⛽ Gasoline vapor pressure (DVPE/RVP)
Determination of gasoline vapor pressure by Reid method (RVP) or automatic DVPE method. Critical parameter of fuel volatility and safety.
Overview
Vapor pressure is one of the most important quality parameters of motor gasoline, defining the fuel's tendency to evaporate at a given temperature. This value has a direct impact on engine starting (especially cold starting), formation of vapor locks in the fuel system, emission of hydrocarbon vapors to atmosphere, and fuel stability during transport and storage.
The Reid method (RVP — Reid Vapor Pressure) is the classic procedure for measuring vapor pressure at 37.8°C (100°F) at a 4:1 air-to-liquid volume ratio. The PN-EN ISO 3007 standard describes the manual method using a so-called Reid bomb — a metal pressure vessel with a manometer. The result is expressed in kPa.
Currently, the automatic DVPE (Dry Vapor Pressure Equivalent) method according to ASTM D5191 / EN 13016-1 is increasingly used, utilizing a small sample volume (about 1-10 mL) and automatic pressure measurement in a measuring chamber. Devices from Grabner Instruments (MiniVap) are reference apparatus recognized by, among others, US EPA.
Seasonal requirements for gasoline in Poland per PN-EN 228: class A (summer) max 60 kPa, class E (winter) 60–90 kPa. Appropriate vapor pressure ensures proper engine starting at low temperatures, while limiting emissions of volatile organic compounds (VOC).
Method principle
Reid method: A gasoline sample at 0–4°C is introduced into the liquid chamber of the Reid bomb, then connected with the air chamber heated to 37.8°C. The air chamber to liquid chamber volume ratio is 4:1. The entire assembly is immersed in a water bath at 37.8°C and shaken periodically until constant pressure is achieved. The manometer reading after correction gives the RVP value.
DVPE method (automatic): The fuel sample is introduced into the apparatus measuring chamber of known volume and temperature. The apparatus automatically establishes liquid-vapor equilibrium at 37.8°C and measures total pressure. The DVPE value is calculated from total pressure minus water vapor pressure, giving a result equivalent to the Reid method.
Applications
- Quality control of motor gasoline according to PN-EN 228 (seasonal classes A–E)
- Monitoring emissions of volatile organic compounds (VOC) from fuel stations
- Assessment of fuel starting properties in winter conditions
- Quality control in refineries — optimization of gasoline blending
- Testing fuel stability during transport and storage
- Determination of crude oil vapor pressure (ISO 3007, ASTM D323)
- Quality control of alternative fuels with bioethanol addition (E5, E10, E85)
- Environmental monitoring — EPA and EU regulations concerning VOC
Key parameters
| Parameter | Value |
|---|---|
| Measurement temperature | 37.8°C (100°F) |
| V/L ratio (Reid method) | 4:1 |
| PN-EN 228 limits (summer) | max 60 kPa (class A) |
| PN-EN 228 limits (winter) | 60–90 kPa (class E) |
| Repeatability (DVPE) | 0.7 kPa |
| Reproducibility (DVPE) | 1.2 kPa |
Standard
- Standard number
- PN-EN ISO 3007:1999
- Title (PL)
- Przetwory naftowe i ropa naftowa — Oznaczanie preznosci par — Metoda Reida
- Title (EN)
- Petroleum products and crude petroleum — Determination of vapour pressure — Reid method
Step-by-step procedure
1. Apparatus preparation (DVPE method)
Turn on MiniVap / other automatic tester. Perform self-calibration test. Check measuring chamber temperature (37.8°C).
2. Sample cooling
Cool gasoline sample to 0–4°C in refrigerator (min. 30 min). Keep at low temperature until dosing.
3. Apparatus verification
Measure reference sample with known DVPE value. Result should be within certified value ± uncertainty.
4. Sample dosing
Quickly introduce cooled sample into apparatus measuring chamber using syringe or dosing system (approx. 1–10 mL, depending on model).
5. Automatic measurement
Apparatus automatically thermostats sample to 37.8°C, establishes liquid-vapor equilibrium and measures pressure. DVPE result displayed after cycle completion.
6. Reid method — bomb filling
Fill liquid chamber with cooled sample. Connect with air chamber heated to 37.8°C. Air volume / liquid volume ratio = 4:1.
7. Reid method — thermostating
Immerse bomb in 37.8°C bath. Shake every 2 min. Continue until constant pressure reading is obtained (approx. 30–60 min).
8. Result reading
Read pressure from manometer (Reid method) or from apparatus display (DVPE). Record result in kPa.
9. Apparatus cleaning
After each measurement, rinse measuring chamber with heptane or acetone. In Reid method, disassemble bomb and wash with heptane.
10. Quality control and reporting
Compare result with PN-EN 228 requirements (appropriate seasonal class). Include information about date and sample seasonal class.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Automatic vapor pressure tester | Grabner MiniVap VPXpert, Grabner MiniVap VP Vision | 60,000–120,000 PLN |
| Reid bomb (manual method) | Koehler K11500, Normalab NRA 440 (all-steel chamber) | 8,000–20,000 PLN |
| Thermostatic water bath | Julabo CORIO CD-300F, Huber CC-304B (37.8 ± 0.1°C) | 6,000–15,000 PLN |
| Reference thermometer | Liquid-in-glass or certified Pt100 thermometer, 0–50°C | 300–1,500 PLN |
| Refrigerator / freezer for sample cooling | Cooling sample to 0–4°C before test | 2,000–5,000 PLN |
| Manometer (Reid method) | Bourdon gauge 0–300 kPa, accuracy class 0.6 | 500–2,000 PLN |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Reference gasoline (CRM) | — | Reference fuel with certified RVP/DVPE value, for apparatus verification |
| Distilled water | 7732-18-5 | For filling thermostatic bath |
| Acetone | 67-64-1 | For cleaning measuring chamber, purity min. 99% |
| n-Heptane | 142-82-5 | Solvent for rinsing apparatus elements |
Health and safety (OHS)
- Gasoline — extremely flammable (H224), vapors form explosive mixtures with air
- Gasoline vapors — toxic, work only under fume hood or in well-ventilated room
- Reid bomb — internal pressure, risk of explosion if damaged, regular inspections
- Sample cooling — risk of frostbite with prolonged contact with frozen sample
- Acetone and heptane — flammable, avoid ignition sources
- Use gloves, safety glasses, protective coat; work in EX zone