⚖️ Density of Fuels and Oils
In short
Determination of density of crude oil and petroleum products in range 600–1100 kg/m³ using oscillating U-tube density meter. The test is performed according to PN-EN ISO 12185:2024; Measurement range: 600–1100 kg/m³. The procedure comprises 9 steps (about 23–41 min in total); it is used for: Commercial fuel settlements — volume to mass conversion at 15°C, Quality control of diesel (PN-EN 590), gasolines (PN-EN 228), Cetane index calculation (ISO 4264) — density as input parameter.
At a glance
- Standard: PN-EN ISO 12185:2024
- Category: Petrochemistry
- Procedure steps: 9
- Total time of stages: 23 min–41 min
- Measurement range: 600–1100 kg/m³
- Resolution: 0.0001 g/cm³ (DMA 4500 M) to 0.000001 g/cm³ (DMA 5000 M)
- Repeatability: ±0.05 kg/m³
Overview
Density is one of the fundamental physicochemical parameters of petroleum products, used for their identification, classification, volume-to-mass conversion in commercial transactions and cetane index calculations. In fuel trading, density at 15°C is the reference parameter for quantity settlements.
The oscillating U-tube method is based on the principle that the oscillation frequency of a glass U-shaped tube filled with the sample depends on the mass (and thus density) of the liquid inside the tube. The density meter measures the tube oscillation period and converts it to density based on prior calibration (water + air or certified density standards).
The method provides very high accuracy — the best density meters achieve resolution of 0.000001 g/cm³ (0.001 kg/m³). The applicability range covers products with density from 600 to 1100 kg/m³, which covers practically all petroleum products: from light gasolines to heavy residual oils. The condition is sample homogeneity at measurement temperature.
Density at 15°C is a mandatory parameter in specifications: diesel fuel (PN-EN 590: 820–845 kg/m³), motor gasolines (PN-EN 228: 720–775 kg/m³), jet fuel Jet A-1 (775–840 kg/m³), biofuels and base oils. It is also one of four input parameters for calculating cetane index per ISO 4264.
Method principle
The liquid sample is introduced into a glass U-shaped measurement tube (U-tube) which is excited into natural oscillations by a piezoelectric exciter. The oscillation frequency (oscillation period) depends on the mass of the oscillating system — the heavier (denser) the liquid, the lower the frequency. A microprocessor converts the measured oscillation period to density based on two-point calibration (air and distilled water at known temperature). A built-in thermostating system maintains measurement temperature with accuracy ±0.01°C.
Applications
- Commercial fuel settlements — volume to mass conversion at 15°C
- Quality control of diesel (PN-EN 590), gasolines (PN-EN 228)
- Cetane index calculation (ISO 4264) — density as input parameter
- Quality control of jet fuel Jet A-1
- Testing of crude oil and gas condensates
- Monitoring lubricating oils — density change indicates degradation
- Control of biofuels and fuel blends (FAME, HVO)
Key parameters
| Parameter | Value |
|---|---|
| Measurement range | 600–1100 kg/m³ |
| Resolution | 0.0001 g/cm³ (DMA 4500 M) to 0.000001 g/cm³ (DMA 5000 M) |
| Repeatability | ±0.05 kg/m³ |
| Reproducibility | ±0.3 kg/m³ |
| Measurement temperature | 15°C (reference), 20°C, others as needed |
| Sample volume | 1–5 mL |
Standard
- Standard number
- PN-EN ISO 12185:2024
- Title (PL)
- Ropa naftowa, przetwory naftowe i produkty pokrewne — Oznaczanie gęstości — Laboratoryjny gęstościomierz z oscylacyjnym czujnikiem U-rurowym
- Title (EN)
- Crude petroleum, petroleum products and related products — Determination of density — Laboratory density meter with an oscillating U-tube sensor
Step-by-step procedure
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Instrument startup and stabilization
Turn on density meter and set measurement temperature (standardly 15.00°C). Wait for thermal stabilization.
-
Calibration/verification
Perform air–water calibration or verification with density standard (CRM). Result should be within ±0.05 kg/m³ of certified value.
-
Sample preparation
Mix sample thoroughly. Bring to temperature close to room temperature. Ensure sample is homogeneous (no sediment, free water, gas bubbles).
-
Sample introduction
Use syringe to introduce sample into U-tube measurement cell. Check on screen (U-View) that there are no air bubbles in cell.
-
Density measurement
Wait for measurement result stabilization (stable density and temperature values). Record density result at measurement temperature.
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Repeat measurement
Rinse cell with solvent, then introduce fresh sample portion. Perform second measurement. Difference should not exceed repeatability (0.05 kg/m³).
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Conversion to 15°C (if required)
If measurement performed at different temperature, convert to 15°C using ASTM D1250/IP 200 tables or algorithm built into density meter.
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Result recording
Record: density in kg/m³ (to 0.1 kg/m³ accuracy), measurement temperature, sample identification, date and density meter number.
-
Measurement cell cleaning
Rinse cell sequentially: kerosene, toluene, acetone and dry air. Check cell cleanliness (air control — air density value).
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Laboratory oscillating density meter | Anton Paar DMA 4500 M, Anton Paar DMA 5000 M | 50 000–120 000 PLN |
| Economical density meter | Anton Paar DMA 500, Mettler Toledo DM40 | 25 000–50 000 PLN |
| Portable density meter | Anton Paar DMA 35 Ex Petrol (ATEX) | 12 000–25 000 PLN |
| Sample dosing syringe | 5–10 mL Luer syringe, stainless steel or plastic | 5–50 PLN/pc |
| Density standard (CRM) | Density standard Paragon Scientific, H&D Fitzgerald | 300–800 PLN/ampoule |
| Peristaltic pump (optional) | For automatic sample introduction and rinsing | 3 000–8 000 PLN |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Distilled water (for calibration) | 7732-18-5 | Bidistilled or deionized water, degassed, for density meter calibration |
| Certified density standard | — | CRM with certified density at 15°C and 20°C, SI traceable, e.g., H&D Fitzgerald or Paragon Scientific |
| Light kerosene (for rinsing) | 8008-20-6 | For initial rinsing of measurement cell after oil samples |
| Ethanol or acetone (for drying) | 64-17-5 | Purity ≥99.5%, for final rinsing and drying of measurement cell |
| Toluene | 108-88-3 | Purity ≥99.5%, solvent for removing heavy fractions from cell |
Health and safety (OHS)
- Petroleum samples — flammable, work in well-ventilated area
- Cleaning solvents (toluene, acetone, kerosene) — flammable and harmful, fume hood
- Safety glasses and nitrile gloves mandatory
- Do not allow sample leakage from density meter — risk of optics damage
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-EN ISO 12185:2024 — “Crude petroleum, petroleum products and related products — Determination of density — Laboratory density meter with an oscillating U-tube sensor”.
How does this method work?
The liquid sample is introduced into a glass U-shaped measurement tube (U-tube) which is excited into natural oscillations by a piezoelectric exciter. The oscillation frequency (oscillation period) depends on the mass of the oscillating system — the heavier (denser) the liquid, the lower the frequency.
What is the measuring range and accuracy?
Measurement range: 600–1100 kg/m³; Resolution: 0.0001 g/cm³ (DMA 4500 M) to 0.000001 g/cm³ (DMA 5000 M); Repeatability: ±0.05 kg/m³; Reproducibility: ±0.3 kg/m³.
How long does the test take?
The times given for the individual stages add up to approximately 23 min–41 min. The procedure comprises 9 steps.
What equipment is required?
Laboratory oscillating density meter, Economical density meter, Portable density meter, Sample dosing syringe, Density standard (CRM), Peristaltic pump (optional). Indicative cost of the core instrument (Laboratory oscillating density meter): 50 000–120 000 PLN.
Where is this test used?
Commercial fuel settlements — volume to mass conversion at 15°C; Quality control of diesel (PN-EN 590), gasolines (PN-EN 228); Cetane index calculation (ISO 4264) — density as input parameter; Quality control of jet fuel Jet A-1; Testing of crude oil and gas condensates; Monitoring lubricating oils — density change indicates degradation; Control of biofuels and fuel blends (FAME, HVO).
What safety precautions apply?
Petroleum samples — flammable, work in well-ventilated area; Cleaning solvents (toluene, acetone, kerosene) — flammable and harmful, fume hood; Safety glasses and nitrile gloves mandatory; Do not allow sample leakage from density meter — risk of optics damage.
Which laboratory can perform this test?
The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number PN-EN ISO 12185.