SIST EN ISO 4256:1998

SLOVENSKI STANDARD
SIST EN ISO 4256:1998
01-maj-1998
8WHNRþLQMHQLQDIWQLSOLQL'RORþDQMHSDUQHJDWODND0HWRGD813,62
Liquefied petroleum gases - Determination of vapour pressure - LPG method (ISO
4256:1978)
Flüssiggase - Bestimmung des Dampfdruckes - LPG-Verfahren (ISO 4256:1978)
Gaz de pétrole liquéfiés - Détermination de la pression de vapeur - Méthode GPL (ISO
4256:1978)
Ta slovenski standard je istoveten z: EN ISO 4256:1995
ICS:
75.160.30 Plinska goriva Gaseous fuels
SIST EN ISO 4256:1998 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 4256:1998

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SIST EN ISO 4256:1998

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SIST EN ISO 4256:1998

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SIST EN ISO 4256:1998

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SIST EN ISO 4256:1998

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SIST EN ISO 4256:1998
INTERNATIONAL STANDARD 4256
~~
INTERNATIONAL ORGANIZATION FOR STANDARDIZATlON*~E~YHAPO~HAR OPrAHM3AL&iR fl0 CTAH~Af'TM3AL(MM~RGANlSATlON INTERNATIONALE DE NORMALISATION
0 Liquefied petroleum gases - Determination of vapour
pressure - LPG method
Gaz de pétrole liquéfiés - Détermination de la pression de vapeur - Méthode GPL
First edition - 1978-11 -01
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UDC 665.725 : 536.423.15 Ref. No : IS0 4256-1978 (E)
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Price based on 6 pages

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SIST EN ISO 4256:1998
FOREWORD
IS0 (the International Organization for Standardization) is a worldwide federation
of national standards institutes (IS0 member bodies). The work of developing
International Standards is carried out through IS0 technical committees. Every
member body interested in a subject for which a technical committee has been set
up has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work.
Draft International Standards adopted by the technical committees are circulated
to the member bodies for approval before their acceptance as International
Standards by the IS0 Council.
International Standard IS0 4256 was developed by Technical Committee
ISO/TC 28, Petroleum products, and was circulated to the member bodies in
March 1976.
It has been approved by the member bodies of the following countries :
Austria Ireland Romania
Belgium Israel South Africa, Rep. of
Brazil Italy Spain
Canada Japan Sweden
Czechoslovakia Mexico Turkey
France Netherlands United Kingdom
Germany, F.R.
Peru U.S.A.
Hungary Philippines U.S.S.R.
India Poland
Iran
Portugal
No member body expressed disapproval of the document.
0 International Organization for Standardization, 1978
Printed in Switzerland

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SIST EN ISO 4256:1998
INTERNATIONAL STANDARD IS0 4256-1978 (E)
Liquefied petroleum gases - Determination of vapour
pressure - LPG method
1 SCOPE AND FIELD OF APPLICATION 33 113 or 40 % by volume of the liquid content of the
apparatus is immediately withdrawn to provide adequate
This International Standard specifies a method for the
free space for product expansion. The apparatus is then
determination of the gauge vapour pressures (see note 1)
immersed in a water bath maintained at the standard test
of liquefied petroleum gas products (see note 2) at temper-
temperature of 37.8 OC or, optionally, at some higher
atures of 37,8 OC up to and including a test temperature
test temperature up to and including a test temperature
of 70 OC.
of 70 OC.
NOTES
3.2 The observed gauge pressure at equilibrium, after
1 Information on the gauge vapour pressures of liquefied
correcting for gauge error and correcting to a standard
petroleum gas products under test temperature conditions in the
barometric pressure, is reported as the "LPG vapour
range from 37.8 to 70 OC is pertinent to problems of selecting
properly designed storage vessels, shipping containers, and customer
pressure " at the selected test temperature.
utilization equipment to ensure the safe handling of such products,
2 For the purpose of this test method, liquefied petroleum gas
products are defined as narrow boiling range hydrocarbon mixtures
consisting predominantly of propane or propylene, or both, butanes
or butylenes, or both, in which the content of hydrocarbon
compounds of boiling point higher than O "C is less than 5 % by
4 APPARATUS
liquid volume, and whose gauge vapour pressure at 37.8 OC is not
greater than approximately 1 550 kPa.1)
0
4.1 Vapour pressure apparatus, constructed as illustrated
in the figure, consisting of two chambers, designated as the
2 REFERENCES
upper and lower chambers, complying with the require-
IS0 3007, Petroleum products - Determination of vapour ments in4.1.1 to4.1.7.
pressure - Reid method.
NOTES
IS0 4257, Liquefied petroleum gases - Determination of
1 CAUTION - To maintain the correct volume ratio between the
sampling characteristics )
upper and lower chambers, they shall be matched in pairs and the
units shall not be interchanged without recalibrating to ascertain
that the volume ratio is within satisfactory limits.
3 PRINCIPLE
2 The "air chamber" of the method described in IS0 3007 is
interchangeable with the "upper chamber" of this method. Similarly,
3.1 The test apparatus, consisting of two interconnected
the "liquid chamber'' (two-opening type) of IS0 3007 is inter-
chambers and equipped with a suitable pressure gauge, is
changeable with the "20 % lower chamber" of this method. The
purged with a portion of the sample which is then
apparatus assembly of IS0 3007 must pass, as a safety precaution,
discarded. The apparatus is then filled completely with a
the hydrostatic test specified in 4.1.6 before being used for
test portion of the test sample to be tested. testing liquefied petroleum gas.
1) 1kPa= 10-2bar
2) In preparation.
1

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SIST EN ISO 4256:1998
IS0 4256-1978 (E)
Straight-through valve
Gauge coupling
Bleeder-valve coupling Lower
chamber
-Upper chamber
-
FIGURE - Typical LPG vapour pressure apparatus
4.1.1 Upper chamber 4.1.3 Lower chamber, 33 I 13 %
This chamber shall be a cylindrical vessel of such a
This chamber shall be a cylindrical vessel 51 f 3 mm in
volume that the ratio of the volume of the upper chamber
diameter and 254 f 3 mm in length, inside dimensions,
of the ends slightly sloped to to the volume of the lower chamber is 2 f 0,03 (see
with the inner surfaces
provide complete drainage from either end when held in a note 1 to 4.1.4).
vertical position. At one end of the chamber, a suitable
bleeder-valve coupling shall be provided to receive the
4.1.4 Lower chamber, 20 %
bleeder-valve assembly and the pressure gauge. At the other
This chamber shall be a cylindrical vessel of such a volume
end of the chamber an opening approximately 13 mm in
that the ratio of the volume of the upper chamber to the
diameter shall be provided for coupling with the lower
volume of the lower chamber is 4 f 0,05 (see notes 1 and
chamber. Care shall be taken that the connections to the
2 below).
end openings do not prevent the chamber from draining
completely.
NOTES
1 In determining the volumetric capacities of the chambers, the
4.1.2 Bleeder-valve assembly
volume of the lower chamber shall be considered as that which is
below the "straight-through" valve closure. The volume above the
The bleeder-valve for purging the apparatus shall be a
"straight-through" valve closure, including the portion of the
nominal 6 mm valve fitted into the side of the bleeder-
coupling attached to the upper chamber, shall be considered as a
valve coupling. The lower end shall be threaded to fit
part of the upper chamber volume. The volume ratios of the
into the end fitting of the upper chamber, and the upper
chambers shall be determined in accordance with the procedure
be threaded to receive the gauge coupling. outlined in the annex of IS0 3007.
end shall
2

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SIST EN ISO 4256:1998
IS0 4256-1978 (E)
2 The apparatus requirements for this method, excluding the
4.3 Vapour pressure water bath, of such dimensions that
bleeder-valve assembly, are identical with those of IS0 3007 with
the vapour pressure apparatus may be immersed so as to
33 1/3 %lower chamber. Although the test
the exception of the
completely cover the bleeder-valve when the assembly
procedural details are different, the air and liquid chambers of
is in an upright position.
IS0 3007 may be used in the present method provided that they
are of sufficient strength to withstand the higher test pressures
(4.1.6).
4.4 Means for maintaining the bath at the test temperature
within the limits as follows :
4.1.5 Valves and method of coupling upper and lower a) test temperature 50 OC and below : +_ 0.1 OC;
chambers
b) test temperature above 50 OC : 0,3 OC.
At one end of the lower chamber, an opening approxi-
In order to check the bath temperatures, the appropriate
mately 19 mm in diameter shall be provided to receive a
bath thermometer (see 4.5) shall be immersed to the test
suitable straight-through valve having a minimum internal
temperature graduation mark on the thermometer scale
channel of 13 mm diameter. The other end of the chamber
throughout the vapour pressure determination.
shall be equipped with a nominal 6 mm inlet valve.
Any method of coupling the chambers may be employed
4.5 Thermometers, complying with the appropriate
provided that the volumetric requirements are met and
specification in table 2 :
that the assembly is free from leaks under the conditions
- low range for indicating test temperatures between
of the test.
35 and 40 OC;
-- middle range for indicating test temperatures
4.1.6 Hydrostatic test
between 40 and 70 OC;
The assembled chambers shall be certified by the
- high range for indicating test temperatures between
manufacturer to withstand approximately 7 O00 kPa gauge
50 and 80 OC.
hydrostatic pressure without permanent deformation.
4.6 Read-weight tester, of satisfactory range, as a means
4.1.7 Checking for freedom from leaks
for checking the accuracy of vapour pressure gauges.
Before placing new apparatus in service, and as often as
necessary thereafter, the assembled vapour pressure
apparatus shall be checked for freedom from leaks by
5 SAMPLING AND SAMPLE HANDLING
filling it with air, natural gas, nitrogen, or other similar
gases, to 3 500 kPa gauge pressure, and then completely
5.1 Samples shall be obtained and stored in accordance
immersing it in a water bath. Only apparatus that will
with IS0 4257 unless the test samples can be taken directly
withstand this test without leaking shall be used.
from the source of the material to be tested.
5.2 Any convenient method of coupling the vapour
4.2 Pressure gauge. Bourdon-type spring gauge of test
pressure apparatus to the sample source may be employe
...