🌫️ Cloud Point Temperature
In short
Determination of cloud point of petroleum products — temperature at which paraffin crystals begin to precipitate causing fuel clouding. The test is performed according to PN-EN ISO 3015:2019; Measurement range: up to +49°C (manual method), down to -95°C (automatic apparatus). The procedure comprises 8 steps (about 1 min in total); it is used for: Quality control of winter diesel (PN-EN 590, winter grades), Evaluation of winter properties of heavy gasolines and jet fuel, Testing lubricating oils — tendency to gel at low temperatures.
At a glance
- Standard: PN-EN ISO 3015:2019
- Category: Petrochemistry
- Procedure steps: 8
- Total time of stages: 1 min
- Measurement range: up to +49°C (manual method), down to -95°C (automatic apparatus)
- Resolution: 1°C
- Repeatability: ±2°C (distillate fuels)
Overview
Cloud point is the maximum temperature at which first visible paraffin (wax) crystals appear in fuel or oil sample during controlled cooling. These crystals cause sample clouding — hence the name "cloud point". It is the most important low-temperature parameter of fuels, especially diesel.
Precipitation of paraffins in diesel fuel at low temperatures causes plugging of fuel filters, restricted fuel flow and consequently vehicle immobilization. Cloud point is the most conservative measure of fuel suitability for winter operation — in practice fuel begins to cause problems already near cloud point. Another parameter — CFPP (cold filter plugging point) — is closer to real operational limit, but cloud point is a more fundamental parameter.
Standard PN-EN ISO 3015 covers transparent petroleum products in 40 mm layer with cloud point below 49°C, including diesel with up to 30% FAME content, paraffinic diesel with up to 7% FAME, 100% FAME and lubricating oils. Method involves gradual sample cooling in cylindrical test jar and visual or optical observation of moment clouding appears at jar bottom.
Winter diesel specification in Poland (PN-EN 590, winter grades) requires appropriately low cloud point depending on climatic class. Fuel producers use depressants (WASA — Wax Anti-Settling Additives) and low-temperature components to lower cloud point of winter fuel.
Method principle
Sample is placed in standardized cylindrical test jar and cooled in baths of strictly controlled temperature, conducting cooling in stages. Every 1°C sample is removed from bath and jar bottom is observed visually (or using optical detector in automatic apparatus). Highest temperature at which clouding (cloud of paraffin crystals) is visible at jar bottom is recorded as cloud point. In automatic apparatus, detection is based on light scattering or decrease in optical transmission through sample.
Applications
- Quality control of winter diesel (PN-EN 590, winter grades)
- Evaluation of winter properties of heavy gasolines and jet fuel
- Testing lubricating oils — tendency to gel at low temperatures
- Monitoring effectiveness of paraffin depressants (WASA)
- Quality control of biofuels — FAME (100%) and blends B7, B20, B30
- Evaluation of crude oil — tendency to precipitate paraffins in pipelines
- Marine fuel specification requirements (ISO 8217)
Key parameters
| Parameter | Value |
|---|---|
| Measurement range | up to +49°C (manual method), down to -95°C (automatic apparatus) |
| Resolution | 1°C |
| Repeatability | ±2°C (distillate fuels) |
| Reproducibility | ±4°C (distillate fuels) |
| Sample volume | 45–50 mL |
| Determination time | 30–90 min (dependent on cloud point) |
Standard
- Standard number
- PN-EN ISO 3015:2019
- Title (PL)
- Przetwory naftowe i produkty pokrewne pochodzenia naturalnego lub syntetycznego — Oznaczanie temperatury mętnienia
- Title (EN)
- Petroleum and related products from natural or synthetic sources — Determination of cloud point
Step-by-step procedure
-
Sample preparation
Heat sample to at least 14°C above expected cloud point (min. to room temperature) to dissolve all paraffin crystals. Mix thoroughly.
-
Test jar filling
Pour sample into clean, dry cylindrical test jar to level mark (~45 mL). Insert thermometer so bulb is at jar bottom.
-
Placement in bath
Close jar with cork containing thermometer and place in 0°C bath (first bath). Maintain jar in vertical position.
-
Observation every 1°C
At each 1°C sample temperature drop — remove jar from bath, observe jar bottom for clouding. Complete observation < 3 s. Immediately return.
-
Bath change
If no clouding observed in 0°C bath — transfer to -18°C bath. Continue to -33°C, -51°C etc. until clouding appears.
-
Cloud point recording
Record highest temperature at which distinct clouding (cloud of paraffin crystals) was observed at jar bottom. This is cloud point.
-
Repeat determination
Repeat test on new sample portion. Difference between two results should not exceed repeatability (±2°C).
-
Reporting
State cloud point in °C to 1°C accuracy. State: method (PN-EN ISO 3015), sample identification, test date.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Automatic cloud/pour point analyzer | PAC OptiCPP (ISL), Anton Paar CPA, Koehler K46100 | 60 000–130 000 PLN |
| Manual cloud point apparatus | Cylindrical test jar + cooling baths per ISO 3015 | 5 000–15 000 PLN |
| Cooling baths (cryostat) | Bath set 0°C, -18°C, -33°C, -51°C, -69°C (cooling mixtures) | 8 000–25 000 PLN |
| Low-temperature thermometer | ASTM thermometer range -80°C to +50°C, resolution 1°C | 300–800 PLN |
| Test jar | Cylindrical, glass, flat bottom, per ISO 3015 | 50–150 PLN/pc |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Acetone (for cleaning) | 67-64-1 | Purity ≥99.5%, for washing and drying test jars |
| Cooling mixture (bath -51°C) | — | Acetone + dry ice (CO₂) mixture or ethanol + liquid nitrogen, for cooling baths (manual method) |
| Liquid nitrogen (for automatic apparatus) | 7727-37-9 | Or compressor cascade cooling systems to -95°C |
| Cloud point CRM | — | Certified reference material with known cloud point, e.g., Paragon Scientific |
Health and safety (OHS)
- Fuels — flammable, work in ventilated area away from ignition sources
- Dry ice (CO₂) and liquid nitrogen — risk of frostbite, cryogenic gloves mandatory
- Cooling baths with acetone + dry ice — flammable solvent at low temperature
- Safety glasses and gloves mandatory
- Ventilation — acetone and fuel vapors in enclosed spaces
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-EN ISO 3015:2019 — “Petroleum and related products from natural or synthetic sources — Determination of cloud point”.
How does this method work?
Sample is placed in standardized cylindrical test jar and cooled in baths of strictly controlled temperature, conducting cooling in stages. Every 1°C sample is removed from bath and jar bottom is observed visually (or using optical detector in automatic apparatus).
What is the measuring range and accuracy?
Measurement range: up to +49°C (manual method), down to -95°C (automatic apparatus); Resolution: 1°C; Repeatability: ±2°C (distillate fuels); Reproducibility: ±4°C (distillate fuels).
How long does the test take?
The times given for the individual stages add up to approximately 1 min. The procedure comprises 8 steps.
What equipment is required?
Automatic cloud/pour point analyzer, Manual cloud point apparatus, Cooling baths (cryostat), Low-temperature thermometer, Test jar. Indicative cost of the core instrument (Automatic cloud/pour point analyzer): 60 000–130 000 PLN.
Where is this test used?
Quality control of winter diesel (PN-EN 590, winter grades); Evaluation of winter properties of heavy gasolines and jet fuel; Testing lubricating oils — tendency to gel at low temperatures; Monitoring effectiveness of paraffin depressants (WASA); Quality control of biofuels — FAME (100%) and blends B7, B20, B30; Evaluation of crude oil — tendency to precipitate paraffins in pipelines; Marine fuel specification requirements (ISO 8217).
What safety precautions apply?
Fuels — flammable, work in ventilated area away from ignition sources; Dry ice (CO₂) and liquid nitrogen — risk of frostbite, cryogenic gloves mandatory; Cooling baths with acetone + dry ice — flammable solvent at low temperature; Safety glasses and gloves mandatory; Ventilation — acetone and fuel vapors in enclosed spaces.
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 3015.