Comments on the Quality Assurance Standard EN14181

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Comments on the Quality Assurance Standard EN14181

• VGB Working Group
• Emissions Monitoring

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VGB Working GroupEmissions 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)

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AMS Quality Assurance the EN14181 model
Source Gould, R., QA of AMS, MCERTS Conference,
Bretby, 2003
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EN14181 Operators 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)

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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

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Areas of Concern (Summary)
2. Low load factor plant 3. Cert range 4. Cal
function 5. Peripherals
6. Determining control limits 7. Easy to trigger
QAL2 (expensive!)

• Requirement for complex uncertainty analysis

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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.

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VGB Proposal (1)

• VGB supports a simplified approach whereby
  instrument certified range must be lt2.5 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

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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!)

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Example low measured concentrations
Source N Faniel, Laborelec
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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 lt1250 hours per
  annum
• Exclusion of calibration time from reported
  unavailability
• Calibration using reference materials where SRM
  not appropriate

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Areas of Concern (3) Calibration Range

• Valid calibration range limited to 10 above max
  measured concentration (ys,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

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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 (lt30
  ELV) should be based on reference materials

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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

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Example High measured concentrations
Source N Faniel, Laborelec
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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

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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

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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

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Areas of Concern (6) QAL3

• 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

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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

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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

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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)

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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)

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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

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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

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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

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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