CFPP tests

The simulated filter plugging point (SFPP) was developed in Europe as a supplement to the CFPP test. Work initiated in 1982 by the Coordinating European Council (CEC) demonstrated that the CFPP can become unreliable whenever the CFPP is lowered more than 50°F (10°C) below the cloud point of the fuel. The SFPP was developed to better predict the operability of fuel at temperatures >50 °F (>10°C) below the fuel cloud point. 

The cold filter plugging point (CFPP) test was developed to predict more accurately low-temperature limits. After the oil is cooled at a specified rate to the test temperature, a 20 mL volume is drawn through a 45 pm wire mesh filter screen under 0.0194 atm vacuum. The method is repeated in 1 °C increments and CFPP is recorded as the lowest temperature where oil safely passes through the filter within 60s (Chandler et al, 1992 Owen and Coley, 1990 Westbrook, 2003 Nadkarni, 2000). Although CFPP holds nearly world-wide acceptance as a standard test, in North America more stringent test conditions are necessary to correlate with performance in the field. Thus, the less user-... 

The solubility of linear alkanes present in diesel quickly decreases with temperature. The temperature at which the first crystals appear is called the cloud point and is one of the most important specifications for fuels concerning their low temperature behaviour. The utilization of a fuel is restricted to temperatures above their cloud point. Cloud point measures the temperature at which the wax crystals form a haze. Below the cloud point, the presence of crystals in suspension impairs the flow, plugging fuel filters. Immediately below the cloud point the fluid stops flowing, reaching what is known as pom point. The CFPP test measmes the highest temperature at which wax separating out of a sample... 

Some additives have the ability to lower the pour point without lowering the cloud point. A number of laboratory scale flow tests have been developed to provide a better prediction of cold temperature operability. They include the cold filter plugging point (CFPP), used primarily in Europe, and the low temperature flow test (LTFT), used primarily in the United States. Both tests measure flow through filter materials under controlled conditions of temperature, pressure, etc, and are better predictors of cold temperature performance than either cloud or pour point for addithed fuels. 

Test method IP 309 is used to determine the low-temperature filterability of distillate fuels including those treated with a cold flow improver. The cold filter plugging point (CFPP) is defined as the highest temperature at which the fuel, when cooled under the prescribed conditions, will not flow through the filter or requires more than 60 seconds for 20 mL to pass through or fails to return completely to the test jar. This method is part of a series of standardized tests developed by the Institute of Petroleum. Test method IP 309 is summarized as follows ... 

A specimen of the sample is cooled under specified conditions and, at intervals of34°F (1°C), is drawn into a pipet under a controlled vacuum through a standardized wire mesh filter. The procedure is repeated, as the specimen continues to cool, for each 34°F (1°C) below the first test temperature. Testing is continued until the amount of wax crystals that have separated out of solution is sufficient to stop or slow down the flow so that the time taken to fill the pipet exceeds 60 seconds or the fuel fails to return completely to the test jar before the fuel has cooled by a further 34°F (1°C). The indicated temperature at which the last filtration was commenced is recorded as the CFPP. 

Some of the primary differences between the CFPP and SFPP test procedures are outlined as follows ... 

CFPP (Cold Filter Plugging Point) A measure of the ability of a distillate fuel to be filtered satisfactorily in cold environments. This test measures the temperature at which fuel wax crystals can reduce or halt the flow of fuel through a standardized test filter. 

Nearly linear correlations for CFPP versus CP and LTFT versus CP were reported for neat biodiesel and its blends with petrodiesel (Dunn and Bagby, 1995,1996 Dunn et al., 1996). For LTFT, the correlation was essentially LIFT CP, suggesting the labor- and time-intensive LTFT test could be spared by simply measuring CP. A major conclusion from these studies was that development of approaches to improve cold flow properties of biodiesel should focus on technologies that decrease CP. 

CP = cloud point PP = pour point CFPP = cold filter plugging point LIFT = low-temperature flow test. 

In practice, this relationship is well obeyed. Figure 29 displays results on the cold filter plugging point (X CFPP) for different diblock compositions plotted against the aggregate surface area. These surface areas were obtained from Eq. 59 using the appropriate diblock copolymer parameters. As may be seen, the cold filter plugging point data relates linearly to the surface area from the SANS results. The CFPP results are from the summation of data obtained from four different test fuels. 

Different standard methods are used to determine or predict the low temperature behavior of a fuel in terms of CP, CFPP and PP. The repeatability and reproducibility tests are not always very good (see above <6 C) and other non-standardized methods can be used such as DSC and thermomicroscopy. These thermal analytical methods were successfully applied to neat petrodiesel and crude oils [9, 19, 26, 33] but also to engine oils [12, 16, 17, 27, 35],... 

Besides CP (ASTM D2500) and PP (ASTM D97), two test methods for the low-temperature flow properties of conventional DF exist, namely the low-temperature flow test (LTFT used in North America ASTM D4539), and cold filter plugging point (CFPP used outside North America for example the European standard EN 116) (CEN). These methods have also been used to evaluate biodiesel and its blends with No. 1 and No. 2 conventional DF. Low-temperature filterability tests were stated to be necessary because of better correlation with operability tests than CP or PP (Owen and Coley, 1995). However, for fuel formulations containing at least 10 vol% methyl esters, both LTFT and CFPP are linear functions of CP (Dunn and Bagby, 1995). Additional statistical analysis showed a strong 1 1 correlation between LTFT and CP (Dunn and Bagby, 1995). 

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