Comparison of manual vs automatic metering readings for oil volume of vertical tank

Five-time manual metering and automatic metering operations on the high/low levels for two vertical metal tanks (5×10⁴ m³), Tank 1201 and 1202, have been carried out and the calculated oil volumes have been compared. Statistical hypothesis testing method is adopted to determine the significant difference of the compared readings so as to separately compare the influencing factors on the metering readings, oil level and oil temperature. Results show that at a 95% confidence level, measured readings from Tank 1201 with the two metering methods have a small difference in oil level data, (only 1 mm on average error), an evident difference in oil temperature data (-0.54 ℃ on average error) and oil volume difference within a range of 2.814~29.225 m³, indicative of no significant differences statistically. While Tank 1201 has an obvious oil level difference (27 mm on average error), a small oil temperature difference (-0.62 ℃ on average error) and an oil volume difference within a range of 36.172~97.017 m³, suggesting significant differences. Since the national automatic metering standards for storage tank are still absent, it can be used to judge whether the measured readings using the two different metering methods have significant differences, and verify the accuracy of automatic metering readings by means of comparing manual vs automatic metering readings.