1. When the sample contains water, the water scattered in the oil during the heating process will vaporize and form water vapor, covering the oil surface, affecting the normal vaporization of the oil and delaying the flash fire time, resulting in higher measured results. Therefore, when the sample contains water, dehydration must be carried out (with a water content not exceeding 0.1%) before the flash point test can be conducted.
2. Heating speed is a key control indicator that affects flash point measurement and has a significant impact on the results of flash point measurement. If the heating speed is too fast and the sample evaporates quickly, it will cause the local concentration of the mixture to reach the explosive bottom line and cause premature flash, resulting in a low measurement result; The heating speed is too slow, the measurement time is long, the ignition frequency is too high, and some oil vapor is consumed, resulting in higher measurement results. Therefore, it is necessary to strictly control the heating rate of 5-6 ℃ according to the standard. Insufficient power of the electric furnace will also affect the results.
3. The size of the flame and the number of times it is ignited. The distance between the flame used for ignition and the liquid surface of the sample, as well as the residence time, must be strictly in accordance with national standards. If the diameter of the spherical flame used for ignition is larger than the specified value, the results obtained will be lower. The longer the flame moves on the liquid surface and the lower it is from the liquid surface, the lower the result obtained; On the contrary, the measured results will be higher. More ignition times will result in higher measurement results, while on the contrary, the measurement results will be lower.
4. According to the standard requirements, the sample in the oil cup should be placed at the circular groove. Adding too many or too few samples will change the height of the space above the liquid level, thereby affecting the mixing concentration of oil vapor and air. Causing inaccurate measurement results. During the sampling process, it is necessary to prevent the sample from splashing. The sample splashes onto the cup wall, as the high temperature of the cup wall can cause the sample to evaporate quickly, resulting in lower results.
5. Atmospheric pressure: The flash point of oil products is related to external pressure. Oil products are prone to volatilization at low pressure, resulting in a decrease in flash point. Conversely, the flash point increases. The standard stipulates that the reference pressure for flash point measurement is 130.3kpa. If there is any deviation, pressure correction is required. When the atmospheric pressure is below 99.3 kPa, the open flash point is corrected according to the following formula.
6. The temperature of the sample during sampling directly affects the rate of oil vapor evaporation and the measured flash point. The sample with a higher temperature has a lower flash point, while the sample with a higher flash point has a higher flash point. When measuring the sample, the temperature of the electric furnace must be lowered to room temperature, otherwise the measurement result will be too low.
