Cold Flow Properties: Cloud Point, Pour Point, Freezing Point and CFPP Analyzers
Online process analyzers for cloud point, pour point, freezing point and cold filter plugging point (CFPP) in diesel, jet fuel and lubricating oils.
What are cold flow properties and why measure them?
As petroleum products cool, the paraffins they contain crystallize; the product first turns cloudy, then plugs filters and finally stops flowing. Four values describe this behavior and set the cold-climate requirements of fuel and lubricant specifications:
- Cloud point: The temperature at which paraffin crystals first form a visible haze in the cooled product.
- Cold filter plugging point (CFPP): The lowest temperature at which diesel fuel still passes through a standard filter within the specified time.
- Pour point: The lowest temperature at which the product still flows under the test conditions.
- Freezing point: For jet fuel, the temperature at which the last hydrocarbon crystals disappear when the cooled sample is warmed again.
In a refinery these values determine blend ratios and the dosage of cold flow additives. Producing further from the specification limit than necessary gives away valuable product, while crossing the limit means an off-spec batch; continuous in-line measurement is therefore preferred to waiting for a laboratory result.
Where are cold flow properties measured?
- Diesel blending and hydrotreater outlets: Cloud point and CFPP for adjusting winter diesel quality and additive dosage.
- Jet fuel (kerosene) lines and fuel terminals: Monitoring freezing point.
- Lube oil and base oil units: Controlling pour point after dewaxing.
- Biodiesel blends: Monitoring CFPP.
How are cold flow properties measured?
Online analyzers turn the laboratory method into an automatic cycle: a small sample taken from the process line is cooled at a controlled rate in a small measuring cell, the relevant event is detected, the cell is heated and flushed, and the cycle repeats.
- Cloud point and freezing point: Light scattered by the crystals is monitored optically.
- Pour point: A small pressure pulse is applied to the sample at set temperature intervals; the temperature at which the sample no longer moves is recorded.
- CFPP: At each step the sample is drawn by vacuum through a standard wire mesh filter; the test ends when the filtration time exceeds the limit.
The online result is verified by periodic comparison with the corresponding laboratory method.
Selecting an analyzer
- Product type and expected temperature range (very low temperatures may require a cryogenically cooled version)
- The laboratory method the result will be compared against
- Sampling, filtration and conditioning requirements; water in the sample disturbs the measurement
- Hazardous area certification and data transfer to the control system
Cold flow measurement with Tetra
Tetra supplies Icon Scientific's Cp (cloud point), Pp (pour point), Fz (freezing point) and CF (cold filter plugging point) online analyzers and integrates the sample system and analyzer cabinet. Installation, commissioning, calibration and service are provided in Türkiye by Tetra.
Frequently asked questions
What is the difference between cloud point, CFPP and pour point?
All three are stages of the same cooling process. At the cloud point the first paraffin crystals become visible, at the CFPP the crystals are numerous enough to plug a filter, and at the pour point the product no longer flows. CFPP therefore usually lies between the cloud point and the pour point.
Which laboratory methods are used for these properties?
Common reference methods are ASTM D2500 for cloud point, ASTM D97 for pour point, ASTM D2386 for the freezing point of jet fuel, and EN 116 and ASTM D6371 for cold filter plugging point. Separate standards also exist for measuring these properties with automatic instruments. The method the online analyzer will be compared against should be defined at the outset.
What is the freezing point limit for jet fuel?
International civil aviation specifications set the freezing point at -47 °C maximum for Jet A-1 and -40 °C maximum for Jet A. Because fuel tanks become very cold at high altitude, this value is a specification parameter critical to flight safety.
What disturbs online cold flow measurement?
Water and solid particles in the sample disturb optical detection and filtration. Paraffin left in the cell from the previous cycle can shift the next reading, which is why heating and flushing the cell in every cycle matters. A long sample line makes the result follow the process with a delay.
Products measuring this parameter
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