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है”ह”ह

IS 15126 (2002): Natural Gas - Standard ReferenceConditions [PCD 3: Petroleum, Lubricants and their RelatedProducts]

IS 15126:2002ISO 13443:1996

Indian Standard

NATURAL GAS — STANDARD REFERENCECONDITIONS

ICS 75.060

!

.,

,,J

@ 61S 2002

BUREAU OF IN DIANSTA ND ARDSMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MAR(3

NEW DELHI 110002

April 2002 PriceGroup 6

I

Natural Gas Sectional Committee, PCD 24

NATIONAL FOREWORD

This Indian Standard which is identical with ISO 13443:1996 ‘Natural gas — Standard referenceconditions’ issued by the International Organization for Standardization (ISO) was adopted by theBureau of Indian Standards on the recommendation of the Natural Gas Sectional Committee andapproval of the Petroleum, Coal and Related Products Division Council.

The text of ISO Standard has been proposed to be approved as suitable for publication as IndianStandard without deviations. Certain conventions are, however, not identical to those used in IndianStandards. Attention is particularly drawn to the following:

a) Wherever the words ‘International Standard’ appear referring to this standard, they shouldbe read as ‘Indian Standard’.

b) Comma (,) has been used as a decimal marker while in Indian Standards, the currentpractice is to use a point (.) as the decimal marker.

In this adopted standard, reference appears to one International Standard for which Indian Standardalso exists. The corresponding Indian Standard, which is to be substituted in its place, is listed belowalong with its degree of equivalence for the edition indicated:

International Corresponding Degree ofStandard Indian Standard Equivalence

ISO 6976:1995 Natural gas — IS 14504:1997 Natural gas — IdenticalCalculation of calorific values, density, Calculation of calorific values,relative density and Wobbe index density, relative density and Wobbefrom composition index from composition

In reporting the results of a test or analysis made in accordance with this standard, if the final value,observed or calculated, is to be rounded off, it shall be done in accordance with IS 2:1960 ‘Rules forrounding off numerical values (revised’.

,-..

i

&

IS 15126:2002ISO 13443:1996

Indian Standard

NATURAL GAS — STANDARD REFERENCECONDITIONS

1 Scope

This International Standard specifies the standard reference conditions of temperature, pressure and humidity to beused for measurements and calculations carried out on natural gases, natural-gas substitutes and similar fluids.

The primary application is expected to be in international custody transfer, where the reduction to a common basisof those physical attributes of a gas which describe both its quality and quantity will simplify the practice of worldtrade and commerce,

2 Normative reference

The following standard contains provisions which, through reference in this text, constitute provisions of thisInternational Standard. At the time of publication, the edition indicated was valid. All standards are subject torevision, and parties to agreements based on this International Standard are encouraged to investigate thepossibility of applying the most recent edition of the standard indicated below. Members of IEC and ISO maintainregisters of currently valid International Standards.

ISO 6976:1995, Natura/ gas — Calculation of calorific values, density, relative density and Wobbe index fromcomposition.

3 Standard referenceconditions

The standard reference (or base) conditions of temperature, pressure and humidity (state of saturation) to be usedfor measurements and calculations carried out on natural gases, natural-gas substitutes and similar fluids in thegaseous state are 288,15 K and 101,325 kPa for the real dry gas.

The physical properties to which these ISO standard reference conditions apply include volume, density, relativedensity, compression factor, superior calorific value, inferior calorific value and Wobbe index. Full definitions ofthese quantities are given in ISO 6976:1995. In the cases of calorific value and Wobbe index, both the volume ofgas burned and the energy released by combustion shall relate to the ISO standard reference conditions.

..-

It is recognized, however, that in certain circumstances it may be impracticable or even unallowable to use theISO standard reference conditions. For example, national legislation or contractual obligations may demand the useof alternative reference conditions, For this reason, annex A provides factors for conversion between several setsof metric reference conditions which are known to be in regular use, and annex B gives equations which enablevalues of properties (relating to any other known reference conditions) to be converted to values for the ISO

1

IS 15126:2002ISO 13443:1996

standard reference conditions. Annex D gives some example calculations. Annex E gives the metric referenceconditions which, at present time, are believed to be those in most common usage in the countries listed.

NOTES

1 Among other considerations, the ISO standard reference conditions have been chosen to conform with those standardizedin ISO 5024[1 I for use in the measurement of petroleum liquids and gases.

2 288,15 K=15°C=590F101,325 kPa = 1,01325 bar = 14,6959 psia = 1 standard atmosphere (atm)

3 In ISO 6976:1995, a dry gas is defined as one for which the mole fraction of water vapour is less than 0,00005, but thiscriterion is unnecessarily restrictive in the context of this International Standard, where a mole fraction of up to 0,001 may be

allowable.

4 The conditions 273,15 K, 101,325 kPa and 288,15 K, 101,325 kPa are commonly referred to as “normal” and “(metric)standard” conditions, respectively, in gas-measurement practice (see lGU/G-6414J,lGU/G-73[s) and lGU/G-76 [G]).This usageshould not be confused with “ NTP” (normal temperature and pressure) and “ STP” (standard temperature and pressure), bothof which conventionally refer to the former conditions. The definitions of “normal” and “standard” given in 1S0 7504[ZI conflictwith the usage given above, and are incorrect.

5 Good practice requires that the relevant reference conditions are incorporated as part of the symbol (and not the unit) forthe physical quantity represented wherever ambiguity is possible. For example:

— use 2(273, 15 K, 101,325 kPa) or ZWC = O,p/atm = 1), not Zn, for compression factor at “normal” conditions;

— use V(273, 15 K, 101,325 kPa) ms for the volume of gas in cubic metres at “normal” conditions, not inns, ins(n), nm~or Nms, and certainly not simply ms;

— use V(f/°C= 15, p/kPa= 101,325) ms for the volume of gas in cubic metres at “standard” conditions, not ms(st), smsor m~s.

Abbreviated versions such as Z(0), V(0)/m3 and V(I 5)/m3, respectively, are acceptable when no misinterpretation ispossible. in the latter case, V(LSO)/m3 is probably the best designation.

.. -

,

2

IS 15126:2002ISO 13443:1996

Annex A

(normative)

Factors for conversion between reference conditions

Toobtalnthe value of aproperty atthereference condition given inrowlblof table A.1 froma known value in the

same units at the reference condition in row [al, multiply by the factor indicated. To carry out the reverseconversion, divide by the factor indicated.

Conversions forproperties of theideal gasareexpected to beaccurate towithin-O,Ol %forall natural gases. Forthe real-gas volumetric properties (volume per unit amount, density, relative density, compression factor), theexpected accuracy is – 0,02 Yo, and for the real-gas combustion properties (calorific values, Wobbe index) – 0,05 Yo.

Conversion factors for non-metric (e.g. Imperial) reference conditions are not provided, as the continued use ofthese — particularly in international trade — is discouraged. Most non-metric reference conditions use atemperature base of 60 “F, but several distinct pressure bases have been invoked. Annex B provides equationswhich will allow the conversion of property values from reference conditions not shown in table Al to equivalentvalues for the ISO standard reference conditions.

In table Al, the pressure base for both combustion and volumetric metering is always 101,325 kPa and the gas istaken to be dry.

3

IS 15126:2002ISO 13443:1996

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Table A.1 — Factors for conversion between reference conditions

Metering r2pC Combustion IIPC

[al fi 20 20 15 25 25 25 20 20 15

to to to to to to to to to

[b] fi 15 00 00 20 15 00 15 00 00

Ideal volume ,,,,,,., . . . . 0,9829 0,9318 0,9479

Ideal density 1,0174 1,0732 1,0549

Ideal relative density 1,0000 1,0000 1,0000

Compression factor,,.,,,,,.,,, 0,9999 0,9995 0,9996

Real volume 0,9828 0,9313 0,9476

Real density,,,.,,,, ............... 1,0175 1,0738 1,0553

Real relative density ..,,.,,..., 1,0001 1,0003 1,0002

Molar-basis ideal superior calorific value

Molar-basis ideal inferior calorific value

Mass-basis ideal superior calorific value

Mass-basis ideal inferior calorific value

Molar-basis real superior calorific value

Molar-basis real inferior calorific value . . . . .

Mass-basin real superior calorific value

Mass-basis real inferior calor!fic value

[a] fi

[b] ti

16 Volume-basis ideal superior calorific value

17 Volume-basis ideal inferior calorific value

18 Ideal Wobbe index

19 Volume-basis real superior calorific value

20 Volume-basis real inferior calorific value

21 Real Wobbe index

1,0005 1,0010 1,0026 1,0005

1,0001 1,0001 1,0003 1,00Q o

1,0005 1,0010 1,0026 1,0005

1,0001 1,0001 1,0003 1,0000

1,0005 1,0010 1,0026 1,0005

1,0001 1,0001 1,0003 1,0000

1,0005 1,0010 1,0026 1,0005

1,0001 1,0001 1,0003 1,0000

1,0021 1,0016

1,0002 1,0002

1,0021 1,0016

1,0002 1,0002

1,0021 1,0016

1,0002 1,0002

1,0021 1,0016

1,0002 1,0002

Combustion rlPC : Metering tJ”C

25:20 25:20 25:20 25:00 25:00 15:15

to to to to to to

25:00 15:15 00:00 15:15 00:00 00:00

1,0732 1,0184 1,0760 0,9489 1,0026 1,0566

1,0732 1,0175 1,0735 0,9481 1,0003 1,0551

1,0732 1,0184 1,0760 0,9489 1,0026 1,0566

1,0738 1,0185 1,0766 0,9486 1,0026 1,0570

1,0738 1,0176 1,0741 0,9477 1,0003 1,0555

1,0736 1,0185 1,0764 0,9487 1,0026 1,0569

* 6,——

IS 15126:2002

ISO 13443: 1996

Annex B

(informative)

Equations for conversion between reference conditions

~quations B. I to B,21, allovi the conversion of values of the properties listed from reference conditions TIK T2/K,pl/kPa and p2/kPa to the equivalent values in the same units of measurement at the ISO standard referenceconditions, The equations given are valid for the ranges: 270< T/K

IS 15126 ;2002ISO 13443:1996

Real density p

p(lSO) = /J(T~, ~2) X [101,325 7’2/288,15p21 X [1 + 0,000 025( T2- 288,15)1 /[1 + 0,000 OZO(P2- 1013Z5)I

Real relative density d

41S0) = J(T2, p2) X [1 + 0,000014 (T2 - 288,15)1 /[1 + 0,000020 (pz --101,325)1

Molar-basis ideal superior calorific value ~~

fi~(lSO) = tif(Tl, pl) X [1 + 0,00010 (TI – 288,15)1

. . . (B.6)

(B.7)

. . . (B.8)

Molar-basis ideal inferior calorific value ~~ ]

~~ (ISO) = ~~ (Tl, pl) X [1 + 0,00001 (TI - 288,15)1 (B.9)

Mass-basis ideal superior calorific value @

fi:(lso) = H: (T1,P1)x [1 + 0,00010 (TI - 288,15)1

Mass-basis ideal inferior calorific value @

fi; (ISO) = fi~ (Tl, pl) X [1 + 0,00001 (T1 - 288,15)1

Molar-basis real superior calorific vahie ~~

~~(lSO) = ~~(TI,pI) X [1 + 0,00010 (~1 - 288,15)1

Molar-basis real inferior calorific value E

E (ISO) = fi (Tl, p~) X [1 + 0,00001 (Tl - 288,15)1

Mass-basis real superior calorific value fi5

fi~(lSO) = fi~ (~l,,Dl)X[l +0,000 1O(TI -288,15)1

Mass-basis real inferior calorific value fil

fil (ISO) = fil (TI, pI) X [1 + 00001 (TI - 288,15)1

Volume-basis ideal superior calorific value @

@ (ISO) = fig (T,, 2“2,pq, p2) X [101,325 T2/288,15p2] X [1 + 0,00010 (Tl – 288,15)1

Volume-basis ideal inferior calorific value fi~

fi~ (ISO) = @ (7’1,T2, pl, p2) X [101,325 7’2/288,15p21 x [1 + 0,00001 (Tl - 288,15)1

Ideal Wobbe index W“

WO(lSO) = WO( Tl, 7’2,p], p2) X [101,3257’z/288,15p21 X [1 + 0,00010 (~1 - 288,15)1

Volume-basis real superior calorific value fi5

fis(lso) = fiS(T1, T2,pl, p2) X [101,325 7’2/288,15p2] X [1 + 0,00010 (TI – 288,15)1x

[1 + 0,000025 (T2 - 288,15)] /[1 + 0,000020 (P2 - 101,325)1

Volume-basis real inferior calorific value fil

fil (ISO) = fil(Tl, TZPI, P2) X [101,325 T2/288,15p2] x [1 + 0,00001 (T1 - 288,15)1 X

[1 + 0,000025 (T2 - 288,15)] /[1 + 0,000020 (pz - 101,325)1

Real Wobbe index W

w(ISO) = w(~l, T2, PI, PZ) X [101,325 T2/288,15P21 x [1 + 000010 (T1- 288115)] x

{[1 + 0,000020 (pz -101 ,325)]/[1 + 0,000036 (7’2- 288,15)])-1/2

(B.10)

(B.11) ‘j

!

(

(B.13)

,.. (B.14)

(B.15) .A.~

. (B.16)

. . (B.17)

. . . (B,18)

(B.19)

. . . (B.20)

(B.21)

6

--4

Annex C

(normative)

Symbols

Meaning

relative density

molar-basis inferior calorific value

mass-basis inferior calorific value

volume-basis inferior calorific value

molar-basis superior calorific value

mass-basis superior calorific value

volume-basis superior calorific value

(absolute) pressure

(absolute) temperature

Celsius temperature = T -273,15

volume

Wobbe index

compression factor

density

IS 15126:2002

ISO 13443: 1996

S1 unit(or multiple)

—

kJ mol-1

M.1 kg-l

MJ m-s

kJ mol-1

MJ kg-l

MJ m-s

kPa

K

‘c

m3

MJ m-s

.

kg m-s

Subscripts

1 for the combustion reference condition

2 for the volumetric or metering reference condition

Superscript

o for the ideal-gas state (no superscript indicates the real-gas state)

7

. A

---4IS 15126:2002ISO 13443:1996

Annex D

(informative)

Example calculations

The examples given below are all for real dry natural gases consisting preponderantly (greater than about 70~o

molar) of methane.

EXAMPLE 1

What is the compression factor at ISO standard reference conditions of a natural gas which has a compressionfactor of 0,9971 at a temperature of 273,15 K and a pressure of 101,325 kPa?

From table Al, line 4, column 3 (used inversely):

z(ISO) = 0,9971 X (1/0,9996) = 0,9975

The same value (to four significant digits) is obtained from equation (B.4).

EXAMPLE 2

What is the volume occupied at ISO standard reference conditions of a natural gas which occupies 1000 msat normal conditions?

The term “normal conditions” is taken to mean 273,15 K (O ‘C) at 101,325 kPa.

From table A.1, line 5, column 3 (used inversely):

v(ISO) = 1 000 x (1/0,947 6) = 1 055,3 ms

The same value (to five significant digits) is obtained from equation (B.5)

EXAMPLE 3

What is the mass-basis superior calorific value at ISO standard reference conditions of a natural gas determined ashaving a calorific value of 54,21 MJkg-1 at 25 “C and a pressure of 100 kPa?

Molar-basis and mass-basis calorific values are taken to be independent of pressure p, within the pressure rangegiven in annex B (which covers the range of normal atmospheric variation); the pressure assignment is thereforeirrelevant in this case.

From table Al, line 14, column 2’

&(lSO) = 54,21 X 1,0010 = 54,26 MJkg-1

The same value (exactly) is obtained from equation (B.14).

8

IS 15126:2002

ISO 13443:1996

EXAMPLE 4

What isthevolume-basis superior calorific value at lSOstandard reference conditions of a natural gas determinedas having a calorific value of 38,57 MJm-3 at 60 “F and 101,560 kPa?

This example cannot be solved using table A.1 because that table is only valid for a pressure of 101,325 kPa anddoes not include the Fahrenheit temperature quoted.

First convert 60 “F to the kelvin scale:

60 “F = [(60 - 32)x 5/9] + 273,15 = 288,706 K

Then, from equation (B.19):

fig (1S0) = {38,57X 101,325X 288,706X [1 + 0,000 10(288,706 -288,1 5)] X[1 + 0,000 025(288,706 - 288,15)]}/{288,15 X 101,560X[1 + 0,000 020(101,560 - 101,325)])

. 38,56 MJm-3 to four significant digits.

EXAMPLE 5

What is the volume-basis inferior calorific value at ISO standard reference conditions of a natural gas determined ashaving a calorific value of 37,35 MJm-3 when the volume of gas burned is measured at O “C, combustion takesplace at 25 “C and the reference pressure in both cases is one standard atmosphere?

The term “one standard atmosphere” is taken to mean 101,325 kPa

From table Al, line 20, column 4:

fil (ISO) = 37,35 x 0,9477 = 35,40 MJm-3

The same value (to four significant digits) is obtained from equation (B.20).

9

,: /* e%-

IS 15126:2002

ISO 13443: 1996

Annex E

(informative)

National usage of reference conditions

For those countries where the use of non-metric (e.g. Imperial) measurement units and reference conditions arestill in use alongside metric units and reference conditions, only the metric reference conditions are listed.

In table E.1 below:

rl/”C = combustion reference temperature

t2pC = volumetric or metering reference temperature

The reference pressure is 101,325 kPa in all cases.

Table E.1 — National usage of reference conditions

Argentina

Australia

Austria

Belgium

Brazil

Canada

China

Czechoslovakia

Denmark

Egypt

Finland

France

Germany

Hong Kong

Hungary

India

tlr’c

15

25

25

15

20

25

25

0

25

t#’c

15

15

0

0

0

15

20

20 and O

0

15

15

0

0

15

0

0

Indonesia

Iran

Ireland

Italy

Japan

Netherlands

New Zealand

Norway

Pakistan

Romania

Russia

Spain

Sweden

United Kingdom

USA

Yugoslavia

t#’c

15

25

0

25

25

25

0

15

15

0

t’zrc

o

15

15

0

0

0

15

15

15

15and0

20 and O

0

0

15

15

0

.

10

IS 15126:2002ISO 13443: 1996

Annex F

(informative)

Bibliography

[11 ISO 5024:1976, Petroleum liquids and gases — Measurement — Standard reference conditions.

[2j ISO 7504:1984, Gas analysis — Vocabulary.

[31 BS 350: Part 1:1974, Conversion factors and tables — Part 1: Basis of tables — Conversion factors.

[4] lGU/G-64 (1964), Report of the committee on documentation and sundry questions — Report of thesubcommittee on units, pp. 24-38.

[51 lGU/G-73 (1973), Report of the committee on documentation and sundry questions — Report of thesubcommittee on units, pp. 83-101.

- ..dj

“..FT.

~,

,J

[6] lGU/G-76 (1976), Report of the committee on statistics, documentation and sundry questions — Report of thesubcommittee on units, pp. 36-43.

11

-4Bureau of Indian Standards

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Copyright

BIS has the copyright of all its publications. No part of these publications may be reproduced in anyform without the prior permission in writing of BIS. This does not preclude the free use, in the course ofimplementing the standard, of necessary details, such as symbols and sizes, type or grade designa-tions. Enquiries relating to copyright be addressed to the Director (Publications), BIS.

Review of Indian Standards

Amendments are issued to standards as the need arises on the basis of comments. Standards are alsoreviewed periodically; a standard along with amendments is reaffirmed when such review indicates thatno changes are needed; if the review indicates that changes are needed, it is taken up for revision.Users of Indian Standards should ascertain that they are in possession of the latest amendments oredition by referring to the latest issue of ’61S Catalogue’ and ‘Standards: Monthly Additions’.

This Indian Standard has been developed from Doc : No. PCD24(1858).

Amendments Issued Since Publication

Amend No. Date of Issue Text Affected

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