate of T LA

4.2.5 Vapor Space Expansion Factor K E

The vapor space expansion factor K E is nominally dimensionless but is assigned units of (1/day) because it

describes the expansion of vapors in the vapor space that occurs due to the diurnal temperature cycle, and

thus it pertains to a daily event

a) For stocks with P VA < 0.1 psia and ΔP B < 0.063 psi (see Equation 18), the vapor space expansion factor K E

The constant 0.0018 has units of 1/°R

ΔT V is the daily vapor temperature range (°R), which may be determined as follows:

where

T MAX and T MIN are determined in 4.2.4;

The constant 0.72 is dimensionless; the constant 0.028 has units of (°R ft2 day)/Btu

Alternatively, if sufficient data are available, API MPMS Ch 19.4, 3rd Edition, Appendix I may be

used for a slight improvement in the estimate of ΔT V

E VAPORATIVE L OSS F ROM F IXED -R OOF T ANKS 7

b) For stocks with P VA > 0.1 or ΔP B > 0.063 psi (see Equation 18):

K E =

VA A

B V LA

V

P P

P P T

T

−

Δ

−Δ+

The constant 0.25 is dimensionless

P VX is the stock true vapor pressure (psia) at the daily maximum liquid surface

temperature T LX

The constant 0.25 is dimensionless

2) A less accurate method for estimating ΔP V is:

where

B is the vapor pressure constant for the stock (°R) Only the B constant from the

two-constant vapor pressure equation that has units of °R and psia is suitable for use in

Equation 15b (See API MPMS Ch 19.4, 3rd Edition, Table 3.);

8 APIMPMSC HAPTER 19.1

P VA is the stock true vapor pressure (psia) at the daily average liquid surface

temperature T LA (use API MPMS Ch 19.4, 3rd Edition, Section 4.2 to determine

vapor pressure P V at a given temperature T);

ΔT V is determined in 4.2.5a);

T LA is determined in 4.2.4

where

P BX is the breather vent maximum pressure setting (psig) (always positive)

If P BX is unknown, assume P BX = 0.03 psig;

P BN is the breather vent minimum pressure setting (psig) (negative if a vacuum setting)

If P BN is unknown, assume P BN = –0.03 psig

If the fixed-roof tank is of bolted or riveted construction in which the roof or shell plates are not gas

tight, assume ΔP B = 0, even if a breather vent is used

P A is the atmospheric pressure (psia) at the tank site

If P A is unknown, assume P A = 14.7 psia

If Equation 13c yields a negative value for K E , use zero as the value of K E This results in an estimated

standing loss of zero because the vent pressure setting range ΔP B is sufficiently high to prevent breathing

loss for the conditions assumed

4.2.6 Stock Vapor Density W V

The stock vapor density W V (lb/ft3) is:

W V =

V

VA V

RT

P M

(19) where

M V is the stock vapor molecular weight (lb/lb-mole) (See API MPMS Ch 19.4, 3rd Edition,

The constants 0.8 and 0.2 are dimensionless; the constant 0.008 has units of (°R ft2 day)/Btu;

The equation for vapor space temperature is reasonable in ambient storage circumstances

because the vapor space achieves thermal equilibrium relatively quickly

E VAPORATIVE L OSS F ROM F IXED -R OOF T ANKS 9

Alternatively, if sufficient data are available, API MPMS Ch 19.4, 3rd Edition, Appendix I may be

used for a slight improvement in the estimate of T V

R is the ideal gas constant (10.731 psia ft3/(lb-mole oR))

4.3 Working Loss L W

4.3.1 General

Working loss occurs when the liquid level in the tank increases The working loss L W (lb/yr) is:

where V Q , K N , K C , and K B are determined in 4.3.2 through 4.3.5, respectively, and W V is determined in 4.2.6

4.3.2 Net Working Loss Throughput V Q

The working loss throughput (ft3/yr) is:

Q is the stock throughput (bbl/yr) Use of the stock throughput Q overestimates V Q if filling

and withdrawal occur simultaneously;

The constant 5.614 has units of ft3/bbl

The constant 180 has units of turnovers/yr

N is the stock turnover rate (turnovers/yr) =

where

ΣH Q is the annual sum of increases in liquid level (ft/yr);

For vertical tanks, H LX = maximum liquid height (ft).;