SIST-TP CEN/TR 17078:2017

SLOVENSKI STANDARD
01-julij-2017
(PLVLMHQHSUHPLþQLKYLURY1DYRGLOR]DXSRUDERVWDQGDUGD(1,62
Stationary source emissions - Guidance on the application of EN ISO 16911-1
Emissionen aus stationären Quellen - Leitlinien zur Anwendung von EN ISO 16911-1
Émissions de sources fixes - Préconisations concernant l’application de l’EN ISO 16911-
Ta slovenski standard je istoveten z: CEN/TR 17078:2017
ICS:
13.040.40 (PLVLMHQHSUHPLþQLKYLURY Stationary source emissions
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

CEN/TR 17078
TECHNICAL REPORT
RAPPORT TECHNIQUE
March 2017
TECHNISCHER BERICHT
ICS 13.040.40
English Version
Stationary source emissions - Guidance on the application
of EN ISO 16911-1
Émissions de sources fixes - Préconisations concernant Emissionen aus stationären Quellen - Leitlinien zur
l'application de l'EN ISO 16911-1 Anwendung von EN ISO 16911-1

This Technical Report was approved by CEN on 20 February 2017. It has been drawn up by the Technical Committee CEN/TC
264.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.
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COMITÉ EUROPÉEN DE NORMALISATION

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CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 17078:2017 E
worldwide for CEN national Members.

Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Symbols and abbreviations . 7
5 General guidance on manual determination of velocity and flow rate in ducts. 7
5.1 General . 7
5.1.1 Role of this CEN Technical Report . 7
5.1.2 How to use this Technical Report . 8
5.2 Scope and structure of EN ISO 16911-1 . 8
5.2.1 Scope of EN ISO 16911-1 . 8
5.2.2 Concept of EN ISO 16911-1 . 8
5.2.3 Relationship to other international standards . 8
5.3 Summary of different requirements for determination of velocity and flow rate . 8
5.3.1 Velocity and flow rate monitoring requirements under the Industrial Emissions
Directive . 8
5.3.2 Velocity and flow rate monitoring requirements under the EU ETS Directive . 8
5.3.3 Other requirements for monitoring velocity and flow rate in ducts and stacks . 9
6 Specific guidance on the application of EN ISO 16911-1 . 9
6.1 Scope . 9
6.2 Normative references . 9
6.3 Terms, definitions . 9
6.4 Symbols and abbreviated terms . 9
6.4.1 Symbols . 9
6.4.2 Abbreviated terms . 10
6.5 Principle . 10
6.5.1 General . 10
6.5.2 Principle of flow velocity determination at a point the duct . 10
6.6 Principle of measurement of flow rate . 10
6.6.1 General . 10
6.6.2 Principle of volume flow rate determination from point velocity measurements . 11
6.6.3 Determination of volume flow rate using tracer dilution measurements . 11
6.6.4 Determination of volume flow rate using transit time tracer measurements . 11
6.6.5 Determination of volume flow rate from plant thermal input . 11
6.7 Selection of a monitoring approach . 11
6.7.1 Measurement objective . 11
6.7.2 Choice of technique to determine point flow velocity . 11
6.7.3 Choice of technique for volume flow rate and average flow determination . 11
6.8 Measuring equipment . 11
6.8.1 General . 11
6.8.2 Measurement of duct area . 12
6.9 Performance characteristics and requirements . 13
6.10 Measurement Procedure — Site survey before testing . 15
6.11 Determination of sampling plane and number of measurement points. 15
6.12 Checks before sampling . 16
6.12.1 General . 16
6.12.2 Pre-test leak check . 17
6.12.3 Check on stagnation and reference pressure taps (S-type Pitot tube) . 18
6.12.4 Test of repeatability at a single point . 18
6.12.5 Swirl or cyclonic flow . 18
6.13 Quality control . 19
6.14 Measurement of flow at locations within the measurement plane . 19
6.15 Post-measurement quality control . 19
6.16 Calculation of results . 20
6.16.1 General . 20
6.16.2 Measurement of velocity . 20
6.16.3 Determination of the mean velocity . 20
6.16.4 Correction of average velocity for wall effects . 20
6.16.5 Calculation of the volume flow rate from the average velocity . 20
6.16.6 Conversion of results to standard conditions . 20
6.17 Establishment of uncertainty results . 20
6.18 Evaluation of the method . 20
7 Annex A: Measurement of velocity using differential pressure based techniques . 20
7.1 A.1: Principle of differential pressure based technique . 20
7.2 A.2: Measuring Equipment . 20
7.2.1 A.2.1: Pitot tubes . 20
7.2.2 A.2.2: Differential pressure flow measurement equipment . 21
8 Annex F: Example of uncertainty budget established for velocity and volume flow
rate measurements by Pitot tube . 22
8.1 F.1: Process of uncertainty estimation . 22
8.1.1 F.1.1: General . 22
8.1.2 F.1.2: Determination of model function. 22
8.1.3 F.1.3: Quantification of uncertainty components. 22
8.1.4 F.1.4: Calculation of the combined uncertainty . 22
8.1.5 F.1.5: Other sources of errors . 23
8.2 F.2: Example uncertainty calculation . 24
8.2.1 F.2.1: Calculation of the physicochemical characteristics of the gas effluent . 26
8.2.2 F.2.2: Calculation of uncertainty associated with the determination of local velocities . 27
8.2.3 F.2.3: Calculation of uncertainty associated with the mean velocity . 35
8.2.4 F.2.4: Calculation of uncertainty in reported values . 36
9 Annexes B, C, D, E, G, H, I and J . 37
Annex A (informative) Degree of swirl determination example method . 38
Annex B (informative) S-type Pitot leak check example method . 39
Bibliography . 40

European foreword
This document (CEN/TR 17078:2017) has been prepared by Technical Committee CEN/TC 264 “Air
quality”, the secretariat of which is held by DIN.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association.
Introduction
This CEN Technical Report provides supporting guidance on the application of EN ISO 16911-1:2013. It
has been produced in response to the request from Member State mirror committees for clarification on
elements of EN ISO 16911-1:2013 and on how certain requirements specified within it should be
interpreted. EN ISO 16911-1:2013 has been written to apply to a range of applications with different
uncertainty requirements. This CEN Technical Report makes recommendations in regards to which
requirements and performance characteristics apply to specified measurement objective(s) and
application area(s) in order to achieve a consistent application of EN ISO 16911-1:2013.
1 Scope
This CEN Technical Report provides guidance only on the application of the European Standard
EN ISO 16911-1:2013.
This CEN Technical Report does not provide guidance on the application of EN ISO 16911-2:2013.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
EN 14181, Stationary source emissions - Quality assurance of automated measuring systems
EN 15259:2007, Air quality - Measurement of stationary source emissions - Requirements for
measurement sections and sites and for the measurement objective, plan and report
EN ISO 16911-1:2013, Stationary source emissions - Manual and automatic determination of velocity and
volume flow rate in ducts - Part 1: Manual reference method (ISO 16911-1:2013)
EN ISO 16911-2:2013, Stationary source emissions - Manual and automatic determination of velocity and
volume flow rate in ducts - Part 2: Automated measuring systems (ISO 16911-2:2013)
ISO 10780, Stationary source emissions — Measurement of velocity and volume flowrate of gas streams in
ducts
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN ISO 16911-1:2013 and the
following apply.
3.1
emission source
separately identifiable part of an installation or a process within an installation, from which relevant
greenhouse gases are emitted and are regulated under the EU Emissions Trading System
[SOURCE: Commission Regulation (EU) No. 601/2012, Article 3, Definition (5)]
3.2
tier
set requirement under the EU Emissions Trading System used for determining activity data, calculation
factors, annual emission and annual average hourly emission, as well as for payload
[SOURCE: Commission Regulation (EU) No. 601/2012, Article 3, Definition (8)]
4 Symbols and abbreviations
For the purposes of this document, the symbols and abbreviations given in EN ISO 16911-1:2013 and
the following apply.
4.1 Symbols:
dl  change in length (m, inches)
L  initial length of measuring rod (m, inches)
α linear temperature expansion coefficient (m/m°C)
t  initial temperature (°C)
t  final temperature (°C)
CF correction factor at position i
i
V  average velocity of fixed device measurements
fav
V  velocity of fixed measurement device at position i
fi
V  corrected velocity at position i
ticorr
V velocity measured
meas
hs corrected height of the indicating fluid to standard temperature
ht  height of the indicating fluid at the temperature when read
ps density of the indicating fluid at standard temperature
pt  density of the indicating fluid at the temperature when read
−2
gs  gravitational acceleration assumed at calibration, ms
−2
gt  gravitational acceleration at test location, ms
θ  latitude (North/South position with the Equator being zero), °
H height above sea level, m
4.2 Abbreviations:
EU ETS Emissions Trading System
CO (e) Carbon Dioxide equivalent
5 General guidance on manual determination of velocity and flow rate in ducts
5.1 General
5.1.1 Role of this CEN Technical Report
The role of this CEN Technical Report is to provide guidance on the application of the European
Standard EN ISO 16911-1:2013 on the manual determination of velocity and flow rate in ducts. This
Technical Report offers clarification on matters of interpretation of EN ISO 16911-1:2013 and provides
recommendations on its application depending on the uncertainty requirements of the measurement
objective. The adoption of the full Technical Report or parts of it may be decided by individual Member
States' regulatory authorities.
Throughout this Technical Report, reference to the Standard refers to EN ISO 16911-1:2013.
5.1.2 How to use this Technical Report
This Technical Report does not follow the numbering of EN ISO 16911-1:2013; however for easier
handling it uses the same headings and sub-headings as EN ISO 16911-1:2013. It does not repeat text,
tables or diagrams from EN ISO 16911-1:2013, instead it refers to the relevant sections of the Standard.
It is therefore essential that the reader has a copy of the Standard to refer to. For sections of the
Standard where this Technical Report does not provide any text or guidance it is deemed that the
relevant section does not require any additional clarification.
An error has been identified in Formula (F.10) of the uncertainty example in EN ISO 16911-1:2013,
Annex F. It is recommended that the uncertainty example provided in this CEN Technical Report
(see Clause 8) replaces the existing one in the Standard.
5.2 Scope and structure of EN ISO 16911-1
5.2.1 Scope of EN ISO 16911-1
EN ISO 16911-1:2013 is applicable to industrial plants falling under the European Industrial Emission
Directive (2010/75/EU). It is also applicable to industrial plants falling under the EU Emissions Trading
System Directive (EU ETS) (2003/87/EC) that are required or have opted to use the measurement-
based methodology as specified in Commission Regulation (EU) No 601/2012 of 21 June 2012 on the
monitoring and reporting of greenhouse gas emissions (MRR).
5.2.2 Concept of EN ISO 16911-1
EN ISO 16911-1 has been written to apply to different measurement objectives with different
uncertainty requirements ranging from very stringent (EU ETS Tier 4 - ± 2,5 %) to less demanding
(support of isokinetic sampling). The performance characteristics and requirements within the
Standard have been specified as a means of achieving the most stringent uncertainty requirements.
Although not explicitly specified within the Standard, it is implied that the level of quality control
should be determined by the uncertainty requirements of the measurement objective. Therefore for
measurement objectives with lesser uncertainty requirements the level of quality assurance and control
can be reduced. It is the role of this Technical Report to make these distinctions and provide guidance
as to the level of quality control that may be applied.
5.2.3 Relationship to other international standards
EN ISO 16911-1 does not replace existing standards. This Technical Report does not reproduce any
detailed procedures; therefore users will have access to the documents referenced in Clause 2 and in
the final Bibliography.
5.3 Summary of different requirements for determination of velocity and flow rate
5.3.1 Velocity and flow rate monitoring requirements under the Industrial Emissions Directive
The measurement of velocity and flow rate is required under the Industrial Emissions Directive as part
of periodic monitoring for compliance purposes or pollution inventory reporting which involves the
determination of mass emissions. It is also required for the control of isokinetic conditions during the
manual sampling of atmospheric pollutants.
5.3.2 Velocity and flow rate monitoring requirements under the EU ETS Directive
The MRR specify that all flow automated measuring systems (AMS) used for the monitoring and
reporting of GHG under the EU ETS, shall follow the quality assurance procedures specified within
EN 14181 and other corresponding EN standards and therefore by deduction require the flow AMS to
adhere to EN ISO 16911-2:2013 and its calibration (procedure specified in EN ISO 16911-2) to be
carried out using one of the techniques specified within EN ISO 16911-1:2013.
The MRR prescribe Tiers and corresponding maximum permissible uncertainties (Table 1) for emission
sources regulated under the EU ETS. An emission source is considered tier 4 if it emits more than 5,000
tonnes of CO (e) per year or contributes more than 10 % of the total annual emissions of the installation
(Commission Decision [EU] No. 601/2012 – 2012). The maximum permissible uncertainty specified for
each tier is the combined uncertainty of the concentration AMS and flow AMS expanded to a 95 %
confidence interval. Under tier 4 – assuming an equal value on both uncertainty components
(concentration and flow) – the target value for each uncertainty component is approximately ± 1,8 %.
The requirement to achieve such a low uncertainty value has dictated the selection and associated
values of certain performance characteristics and requirements specified within EN ISO 16911-1.
Table 1 — Maximum permissible uncertainty for measurement-based methods
Tier 1 Tier 2 Tier 3 Tier 4
CO emission ±10 % ±7,5 % ±5 % ±2,5 %
sources
N O emission ±10 % ±7,5 % ±5 % N/A
sources
Source: Commission Regulation (EU) No. 601/2012 of 21 June 2012 on the monitoring and reporting of
greenhouse gas emissions pursuant to Directive 2003/87/EC of the European Parliament and of the Council.

5.3.3 Other requirements for monitoring velocity and flow rate in ducts and stacks
A flow profile characterization at the measurement plane may be required. This may be part of the pre-
installation work carried out before a new flow AMS is commissioned and installed or for any other
measurement objective that may require information on the uniformity of flow at the measurement
plane.
The majority of times the calibration of a flow AMS is carried out for reasons of compliance with the EU
ETS Directive. However the calibration of a flow AMS for any other regulatory reasons is not excluded
from the scope of EN ISO 16911-1. The user should adopt those elements required to achieve the
specified uncertainty requirement for their application.
6 Specific guidance on the application of EN ISO 16911-1
6.1 Scope
No guidance required.
6.2 Normative references
No guidance required.
6.3 Terms, definitions
No guidance required.
6.4 Symbols and abbreviated terms
6.4.1 Symbols
No guidance required.
6.4.2 Abbreviated terms
No guidance required.
6.5 Principle
6.5.1 General
No guidance required.
6.5.2 Principle of flow velocity determination at a point the duct
EN ISO 16911-1 specifies the use of 2D Pitot tubes as one of the techniques for the determination of
flow velocity at a measurement point within a duct or stack. In regard with quality assurance and
control of 2D Pitot tubes it refers users to US EPA Method 2G. Table 2 of this Technical Report
reproduces the main performance characteristics and requirements for 2D Pitot tubes as specified in US
EPA Method 2G. For test laboratories wishing to use 2D Pitot tubes the full set of specifications and
requirements of US EPA Method 2G should be adhered to. These requirements only apply to 2D Pitot
tubes that are not covered in detail in EN ISO 16911-1. For example they do not apply for manual S-type
Pitot tubes as the performance characteristics for these are specified within the main text of the
Standard.
Table 2 —Performance characteristics and requirements for 2D Pitot tubes as specified in US
EPA Method 2G
Performance characteristic Criterion Frequency
Calibration acceptance criterion ±3° at 0° Prior to use
for 2D-Probe (yaw and pitch
angles)
Width of reference scribe line (to ≤ 1,6 mm Prior to use
determine yaw angles of flow)
Diameter of tubing used to ≥ 3,2 mm Prior to use
connect the probe and pressure
readout device
Uncertainty of yaw angle- ≤ ± 1° Prior to use
measuring device
Horizontal straightness check < 5° Before field measurement
Rotational positional check of ±1° Before field measurement
angle measuring device
Rotational positional check of ±2° Post field measurement check
angle measuring device
Calibration acceptance criterion ±2° of a known angle θ of the Prior to use
for yaw-angle measuring device triangular block used for
calibration
6.6 Principle of measurement of flow rate
6.6.1 General
No guidance required
6.6.2 Principle of volume flow rate determination from point velocity measurements
EN ISO 16911-1 specifies the use of S-type, 3D or 2D Pitot tubes for the determination of swirl at a
measurement plane. This Technical Report recommends the use of L-type Pitot tubes as another viable
technique for this type of measurement. For more information on the procedure for measuring the
degree of swirl at the measurement plane see 6.12.5.
6.6.3 Determination of volume flow rate using tracer dilution measurements
No guidance required.
6.6.4 Determination of volume flow rate using transit time tracer measurements
No guidance required.
6.6.5 Determination of volume flow rate from plant thermal input
No guidance required.
6.7 Selection of a monitoring approach
6.7.1 Measurement objective
This Technical Report adopts a slightly different grouping for measurement objectives than
EN ISO 16911-1. This is in order that objectives are grouped based on the proposed quality control that
will be recommended throughout this Technical Report. The grouping of measurement objectives is as
follows:
a) periodic monitoring for compliance purposes according to EN 15259 or pollution inventory
reporting which involves the determination of mass emissions and for the control of isokinetic
conditions during manual sampling;
b) calibration of flow AMS under EN 14181 and EN ISO 16911-2 and/or flow profile characterization
either to meet the requirements of the EU ETS Directive or any other regulatory requirements;
c) any other periodic measurements under the requirements of the EU ETS Directive.
For simplicity any reference throughout this Technical Report to measurement objective 1, 2 or 3 refers
to the above list.
On the selection of techniques for different measurement objectives as aforementioned in 6.2.2 of this
document the inclusion of L-Type Pitot tubes as another technique for the determination of swirl at the
measurement plane is recommended by this Technical Report.
6.7.2 Choice of technique to determine point flow velocity
No guidance required.
6.7.3 Choice of technique for volume flow rate and average flow determination
No guidance required.
6.8 Measuring equipment
6.8.1 General
No guidance required.
6.8.2 Measurement of duct area
EN ISO 16911-1 prescribes the use of direct dimensional measurements for the determination of the
internal duct area and excludes the use of engineering drawings or specifications without verification.
The use of design information is allowed as a verifying tool of the direct dimensional measurement
approach (see EN ISO 16911-1, 9.3.1). It is recommended that these may be used when accurate direct
measurement of the internal duct area is challenging due to access restrictions, irregular dimensions,
non-constant wall thickness and/or other complications. In such cases engineering drawings may be
used for additional information in order to verify and increase confidence of the direct dimensional
measurement approach. In extreme cases where any sort of direct dimensional measurement is
impossible due to one or more of the above reasons the use of engineering drawings may be the only
viable option to determine stack dimensions. In this case great care should be taken that this approach
does not introduce large errors and that the uncertainty criterion on stack dimension can still be met.
For example, in the case of a circular stack, the external circumference can be measured and the
cladding thickness and wall thickness then subtracted from the external diameter, in order to cross-
check the internal diameter given on the drawing. It is recommended that this is reported as a deviation
and that the site operator is notified and advised that improvements to allow a direct dimensional
measurement should be considered and if implemented would improve the uncertainty of the
measurement. However, it should also be noted that the dilution tracer method, also described in
EN ISO 16911-1, determines stack flow rate directly and does not require stack dimensions.
EN ISO 16911-1 requires the measurement of the length of all sampling ports and wall thickness at each
one and the use of the mean value (as sampling port length and/or wall thickness) unless one or more is
“significantly different” than the mean. The Standard purposely does not quantify this statement as it is
intended to depend on the measurement objective and corresponding uncertainty requirement. As
general guidance a difference between individual port depth measurement and the mean value
of < 10 % can be considered as not “significantly different”. However, for measurement objectives with
strict uncertainty specifications, such as EU ETS tier 4, a lower value may be selected as a means to
achieve the overall required uncertainty.
NOTE If the port protrudes beyond the inside wall, the extent of the protrusion needs to be estimated e.g.
with a U-shaped wire inserted through the port and then retracted until the inside wall is found.
The requirement of the Standard to consider temperature effects on measuring rods can be accounted
for by using the following formula:
dl= L⋅⋅α t− t (1)
( )
0 10
where
dl is the change in length (m, inches)
L is the initial length (m, inches)
α is the linear expansion coefficient (m/m°C)
t is the initial temperature (°C)
t is the final temperature (°C)
Where the duct area value is corrected for temperature effects using Formula (1) they do not need to be
accounted for within the uncertainty assessment.
6.9 Performance characteristics and requirements
EN ISO 16911-1 prescribes performance characteristics and performance criteria, for the manual
determination of the point velocity across a measurement plane. These characteristics have all been
demonstrated for the techniques specified within the Standard during the validation laboratory and
field studies. Any technique used which is not specified within the Standard will have to demonstrate
that it meets the same performance requirements.
As part of ongoing quality control it is recommended that test laboratories carry out checks at periodic
intervals to demonstrate that their measuring systems continue to meet the requirements of the
Standard. It is recommended that test laboratories follow Table 3 of this Technical Report which lists
the checks and minimum required frequency of these depending on the measurement objective.
The acceptance criteria specified apply to the whole measurement system (with the exception of
standard deviation of repeatability in the laboratory). Therefore, it is preferable that they are carried
out on the whole measurement system. However, as the majority of test laboratories use
interchangeable parts (e.g. different differential pressure readout devices with different Pitot tubes and
vice versa) it is recognized that this is not always possible in which case this Technical Report
recommends that one of the two following procedures is adhered to in order for compliance with the
acceptance criteria is demonstrated:
Method 1 – Table 3 checks are carried on the whole measurement system and the requirements of
Table 3 are demonstrated on the whole system. The checks can be carried out either by the test
laboratory and/or a calibration laboratory.
Method 2 – Table 3 checks are carried out separately on individual parts of a measurement system, in
which case the test laboratory will have to ensure that results for each check are combined in order to
demonstrate compliance with each acceptance criterion. If the worst Pitot tube result for a specific
performance characteristic is combined with the worst differential pressure readout device result of the
same performance characteristic and the combined result meets the acceptance criterion it can be
safely assumed that all different combinations meet the required value. For components that may have
only been checked once (e.g. Pitot tubes for lack-of-fit) this value can be carried over annually to use in
combination with a value from a differential pressure readout device check in order to demonstrate
compliance with an acceptance criterion. The checks can be carried out either by the test laboratory
and/or a calibration laboratory.
This Technical Report recommends that the check of the standard deviation of repeatability in the
laboratory is only carried out on the differential pressure readout device. For measurement objectives 2
and 3 the demonstration of this criterion on the whole measurement system in the Standards’
laboratory validation studies and the repeatability check of the whole system in the field prior to
measurement (see 6.12.4) are deemed acceptable for the uncertainty requirements of these application
areas. For measurement objective 1 the demonstration of this criterion in the Standards’ laboratory
validation studies on the whole measurement system is deemed acceptable for these application areas.
Table 3 — Ongoing quality control checks
Checks Component Frequency Measurement Acceptance
objective Criteria
Standard Differential At least every year 1 < 1 % of
deviation of pressure calibration range
repeatability of readout device
2 and 3 < 1 % of
measurement in
calibration range
the laboratory
for differential
pressure ≤ 60 Pa
< 1 % of value for
differential
pressure ≥ 60 Pa
Lack-of-fit Pitot tubes At least once and every 1 < 2 % of range
(linearity) time they fail a visual (including
inspection differential
pressure readout)
(see EN ISO 16911-1:2013,
9.3.1 for visual inspection
2 and 3 < 2 % of value
checklist)
(including
differential
pressure readout)
Differential At least every year 1 < 2 % of range
pressure (including Pitot
readout device tube)
2 and 3 < 2 % of value
(including Pitot
tube)
Uncertainty due Pitot tubes At least every year 1,2 and 3 < 2 % of range of
to calibration differential
Differential
pressure readout
pressure
device (including
readout device
Pitot tube)
Lowest Pitot tubes After calibration 1,2 and 3 Lowest
measureable measurable flow is
flow intended to be the
lowest point at
which the system
Differential
has been
pressure
calibrated at. Any
readout device
use below this
point will have to
have been
validated by the
user before a
measurement is
made.
6.10 Measurement Procedure — Site survey before testing
EN ISO 16911-1 requires the measurement plan to be designed to average out flow variations when
these are unstable and are expected to change over the duration of the measurement period (peak-to-
peak variation > 10 % of the average flow conditions). In these circumstances – or indeed for all
circumstances that variations of flow with time need to be accounted for – test laboratories can either
use two measurement devices (one at a fixed point and one that traverses the measurement plane) or
increase the time measuring each measurement point in order for flow variations to be accounted for.
The above requirement is important for measurement objectives 2 and 3 especially when
characterizing a flow profile. If flow variations are not considered there is a risk that a flow profile may
seem to be asymmetric due to time varying flow when it is actually not; and so this may mean
incorrectly assuming that a measurement plane is not suitable for the installation of a flow AMS or more
effort is needed than is actually required for the calibration of an existing cross duct flow AMS.
The correction factor to account for flow variations over time when using two devices can be
determined by the following formula:
CF = V / V (2)
i fav fi
V CFi× V (3)
ticorr ti
where:
CFi is the correction factor at position i
V is the average velocity of fixed device measurements
fav
Vfi is the velocity of fixed measurement device at position i
V is the corrected velocity at position i
ticorr
V is the velocity of traverse measurement device at position i
ti
For measurement objective 1, especially when measuring flow to maintain isokinetic conditions,
accounting for flow variations with time is not as significant and it is recommended by this Technical
Report that only one traverse measurement device is required. Test laboratories may consider
extending the time spent measuring flow at each measurement point when carrying out a flow traverse
for the determination of mass emissions if flow variations are to be expected.
EN ISO 16911-1 prescribes that the area of the measurement assembly shall not obstruct more than
5 % of the measurement plane area. For flow measurement assemblies that have integrated sampling
devices (nozzle arm and nozzle, in-stack filter, etc.), mainly for the support of isokinetic sampling, this
Technical Report recommends the adoption of the provisions of the UK Method Implementation
Document (MID) for EN ISO 16911-1. These provisions allow for an obstruction of the measurement
plane area of up to 10 % for stack or duct areas of less or equal to 1,5 m to account for the larger
measurement assembly area resulting from the integrated sampling device. For stacks with a very small
sample plane area it may not be possible to carry out isokinetic sampling and measure flow at the same
time because the area of the sampling equipment may obstruct more than 10 % of the stack or duct
sampling area. Under these circumstances the MID for EN ISO 16911-1 allows for the flow
measurement to be carried out prior to the isokinetic sampling and the values derived from the flow
traverse to be used to control isokinetic conditions.
6.11 Determination of sampling plane and number of measurement points
No guidance required.
=
6.12 Checks before sampling
6.12.1 General
Experience with low cost electronic pressure readout devices has shown that on occasion their
calibration can be invalidated in the field leading to an increased level of uncertainty. This can be simply
through wear and tear, e.g. accidental drops or bumps during transport to site and/or transfer to the
sampling location, that may lead to internal problems within the devices and which may not be
detectable through a visual inspection. It is with this in mind that EN ISO 16911-1 specifies that a
calibration check of electronic pressure readout devices is carried out prior to measurement. More
costly manometers tend to be more robust and less susceptible to damage. This Technical Report
recommends that the calibration check of electronic pressure readout devices should be carried out
only for measurement objectives 2 and 3 that have stricter uncertainty requirements. It recommends
that the check may be made against a device with a better or equal uncertainty to the electronic
pressure readout device under test. The Technical Report recognizes that some test laboratories may
only possess one type and model of differential pressure readout devices from the same manufacturer
with very similar uncertainties. For measurement objective 1 test laboratories should consider carrying
out a set of functional checks prior to use. These may include, but are not limited to checking the zero
value of the device, checking that the instrument responds to gas flow and ensuring if required that the
correct input values are stored within the manometer when conversions from differential pressure to
velocity are carried out internally.
Inclined manometers do not have any parts that can wear or age. However, they too can suffer damage
from accidental drops or bumps and the associated damage can affect the manometer’s accuracy,
although this is usually easily detected by a simple visual inspection.
EN ISO 16911-1 also prescribes the use of electronic pressure readout devices with a resolution of at
least 2 decimal places per Pa. These electronic pressure readout devices are not commonly used by test
laboratories mainly due to their high c
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