EPA Precursor Gas Training Workshop NCore Calibration Issues Meeting the new QC Requirements Lewis...

EPA Precursor Gas Training Workshop

NCore Calibration IssuesMeeting the new QC Requirements

Lewis Weinstock and Dennis Mikel EPA Office of Air Quality, Planning

and Standards


• Overview of NCore technical requirements

• Mass Flow Controllers (MFC) Calibrators

• Compressed Gas Cylinders

• Zero Air Generators

• Summary

Key Topics


NCore Calibration Challenges

• Operating analyzers on lower ranges where ambient data are more affected by instrument drift and interferences– Old CO range 0 – 50 ppm for NAAQS compliance

– Typical NCore CO range 0 – 5 ppm or even lower

• More frequent QC checks advised so calibration automation is important

• Integration of data systems and calibrators important for QC validation and timely reporting of problems

• Calibration standard certification periods are shorter for lower concentration standards

• Zero air purity is more critical than ever• Reviewing your calibrator capabilities and potentially upgrading

hardware may be the most important part of designing and implementing a successful NCore gas monitoring system


• QC Checks (Precision): – Required (40 CFR 58 Appendix A)– Minimum: Once every two weeks – daily is recommended– Daily Level 1 Zero and Spans recommended

• Multi-point calibrations: – Quarterly (according to TAD) or if drift is an ongoing issue– Draft MQO Table - 1 in 6 months, upon instrument startup,

repair, or exceeded drift tolerance

• MDL Tests (New requirement): – Annually or after major analyzer repair

• Consider entire system when troubleshooting QC problems – zero air or calibrator issues may be the cause– Don’t just recalibrate repeatedly when analyzer drift and/or

linearity problems are indicated

NCore Calibration and QC Check Requirements


Item CO SO2 NOy

Full Scale Range 0 to 5000 ppb 0 to 100 ppb 0 to 200 ppb

Cylinderconcentration

200 – 300 ppm 10 - 15 ppm 10 – 30 ppm

Calibration ranges

Zero(action tolerance)

+ 40 ppb + 0.100 ppb + 0.050 ppb

Level I Span(action tolerance)

4500 ppb + 10% 90 ppb + 10% 180 ppb + 10%

Mid Point Span 2500 ppb 50 ppb 100 ppb

Precision Level 250 - 500 ppb 5 - 10 ppb 20 - 40 ppb

MeasurementUncertainty Goal

10%upper 90 percent confidence

limit for CV


limit for CV


limit for CV

Calibration and QC Check Concentrations** For a typical urban NCore station


Example QC Control Chart

CO TEI - Precision Drift - Burdens Creek (500 ppb)

-20.0%

-15.0%

-10.0%

-5.0%

0.0%

5.0%

10.0%

15.0%

20.0%


Method Detection Limit Test(How do you run it?)

• Use a concentration of 2.5 to 5 times the instrument signal/noise• Run zero gas through analyzer• Dilute the calibration gas to estimated concentration level and collect

readings for a predetermined length of time: – Suggested: 20-25 1 minute observations, repeated 7 times over the

course of 5 -14 days. Average the concentration from these readings.

• Calculate the MDL as:

stMDL n 1,01.

Where represents the 99th quantile of a Student’s t distribution with (n-1) degrees of freedom and n represents the number of replicate measurements and s is the standard deviation.

1,01. nt


Method Detection Limit Test

• Confirms that a trace-level analyzer is really performing as a trace level– Perform as part of acceptance testing– Annually as part of regular QA program– After a major repair such as detector replacement

• Operational challenges– Need to accurately and repeatedly generate a very small

concentration– Will need dedicated low-level gas cylinder standards in the 1 ppm

range for NO and SO2, and 10 ppm range for CO• Agencies can share cylinders• Possible development of cylinder “bank”

– Dilution challenges capacity of zero air scrubbing system at high flows (~ 20 LPM)


Example Method Detection Limit Test

CO Analyzers MDL Test 2/4(Red=T-CO, Blue=A-CO)

-50

-30

-10

10

30

50

70

90

110

130

150

11:3

0

11:4

0

11:5

0

12:0

0

12:1

0

12:2

0

12:3

0

12:4

0

12:5

0

13:0

0

13:1

0

13:2

0

13:3

0

13:4

0

13:5

0

14:0

0

14:1

0

14:2

0

14:3

0

14:4

0

14:5

0

15:0

0

15:1

0

15:2

0

15:3

0

15:4

0

stMDL n 1,01.

API CO MDL TESTS4-Feb 83.315-Feb 87.446-Feb 76.677-Feb 77.228-Feb 75.059-Feb 76.59

10-Feb 73.8111-Feb 75.6612-Feb 67.0313-Feb 80.2914-Feb 78.78

STDev 5.26Avg 77.44

99% 99.50% 99.75% 99.90% 99.95%1 31.82 63.66 127.3 318.3 636.6

2 6.965 9.925 14.09 22.33 31.6

3 4.541 5.841 7.453 10.21 12.92

4 3.747 4.604 5.598 7.173 8.61

5 3.365 4.032 4.773 5.893 6.869

6 3.143 3.707 4.317 5.208 5.959

7 2.998 3.499 4.029 4.785 5.408

8 2.896 3.355 3.833 4.501 5.041

9 2.821 3.25 3.69 4.297 4.781

10 2.764 3.169 3.581 4.144 4.587

MDL = (2.764) * 5.26 = 14.54 ppb

Student's t-distributionFrom Wikipedia, the free encyclopedia


Typical Mass Flow Controller (MFC) TheoryCalibrator Diagram

Zero Air MFC


Calibrator Critical Specifications

• Gas Flow – 0 to 100 cc/min • Air Flow – 0 – 20 L/min• Multiple Gas ports - optional• Built in traceable ozone

generator • Accuracy +/- 1% Full Scale• Precision +/- 1% Full Scale • Linearity +/- 1% Full Scale

Environics 9100


Calibrator Specification Matrix (EPA Research 2006)

Calibrator Gas* Flow

Air*

Flow

Gas input Ports

Ozone

Gen.

Flow Accuracy

Flow

Precision

Linearity

Ecotech 1100

0-500 sccm

0-20 lpm 4 Std. Yes, 0 – 1ppm

+/- 1.0%

Full Scale

+/- 0.15%

Full Scale

0.15%

Full Scale

Environics

9100

0-100 sccm

0-20 lpm 2 Std. Yes, 0.5 – 1.25 ppm

+/- 1.0%

Full Scale

+/- 1.0%

Full Scale

1.0%

Full Scale

Sabio

4010L

0-1000

sccm

0-20 lpm Yes Yes, 0 –

2 ppm

+/- 1.0%

Full Scale

+/- 0.15%

Full Scale

0.5%

Full Scale

Tanabyte

300

0-100 sccm

0-10** lpm

Yes Yes, 0 –

2 ppm

+/- 0.5%

Full Scale

+/- 0.1%

Full Scale

0.5%

Full Scale

Teledyne- API 700E

0-200 sccm

0-20 lpm 4 Std. Yes, 0.1 – 10 ppm

+/- 1.0%

Full Scale

+/- 0.2%

Full Scale

0.5%

Full Scale

Thermo

146C

0-200 sccm

0-20 lpm NA Yes +/- 1.0%

Full Scale

+/- 1.0%

Full Scale

1.5%

Full Scale

* Highest optional ranges. ** Tanabyte offers a 0 – 20 lpm option


Calibrator Critical Features

• Option for multiple gas flow controllers to expand dynamic dilution range– Want to stay away from flows less than 10% or greater than

90% of MFC full scale

• Internal calculation of MFC flow response• Programmable scheduled tasks • Remote access and control ready (accept direct

digital commands)• Digital Inputs – controlled by remote access• Digital Outputs – signals to remote device• Capability to directly control solenoids without

external power supplies


Calibrator Feature Matrix (EPA Research 2006)

Calibrator Programmable Calibrations

Display Digital Inputs Digital Outputs

Ecotech 1100 Yes, 20 sequences cycled through 5 points

4 line LCD Relay contact closures or TTL logic

8 digital outputs for sequence indication

Environics

9100

Yes, 21 sequences (3/day) through 5 points

LCD Optional RS-232 serial data interface

8 digital outputs for sequence indication

Sabio

4010L

20 timer driven cal routines, user defined sequences on a 7 day calendar

Bright active matrix color display

24 bit Digital Input, TTL logic levels, RS-232

24 bit output,

2 serial ports for communication

Tanabyte

300

Menu operation allows auto or manual calibrations

LCD TTL contact closures allows remote operation

Via RS-232 300 -9600 baud

Transparent pass serial I/0 after programmable pass-code is received

Teledyne- API 700E

Readout and control by front panel

2 line LCD Via RS-232

12 opto-isolated inputs

Via RS-232

12 opto-isolated outputs

Thermo

146C

10 calibration events 4 line LCD RS-232 remote access RS-232 remote access


Certifying your Calibrator Flows

• Initial calibration should be provided with purchase – always recheck after delivery

• Certify flow controllers against a NIST traceable flow device (such as a Bios DryCal, Gilibrator or Hastings Bubble Kit or other flow device)

• NIST Traceable flow device should be certified annually (or if you suspect a problem)

• Perform quarterly or semi-annual checks of your MFCs (or until establish trend)

• Calculate observed flow vs set points at STP (25 degrees Celsius and 760 mm Hg)


MFC Calibration - Burdens Creek (1-23-2007)Environics 9100 #A50930

ZERO AIR FLOW CONTROLLER MFC1 LAST CERTIFICATION: 8/21/2006L/M (5 REPLICATES PER READING)

POINT# DISPLAY/SET DRYCAL1 DRYCAL2 DRYCAL3 DRYCAL4 DRYCAL5 AVERAGE1 20.0 19.90 19.80 19.82 19.81 19.80 19.8262 18.0 17.58 17.60 17.61 17.58 17.58 17.5903 16.0 15.67 15.68 15.67 15.68 15.67 15.6744 14.0 13.71 13.72 13.74 13.74 13.72 13.7265 12.0 11.82 11.83 11.84 11.83 11.82 11.8286 10.0 9.90 9.91 9.92 9.91 9.91 9.9107 8.0 7.95 7.95 7.94 7.94 7.94 7.9438 6.0 5.98 5.98 5.98 5.98 5.98 5.9809 4.0 4.01 4.01 4.01 4.01 4.00 4.00810 2.0 1.99 2.00 1.99 1.99 2.00 1.99411 1.0 0.976 0.987 0.976 0.981 0.978 0.980

ENVIRONICS 9100 MFC 1 y = 0.9812x + 0.0493

R2 = 0.9999

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

20.00

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0

SET FLOW

OB

S F

LO

W


MFC Calibration - Burdens Creek (1-23-2007)Environics 9100 #A50930

GAS AIR FLOW CONTROLLER MFC2 LAST CERTIFICATION: 8/21/2006SCCM (5 REPLICATES PER READING EXCEPT LOWEST 3PTs)

POINT# DISPLAY/SET DRYCAL1 DRYCAL2 DRYCAL3 DRYCAL4 DRYCAL5 AVERAGE1 100.0 97.59 97.61 97.41 97.04 97.83 97.4962 90.0 87.65 88.14 87.93 87.94 87.76 87.8843 80.0 76.12 76.58 76.69 76.88 76.35 76.5244 70.0 68.10 67.80 67.72 67.69 68.41 67.9445 60.0 58.86 59.10 59.17 58.67 58.53 58.8666 50.0 49.09 49.07 48.99 49.19 49.12 49.0927 40.0 39.32 39.52 39.45 39.68 39.55 39.5048 30.0 29.29 29.07 28.98 29.10 29.10 29.1089 20.0 19.17 19.10 19.22 19.15 19.00 19.128

10 10.0 9.55 9.72 9.59 9.63 9.43 9.58211 5.0 4.47 4.59 4.45 4.49 4.62 4.525

ENVIRONICS 9100 MFC 2 y = 0.9741x - 0.0883

R2 = 0.9997

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

100.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0

SET FLOW

OB

S F

LO

W


Compressed Gas Cylinders - Features

• Come in variety of sizes (size 50 or 150)• Recommend using Aluminum cylinders• Get EPA Protocol certification from experienced vendors

– http://www.epa.gov/appcdwww/pubs/600r97121/600r97121.htm– Note: certification periods can be shorter than expected for low

concentration cylinders (next slide)• Use Stainless Steel regulators and cylinder valves• Use Stainless steel or Teflon lines from Regulator to

MFC (Teflon recommended)• Recommended Cylinder Concentrations for the NCore

Sites: – SO2: 10 – 15 ppm– NO: 10 – 30 ppm– CO: 200 – 300 ppm – Oxygen free - Balance Nitrogen


Zero Air Systems - Features


Zero Air Source - Issues

• The air system should be able to provide clean air below the stated Lower Detection Limits (LDL) of the instruments you are operating at maximum required flow rates (up to 20 l/min)– NO: 50 ppt– SO2: 100 ppt – CO: 40 ppb

• Check the specifications before you purchase

• Regularly maintain/replace scrubbing materials TEI Model 111

T_API Model 701


Zero Air Generation - Issues

Ultra Pure Cylinder Air vs. Zero Air Generators

Trade off:

Quantity Used vs. Costs for cylinders– High flow rates – Humidity issues– Purity of air generated– Use Ultra Pure Cylinder air to verify Generator purity

(recommended)


Summary

• QC Checks and calibrations are required for NCore Monitoring Stations

• The MFC systems available today are compatible with the PG instruments and support a high degree of automation

• Calibration systems should be regularly flow certified with NIST-traceable devices

• Lower concentrations cylinders are required since PG instruments have lower ranges and levels of detection

• Gas cylinders should be certified – EPA Protocol• Zero air generators should be able to “scrub”

below the LDLs of the PG instruments

EPA Precursor Gas Training Workshop NCore Calibration Issues Meeting the new QC Requirements Lewis...

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