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Significance and Use
5.1 LPG samples can change composition during storage and use from preferential vaporization of lighter (lower molecular weight) hydrocarbon components, dissolved inert gases (N2, Ar, He, and so forth) and other dissolved gases/liquids (NH3, CO2, H2S, H2O, etc.). Careful selection of cylinder type, cylinder volume, and use of inert gas for pressurizing cylinders is required to ensure that composition changes are small enough to maintain the integrity of LPG when used as a QC reference material for various LPG test methods.
5.2 Monitoring of ongoing precision and bias on QC materials using control chart techniques in accordance with Practice D6299 can be used to establish the need for calibration or maintenance.
1.1 This practice covers information for the storage and use of LPG samples in standard cylinders of the type used in sampling method, Practice D1265 and floating piston cylinders used in sampling method, Practice D3700.
1.2 This practice is especially applicable when the LPG sample is used as a quality control (QC) reference material for LPG test methods, such as gas chromatography (GC) analysis (Test Method D2163) or vapor pressure (Test Method D6897) that use only a few mL per test, since relatively small portable Department of Transportation (DOT) cylinders (for example, 20 lb common barbecue cylinders) can be used. This practice can be applied to other test methods. However, test methods that require a large amount of sample per test (for example, manual vapor pressure Test Method D1267) will require QC volumes in excess of 1000 L if stored in standard DOT cylinders or American Society of Mechanical Engineers (ASME) vessels.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
D1265 Practice for Sampling Liquefied Petroleum (LP) Gases, Manual Method
D1267 Test Method for Gage Vapor Pressure of Liquefied Petroleum (LP) Gases (LP-Gas Method)
D2163 Test Method for Analysis of Liquefied Petroleum (LP) Gases and Propene Concentrates by Gas Chromatography
D3700 Practice for Obtaining LPG Samples Using a Floating Piston Cylinder
D6299 Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
D6897 Test Method for Vapor Pressure of Liquefied Petroleum Gases (LPG) (Expansion Method)
ICS Number Code 75.200 (Petroleum products and natural gas handling equipment)
UNSPSC Code 15111510(Liquified petroleum gas)