SIST EN ISO 6327:2008

SLOVENSKI STANDARD
SIST EN ISO 6327:2008
01-marec-2008
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Gas analysis - Determination of the water dew point of natural gas - Cooled surface
condensation hygrometers (ISO 6327:1981)
Gasanalyse - Bestimmung des Wassertaupunktes von Erdgas - Kondensations-
Hygrometer mit gekühlter Oberfläche (ISO 6327:1981)
Analyse des gaz - Détermination du point de rosée des gaz naturels - Hygromètres à
condensation à surface refroidie (ISO 6327:1981)
Ta slovenski standard je istoveten z: EN ISO 6327:2008
ICS:
75.060
SIST EN ISO 6327:2008 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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EUROPEAN STANDARD
EN ISO 6327
NORME EUROPÉENNE
EUROPÄISCHE NORM
January 2008
ICS 75.060

English Version
Gas analysis - Determination of the water dew point of natural
gas - Cooled surface condensation hygrometers (ISO
6327:1981)
Analyse des gaz - Détermination du point de rosée des gaz Gasanalyse - Bestimmung des Wassertaupunktes von
naturels - Hygromètres à condensation à surface refroidie Erdgas - Kondensations-Hygrometer mit gekühlter
(ISO 6327:1981) Oberfläche (ISO 6327:1981)
This European Standard was approved by CEN on 15 December 2007.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the
official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2008 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 6327:2008: E
worldwide for CEN national Members.

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EN ISO 6327:2008 (E)






Foreword



The text of ISO 6327:1981 has been prepared by Technical Committee ISO/TC 193 "Natural
gas” of the International Organization for Standardization (ISO) and has been taken over as EN
ISO 6327:2008 by Technical Committee CEN/SS N21 "Gaseous fuels and combustible gas", the
secretariat of which is held by CMC.

This European Standard shall be given the status of a national standard, either by publication of
an identical text or by endorsement, at the latest by July 2008, and conflicting national
standards shall be withdrawn at the latest by July 2008.
Attention is drawn to the possibility that some of the elements of this document may be the
subject of patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any
or all such patent rights.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium,
Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United
Kingdom.

Endorsement notice

The text of ISO 6327:1981 has been approved by CEN as EN ISO 6327:2008 without any
modifications.

2

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International Standard
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION.ME~YHAPO~HAR OPt-AHM3ALWlfl ll0 CTAH~APT~3AUlM@ORGANISATION INTERNATIONALE DE NORMALISATION
Gas analysis - Determination of the water dew Point of
natura1 gas - Cooled surface condensation hygrometers
Hygromktres a condensation & surface refroidie
Determination du Point de roske des gaz naturels -
Analyse des gaz -
First edition - 1981-03-15
Ref. No. ISO6327-1981 (E)
UDC 665.612.3 : 543.27 : 533.275
üi
-
tests, water vapour tests, determination, vapour pressure, humidity, dew Point, test
Descriptors : gas analysis, natura1 gas, hygrometers,
83
I
equipment.
M
t2
Price based on 5 pages

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Foreword
OS0 (the International Organization for Standardization) is a worldwide federation of
national Standards institutes (ISO member bedies). The work of developing Inter-
national Standards is carried out through ISO 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 ISO Council.
International Standard ISO 6327 was developed by Technical Committee ISO/TC 158,
Analysis of gases, and was circulated to the member bodies in September 1979.
it has been approved by the member bodies of the following countries :
Australia India Poland
Belgium Korea, Rep. sf Romania
Libyan Arab Jamahiriya South Africa, Rep. of
Czechoslovakia
Egypt, Arab Rep. of Mexico United Kingdom
France Netherlands USSR
Germany, F. R. Philippines
No member body expressed disapproval of the document.
International Organkation for Standardkation, 1981
Printed in Switzerland

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ISO 6327-1981 (E)
INTERNATIONAL STANDARD
Determination of the water dew Point of
Gas analysis -
natura1 gas - Cooled surface condensation hygrometers
1 Scope 3.2 Determination of water vapour pressure
The partial water vapour pressure in the gas samples is the
This International Standard describes hygrometers used for the
determination of the water dew Point of natura1 gases by detec- saturated vapour pressure corresponding to the observed dew
Point, provided that the gas in the hygrometer is at the same
ting water vapour condensation occurring on a cooled surface
or by checking the stability of the condensation on this surface. pressure as the gas at the time of sampling.
Published documents are available giving the relationship be-
tween saturated vapour pressure and temperature.
2 Field of application
lt should be noted that if methanol is present, this method
determines methanol in addition to water. However, if the
The water dew Point of processed natura1 gases in transmission
methanol content is known, the annex gives, for information,
lines normally lies between - 25 OC and + 5 OC, which cor-
responds to water concentrations of 50 to 200 ppm (V/ v), correction factors allowing determination of the actual water
dew Point.
according to the pressure of the gas.
3.3 Precautions to be taken
The hygrometers considered in this International Standard may
be used for determining water vapour pressure, without requir-
lt is essential that all Sample lines be as short as possible and be
ing calibration, in a System operating under total pressures
sized to produce a negligible pressure drop during measure-
greater than or equal to atmospheric pressure. The relationship
ment. The Sample lines and the hygrometer, apart from the
between water vapour partial pressure and the observed dew
mirror, shall be above the water dew Point temperature.
Point confers on the method the quality of absolute measure-
ment.
4 Characteristics of the apparatus
If the test atmosphere contains gases which condense at a
temperature in the region of, or above, that of the water dew
4.1 General
Point, it is very difficult to detect the condensed water vapour.
Condensation apparatus may be designed in various ways. The
differentes lie mainly in the nature of the condensation surface,
the methods used for cooling the surface and for controlling its
3 Principle
temperature, the methods used for measuring the surface
temperature and the method of detecting the condensation.
The mirror and its associated components are normally placed
3.1 Principle of the apparatus
in a small cell through which a Sample of the gas flows; at high
pressures, the mechanical strength and leak tightness of the
With this type of apparatus, which determines the water con-
cell have to be suitable.
tent of a gas by measuring the corresponding dew Point, a sur-
face (generally a metallic mirror), the temperature of which may
lt is recommmended that the mirror should be easily removable
be artificially lowered and accurately measured, is exposed to a
for cleaning.
Sample of the gas being tested. The surface is then cooled to a
temperature at which condensation occurs and is observed as
Adequate precautions shall be taken if measurements are to be
dew.
made in the presence of condensable hydrocarbons.
Measurements tan be carried out manually or automatically.
Below this temperature, condensation increases with time,
whilst above it, condensation decreases or does not occur. This
Caution : Manufacturers’ instructions should be carried out
surface temperature is then (for practical applications) taken as
before gas at high pressure is admitted to the cell.
the dew Point of the gas flowing through the apparatus.

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In the absence of any condensation, -[he aiffused light failing cr;
the phototeil must be reduced. The effects of BEght diffused
Lkvices for measuring dew point tan be designed tcd make from internal surfaces of the cell tan be reduced Dy blackening
isoiated measurements at different times or to make more or these surfaces ahd this precaution EX be stipplernen-ted by an
iess continuous measurements. For isolated measurements, arrangement sf the optical system so that only the mirror Os
imethods of mir-kor cooling may be Chosen which require con- illuminated and the photocell vievvs oniy the ,mirror.
tinwous attention by the Operator responding to changes in the
zcndensed deposit which is observed by the naked eye. Bf there
!s jess moisture in the gas Sample, i.e. if the gas has a lower
(3ebv Point, the rate at which water vapour flows through the
apparatus per unit time decreases so that condensation forms
more siowjy, and it becomes more difficult to judge whether
The following methods are used for reducing and adjusting the
eowdensation is increasing or diminishing. Observation sf the
mirror temperature. The methods described in 4.4% and 4.42
deposi; tan be made easier by using a photoelectric cell or any
require constant ütter-hn frcmi the operatot- and are 7laC
,--%er deiice which is sensitive to Iight, if a simple indicator SS
suitabhe for autcmatic devices. 521) automatic deviees, two
-ice&yj,
while maintaining manual control of the cooling
-ietdjge.
cooling methods are used : indirect cantact with a coslant EX-
csoling by the thermoelectric (Peitier) effect as described In
4.4.3 and 4.44. In any case; the rate :isl eooirng 0-F the a-~riu-~~-
L%%?-~ certain types of manually operated instrumenrs, it is very
shall not exceed 1 “C per n?in~Gie.
-~+?%xI~ to observe the water dew Point in the presence of con-
c.31 1
d~~sed hydrocarbons. In such cases, a liquid Paraffin bubbler
Z-ISS be used to assist such observations. It is very important,
however, that the principles involved and the Iimitations in the
kse of such a bubbler are understood.
A volatile liquid in contact v&n :he Keas’ face ~9 P!X mirrcr tan
be evaporated and cooled by an air ibw. Hand beliovvs are
& equiiibrium is establis
...