Cloud and pour points

Lubricating oils derived from petroleum usually contain di.ssolved paraffin wax and other asphaltic or resinous impurities, their amounts depending on the 

If the cooling is continued further, the amount of the separating material increases and a stage is reached when the oil solidifies and stoj)s (lowing. The lowest temperature at which an oil will How or pour under prescribed conditions, when it is cooled undisturbed at a fixed rate, is called its Pour Point. 

The cloud point determination is limited only to transparent oils otherwise there may be slight variation in results due to the human error involved, since the decrease in transparency is to be visually observed. 

Cloud point of a lubricant to be applied by a capillary feed system or wicking arrangement imisl be low so that the oil How does not stop due to deposition of crystals of wax in the capillary or wick interstice. -. Cloud point is hcli)ful in identifying the temperatures at which wax separation may clog the filter screens in the fuel intake system of diesel engines. Oils of naphthenic type, which are almost wax-free, show o ry low cloud iKiinfs and this fact may l-rc useful in identifying the source of the oil. 

Pour Point is tnore importaiil since in the lubrication of any machine subjected to low temperature, the lubricant nuist tlow freely, especially dtiring the start-up period. A high pour itoint may lead to solidification of the lubricant that may cause jamming of the machine. Pour point also establishes the lowest temperature at which an oil can be transferred by pouring or below which, because of extremely poor mobility of the oil, lubrication by gravity How process is less reliable. 

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Performance can be illustrated for example by the time necessary for deaeration or de-emulsification of oils, anti-rust properties, copper strip corrosion test, the flash point in closed or open cup, the cloud and pour points, the foaming characteristics, etc. 

Fuel which does not contain a wax crystal modifier will have temperature differences between the cloud and pour points typically from 15°F to 20°F (8.3°C to 11.1°C). If the difference between the cloud and pour point values is greater than 25°F (13.9°C), it is quite reasonable to believe that the fuel contains a wax crystal modifier. 

For most distillate fuels, cloud point temperatures can range from 50°F to -10°F (10.0°C to -23.3°C) or lower. However, typical cloud point temperatures fall between 6°F and 16°F (-14.4°C and -8.9°C). Distillate blends having a high paraffin content will often have cloud point and pour point values close together, sometimes within 5°F (2.8°C). Highly aromatic blends will usually have cloud and pour point values further apart in temperature. 

If possible, measure viscosity vs. temperature between cloud and pour points look for a dramatic increase rather than a gradual increase in slope. 

The denormal oils recovered from the experiments were separated from the solvent by batch distillation. Vacuum and nitrogen stripping were applied towards the end, stopping when the oil temperature in the reboiler reached 473 K. Cloud and pour points were determined on the oil products. 

The products obtained were analyzed for composition using high-performance liquid chromatography (HPLC) (LC -10AT Shimadzu, Kyoto, Japan), which consisted of a column (STR ODS-II, 25 cm in length x 4.6 mm in id Shinwa Chemical, Osaka, Japan) operated at 40°C at a flow rate of 1.0 mL/min with methanol as a carrier solvent. The column was packed with silica particles (5-pm particle diameter and 12-nm pore diameter). The cloud and pour points of the obtained biodiesel were then determined by a mini-cloud/pour point tester (Model MPC-102 Tanaka Scientific, Tokyo, Japan) based on ASTM D2500 for cloud point and ASTM D6749 for pour point (14). 

Cloud and Pour Point of Biodiesel Prepared by Supercritical Alcohol Treatment at 350°C and Alkaline-Catalyzed Method... 

Table 2 presents cloud and pour points of biodiesel prepared by our supercritical alcohol method at 350°C. For comparison, the results of the commercial biodiesel fuels are also shown. These results demonstrate that the cloud point of ethyl esters was 3°C lower than that of methyl esters, while that of butyl esters was even lower. The cloud point of methyl ester was similar to that of commercial biodiesel fuels. 

Problems encountered in handling vegetable oil-based fuels include higher viscosity and higher cloud and pour points, which... 

Sometimes additives are used to improve the low-temperature fluidity of diesel fuels. Such additives usually work by modifying the wax crystals so that they are less likely to form a rigid structure. Thus, although there is no alteration of the cloud point, the pour point may be lowered dramatically. Unfortunately, the improvement in engine performance as a rule is less than the improvement in pour point. Consequently, the cloud and pour point temperatures cannot be used to indicate engine performance with any accuracy. 

As the temperature continues to decrease below the cloud point, the formation of wax crystals is accelerated. These crystals clog fuel filters and lines and thus reduce the supply of fuel to the burner. Because the cloud point is a higher temperature than the pour point (4 to 5°C/7 to 9°F, and even higher), the cloud point is often considered to be more important than the pour point in establishing distillate fuel oil specifications for cold weather usage. The temperature differential between cloud and pour point depends on the nature of the fuel components, but the use of wax crystal modifiers or pour depressants tends to accentuate these differences. 

Cloud and pour point. These tests measure the cold-temperature handling characteristics of the fuel. 

Cloud and Pour Points. The pour point is the temperature at which the fuel will not flow. The cloud point is the temperature at which the wax crystals separate from the fuel. The cloud point must be no more than 10°F (5.5°C) above the pour point so the wax crystals will not settle out of the fuel and plug the filtration system. The cloud point should also be at least 10°F (5.5°C) below the ambient temperature to allow the fuel to move through the Unes. 

Thermometer—For observing temperatures below -45°C. The Low Cloud and Pour Point Thermometer, conforming to the requirements for ASTM Thermometer 6C, as prescribed in Specification E 1, is satisfactory. Thermometer 6C has a range from -80 to -l-20°C. 

Cloud and Pour Points. The cloud and pour points are useful in estimating the relative amount of wax in an oil. However, all oils will solidify if cooled to a low enough temperature and hence these tests do not indicate the actual amount of wax or solid material in the oil. They do indicate that most of the wax, melting above the pour point, has been removed. 

Finally, biolubricants based on canola biodiesel have the potential to substitute petroleum-based automotive lubricants thus they present low cloud and pour point properties, good friction and antiwear properties, low phase transition temperature, and low viscosity (Sharma et al., 2015). 

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