Take opening gauges, temperatures, samples, and water measurements of each tank to be used in the transfer. Any significant difference between the observed reference height and the reference height shown on the tank capacity tables should be noted and questioned. Manual gauging requires obtaining either two identical consecutive gauge readings or three consecutive readings within an absolute range of 3 mm (1/8 inch), as per “API MPMS Chapter 3.1A - Standard Practice for the Manual Gauging of Petroleum and Petroleum Products”. If the first two readings are identical, this reading shall be reported to the nearest 1 mm if metric tapes are used or to the nearest 1/8 inch. if customary tapes are used. When three readings are taken, all three readings must be within the 3 mm (1/8 inch.) range and readings averaged to the nearest 1 mm for metric tapes and 1/8 inch. for customary tapes. If the tank contents are determined to be in motion and waiting for equilibrium is not possible, the tank measurements should be recorded, and all parties advised. If the situation cannot be resolved, a letter of protest should be issued. If available, record the automatic gauges for comparison purposes. In the case of tanks with floating roofs, gauging should be avoided while the roof is in the critical zone. The placement of roof legs in high or low position and the critical zone should be recorded.
preferred equipment for obtaining temperatures. The PET should have a calibrated range of accuracy that meets the desired temperature range of the material from which a temperature is to be taken. For example, a PET with a calibrated microchip accurate to 300 ° F/149 ° C is not acceptable for asphalt products that are stored at 350 ° F/177 ° C. (See API MPMS Chapter 7.2)
2.4 Temperature Determination
Temperature determination of cargoes in a storage tank is critical to the custody transfer process at the time of gauging, therefore, temperatures should be carefully taken. Heavy cargoes, heated cargoes, blended cargoes, and cargoes in unheated tanks in very cold weather may tend to have temperature stratification within each tank. When this situation is determined, extra temperature measurements should be taken. On high heat cargoes such as asphalt, it may be impossible to obtain representative temperatures with the use of a liquid-in-glass or portable electronic thermometer (PET); therefore, it may be necessary to use permanently installed temperature measuring devices. The use of a permanently installed measuring device should be noted in the report, along with when and how the device’s accuracy was verified. Caution: temperatures taken at or near heating elements may distort temperature profiles.
2.4.2 Liquid-in-Glass Thermometer
Liquid-in-glass thermometers must remain in the liquid long enough to reach the temperature of the liquid that is being measured (see API MPMS Chapter 7.1). Some liquids have the potential for temperature stratification to occur; in these scenarios, the time constraints involved in using a liquid-in-glass thermometer to profile a tank will usually necessitate the use of a PET. 2.4.3 Dynamic Temperature Measurement If a temperature probe in the shore pipeline is used to determine the temperature for the correction of metered quantity loaded or establish the product temperature in the shore pipeline that is then used in the quantification of a load, discharge, or transfer operation, verify and record the last two times that the probe was checked for accuracy.
2.4.1 Portable Electronic Thermometer
The portable electronic thermometer (PET) is the
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