API MPMS 7.4:1993 pdf download.Manual of Petroleum Measurement Standards Chapter 7- Temperature Determination
This standard covers the static determination of tempera- tures of petroleum and petroleum products in stationary aboveground bulk storage tanks using fixed automatic tank temperature (ATT) systems that include precision tempera- ture sensors, field-mounted transmitters for electronic signal transmission, and readout equipment. This standard dis- cusses temperature measurement in general, the require- ments for custody transfer, and inventory control applications. It also discusses the requirements for data col- lection, transmission, and receiving. Appendix A of this slandard describes local reading thermometers. This standard does not cover the determination of temper- ature for hydrocarbons having a Reid vapor pressure above 15 pounds per square inch absolute (101 kPa). Safety and material compatibility precautions should be taken into consideration when using fixed ATT systems. The manufacturer’s recommendations on the use and instalation of the equipment should be followed. Users of fixed ATT systems should comply with all applicable codes, regula- tions, and API standards and the National Electric Code (NEC).
3.1.2 PHYSICAL CHARACTERISTICS AND FIRE CONSIDERATIONS
Personnel involved with the handling of petroleum-related substances (and other chemical materials) should be familiar with their physical and chemical characteristics, including their potential for fire, explosion, or chemical reaction. They should be familiar with the appropriate emergency proce- dures to follow in such cases. They should comply with in- dividual company safe operating practices and with local, state, and federal regulations, including the use of proper protective clothing and equipment. Personnel should be alert to avoid potential sources of ignition and should keep con- tainers of materials closed when not in use. INFORMATION REGARDING PARTICULAR MATE- RIALS AND CONDITIONS SHOULD BE OBTAINED FROM THE EMPLOYER, THE MANUFACTURER OR SUPPLIER OF THAT MATERIAL, OR THE MATERIAL SAFETY DATA SHEET.
3.3.3 AVERAGE TANK TEMPERATURE MEASUREMENT
Temperatures in large tanks (5,000 barrels or larger) are normally stratified unless the tank contents are thoroughly mixed. Vertical temperature differences of as much as 5F or 3°C are normal, and differences of 10F or 5°C are not un- common. In the horizontal direction, the temperature differ- ences are typically less than 1°F or 0.5°C for low and medium viscosity petroleum liquids. Somewhat higher differ- ences may be expected in high viscosity petroleum liquids. The horizontal temperature differences that occur adjacent to the tank shell do not have a significant effect on the aver- age tank temperature. For custody transfer measurement, when automatic tank gauges (ATGs) that measure level are used (for example, float-operated ATGs, servo-operated ATGs, or radar ATGs), an average temperature (not a single-point temperature) should be used. In tanks with vertical temperature stratification, the temper- ature gradient is rarely linear. An average temperature is needed for custody transfer. The mid-level temperature of the tank contents might not give an accurate average temperature. When hydrostatic tank gauges (HTGs) are used, which compute standard volume using pressure sensors, a single temperature sensor, located about halfway between the lower pressure sensors, may be adequate.
API MPMS 7.4:1993 pdf download
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