Attachment_5_-_CARB_Gravimetric_Analysis_Requirements.pdf

State of California 6830-BS-0215676-2 Bid Specifications Event ID 0000033449

Attachment 5

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Gravimetric Analysis Requirements for California Air Resources Board Primary Gas Standards

1) Scope/Requirements:

The purpose of this procedure is to define the requirements for the California Air Resources Board (CARB) primary gas standards. Gravimetric certification for CARB purposes is defined as adding a carefully measured weight of component as to an evacuated cylinder, followed by the addition of a carefully measured weight of balance gas.

The two (2) weights are converted by appropriate calculations into molar volumes and then given the appropriate gas concentration ratio in units of parts-per-million (ppm).

A sample example is as follows.

Example: Component Gas: 2000 ppm CO, Balance Gas: N2

1. Establish tare weight of cylinder (within + 0.05 grams).

2. Added weight of CO (component gas) = 13.573 g (within + 0.05 grams).

3. Added wt. of N2 (balance gas) = 6617.10 g.

4. Calculated molar quantities.

13.573 g-CO = 0.4846 moles for CO

28.01 g/mole

6617.10 g-N2 = 236.241 moles for N2

28.01 g/mole

Total Moles = 0.4846 + 236.241= 236.73 moles

5. Calculated Concentration (ppm) based on molar quantities.

0.4846 moles CO x 106 = 2051.2 ppm CO (mole/mole)

236.73 moles (Total)

Accuracy (± %)

100 x (twice total weighing error) = 100 x 2 x 0.05 = ± 0.74% (weight of component gas) 13.573

Attachment 5

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Mixture Accuracy

The accuracy of the mixture shall be within ± 1% of the calculated value including all weighing tolerances.

Scale Capacity and Accuracy

The scale used to measure the gaseous components, and the treated aluminum and steel cylinders shall be capable of weighing to within ± 0.05 grams, including all hysteresis and readability errors.

Accuracy of the scale must be traceable to the U.S. National Institute of Science and Technology (NIST). The date of the last certification must be included in the data submitted. In addition, the actual accuracy must be included with the analysis.

Balance Gases

The balance gas shall be as specified in Pricing Worksheet.

Component Gas

Component gas purity shall be stated in the analysis. In order to guarantee a ± 1% mixture accuracy, it will be necessary to use a diluted component gas in the preparation of gas mixtures below approximately 2000 ppm. If the component gas is a diluted mixture, it must also have a traceable gravimetric analysis consistent with this procedure. The final product delivered shall be accompanied by a certificate of analysis of the contents.

Certification

All gravimetric mixtures to be analyzed against an existing gravimetric prior to certification. For zero air and zero nitrogen, the impurities must be verified against analytical standards traceable to NIST by weight and/or analysis. All primary standard gases mixtures must be traceable to NIST weights and/or NIST gas mixture reference materials within 1%, including all measurement tolerances.

Blend Tolerance

Primary gases shall meet the blend tolerances below. If they do not meet the necessary criteria, they will be returned to the contractor.

Attachment 5

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Gas/Bal Gas Target Concentration

Blend Tolerance

Range Value

Span Gas Conc.

Tolerance

Lower Conc. Limit

Upper Conc. Limit

2 C1 0.60 ppm3 10% 0.54 0.66 5 C1 1.50 ppm3 10% 1.35 1.65 10 C1 3.0 ppm3 10% 2.7 3.3 20 C1 6.3 ppm3 5% 5.99 6.62 30 C1 9.5 ppm3 5% 9.025 9.975 100 C1 32 ppm3 4% 30.72 33.28 180 C1 57 ppm3 5% 54.15 59.85 C3H8/Air 300 C1 95 ppm3 5% 90.25 99.75 1,100 C1 348 ppm3 5% 330.6 365.4 1,500 C1 475 ppm3 5% 451.25 498.75 3,000 C1 950 ppm3 5% 902.5 997.5 6,800 C1 2,153 ppm3 5% 2045.35 2260.65 10,000 C1 3,167 ppm3 5% 3008.65 3325.35 20,000 C1 6,333 ppm3 5% 6016.35 6649.65 1 ppm 0.9 ppm 10% 0.81 0.99 5 ppm 4.5 ppm 10% 4.05 4.95 10 ppm 9 ppm 10% 8.1 9.9 30 ppm 28.5 ppm 5% 27.075 29.925 50 ppm 47.5 ppm 5% 45.125 49.875 NOx/N2 100 ppm 95 ppm 5% 90.25 99.75 300 ppm 285 ppm 5% 270.75 299.25 500ppm 470ppm 5% 446.5 493.5 1,000 ppm 950 ppm 5% 902.5 997.5 1,500 ppm 1,425 ppm 5% 1353.75 1496.25 2,000 ppm 1,900 ppm 5% 1805 1995 10,000 ppm 9,500 ppm 5% 9025 9975 10 ppm 9 ppm 5% 8.55 9.45 25 ppm 23 ppm 5% 21.85 24.15 50 ppm 47.5 ppm 5% 45.125 49.875 CO/N2 300 ppm 285 ppm 5% 270.75 299.25 2,000 ppm 1,900 ppm 5% 1805 1995 1% 9,500 ppm 5% 9025 9975 5% 47500 ppm 5% 45125 49875 5 ppm 4.5 ppm 10% 4.05 4.95 10 ppm 9 ppm 10% 8.1 9.9 50 ppm 47.5 ppm 5% 45.125 49.875 CH4/Air 200 ppm 190 ppm 5% 180.5 199.5 250 ppm 238 ppm 5% 226.1 249.9

Attachment 5

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500 ppm 475 ppm 5% 451.25 498.75 1000 ppm 1000 ppm 5% 950 1050 1,500 ppm 1,425 ppm 5% 1353.75 1496.25 2,000 ppm 1,900 ppm 5% 1805 1995 10,000 ppm 9,500 ppm 5% 9025 9975 1% 0.98% 1% 0.97% 0.99% 2% 1.96% 1% 1.94% 1.98% C02/N2 5% 4.90% 1% 4.85% 4.95% 15% 14.70% 1% 14.55% 14.85% 18% 17.60% 1% 17.42% 17.78%

2.5 ppm 2.25 ppm 10% 2.025 2.475 5 ppm 4.5 ppm 10% 4.05 4.95 10 ppm 9 ppm 10% 8.1 9.9 20 ppm 19 ppm 5% 18.05 19.95 N2O/N2 50 ppm 47.5 ppm 5% 45.125 49.875 100 ppm 95 ppm 5% 90.25 99.75 200 ppm 190 ppm 5% 180.5 199.5 500 ppm 475 ppm 5% 451.25 498.75 1,000 ppm 950 ppm 5% 902.5 997.5 50 ppm 47.5 ppm 5% 45.125 49.875 300 ppm 285 ppm 5% 270.75 299.25 NH3/N2 500 ppm 475 ppm 5% 451.25 498.75 1,000 ppm 950 ppm 5% 902.5 997.5 1,500 ppm 1,425 ppm 5% 1353.75 1496.25 2.50% 2.45% 1% 2.43% 2.47% O2/N2 5% 4.90% 1% 4.85% 4.95% 25% 24.50% 1% 24.26% 24.75% SO2/N2 10 ppm 9 ppm 10% 8.1 9.9 50 ppm 48 ppm 4% 46.08 49.92 NO2/AIR 100ppm 90ppm 5% 85.5 94.5 500ppm 470ppm 5% 446.5 493.5 90ppm 90ppm 5% 85.5 94.5 Ethane/AIR 150ppm 150 ppm 5% 142.5 157.5 750ppm 750 ppm 5% 712.5 787.5 Quad Gas (NO) 1500ppm 1500ppm 5% 1425 1575 Quad (THC) 600ppmc1 200ppm3 5% 190 210 Quad (CO) 1% 1% 5% 0.95% 1.05% Quad (CO2) 16% 16% 5% 15.20% 16.80%

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