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D2598-21 – Standard Test Method Technical Guide
🧪 Scope and Application of ASTM D2598-21
ASTM D2598-21 provides a standardized practice for the approximate determination of critical physical properties of Liquefied Petroleum (LP) Gases through compositional analysis. This practice specifically covers the calculation of vapor pressure, relative density, and motor octane number (MON) for commercial propane, special-duty propane, propane/butane mixtures, and commercial butane as governed by Specification D1835.
It is critical to note that this practice is not applicable to any product exceeding the specifications for nonvolatile residues, as determined by Test Method D2158. Additionally, the motor octane number calculation is strictly validated only for mixtures containing 20 % or less propene and is based exclusively on the hydrocarbon components detailed in the standard’s calculation table.
| 🟦 LP-Gas Type | 📏 Max Propene Content | 🎯 Properties Calculated | ⚡ Reference Spec |
|---|---|---|---|
| Commercial Propane | 0 % | VP, RD, MON | D1835 |
| Special-Duty Propane | 0 % | VP, RD, MON | D1835 |
| Commercial B/P Mixes | ≤20 % | VP, RD, MON | D1835 |
| Commercial Butane | ≤20 % | VP, RD, MON | D1835 |
⚙️ Calculation Methodology and Referenced Standards
The compositional analysis of the LP-gas sample is primarily obtained using Test Method D2163 (Gas Chromatography). The practice mandates that the analysis be expressed in liquid volume percent. If the data is on a mole, gas volume, or weight basis, it must be converted using Practice D2421 before the calculations proceed. From this compositional data, the vapor pressure, relative density