(1) Related to the type of instrument used in the measurement
Usually, the results of open flash point testers are higher than those of closed flash point testers. This is because the steam formed by the open flash point tester freely diffuses into the air, resulting in a partial loss of steam.
(2) Related to the amount of test oil added
The cup of the sealed flash point tester contains a large amount of test oil, resulting in lower measurement results; If the oil quantity is low, the measurement result is higher than normal. Because the oil content will affect the volume of the space above the liquid level and affect the concentration of the mixture of oil vapor and air.
(3) It is related to the size of the ignition flame, the height above the liquid level, and the residence time
If the diameter of the spherical flame used for ignition is greater than the specified diameter, the result will be lower. The longer the flame moves on the liquid surface, the lower the liquid level, and the lower the result. On the contrary, it is above normal levels.
(4) Related to heating speed
When the heating speed is fast, more heat is given to the oil per unit of time, and evaporation is also fast, causing the concentration of oil vapor in the air to reach the lower explosion limit in advance, and the measurement result is low. When the heating speed is too slow, the measurement time is longer, there are many ignition times, some oil vapor is lost, and the time when the mixture of oil vapor and air reaches the flash point concentration is delayed, resulting in high results.
(5) Related to atmospheric pressure
The flash point of oil is related to external pressure. Low pressure causes oil to slip easily, resulting in a lower measured flash point and a higher measured flash point. This standard stipulates that the flash point measured at 101.3 kPa atmospheric pressure is the flash point at standard pressure. If the atmospheric pressure deviates, the measured flash point needs to be corrected for the atmospheric pressure. When the pressure changes by 0.133kpa, the average flash point changes by 0.033-0.036C.
(6) Related to the moisture content of the sample
When the sample contains water, it must be dehydrated before determining the flash point. The closed flash point measurement method specifies that the moisture content is greater than 0.05%, while the open flash point measurement method requires dehydration when the moisture content is greater than 0.1%. This is because when heating the oil for testing, the water dispersed in the oil will evaporate to form water vapor, sometimes forming bubbles covering the liquid surface, affecting the normal evaporation of the oil, thereby delaying the flash ignition time and achieving higher measurement results. For heavy oil with a large amount of water, when using an open flash point tester to measure the flash point, it will be heated to a certain temperature, and the test oil can easily overflow from the cup, making it impossible to conduct experiments.