Abstract: The irrationality of continuous cooling method in industry standard for "Determination of wax appearance temperature of crude oil-test method by rotational viscometer" is analyzed through investigation on temperature controlling principle of rheometer, and the suggestion by staged cooling process is put forward. In the matter of the program of calculating wax appearance temperature, if calculating by software recommended in the standard, low or high wax appearance temperature will appear when the curves of low temperature section become nonlinearity. The improvement suggestion is given that the wax appearance temperature of crude oil should be determined based on the deviating degree of low temperature section curve and simulated straight line of high temperature section.

Key words: rotational viscometer, wax appearance temperature, cooling process, segment temperature decline