# Presentation: 438687

## Quality-Assurance Requirements for Continuous Monitoring Systems in the  NOx Budget Program Robert F. VollaroU.S. EPAClean Air Markets Division

## What Types of Continuous Monitoring Systems are Required by the NOx Budget Program ?

- Continuous monitoring systems are required for all NOx  Budget Program units, with one possible exception---i.e., qualifying oil and gas-fired units for which the low mass emissions (LME) methodology in 75.19 is used.
- The principal types of continuous monitoring systems used in the NOx Budget Program to quantify NOx mass emissions and heat input rate include:
- NOx-diluent systems, which measure NOx emission rate in units of pounds per million Btu (lb/mmBtu)
- NOx concentration systems, which measure NOx emissions in units of parts per million (ppm)

## What Types of Continuous Monitoring Systems are Required by the NOx Budget Program ? (cont’d)

- Flow monitoring systems which measure stack gas volumetric flow rate in units of standard cubic feet per hour (scfh)
- Moisture monitoring systems, which measure the stack gas moisture content in units of percent H2O
-  Diluent gas (O2 or CO2) monitoring systems (used for heat input rate determinations), which measure the O2 or CO2 concentration in the stack gas, in units of percent O2 or CO2
- Fuel flowmeter systems, which measure the quantity of oil and gas combusted in the affected unit, on a volumetric or mass basis
- Appendix E monitoring systems, which estimate NOx emission rate in lb/mmBtu, based on a correlation curve of heat input rate _vs_ NOx emission rate (applies to oil and gas-fired peaking units, only)

## What Types of Continuous Monitoring Systems are Required by the NOx Budget Program ? (cont’d)

- The specific continuous monitoring systems required for your affected unit depends primarily on:
- The type of fuel combusted;
- The selected monitoring methodology; and
- The mathematical equations used in the emission calculations.

## What Tests are Required to Certify the NOx  Budget Program Monitoring Systems ?

- The certification requirements for Part 75 CEMS are found in section 75.20 (c):
- For a NOx-diluent system:
- 7-day calibration error tests of the NOx and diluent components
- Linearity checks of both components
- Upscale and downscale cycle time tests of both components
- Relative accuracy test audit (RATA) of the system, on a lb/mmBtu basis, and a bias test
- For a NOx concentration system:
- 7-day calibration error test
- Linearity check
- Cycle time test
- RATA, on a ppm basis, and a bias test

## What Tests are Required to Certify the NOx  Budget Program Monitoring Systems ? (cont’d)

- For a flow monitor:
- 7-day calibration error test
- RATA at 3 load levels and a bias test
- For a moisture monitoring system:
- 7-day calibration error test (wet-dry O2 systems, only)
- Linearity check (wet-dry O2 systems, only)
- Cycle time test (wet-dry O2 systems, only)
- RATA, on a % H2O basis

## What Tests are Required to Certify the NOx  Budget Program Monitoring Systems ? (cont’d)

- For a diluent gas monitoring system
- 7-day calibration error test
- Linearity check
- Cycle time test
- RATA, on a % CO2 or % O2 basis (as applicable)
- The certification test requirements for Appendix D and E monitoring systems are found in section 2.1.5 of Appendix D and section 2.1 of Appendix E
- For a fuel flowmeter system:
- Either calibrate the system with a flowing fluid, at 3 points covering the normal operating range of the affected unit  _or_

## What Tests are Required to Certify the NOx  Budget Program Monitoring Systems ? (cont’d)

- If the flowmeter is an orifice, nozzle or venturi-type and it meets certain design criteria, you may certify it by performing a visual inspection and calibrating the pressure, delta-P, and temperature transducers
- For an Appendix E monitoring system:
- Perform NOx emission rate testing at 4 load levels covering the operating range of the affected unit
- Measure the heat input rate during the NOx emission testing, using data from a certified Appendix D fuel flowmeter system in conjunction with the gross calorific value (GCV) of the fuel
- Construct the correlation curve of NOx emission rate _vs_ heat input rate from the test data

## Are There Exceptions to These Certification Requirements ?

- Part 75 provides the following exceptions to the continuous monitoring system certification requirements.  Specifically:
- Peaking units are exempted from 7-day calibration error testing (Appendix A, sections 6.3.1 and 6.3.2)
- NOx span values of 50 ppm or less are exempted from 7-day calibration error testing (Appendix A, section 6.3.1)
- NOx span values of 30 ppm or less are exempted from linearity checks (Appendix A, section 6.2 and Appendix B, section 2.2.1)
- Flow RATAs may be done at fewer than 3 load levels if the source has an approved petition or technical justification (Appendix A, sections 6.5.2 (c) and (e)).

## Are There Exceptions to These Certification Requirements ? (cont’d)

- A default moisture value (from Part 75 or approved by petition) may be used in lieu of certifying a continuous moisture monitoring system (sections 75.11(b) and 75.12(b)).
- For saturated gas streams, you may use a temperature sensor and the psychrometric chart to monitor the stack gas moisture content.  A DAHS verification at 3 representative temperatures is required. (section 75.20(c)(7)).

## What Performance Specifications Must be Met for Initial Certification ? 

- For CEMS, the performance specifications for initial certification are found in Part 75,  Appendix A, sections 3.1 through 3.5
- The primary performance specifications are expressed as percentages (e.g., % of span, % of reference gas value, % relative accuracy).
- There are a number of alternative specifications, expressed as the absolute difference between the mean values of the reference and CEMS measurements.  These alternative specifications provide relief from the primary specifications, for low-emitting sources and low span values.
- The CEMS may be certified either by meeting the primary or the alternative specifications

## What On-Going Quality-Assurance is Required for the Monitoring Systems ?

- After initial certification, periodic quality-assurance (QA) testing of all Part 75 continuous monitoring systems is required
- For continuous emission monitoring systems (CEMS), these QA test requirements are found in either:
- Appendix B of Part 75, for sources that report emissions data year-round; or
- Section 75.74(c), for sources that report emissions data only during the ozone season

## What On-Going Quality-Assurance is Required for the Monitoring Systems ? (cont’d)

- For fuel flowmeter systems, the on-going QA test requirements are found in section 2.1.6 of Part 75, Appendix D
- For Appendix E monitoring systems, the on-going QA test requirements are found in sections 2.2 and 2.3 of Part 75, Appendix E

## On-Going QA Requirements for Year-Round Reporters

- For NOx Budget sources that report emissions data year-round:
- If a CEMS-based methodology is used, QA testing of of the CEMS is required at three basic frequencies:
- Daily
- Quarterly
- Semiannual/Annual
- For sources using fuel flowmeters, the basic QA test frequency is annual, but may be extended up to 5 years (20calendar quarters) if certain conditions are met
- For Appendix E sources, the basic QA test frequency is once every 5 years (20 calendar quarters), provided that certain conditions are met

## On-Going QA Requirements for Year-Round 		Reporters (cont’d)			

- Periodic QA Testing of CEM Systems
- Daily Assessments
- Calibration error tests  (required for all gas and flow monitors)
- Interference checks (required for all flow monitors)
- Quarterly Assessments
- Linearity checks
- Required for gas monitors in every “QA operating quarter” (i.e., a calendar quarter with _>_ 168 hrs of unit operation
- For dual-range analyzers, required on each range used in the QA quarter
- Required at least once every 4 calendar quarters on each range, regardless of unit operating hours or whether the range was used
- NOx span values _<_ 30 ppm are exempted
- A 168 unit operating hour grace period is available

## On-Going QA Requirements for Year-Round 	Reporters (cont’d)

- Flow-to-load ratio test
- Required for units with stack flow monitors, to assess flow monitor  accuracy in-between successive annual RATAs
- Required only in QA operating quarters
- Analyzes a segment of the quarterly flow rate data.  Compares hourly flow-to-load ratios to a reference ratio determined during the most recent normal load RATA
- As an alternative, the test may be done on a gross heat rate (GHR) basis, i.e., the ratio of heat input rate to load
- Complex exhaust configurations may be exempted from the flow-to-load test by petition under 75.66
- Leak check
- Required only for differential pressure-type stack flow monitors
- Required only in QA operating quarters
- A 168 unit/stack operating hour grace period is available

## On-Going QA Requirements for Year-Round 	Reporters (cont’d)

- Semiannual and Annual Assessments
- RATA
- Required for gas monitoring systems, flow monitors, and moisture monitoring systems
- Depending on %RA achieved in the last RATA, the next test is required either annually (within 4 QA operating quarters) or semiannually (within 2 QA operating quarters)
- Gas and moisture system RATAs are always performed at normal load
- The basic flow RATA requirement is at 2 loads.  From year-to-year, sources can qualify for single-load test if _>_ 85% of load data since the last annual RATA is in one load band (Low, Mid, or High)
- Limited extension of RATA deadlines is allowed for non-QA operating quarters, up to 8 calendar quarters between successive RATAs
- A 720 unit operating hour grace period is available
- A bias test is required for NOx systems and flow monitors

## On-Going QA Requirements for Year-Round 	Reporters (cont’d)

- Fuel flowmeter accuracy tests
- Required once every 4 “fuel flowmeter QA operating quarters” (i.e., a quarter in which the fuel measured by the flowmeter is combusted for    _>_ 168 hrs)
- The accuracy test consists of either calibration against a flowing fluid or (for orifice, nozzle and venturi-type meters that were certified by design) calibration of the transmitters
- For orifice, nozzle or venturi-type flowmeters that were certified by design, a visual inspection of the primary element is also required every 3 years
- Accuracy test deadlines may be extended for infrequent use of the fuel flowmeter (non-QA operating quarters) or if the optional quarterly fuel flow-to-load ratio test is performed and passed (Appendix D, 2.1.7)
- The maximum possible extension of an accuracy test deadline is 20 calendar quarters from the quarter of the last test

## On-Going QA Requirements for Year-Round 	Reporters (cont’d)

- 5-year assessments
- For stack flow monitors, a 3-load RATA is required once every 5 calendar years
- For Appendix E sources, the basic re-testing frequency is once every 5 years (20 calendar quarters), provided that none of the monitored parameters are outside the acceptable ranges for more than 16 consecutive operating hours.  An additional re-test is required when this condition is not met.

## On-Going QA Requirements for Year-Round 	Reporters (cont’d)

- When must the on-going QA tests begin ?
- Daily assessments---These requirements become effective as of the date when certification testing of the CEMS is completed (i.e., “date of provisional certification”)
- Quarterly assessments---These assessments begin in the quarter following the quarter in which the CEMS is provisionally certified
- Semiannual, annual and 5-year assessments---Reckon the deadline for the next test starting with the quarter following the quarter in which the monitoring system is provisionally certified
- _See:_  Appendix B, sections 2.1, 2.2, and 2.3

## On-Going QA Requirements for Ozone Season-Only Reporters

- For NOx Budget sources that report emissions data on an ozone season-only basis, there are QA test requirements both:
- Outside the ozone season (October 1-April 30); and
- Inside the ozone season (May 1-September 30)
- For CEMS-based methodologies:
- Daily calibrations of all monitors are required inside the ozone season.  Outside the ozone season, calibrations are required from the hour of any passed off-season RATA or linearity check, through April 30
- Daily interference checks of flow monitors are required inside the ozone season.  Outside the ozone season, these checks are required from the hour of any passed flow RATA, through April 30

## On-Going QA Requirements for Ozone Season-Only Reporters (cont’d)

- A linearity check of each gas monitor is required outside the ozone season.  Inside the ozone season, linearity checks are required in the 2nd and 3rd quarters, if those quarters are “QA operating quarters”.
- A 168 operating hour grace period is allowed at the beginning of the ozone season for the “off-season” check, if a linearity was passed in the previous year and if the unit operated < 336 hrs in the last ozone season
- No grace periods are allowed for the required 2nd and 3rd quarter linearity checks inside the ozone season
- Only unit operating hours in May and June are used to determine whether the 2nd quarter is a QA operating quarter
- For flow monitors, the flow-to-load ratio test is required only in the 2nd and 3rd quarters, if those quarters are “QA operating quarters”.

## On-Going QA Requirements for Ozone Season-Only Reporters (cont’d)

- For DP-type flow monitors, leak checks are required only in the 2nd and 3rd quarters, if those quarters are “QA operating quarters”.
- RATAs of all gas, flow, and moisture monitoring systems are required semiannually or annually.
- The RATAs may be done either inside or outside the ozone season
- Depending on the %RA achieved, the frequency is semiannual or annual and the next test is due in either 2 or 4 _calendar_ quarters.
- The QA operating quarter concept does not apply.
- The window of data validation extends either to:
- The end of the 2nd quarter following the quarter of the RATA, if the RATA frequency is semiannual; or
- The end of the 4th quarter following the quarter of the RATA, if the RATA frequency is annual.

## On-Going QA Requirements for Ozone Season-Only Reporters (cont’d)

- If a scheduled off-season RATA is not completed by April 30:
- A 720 operating hour grace period is available if a RATA was passed in the previous year and the unit operated < 336 hrs in the last ozone season
- If you do not qualify for the grace period, you may use the conditional data validation procedures in 75.20(b)(3), with certain restrictions
- Grace periods do not apply when the owner or operator elects to schedule and perform RATAs  inside the ozone season
- A bias test is required for all NOx  monitoring systems and flow monitors.
- For flow monitors, 2-load RATAs are required for routine QA, and a 3-load test must be performed once every 5 years.  The option to qualify for single-load annual flow RATAs is not available to ozone season-only reporters.

## On-Going QA Requirements for Ozone Season-Only Reporters (cont’d)

- Accuracy tests of fuel flowmeters and Appendix E re-tests are required at the same frequency as for year-round reporters. _All_ calendar quarters in the year are included when determining the test deadlines.

## What Performance Specifications Must be Met for On-Going QA ?

- The performance specifications that must be met for the on-going QA tests of the continuous monitoring systems are basically the same as for initial certification, with one notable exception
- For CEM systems:
- The daily calibration error specifications in section 2.1.4 of Appendix B are less stringent than the 7-day calibration error test specifications in  section 3.1 of Appendix A.
- The linearity specifications are the same as in section 3.2 of Appendix A

## What Performance Specifications Must be Met for On-Going QA ? (cont’d)

- The RATA specifications are the same as in sections 3.3.2 through 3.3.7 of Appendix A.
- For reduced RATA frequency (i.e., annual _vs_ semiannual), the specifications are found in section 2.3.1.2 of Appendix B and are summarized in Figure 2 of Appendix B.
- For fuel flowmeter systems, the accuracy requirements for on-going QA tests are the same as for initial certification and are found in sections 2.1.5 and 2.1.6 of Appendix D