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Measurement of liquid flash point is one of important experiments to safety engineering specialty. Its importance was analyzed by author and its available measurement methods were introduced. Then problems in teaching process of liquid flash point measurement were analyzed. Finally, some measures were brought forward to improve experiment conditions in existence. Introduction Statistics show that there have been 86 colleges setting undergraduate professional of safety engineering in China [1]. Its target is to cultivate advanced persons who will be engaged in evaluation, design, construction, management, supervision and labor protection in the field of safety engineering [2]. Therefore, some courses involved fire have been set among course system of safety engineering specialty, including experiment course to measure liquid flash point [3-7]. Flash point is the lowest temperature that flash can take place at the surface of liquid under the specified experiment conditions [8]. It is an index that is used to judge fire risk of flammable liquid, also is a basis to classify the first, second and third hazardous liquid. The fire resistance level, fire prevention distances and explosion prevention facilities of plants and storehouses that produce or save flammable liquid are determined by flash point. Flash point is one of bases to determine fire extinguishing agent’s furnishing quantity too [9,10]. Flash point experiment dates back to 19th century, and it was used to measure quality of fuel and lube at that time. Closed-cup flash point experiment was invented by Berthold Pensky who is Germany. Furthermore, Berthold Pensky, coupled with Kaiser Wilhelm Institute, drafted recognized Pensky-Martens method. GB/T261and SH/T0733 are primary closed-cup methods to measure flash point in China [11]. Based on closed-cup flash point measurement and its steps, problems of available method and corresponding improved measures were discussed. Importance to measure liquid flash Flammable liquid’s boiling point is lower than its ignition point. And its combustion process is that fuels evaporate into steam firstly, and then it will be mixed with air for burning, which indicates that it is different from flammable gas’s combustion process. The combustion process is shown as Fig.1. International Conference on Advances in Mechanical Engineering and Industrial Informatics (AMEII 2015) © 2015. The authors Published by Atlantis Press 1153 Fig.1 Combustion process of flammable liquid According to vapor pressure theory, there is a one-to-one relationship between its temperature and vapor pressure or vapor concentration for given flammable liquid. When vapor concentration reaches upper limit or lower limit of explosion, corresponding temperatures are upper limit or lower limit of explosion temperature respectively that are expressed by tu and t1. Besides, lower limit of explosion temperature is actually flash point. It is shown as Fig.2. Fig.2 Corresponding relation of liquid temperature and vapor concentration In Fig.2, T represents flammable liquid’s temperature, C represents its vapor concentration, L is lower limit of vapor explosion concentration, and U is upper limit of vapor explosion concentration. If ambient temperature is higher than flash point, its saturation vapor concentration or unsaturated vapor concentration will be in the scope of vapor explosion concentration. Once meeting fire, explosion or combustion will take place. Therefore, flash point is an important basis to evaluate fire risk of flammable liquid. For flammable liquid, it is necessary to measure its flash point accurately in order to prevent explosion and combustion effectively and carry out corresponding safety measures. Therefore, measuring flash point is reviewed as an important experiment in the teaching scheme of safety engineering specialty. Brief introduction of measuring flash point Its measuring equipment is shown in Fig.3. Experiment principle With liquid’s temperature increasing, vapor concentration above liquid will also increase gradually. If it increases to lower limit of explosion and meets fire, flash will take place. And corresponding temperature is flash point of this liquid. Experiment steps Now, taking diesel oil as an example, introduce the measurement of flash point steps. 1) Inject oil into cup until liquid surface reaches orbicular sign marked on cup; 2) Cover oil cup, connect mixing flexible axle, plug into a thermometer, open electrical source, adjust voltage (about 40~50 V), and open mixing switch; 3) Drop voltage to 10~20 V when temperature reaches 40C for slowing down calefaction tu tl T C

Problems Existing in Measurement of Liquid Flash Point and Upswing Measures of Experiment Process