ASTM D2140 for carbon-type composition of insulating oils
ASTM D2140 standard test method for carbon-type composition of insulating oils of petroleum origin
4. Summary of Test Method
4.1 A sample of the oil to be analyzed by this method is first tested to determine its viscosity, density and relative density (specific gravity), and refractive index. From these measured properties the viscosity-gravity constant (VGC) and refractivity intercept (ri) are obtained by calculation, using the equations given. The calculated values of VGC and ri are used with Fig. 1, to correlate those parameters with carbon-type composition. The composition in terms of % CA, % CN, and % CP may be read directly from Fig. 1.
NOTE 2 - Fig. 1 is a form of correlation chart that has been found satisfactory for use with this method. Other chart forms may be devised and used in preference to Fig. 1 if it is determined that the data obtained are consistent with similar data from Fig. 1. In addition, some users will find it convenient to develop a computer program or spreadsheet which will provide a consistent evaluation of the data.
5. Significance and Use
5.1 The primary purpose of this test method is to characterize the carbon-type composition of an oil. It is also applicable in observing the effect on oil constitution, of various refining processes such as hydrotreating, solvent extraction, and so forth. It has secondary application in relating the chemical nature of an oil to other phenomena that have been demonstrated to be related to oil composition.
5.2 Results obtained by this method are similar to, but not identical with, results obtained from Test Method D3238. The relationship between the two methods and the equations used in deriving Fig. 1 are discussed in the literature.
5.3 Although this test method tends to give consistent results, it may not compare with direct measurement test methods such as Test Method D2007.
