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EPA 2003 Blind Audit of Protocol Gases
John Schakenbach, USEPA, CAMDScott Shanklin, Cadmus Group
Bob Wright, USEPA, ORD
EPRI CEM User GroupMilwaukee, WIMay 4-6, 2004
What is the Problem?
Historically, blind audits of calibration gases have shown poor quality initially
SO2 RATA using plant’s incorrect cal gas (low by 15%). Source could underreport SO2 by 15% and be undetected for at least 6 months.
Other Reasons Why Accurate Cal Gas is Important
Only daily assurance CEM is really working
Reference Method analyzers need accurate calibration gases to produce accurate RATA results
Purpose of Blind Audits
Help vendors improve gas quality Help sources identify good vendors
History 1970’s -1996 EPA audited gases Posted results
– In 1995, one vendor off by -16.3% (CEM would underreport)
Strong utility and vendor support Auditing strongly correlated with improved
gas quality
Current Gas Analysis First audit in 7 years Blind audit 14 national gas vendors Similar procedures as in past SRMs and NTRMs used 42 Protocol tri-blend cylinders MACTEC (UV and NDIR) and Spectral
Insights (FTIR)
Tri-blend Protocol GasesCO2(%)
NO(ppm)
SO2(ppm)
Low 5 50 50
Medium 12 400 500
High 18 900 1000
Instrumentation NO - API Model 200AH chemiluminescence NO - AMETEK Model 922M differential absorption
UV SO2 - Bovar Model 721M differential absorption
UV CO2 - California Analytical Model 3300A NDIR NO, SO2 and CO2 - Nicolet Nexus Model 760 FTIR Environics (Graseby-Nutech) Series 3740 gas
dilution system
UHP N2
Zero
CO2
Reference
NOReference
SO2
Reference
CandidateStandard
CandidateStandard
CandidateStandard
PressureRegulator
GasFlow Selector
PressureGauge
CAI 3300A CO2
Analyzer
AMETEK 922M NOx
Analyzer
AnalogDigital
Converter
DataAcquisition
PC
Bovar 721M SO2 Analyzer
Schematic of Mactec Assay Apparatus
Vent
Candidate, Zero, SRM or NTRM Gas Standards
FTIR Spectrometer
Cel
l
Vacuum Pump
Selector Valve
Isolation Valves
Vent
PT
Computer
Transducers
Check Valves
Toggle Valves
Vent
Gas Manifold/Regulator
Manifold Vent Valve
Vent
Spectral Insights Assay Apparatus
Accuracy Criterion
Part 75, Appendix A, sec 5.1.4 requires 2.0% of tag value
Protocol procedures achieve +2% of tag value:
1% Standard Reference Material
plus1% EPA Protocol methodology
Problems CO2 quenching biased the NO concs from
chemiluminescent analyzer low– Chemiluminescent NO concs thrown out– Measurements repeated with a UV analyzer
UV analyzer was set up for 0 - 500 ppm NO, but should have been for 0-1000 ppm– Threw out high level NO concs– Repeated high level NO measurements using FTIR
Problems SO2 interfered with UV analyzer NO
readings– Injected SO2 in N2 to develop a correction
Ran out of high level CO2 SRM for FTIR– Threw out the high level CO2 FTIR results and
relied on NDIR
Results EPA presents the following information without
assigning a rating to the gas vendors. If EPA’s and vendor’s values differ by 2.0% or less,
then because of uncertainties in the measurement system, statistically, there is no difference between the two values, e.g., a difference of 2.0% and 0.5% are considered equal.
All vendors that failed are re-analyzing their gas cylinders. When EPA receives the re-analyzed results, they will be posted.
Gas
Conc. Tag ValueAudit
Tag ValueAudit
Tag Value Audit
Level (ppm NO) Result (ppm SO2) Result (% CO2) Result
Air Liquide Low 54.0 Pass 47.5 Pass 4.97 PassAir Liquide Mid 401 Pass 499 Pass 12.1 PassAir Liquide (a) High 911 Pass 981 Pass 17.7 Fail
Airgas Southwest Specialty Gases (a) Low 48.90 Fail 47.73 Pass 5.01 PassAirgas Southwest Specialty Gases Mid 406.0 Pass 496.8 Pass 12.00 PassAirgas Southwest Specialty Gases (a) High 900.0 Fail 994.6 Pass 17.99 Pass
Airgas NCN Specialty Gases Low 51.4 Pass 50.4 Pass 5.01 PassAirgas NCN Specialty Gases Mid 388 Pass 500 Pass 12.0 PassAirgas NCN Specialty Gases (a) High 845 Fail 1000 Pass 18.0 Pass
Airgas South Specialty Gases (a) Low 50.05 Fail 50.23 Pass 5.041 PassAirgas South Specialty Gases Mid 397.5 Pass 502.8 Pass 12.00 PassAirgas South Specialty Gases High 900.0 Pass 998.8 Pass 18.07 Pass
BOC Gases Low 49.8 Pass 50.9 Pass 5.00 PassBOC Gases (a) Mid 407.8 Fail 500.4 Pass 11.98 PassBOC Gases (a) High 900 Fail 1000 Pass 18.02 Pass
AGA / Linde Gas Group Low 50.4 Pass 48.7 Pass 5.20 PassAGA / Linde Gas Group Mid 396 Pass 466 Pass 12.5 PassAGA / Linde Gas Group High 904 Pass 956 Pass 18.3 Pass
Matheson Tri-Gas (a) Low 48.9 Fail 49.5 Pass 5.23 FailMatheson Tri-Gas (a) Mid 410 Fail 504 Pass 12.2 PassMatheson Tri-Gas High 904 Pass 988 Pass 17.9 Pass
Gas Vendor
NO SO2 CO2
Gas
Conc.Tag
Value AuditTag Value
AuditTag
Value AuditLevel (ppm NO) Result (ppm SO2) Result (% CO2) Result
Messer MG Industries Low 50.0 Pass 50.1 Pass 5.05 PassMesser MG Industries Mid 398 Pass 501 Pass 12.1 PassMesser MG Industries High 888 Pass 1004 Pass 18.2 Pass
Messer MG Industries (Spec Air Specialty Gas) Low 50.0 Pass 49.3 Pass 5.07 PassMesser MG Industries (Spec Air Specialty Gas) Mid 403 Pass 496 Pass 12.1 PassMesser MG Industries (Spec Air Specialty Gas) High 894 Pass 1004 Pass 18.3 Pass
National Specialty Gases (a) Low 46.2 Fail 51.8 Fail 4.90 PassNational Specialty Gases Mid 398 Pass 500 Pass 12.0 PassNational Specialty Gases (a) High 930 Pass 991 Pass 17.8 Fail
Praxair Low 51.2 Pass 50.0 Pass 5.00 PassPraxair Mid 406 Pass 509 Pass 12.18 PassPraxair (a) High 914 Pass 999 Pass 17.59 Fail
Scott Specialty Gases Low 50.0 Pass 50.4 Pass 5.04 PassScott Specialty Gases Mid 402 Pass 503 Pass 12.10 PassScott Specialty Gases High 911 Pass 1011 Pass 17.97 Pass
Scott-Marrin In. Low 50.8 Pass 50.9 Pass 5.11 PassScott-Marrin In. Mid 397 Pass 504 Pass 12.02 PassScott-Marrin In. High 886 Pass 997 Pass 17.92 Pass
Spectra Gases Inc. Low 50.1 Pass 50.2 Pass 5.02 PassSpectra Gases Inc. Mid 405 Pass 495 Pass 12.03 PassSpectra Gases Inc. High 923 Pass 988 Pass 18.07 Pass
Gas Vendor
NO SO2 CO2
Results Overall failure rate: 14 of 126 analyses (11%) 57% of vendors failed SO2: Worst tag value ~2.5% high NO: Worst tag value ~8% low CO2: Worst tag value ~4.9% high All 42 cylinders met the Protocol Procedure
documentation requirements
- - -- - -3/140/143/140/14- - -3/14- - -High
0/141/140/140/140/140/142/143/142/14Mid
1/141/141/141/141/146/144/144/146/14Low
BothFTIRNDIRBothFTIRUVBothFTIRUV
CO2 AnalysesSO2 AnalysesNO Analyses
EPA Protocol Gases not meeting Acceptance Criterion
Percent Failure Rate by Vendor Technology
NO SO2 CO2
Chem NDIR FTIR NDIR UV FTIR NDIR FTIR TCD
14.3 16.7 27.8 0.0 0.0 6.7 4.2 20.0 0.0
Lessons Learned Detailed standard operating procedures for
analyzing single and multicomponent mixtures are needed in EPA’s Protocol Procedures, especially for FTIR
First ensure lab can correctly analyze single component cylinders
Then check for interferences by measuring a multicomponent cylinder simultaneously with analyzers for each component gas
Use an SRM or NTRM to get reference spectrum for FTIR measurements
Audits Can Be Effective
Failure Rate on Cal Gas Blind Audits
0.00
10.00
20.00
30.00
40.00
1992 1993 1994 1995 1996 2003
Audit Program Issues
Scope Stringency Structure
Options - Scope
Part 75 only All source-level programs, e.g.,
Part 75, NSPS, SIP, NSR All source and ambient-level
programs
Options - Stringency
Work with vendors to fix problems
Work with vendors and post audit results on web sites
Formal gas vendor certification program
Options - Structure Spin-off to 3rd party (A2LA, NVLAP, NSF,
etc.) to purchase and analyze cylinders (set up fee-based system) with EPA oversight
Through EPA task order, contractor purchases and analyzes cylinders from major suppliers (EPA used to do this)
Other (NELAC, gas vendor-developed mechanism, NIST, EPA lab, etc.)
Initial Recommendations
ScopeAll source and ambient-level programsStringencyWork with vendors; post audit resultsStructureSet up fee-based system to purchase and
analyzecylinders using 3rd party with EPA oversight; orpossibly use gas vendor-developed mechanism
Example 3rd Parties for Spin Off
American Association for Laboratory Accreditation (A2LA)
National Voluntary Laboratory Accreditation Program (NVLAP)
National Sanitation Foundation (NSF)
Next Steps
Get more feedback from gas vendors and other interested parties
For a Copy of Presentation
www.epa.gov/airmarkets, click on
“Recent Additions” near top left corner or
John SchakenbachPhone: 202-343-9158