What is the Cloud Point?

T. Raleigh
T. Raleigh
Scientist with beakers
Scientist with beakers

Petroleum is predominantly comprised of various hydrocarbons in gas, liquid, or solid states. Crude oil and natural gas are members of this group. One hydrocarbon in crude oil is paraffin, which is commonly known in food preservation. During the refining process, various temperatures yield different products, and the temperature at which the wax begins to emerge in the fuel or oil is known as the cloud point.

Crude oil in its natural state is relatively useless. The distillation in the refining process creates more a more usable product. Different methods are employed utilizing variations of heat and pressure to achieve the desired result. The refinery contains various units, such as coker, cracking, and alkylation that produce levels of practical goods. Some commonly known examples are diesel, gasoline, kerosene, benzine, butane, heating oil, lubricating oil and industrial fuel.

A refinery uses all of its resources, including heat and air, when distilling crude oil. The raw material is transformed into a progressively more a polished product. Even some of the byproducts are useful when refined further. Asphalt, used in road construction, and petroleum coke, used in dry cell battery or electrode manufacturing, are a couple of examples.

Every one of these products has its own cloud point. A specific temperature where that fuel or oil begins to get cloudy from the appearance of wax crystals. It is important during the process that the refiner knows what this temperature is for each product. These wax particles can cause damage if left in fuel destined for combustion engines, such as gasoline.

Wax, which appears at the cloud point, can be harmful and destructive if not discovered in refined fuels. Filters and fuel injector systems in fuel-powered engines can be clogged from wax build up. Even in the refinery itself, it can be a nuisance by accumulating and blocking pipelines and other pieces of equipment that operating at cloud point temperatures.

The American Society for Testing and Materials (ASTM) provides an outline of the goal of tests to determine cloud point. Standardized testing allows uniformity compliance for those offering testing methods, as well as the refineries that employ them. Generally, cloud points for all fuel and oil levels are analyzed in transparent layers that are 40 mm thick.

Methods for finding the cloud point vary. Constant cooling rate is one standard method used to determine the cloud point in both pure and blended fuels and oils. This method cools the fluid at a steady rate, such as two degrees per minute, making it easier to determine the precise temperature at which the wax crystals form, thus giving a precise cloud point.

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      Scientist with beakers