EN 14790:2005

SLOVENSKI STANDARD
01-december-2005
(PLVLMHQHSUHPLþQLKYLURY'RORþHYDQMHYRGQHSDUHYRGYRGQLNLK
Stationary source emissions - Determination of the water vapour in ducts
Emissionen aus stationären Quellen - Bestimmung von Wasserdampf in Leitungen
Emissions de sources fixes - Détermination de la vapeur d'eau dans les conduits
Ta slovenski standard je istoveten z: EN 14790:2005
ICS:
13.040.40 (PLVLMHQHSUHPLþQLKYLURY Stationary source emissions
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 14790
NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2005
ICS 11.040.40
English Version
Stationary source emissions - Determination of the water vapour
in ducts
Emissions de sources fixes - Détermination de la vapeur Emissionen aus stationären Quellen - Bestimmung von
d'eau dans les conduits Wasserdampf in Leitungen
This European Standard was approved by CEN on 30 September 2005.
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 Central Secretariat 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 Central Secretariat has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, 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
© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 14790:2005: E
worldwide for CEN national Members.

Contents Page
Foreword .4
1 Scope.5
2 Normative references.5
3 Terms and definitions.6
4 Principle.9
4.1 General.9
4.2 Adsorption or condensation/adsorption method .9
4.3 Temperature method.9
5 Apparatus.10
5.1 General.10
5.2 Sampling probe.10
5.3 Filter housing.10
5.4 Particle filter.11
5.5 Trapping unit.11
5.6 Cooling System (optional).11
5.7 Sampling pump.11
5.8 Gas volume meter.11
5.9 Barometer.12
5.10 Balance.12
5.11 Temperature measurement.12
6 Measurement procedure.12
6.1 General requirements.12
6.2 Preparation and installation of equipment.12
6.2.1 Sampling location.12
6.2.2 Sampling point.13
6.2.3 Assembling the equipment .13
6.3 Leak test.13

6.4 Performing of the sampling.14
6.4.1 Introduction of the probe in the duct.14
6.4.2 Sampling.14
6.5 Repeatability of the weighing.14
6.6 Procedure for gas streams saturated with water (droplets present) .15
7 Determination of the characteristics of the method: sampling and analysis.15
7.1 Introduction.15
7.2 Relevant performance characteristics of the method and performance criteria .15
7.3 Establishment of the uncertainty budget.16
7.4 Equivalency with an alternative method .17
8 Evaluation of the method in the field.17
9 Water vapour determination.18
10 Report.20
Annex A (normative) Determination of water vapour concentration for water saturated gas, at P
std
= 101,325 kPa.21
Annex B (informative) Type of sampling equipments .25
Annex C (informative) Example of assessment of compliance of reference method for water
vapour with requirements on emission measurements.26
C.1 General.26
C.2 Process of uncertainty estimation.26
C.2.1 Determination of the model equation.26
C.2.2 Quantification of uncertainty components .26
C.2.3 Calculation of the combined uncertainty.26
C.3 Specific conditions in the field .27
C.4 Performance characteristics of the method .28
C.5 Calculation of standard uncertainty of the concentration .28
C.5.1 Model equation and application of the rule of the uncertainty propagation .29
C.5.2 Results of standard uncertainties calculations.33
C.5.3 Estimation of the combined uncertainty.36

Annex D (informative) Evaluation of the method in the field .37
D.1 General.37
D.2 Characteristics of installations.37
D.3 Repeatability and reproducibility in the field.38
D.3.1 Repeatability.39
D.3.2 Reproducibility.40
Annex ZA (informative) Relationship between this European Standard and the Essential
Requirements of EU Directive.41
Bibliography.42

Foreword
This European Standard (EN 14790:2005) has been prepared by Technical Committee CEN/TC 264 “Air
qualilty”, the secretariat of which is held by DIN.
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 May 2006, and conflicting national standards shall be withdrawn at the
latest by May 2006.
This European Standard has been prepared under a mandate given to CEN by the European Commission
and the European Free Trade Association, and supports essential requirements of EU Directive(s).
For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this European
Standard.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland
and United Kingdom.
1 Scope
This European Standard describes the condensation/adsorption technique, including the sampling system, to
determine the water vapour concentration in the flue gases emitting to atmosphere from ducts and stacks.
This technique is usually used all over Europe for water vapour monitoring. However to be implemented as
the Standard Reference Method (SRM), the user has to demonstrate that the performance characteristics of
the method are better than the performance criteria defined in this European Standard and that the overall
uncertainty of the method is less than ± 20 % of the measured value. This European Standard as the
Standard Reference Method (SRM) is used for periodic monitoring and for calibration or control of Automatic
Measuring Systems (AMS) permanently installed on a stack, for regulatory purposes or other purposes.
An Alternative Method to this SRM may be used provided that the user can demonstrate equivalence
according to the Technical Specification CEN/TS 14793, to the satisfaction of his national accreditation body
or law.
The determination of water vapour is mainly necessary for:
 regulatory purposes, to express the concentration at standard conditions (on dry gas);
 adjust the flow rate for isokinetic sampling, when a dry gas flow rate metering device is used.
For both applications, the quantity to be measured is the amount of water present in the gas phase (vapour),
which does not include water droplets.
This European Standard is applicable in the range from 4 % to 40 % relative humidity and for water vapour
3 3
concentration from 29 g/m to 250 g/m as a wet gas, although for a given temperature the upper limit of the
method is related to the maximum pressure of water in air or in the gas.
This European Standard has been evaluated during field tests on waste incineration, co-incineration and large
combustion installations. It has been validated for sampling periods of 30 min in the concentration range of
7 % to 26 % volume.
In this European Standard all the concentrations are expressed in normal conditions (273 K and 101,3 kPa).
NOTE For saturated conditions the condensation/adsorption method is not applicable. Some guidance is given in this
European Standard to deal with flue gas when droplets are present.
2 Normative references
The following referenced documents are indispensable for the application of this European Standard. For
dated references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ENV 13005, Guide to the expression of uncertainly in measurement.
CEN/TS 14793, Stationary source emission - Intralaboratory validation procedure for an alternative method
compared to a reference method.
EN ISO 14956, Air Quality – Evaluation of the suitability of a measurement procedure by comparison with a
required measurement uncertainty (ISO 14956:2002).
3 Terms and definitions
For the purposes of this European Standard, the following terms and definitions apply.
3.1
absorber
device in which water vapour is absorbed
3.2
detection limit (L )
D
concentration value of the measurand below which there is at least 95 % level of confidence that the
measured value corresponds to a sample free of that measurand
3.3
dew point
temperature below which the condensation of water vapour begins at the given pressure condition of the flue
gas
3.4
droplets
small liquid particles of condensed water vapour or water liquid in the flue gas (e.g. coming from a scrubber)
NOTE In adiabatic equilibrium conditions, droplets could arise only if a gas stream is saturated with water.
3.5
measurand
particular quantity subject to measurement
[VIM 2.6]
3.6
measuring series
several successive measurements carried out at the same sampling plane and with the same process
operating conditions
[EN 13284-1]
3.7
repeatability in the laboratory
closeness of the agreement between the results of successive measurements of the same measurand carried
out under the same conditions of measurement
NOTE 1 Repeatability conditions include:
 same measurement procedure;
 same laboratory;
 same sampling equipment, used under the same conditions;
 same location;
 repetition over a short period of time.
NOTE 2 Repeatability may be expressed quantitatively in terms of the dispersion characteristics of the results.
In this European Standard the repeatability is expressed as a value with a level of confidence of 95 %.
[VIM 3.6]
3.8
repeatability in the field
closeness of the agreement between the results of simultaneous measurements of the same measurand
carried out with two equipments under the same conditions of measurement
NOTE 1 These conditions include:
 same measurement procedure;
 two equipments, the performances of which are fulfilling the requirements of the reference method, used under the
same conditions;
 same location;
 implemented by the same laboratory;
 typically calculated on short periods of time in order to avoid the effect of changes of influence parameters
(e.g. 30 min).
NOTE 2 Repeatability may be expressed quantitatively in terms of the dispersion characteristics of the results.
In this European Standard the repeatability under field conditions is expressed as a value with a level of
confidence of 95 %.
3.9
reproducibility in the field
closeness of the agreement between the results of simultaneous measurements of the same measurand
carried out with several equipments under the same conditions of measurement
NOTE 1 These conditions include:
 same measurement procedure;
 several equipments, the performances of which are fulfilling the requirements of the reference method, used under
the same conditions;
 same location;
 implemented by several laboratories.
NOTE 2 Reproducibility may be expressed quantitatively in terms of the dispersion characteristics of the results.
In this European Standard the reproducibility under field conditions is expressed as a value with a level of
confidence of 95 %.
3.10
sampling location
specific area close to the sampling plane where the measurement devices are set up
3.11
sampling plane
plane normal to the centreline of the duct at the sampling position
[EN 13284-1]
3.12
sampling point
specific position on a sampling line at which a sample is extracted
[EN 13284-1]
3.13
standard reference method (SRM)
measurement method recognised by experts and taken as a reference by convention, which gives, or is
presumed to give, the accepted reference value of the concentration of the measurand (3.5) to be measured
3.14
uncertainty
parameter associated with the result of a measurement, that characterises the dispersion of the values that
could reasonably be attributed to the measurand
3.14.1
standard uncertainty u
uncertainty of the result of a measurement expressed as a standard deviation u
3.14.2
expanded uncertainty U
quantity defining a level of confidence about the result of a measurement that may be expected to encompass
a specific fraction of the distribution of values that could reasonably be attributed to a measurand
U = k x u
NOTE In this European Standard, the expanded uncertainty is calculated with a coverage factor of k = 2, and with a
level of confidence of 95 %.
3.14.3
combined uncertainty u
c
standard uncertainty uc attached to the measurement result calculated by combination of several standard
uncertainties according to GUM
3.14.4
overall uncertainty U
c
expanded combined standard uncertainty attached to the measurement result calculated according to GUM
U = k x u
c c
3.15
uncertainty budget
calculation table combining all the sources of uncertainty according to ISO 14956 or ENV 13005 in order to
calculate the overall uncertainty of the method at a specified value
3.16
vapour pressure
pressure of water in vapour form
4 Principle
4.1 General
This European Standard describes the Standard Reference Method (SRM) for determining water vapour
content emitting to atmosphere from ducts and stacks. The specific components and the requirements for the
measuring system are described. A number of performance characteristics, together with associated minimum
performance criteria are specified for the measurement method (see Table 1 in 7.2). The overall uncertainty of
the method shall meet the specifications given in this European Standard.
The method described hereafter is appropriate when the flue gas is free of droplets.
Within the scope of this European Standard, it is assumed that gas streams in stacks or ducts are more or
less in adiabatic (thermodynamic) equilibrium. In those conditions, droplets can arise only if a gas stream is
saturated with water. When no droplets are present in the gas stream, the gas stream is then assumed to be
unsaturated with water. A gas sample is extracted at a constant rate from the stack. The water vapour of that
sample is subsequently trapped by adsorption or by condensation plus adsorption; the mass of the vapour is
then determined by weighing the mass gain of the trapping unit.
When droplets are present in the gas stream, the implementation of the method described in this European
Standard leads to an overestimation of the water vapour content. If the measured value is equal to or higher
than the expected value shown in the table in Annex A for saturated conditions at the temperature and
pressure of the flue gas, that means that the presence of droplets can lead to biased results; such results shall
be rejected.
In such cases, the evidence suggests that the gas stream is saturated with water vapour. Under these
conditions, the method is abridged to a determination of the gas temperature. Then, the water vapour
concentration is calculated from the theoretical mass of water vapour per unit of standard gas volume at
liquid-gas equilibrium, given the actual temperature, pressure and composition of the gas stream.
4.2 Adsorption or condensation/adsorption method
A measured quantity of sampled gas is extracted from the gas stream through a trapping unit, which meets
the specifications of efficiency (see 6.4.2). The mass gain of the trapping unit is measured and divided by the
volume sampled in order to determine the mass concentration of water vapour.
4.3 Temperature method
This method applies when gases are water saturated.
A temperature probe is placed in the gas stream saturated with water vapour, until it reaches equilibrium. The
amount of water vapour present in the gas is subsequently derived from the temperature, using a water liquid-
gas equilibrium chart or table (see Annex A).
5 Apparatus
5.1 General
A known volume of flue gas is extracted representatively from a duct or chimney during a certain period of
time at a controlled flow rate. A filter removes the dust in the sampled volume; thereafter the gas stream is
passed through a trapping unit. It is important that all parts of the sampling equipment upstream of the
trapping unit are heated and that the components shall not react with or absorb water vapour (e.g. stainless
steel, borosilicate glass, quartz glass, PTFE or titanium are suitable materials).
An example of suitable sampling trains are shown in Annex B. The user can choose between a trapping unit
made up with either:
 adsorption unit (Figure B.1); or
 condensation and an adsorption unit (Figure B.2).
The choice shall be made to fulfil the efficiency that is required in 6.4.2.
5.2 Sampling probe
In order to access the representative measurement point(s) of the sampling plane, probes of different lengths
and inner diameters may be used. The design and configuration of the probe used shall ensure the residence
time of the sample gas within the probe is minimised.
The procedure of clause 6.2.2 can be used when the operator suspects that the flue gas is inhomogeneous.
The probe may be marked before sampling in order to demonstrate that the representative measurement
point(s) in the measurement plane has (have) been reached.
The sampling probe shall be surrounded by a heating jacket capable of producing a controlled temperature of
at least 120 °C and 20 °C higher than the (acid) dew point of gases and shall be protected and positioned
using an outer tube.
NOTE 1 It is possible to perform the sampling of SO and water vapour simultaneously with the same probe (without
nozzle providing no droplets are present).
NOTE 2 It is possible to perform the sampling of HCl and water vapour simultaneously with the same probe (without
nozzle providing no droplets are present).
5.3 Filter housing
The filter housing shall be made of materials inert to water vapour and shall have the possibility to be
connected with the probe thereby avoiding leaks.
The filter housing may be located either:
 in the duct or chimney, mounted directly behind the entry nozzle (in-stack filtration); or
 outside the duct or chimney, mounted directly behind the suction tube (out-stack filtration).
The filter holder shall be connected to the probe without any cold path between the two.
NOTE In special cases where the sample gas temperature is > 200 °C, the heating jacket around the sampling probe,
filter holder and connector fine may be omitted. However the temperature in the sampled gas just after the filter housing
should not fall below the acid dew point temperature.
5.4 Particle filter
Particle filters and filter housings of different designs may be used, but the residence time of the sample gas
should be minimised.
5.5 Trapping unit
The trapping unit shall be made up with:
 adsorption unit; or
 condensation and an adsorption unit.
a) When using the adsorption unit alone, it shall consist of at least one cartridge, impinger or absorber, filled
with a suitable drying agent, for example: coloured silica gel.
b) Condensation and adsorption unit shall consist of two stages:
1) the first one shall be a condensation stage with an optional cooling system;
2) the second one shall be an adsorption stage as described in a).
The temperature at the outlet of the condensation unit shall be as low as possible.
The efficiency of the sampling system shall be checked according to the procedure described in 6.4.2.
NOTE The trapping efficiency can be increased by increasing the residence time of sampled gases in the trapping
unit and/or by improving the efficiency of the cooling system. The sampled volume should be sufficient to reach an
appropriate accuracy of the measurement (see clause 5.8 and 7).
Condensation of water shall be avoided in all parts of the sampling system that are not weighed.
5.6 Cooling System (optional)
Any kind of cooling system may be used to condense water vapour in the sampled flue gas (e.g. crushed ice
or cryogenic system).
5.7 Sampling pump
A leak-free pump capable of drawing sample gas at a set flow-rate is required.
NOTE 1 A rotameter (optional) could make easier the adjustment of the nominal sampling flow-rate.
NOTE 2 A small surge tank may be used between the pump and rotameter to eliminate the pulsation effect of the
diaphragm pump on the rotameter.
NOTE 3 A regulating valve (optional) would also be useful for adjusting the sample gas flow-rate.
5.8 Gas volume meter
Two variants of gas volume meter may be used:
 dry-gas volume meter; or
 wet-gas volume meter.
a) Gas volume meter (wet or dry) shall have a relative uncertainty not exceeding ± 2,0 % of the measured
volume (actual conditions).
The gas volume meter shall be equipped with a temperature measuring device (uncertainty less than ± 2,5 K)
and shall be associated to an absolute pressure measurement (uncertainty less than ± 1,0 %).
b) When using a dry gas volume meter, a condenser and/or a gas drying system shall be used which can
achieve a residual water vapour content of less than 10,0 g/m (equivalent to a dew point of 10,5 °C or a
volume content χ(H O) = 1,25 %).
NOTE For example, a glass cartridge or adsorption bottle packed with silica gel (1 mm to 3 mm particle size) which
has been previously dried at least at 110 °C for at least 2 h.
When using a wet gas volume meter, a correction shall be applied for water vapour, using table of Annex A.
5.9 Barometer
Barometer capable of measuring atmospheric pressure present at the sampling location, with an uncertainty
that does not exceed ± 1 kPa.
5.10 Balance
The resolution of the balance shall be equal or better than 0,1 g or 2,0 % of the water weight to be measured.
5.11 Temperature measurement
Calibrated thermometer for flue gas temperature determination with a measuring range 273 K – 373 K, with an
uncertainty of ± 2,5 K or better. That thermometer shall have a low thermal inertia, in order to be rapidly in
thermal equilibrium with the stack gas.
6 Measurement procedure
6.1 General requirements
The sample and the point of measurement shall be representative of the emission of the process.
The following points should be considered when sampling:
 nature of the plant process e.g. steady state or discontinuous. If possible the sampling and measuring
programme should be carried out under steady operating conditions at the plant;
 expected concentration to be measured and any required averaging period, both of which can influence
the measuring and sampling time.
The minimum sampling period is 30 min and the minimum sample gas volume is 50 l. When the expected
mass concentration of water vapour is low, the sampling period or the sampling volume may be extended.
6.2 Preparation and installation of equipment
6.2.1 Sampling location
The sampling location chosen for the measurement devices and samplings shall be of sufficient size, easily
passable and made in such a way that an emission measurement representative for the measurement task
and technically perfect is possible. In addition, the sampling location shall be chosen with regard to safety of
the personnel, accessibility and availability of electrical power.
6.2.2 Sampling point
It is necessary to ensure that the gas concentrations measured are representative of the average conditions
inside the waste gas duct. In most cases, a single sampling point situated in the middle of the duct shall be
selected. For larger ducts, this point can be situated closer to the sampling port but not too close to avoid any
disturbance of the flow or concentration due to influences from the sampling port.
However, when non-homogeneity of the flue gas is suspected, it shall be demonstrated if the flue gas is
homogeneous or not. The homogeneity can be demonstrated with a continuous measurement of O or CO
2 2
using a fixed and a moving probe. Sampling in non-homogeneous flue gases requires following the relevant
European Standards or technical specifications proposed by CEN/TC 264.
6.2.3 Assembling the equipment
When using a condensation unit with impingers or absorbers, these shall be filled with water, the volume of
which is less than half the content of the absorber.
The water can be replaced by the appropriate absorption solution used in EN 14791, EN 1911-3 or in any
other European Standards using water in the preparation of the absorption solution, when the operator wants
to collect water vapour with the same sampling train as for SO , HCl or any other component. When using an
adsorption unit, fill the last impinger or absorber or cartridge with a drying agent.
NOTE This European Standard has only been validated with silica gel even if this commonly used drying agent can
absorb carbon dioxide; this error has been accepted.
Assemble the trapping unit, including junctions. Weigh and record the elements of the trapping unit including
junctions, with a resolution equal or better than 0,1 g or 2,0 % of the water weight to be measured. Then
assemble the whole sampling train.
If applicable, turn on the probe heater and the filter heating system to a controlled temperature of at least
120 °C and 20 °C higher than the (acid) dew point of gases, to prevent water condensation in front of the
condenser. Allow time for the temperatures to stabilise.
6.3 Leak test
Perform a leak test on the sampling train. Check the sampling line for leakage according to the following
procedure or any other relevant procedure:
 assemble the complete sampler system, including charging the filter housing and absorbers;
 seal the nozzle inlet;
 switch on the pump(s);
 after reaching minimum pressure read the flow rate;
 leak flow rate shall be measured (e.g; by a rotameter) and shall not exceed 2 % of the expected sample
gas flow rate.
Perform the leak test at the operating temperature unless this conflicts with safety requirements.
Integrity of the sampling system can be also tested during sampling by continuously measuring the
concentration of a suitable stack gas component (e.g. O ) directly in the stack and downstream the sampling
line. Any systematic difference between those concentrations indicates a leak in the system.
6.4 Performing of the sampling
6.4.1 Introduction of the probe in the duct
Immediately after the leak test, insert the sampling probe through the sampling port and place the probe at the
chosen representative measurement point within the measurement plane.
Seal the resultant space around the sampling probe and the access hole with an appropriate sealing material
such that ambient air is not induced into the duct (nor should any flue gas escape from the duct). In cases
where large pressure differences exist between the ambient air and sample gas, care shall be taken that no
condensate leaves the absorber.
Control the jacket and filter holder temperatures.
6.4.2 Sampling
Start the sampling pump and adjust the regulating valve to give the desired sample gas-volume flow rate. The
selected sample gas flow-rate shall be kept within ± 10 % of the nominal flow rate (see note 2). However,
when non-homogeneity is suspected, it shall be demonstrated if the flue gas is homogeneous or not.
Sampling in non-homogeneous flue gases shall follow the requirements of relevant Standards or Technical
Specifications proposed by CEN/TC 264.
Record the reading on the gas meter V and the time.
Record the reading on the gas meter temperature device T and the absolute pressure P on the gas meter at
j m
least 5 min after starting sampling and at the end of the sampling period.
NOTE For a sampling train as shown in Figure B.1 in Annex B, with gas meter placed downstream pump, absolute
pressure on the gas meter is close to atmospheric pressure.
During the whole sampling run, check that the trapping capability of the trapping unit is not exceeded. This
can be achieved:
 either by measuring the temperature at the outlet of trapping unit. This temperature shall not be greater
than 4 °C; or
 by checking visually the amount of silica gel having faded in the last impinger or cartridge. This amount
shall not exceed 50 %.
At the end of the sampling period, switch off the sampling pump, record the time and the reading on the gas
meter V
2.
Disassemble the sampling train (adsorption unit). When using a cooling bath, the outside of the trapping unit is
thoroughly wiped (e.g. with a dry cloth) before weighing. Next, determine the increase in weight of the whole
trapping unit. Record the weighing results.
6.5 Repeatability of the weighing
To determine the repeatability of the weighing in the field in order to take into account the influence of
environmental conditions:
 carry out 10 independent weightings of the trapping unit;
 calculate the mean value and the standard deviation.
6.6 Procedure for gas streams saturated with water (droplets present)
When droplets are present, the method produces values for water vapour which are larger than those would
be expected for saturated conditions at the temperature of flue gas. Under such conditions the result is
consequently biased; therefore water vapour concentration can be determined by using the table of Annex A.
This table shows the water vapour concentration for saturated gases for the corresponding average
temperature of the flue gas in the sampling plane.
In order to measure the temperature, the probe is inserted at a representative point in the stack. Care shall be
taken to wait for the stabilisation of the recorded temperature.
7 Determination of the characteristics of the method: sampling and analysis
7.1 Introduction
When this European Standard is used as the SRM, the user shall demonstrate that the performance
characteristics of the method given in Table 1 are better than the minimum performance criteria and that the
overall uncertainty calculated by combining values of selected performance characteristics by means of an
uncertainty budget is less than ± 20,0 % relative of the measured value.
The values of the selected performance characteristics can be evaluated by means of a laboratory test and a
field test implemented by the user, providing that this user is recognised by the competent authority (e.g.
through an accreditation system).
7.2 Relevant performance characteristics of the method and performance criteria
The uncertainty of the measured values is influenced by:
 sampling system;
 sampling procedure;
 weighing;
 specific site conditions.
The evaluation of the uncertainty is described in 7.3.
Table 1 gives an overview of the relevant performance characteristics and minimum performance criteria,
which shall be determined during the laboratory and field tests.
Table 1 — Minimum performance characteristics of the measurement method
Performance characteristic Lab. Field Performance criterion
test test
Volume gas meter:
uncertainty ≤ ± 2,0 % of the volume of
a a
 sample volume X
b
sampled gas
a a b
 temperature X uncertainty ≤ ± 2,5 K
uncertainty ≤ ± 1,0 % of the absolute
a a
 absolute pressure X
b
pressure
Leak in the sampling line X
≤ 2,0 % of the nominal flow rate
Weighing of collected water:
c
 uncertainty associated to the balance X X
d
X
 repeatability in the field of weighing
a
The uncertainty of sampling volume gas is a combination of uncertainties due to calibration, resolution, reading and drift.
The uncertainty related to the temperature and absolute pressure of the gas meter is a combination of the uncertainties due to
calibration, resolution, reading, drift and repeatability. When a barometer is used see chapter 5.9.
b
Performance criteria correspond to the uncertainty of calibration.
c
The uncertainty contributions of the balance can be for example: linearity of balance, resolution, reading and calibration
tare. See chapter 5.10.
d
When weighing is carried out in the field, variations of ambient conditions can be an uncertainty source, for example
temperature variations, air currents and vibrations.
7.3 Establishment of the uncertainty budget
An uncertainty budget shall be established to evaluate whether or not the method fulfils the requirements for a
maximum allowable overall uncertainty. This uncertainty budget shall be drawn up according to the
procedures described in ENV 13005, taking into account at least all the relevant characteristics given in
Table 1.
The overall uncertainty for this method used as a reference shall be lower than ± 20,0 % of the measured
value, before correction at the reference concentration of O .
The principle of calculation of the overall uncertainty is based on the law on propagation of uncertainty laid
down in the ENV 13005:
 determine the standard uncertainties attached to the performance characteristics to be included in the
calculation of the uncertainty budget by means of laboratory or field tests, and according to ENV 13005;
 calculate the uncertainty budget by combining all the standard uncertainties according to ENV 13005, and
taking the variations range of the influence quantities of the specific site conditions into account;
 all the components of standard uncertainties that are less than 5 % relative of the maximum standard
uncertainty can be neglected;
 calculate the overall uncertainty at the measured value.
An example of the evaluation of the overall uncertainty is given in Annex C.
7.4 Equivalency with an alternative method
In order to show that an alternative method is equivalent to the reference method, follow the procedures
described in the CEN/TS 14793.
The maximum allowable standard deviation of repeatability expressed in % for this reference method is:
(C)=0,0218C+0,247 (1)
s
limit
r
where
C is the concentration in %.
The standard deviation of reproducibility expressed in % for this reference method is:
s (C)=0,03C+0,37 (2)
R
where
C is the concentration in %.
8 Evaluation of the method in the field
The method has been evaluated during six field tests, on waste incineration installations, co-incineration
installations and large combustion plants. Each test was performed by at least four different measuring teams
originating from ten European Union member states.
The characteristics of installations, the conditions during field tests and the values of repeatability and
reproducibility in the field are given in Annex D.
9 Water vapour determination
Calculate the mean value temperature T at the gas meter:
m
T =(T +T +.+T )/n(K) (3)
m 1 2 n
where
n is the number of the temperature T readings got during the test.
j
Calculate the dry gas volume sampled from the gas meter, at standard conditions, in cubic meter V :
m(std)
T P
std m
if a dry-gas volume meter is used V =(V −V )× × (4)
m(std) 2 1
T P
m std
P −P
T m sat(T )
std
m
if a wet-gas volume meter is used V =(V −V )× × (5)
m(std) 2 1
T P
m std
where
V is the dry gas volume measured, corrected to standard conditions, in m3;
m(std)
V -V is the sampled gas volume, at actual conditions of temperature, pressure and humidity, in m3;
2 1
Tm is the mean temperature of the sampled gas at the gas-meter, in K;
Tstd is the standard temperature, 273 K;
Pm is the absolute pressure at the gas meter, in kPa;
P is the saturation vapour pressure of water at the temperature of the gas meter, in kPa;
sat(Tm)
P is the standard pressure, 101,3 kPa.
std
The water vapour content in grams per cubic meter in standardised conditions of temperature and pressure
and on dry basis is:
...