Oils and fuels are subject to numerous test methods to ensure quality and safety. One subset comprises the methods for the analysis of their behavior at low temperature. Typically these tests are applied to fuels, but they also have relevance to crude and refined oil, as well as other petroleum derivatives.

The following test methods fall into the category of cold behavior analysis: cloud point, freeze point, cold filter plug point and pour point. Instruments for these tests adhere to the specific test methods promulgated by ASTM and other similar standards organizations. The instrument systems make these analyses more efficient through automation of the method.

Cloud point refers to the temperature at which components in the fuel or oil sample solidify into small crystals. This causes the fuel to become cloudy, which can be detected via a light-scattering or similar optical detector. As with most of these tests, cloud point offers information on how fuels will behave in engines or pumping systems at low temperature; crystal formation can lead to clogged filters or build up of solids that can obstruct flow.

The freeze point is closely related to the cloud point. Freeze point is determined by cooling the sample until crystals appear. Then, while the sample is slowly warmed, detectors monitor the crystals in the sample. The freeze point is the temperature at which the last crystals disappear.

The cold filter plugging point is determined by passing the sample (via vacuum suction) through a standardized filter. As the test is repeated at lower temperatures and the fluid thickens, it takes longer for the sample to pass through the filter. The cold filter plugging point is the lowest temperature at which the sample passes through the filter in the allotted time.

Pour point is the lowest temperature at which the sample will flow appreciably. The sample is cooled and occasionally tilted, with optical sensors or a similar system confirming whether the sample flows.

Applications for cold behavior analysis systems are relatively circumscribed. Samples are fuels, crude and refined oils. Oil and gas producers use these instruments as a judge of quality and for distinguishing different grades. Aviation is market. The behavior of jet fuel under the cold conditions that pertain to high-altitude flight is critical. In order to guarantee flight safety, fuel behavior is checked at multiple places along the supply chain. Other applications focus on the testing of other fuels, biofuels and lubrication oils. As lubricants degrade from use and thermal cycling, cold behavior can change, requiring more frequent testing for demanding applications.

Most vendors of cold behavior instruments are also involved in other areas of fuel and petroleum analysis. The most significant vendor is PAC. Other major suppliers include Koehler Instrument, Normalab, Stanhope-Seta and Tanaka Scientific. Numerous smaller suppliers also exist. The total lab market for cold behavior analysis was about $15 million in 2010.

Cold Behavior Analyzers

at a Glance:

Leading Suppliers

• PAC (Roper Industries)

• Normalab

• Tanaka Scientific

Largest Markets

• Oil and Gas

• Aviation

• Petrochemicals

Instrument Cost

• $2,000–$35,000