Transcript Comments on the Quality Assurance Standard EN14181

Comments on the
Quality Assurance
Standard EN14181
VGB Working Group
Emissions Monitoring
VGB Working Group
Emissions Monitoring

The following organisations
are represented on the
working group:
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VGB PowerTech (DE) - Chair
KEMA (NL)
EDF (FR)
ESB (IRL)
Laborelec (BE)
E.ON (UK)
Helsingin Energia (FI)
E.ON (DE)
AMS Quality Assurance – the
EN14181 model
Source: Gould, R., QA of AMS, MCERTS Conference, Bretby, 2003
EN14181 – Operator’s
Responsibilities
Installation of compliant equipment
(QAL1, EN14956)
 Initial and periodic calibration of
equipment (QAL2)
 Annual verification of calibration (AST)
 Ongoing zero and span checks (QAL3)
 Retention of records on file
 Checking measured values are within cal.
range (weekly)

EN14181 – Industry Response

Welcome structure, clarity and consistency
provided by new standard.
Significant extra costs to industry
 Concerns relate to certain aspects
considered to be

– inappropriate or impractical to implement, or
– impose excessive cost or burden on operator

Request early revision to standard to
address these areas of concern
Areas of Concern (Summary)
1. Requirement
for complex
uncertainty
analysis
2. Low load
factor plant
3. Cert range
4. Cal function
5. Peripherals
6. Determining
control limits
7. Easy to
trigger QAL2
(expensive!)
Areas of concern (1) – QAL1

Impractical to do a full uncertainty
analysis for each analyser:
– Statistical approach too complicated
– Lack of available data for older sites
– Uncertainty analysis excludes
measurement location
– Confusion regarding which performance
parameters should be included.
VGB Proposal (1)


VGB supports a simplified approach
whereby instrument certified range
must be <2.5 x ELV, per type
certification in field trials
This substitutes performance testing,
under the recognised certification
schemes, for uncertainty analysis

Outcome similar to existing requirement

Already applies in some member states
Areas of Concern (2) – QAL2



Low load factor plant should not be
required to operate to prove the AMS
Similarly for a second fuel or configuration
used for a small proportion of the time
Where emissions concentrations are very
low, QAL2 using SRM yields “random” cal
functions (but may pass variability test!)
Example: low measured concentrations
Calibration functions for CO (AMS1)
30
25
SRM
20
15
10
5
0
0
10
Source: N Faniel, Laborelec
AMS
20
30
VGB Proposal (2)

VGB supports a flexible interpretation
for cases of low load factor plant or
very low emissions levels, including:
– Exemption of plant operating <1250 hours per
annum
– Exclusion of calibration time from reported
unavailability
– Calibration using reference materials where
SRM not appropriate
Areas of Concern (3) – Calibration
Range


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Valid calibration range limited to 10%
above max measured concentration (ŷs,max
+ 10%)
Limit is too narrow; creates perverse
incentive to maximise emissions during
test (e.g., deliberate burning of highest
sulphur fuel)
Inappropriate to apply this limit to hourly
average measurements, will repeatedly
trigger costly QAL2
VGB Proposal (3)

VGB supports the extension of the
valid calibrated range to 2.5 x ELV in
accordance with the linearity test
– This is consistent with the instrument range
advised in the standard
– Would allow plant to be operated normally
during the tests
– Calibration of plant with low emissions (<30%
ELV) should be based on reference materials
Areas of Concern (4) – Calibration
Function

Where measured data is clustered at high
levels, poor quality calibration function
may result. Inclusion of zero values would
add information
High measured values lead to difficulties in
passing the variability criterion, even
where R2 correlation is close to 1.
 Conversely, with low measured values,
variability test may validate poor cal
function

Example: High measured concentrations
Calibration functions: SO2
350
300
SRM
250
200
y = 0,89x + 42,50
150
y = 0,75x + 89,10
100
50
0
0
100
Source: N Faniel, Laborelec
AMS 200
300
VGB Proposals (4)


VGB supports a clarification of the
standard to allow inclusion of
measured zero values in the
calculation of the cal. function
VGB supports a flexible interpretation of
the standard for plant with very low
emissions, or dust monitors close to the
ELV
Areas of Concern (5) - Peripherals
Variations between AMS and SRM
peripheral readings may be due to actual
differences between locations
 It is unjustified to force the AMS and SRM
to read the same by applying a QAL2-style
calibration
 Functional check is more appropriate
 Calculated H2O may be more accurate
than measured

VGB Proposals (5)


VGB supports the view that functional
checks, rather than QAL2 calibrations,
are appropriate for peripheral
measurements
VGB recommends that where fuel
composition is well known, calculated
values of H2O may be used
Areas of Concern (6) – QAL3
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Control limits of analyser based on SAMS –
difficult to determine
Complex uncertainty analysis required.
Not clear what parameters to include;
data may be unavailable
Unfair to penalise analysers with better
performance
Control limit should be fixed percentage of
ELV
VGB Proposal (6)


VGB supports a simplified approach that
eliminates the need for uncertainty
analysis by the operator, and specifies
control limits as a fixed percentage of
the ELV.
Auto-calibration, with recording of
cumulative drift, should be allowed as
QAL3
Areas of Concern (7) - AST

Many situations trigger a QAL2 (e.g. a
change in fuel), in some of which an AST
may be sufficient to verify the cal function
QAL2 “triggers”
On installation and every 5 (3) years
 Change of fuel, process or abatement
system
 Modification or repair to AMS
 AST: cal function fails on validity or
variability criteria
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40% of measured values outside
calibration range over a week (or 5% over
5 weeks)
QAL2 “triggers”
On installation and every 5 (3) years
 Change of fuel, process or abatement
system
 Modification or repair to AMS
 AST: cal function fails on validity or
variability criteria
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
40% of measured values outside
calibration range over a week (or 5%
over 5 weeks)
Areas of Concern (7) - AST
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Many situations trigger a QAL2 (e.g. a
change in fuel), in some of which an AST
may be sufficient to verify the cal function
On failure of AST, temporary adjustment
of cal function should be allowed, pending
QAL2
On-site Cross-interference testing is
onerous and should not be necessary
where equipment is certified
Areas of Concern (7) – AST
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Functional tests could reasonably be
carried out by operator and audited by
accredited lab
The available 10% extension of the
calibrated range is too limited
No acknowledgement of the uncertainty of
the SRM, which may be similar to that of
the AMS
VGB Proposal (7)
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VGB supports:
Use of an AST in some circumstances
where a QAL2 is currently specified;
Flexibility in allowing operators to carry
out functional checks;
Explicit treatment of uncertainty of
test methods
Conclusions
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The standard brings welcome benefits
We have identified certain aspects that we
consider impractical in implementation or
inappropriate, or to impose unnecessary
costs or burdens on the operator
We respectfully propose modification of
these aspects and request early revision of
the standard incorporating these proposals