The reason why petroleum product determination methods are divided into closed cup method and open cup method mainly depends on the nature and use conditions of petroleum products. Usually the closed flash point tester is mostly used for light petroleum products with large evaporation type, such as transformer oil, fuel oil, solvent oil, etc. Since the measurement conditions are similar to the actual storage and use conditions of light oil products, it can be used as a fire safety control basis for the indicator. The open flash point tester is mainly used for lubricating oil and heavy petroleum products. Because when the open flash point is measured, the vapor formed after the petroleum product is heated continuously diffuses to the surrounding air, which makes the measured flash point higher. For most lubricating oils and heavy oils, especially when used in non-sealed parts or under low temperature conditions, even a very small amount of light blends will evaporate during use, and will not cause fire or There is a danger of explosion, so these products are measured with an open flash point tester.
In some lubricating oil specifications, there are two quality indicators of opening and closing. Its purpose is to check the width of lubricating oil fractions and whether light components are mixed with the difference between open and closed flash points. Some lubricating oils are used in airtight containers. During use, high temperatures are often generated due to various reasons (such as high speed or other reasons that cause equipment overheating, current disconnection, arcing, etc.), so that the lubricating oil may form decomposition products, or from other components. Infused with lightweight ingredients. These light components present a fire and explosion hazard when evaporated and mixed with air in closed containers. However, when the open flash point is used to measure, the existence of such light components that are easy to evaporate may not be found, so it is stipulated to use a closed flash point tester for measurement. This type of oil includes electrical oil, high-speed mechanical oil, and certain aviation lubricants. It is also determined by open flash point determination in light petroleum products, such as solvent kerosene. This is entirely to adapt to the conditions of use so that the measured flash point is similar to the actual situation in use.