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Comments on the Quality Assurance Standard EN14181 VGB Working Group Emissions Monitoring.

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Presentation on theme: "Comments on the Quality Assurance Standard EN14181 VGB Working Group Emissions Monitoring."— Presentation transcript:

1 Comments on the Quality Assurance Standard EN14181 VGB Working Group Emissions Monitoring

2 VGB Working Group Emissions Monitoring  The following organisations are represented on the working group: –VGB PowerTech (DE) - Chair –KEMA (NL) –EDF (FR) –ESB (IRL) –Laborelec (BE) –E.ON (UK) –Helsingin Energia (FI) –E.ON (DE)

3 AMS Quality Assurance – the EN14181 model Source: Gould, R., QA of AMS, MCERTS Conference, Bretby, 2003

4 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)

5 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

6 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!)

7 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.

8 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

9 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!)

10 Example: low measured concentrations Source: N Faniel, Laborelec

11 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

12 Areas of Concern (3) – Calibration Range  Valid calibration range limited to 10% above max measured concentration (ŷ s,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

13 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

14 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 R 2 correlation is close to 1.  Conversely, with low measured values, variability test may validate poor cal function

15 Example: High measured concentrations Source: N Faniel, Laborelec Calibration functions: SO2 y = 0,75x + 89,10 y = 0,89x + 42, AMS SRM

16 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

17 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 H 2 O may be more accurate than measured

18 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 H 2 O may be used

19 Areas of Concern (6) – QAL3  Control limits of analyser based on S AMS – 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

20 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

21 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

22 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  40% of measured values outside calibration range over a week (or 5% over 5 weeks)

23 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  40% of measured values outside calibration range over a week (or 5% over 5 weeks)

24 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  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

25 Areas of Concern (7) – AST  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

26 VGB Proposal (7)  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

27 Conclusions  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


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