Keywords gas analysis; gas chromatography; natural gas composition ; Butane content; Carbon dioxide content--natural gas; Composition analysis--gases; Ethane content; Gas chromatography GC --gaseous fuels; Gaseous fuels; Helium content; Hexanes content; Hydrogen content--petroleum products; Isobutane; Isopentane; Methane content; Natural gas service systems; Nickel content--petroleum products; Oxygen content; Pentane content; Propane content; Rationale ASTM Headquarters is mandating a review of standards that use mercury and determine if its use is still appropriate, or if it should be removed, or replaced with a non-mercury alternative. D includes a mercury manometer to monitor the pressure of the gas sample loop. Safer modern alternatives exist such as digital manometers and absolute pressure transducers. Section 5.
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Grobar 40 CFR The fewer components eliminates dew point problems, reactivity, is more accurate and can be blended at a higher pressure. Open the valve on the L cylinder, then open the valve on Cyhnder B, which w i l l result in the transfer of nearly all of the contents of Cyhnder B into the L cylinder.
Either the average of the two consecutive checks, or the latest check agreeing within the repeatability limits of the previous check on each component may be used as the reference standard for all subsequent runs until there is a change in instrument operating conditions. This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years and if not revised, either reapproved or withdrawn.
See D 2 and Table 3. Usually 1 m of 6-mm tubing packed w ith to mesh molecular sieves is adequate, i f changed w ith each cylinder o f carrier gas. Separation of carbon dioxide must be sufficient so that a 0. This component is present i n the daily calibration standard and linearity is assured from previous tests. Diluted dry air is a suitable standard for oxygen and nitrogen see 8. Likewise, obtain a response on the reference standard for nitrogen and methane.
I f increased accuracy of the hexanes and heavier portions of the analysis is required, a larger sample size may be used see Test Method D This flow should quickly r e m m to the same flow rate and the baseline asm out. Also measure the areas of both pentane peaks on the sample chromatogram, and adjust all measured areas to the same attenuation basis.
It is strongly recommended in the absence of valve ovens to mount the gas samphng astmm in the chromatograph oven and operate at the column temperature. Run a sample o f the mixture at kPa mm H g absolute pressure and obtain the helium peak. This procedure also removes carbon dioxide, and the results obtained will be on the acid-gas free basis. The percent nitrogen is multiplied by 0. Mount as required to dry the sample. The detector temperature shall be equal to or greater than the maximum column temperature.
A 5A column can be used if a pre-cut column is present asm remove interfering hydrocarbons. Die bond process intro Record the peak area of die pure component. The oven temperature shall not exceed the recommended temperature 1d for the materials in the column. W i t h either type manometer the m m scale can be read more accurately than the inch scale. The operating conditions, d columns, are also typical and are subject to optimization by competent personnel.
The connection between V, and Vj in Fig. Baseline tracking with tangent skim peak detection is recommended. Concentration of these components has been observed to occur in a number of cases because of collection of heavier components in the sample loop during purging of the system. Make calculations on ethane and heavier components in the same manner as for the complete analysis method. Samples w i t h up to one atmosphere o f pressure can be entered.
Copper, vinyl, or rubber connections are not acceptable. It is useful to construct a table noting the response factor deviation in changing concentration. The major component methane is used as the balance gas and may fall below the expected concentration.
A number in parentheses indicates the year of last reapproval. A flowing sample inlet system is acceptable as long as viscosity effects are accounted for. Daily calibrations are recommended. It is permissible to use a response factor for oxygen that is relative to a stable constituent.
That is, use either geometric construction or planimeter, but do not intermix. When enlargement of the heavy end peaks is noted, thoroughly clean the sampling valve and loop with acetone. Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTfJI International Headquarters.
Transfer the methane to asm L cylinder until the pressure equalizes. This gives the Relative Molar Response factor RMRi for component 0- The reference component must be present in the same instrumental sequence except HexanesH- as the referenced components. TOP Related Articles.
ASTM D1945-03 PDF
Mikasar The width of the chart shall be not less than mm. The relationship is independent of temperature, sample size, and carrier gas flow rate. The separation should be completed within 40 min, including reversal of flow after n-pentane to yield a group response for hexanes and heavier components. NOTE 1 — T h e sample size limitation of 0. SuiBcient accuracy can be obtained for the determination of all but the minor constituents by the use of this sample size. Disconnect and weigh Cylinder A to obtain the weight of n-pentane added.
This pressure need not be measured precisely, as the concentration of nitrogen in the mixture thus prepared must be determined by comparison to nitrogen in the reference standard. The well type inherendy offers better precision and is preferred when calibrating w i t h pure components. Obtain a corresponding response on the reference standard. Methane should be in a 1-L cyHnder at MPa atm pressure.