Low-temperature flow test

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. 

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

Alternatively, low-temperature flow test (ASTM D-4539) results are indicative of the low-temperature flow performance of fuel in some diesel vehicles. This test method is especially useful for the evaluation of fuels containing flow improver additives. In this test method, the temperature of a series of test specimens of fuel is lowered at a prescribed cooling rate. At the commencing temperature and at each 1°C interval thereafter, a separate specimen from the series is Altered through a 17-mm screen until a minimum low-temperature flow test pass temperature is obtained. The minimum low-temperature flow test pass temperature is the lowest temperature, expressed as a multiple of 1°C, at which a test specimen can be Altered in 60 s or less. 

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). 

This wax can accumulate on fuel filter media and can lead to plugging of small orifices and lines. This plugging temperature can be measured and is commonly referred to as the filter plugging temperature. Testing methods utilized to predict the filter plugging temperature and the low-temperature flow properties of distillate fuel are listed in TABLE 4-5. 

PM2 5 PM10 PMA PMC PNA Pour point Particulate matter less than 2.5 ptm and 10 jam in diameter. Polymetacrylate viscosity index improver or viscosity modifier. Pensky-Martin closed cup-flash point test. Polynuclear aromatic. Measure of lubricant low-temperature flow which is 3°C above the temperature at which a normally liquid petroleum product maintains fluidity. Oil forms a honeycomb or crystals at low... 

F ow P/LOpcAtlei Under this heading come the viscosity of the fluid and the effect of temperature on viscosity. The latter might be a theoretically derived function, or an arbitrary function such as the viscosity index, or even a grossly empirical evaluation of the viscosity at two or more selected temperatures. Low temperature flow properties are frequently evaluated by the ASTM pour point determination [5], but the inadequacies of this method of evaluation have led to the use of pumpability tests which have a better empirical relation to service conditions. 

The second but fictitious test case is related to a frozen particle being placed in an upward adiabatic low temperature flow as shown in Fig. 10.27. Particles of different size (i.e. between 5 and 500 pm) are considered and their heat-up time is determined. The inflow velocity was adjusted to the terminal velocity of the considered particle size so that the particles are levitated. At the side faces of the computational domain, slip boundary conditions are applied (Fig. 10.27). The particle diameter was always resolved by ten grid nodes and also the heat... 

XI.1.1 The low-temperature flow properties of a waxy fuel oil depend on handling and ston conditions. Thus, they may not be truly indicated by pour point. The pour point test does not indicate what haqppens when an oil has a considerable head of pressure behind it, such as when gravitating from a storage tank or being pumped along a pipeline. Failure to flow at the pour point is normally attributed to the separation of wax from the fuel however, it can also be due to the effect of viscosity in the case of very viscous fuel oils. In addition pour points of residual fuels are influenced by the previous thermal history of the specimens. A loosely knit wax structure built up on cooling of Ae oil can be normally broken by the application of relatively little pressure. 

XI. 1.2 The usefulness of the pour point test in relation to residual fuel oils is open to question, and the tendency to regard the pour point as the limiting temperature at which a fuel will flow can be misleading. The problem of accurately specifying the handling behavior of fuel oil is important, and b use of the technical limitations of the pour point test, various pumpability tests have been devised to assess the low-temperature flow characteristics of heavy residual fuel oils. Test Method D 3245 is one such method. However, most alternative methods tend to be time-consuming and as such do not find ready acceptance as routine control tests for determining low-temperature flow properties. One method which is relatively quick and easy to perform and has found limited acceptance as a go-no-go method is based on the appendix method to the former Test Method D 1659 - 65. The method is described as follows. 

Years ago the industry had a specified cold test which indicated the capacity of the oil to flow after Vigorous stirring at a low temperature. This test proved to be inadequate and should not be confused with the cloud or pour tests of today. 

The condenser design and surface can handle the vapor flow during main drying of this test. The possible low temperatures could be needed during secondary drying. 

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