API MPMS 3.1B:2018 covers level measurement of liquid hydrocarbons in stationary, aboveground, atmospheric storage tanks using automatic tank gauges (ATGs). The standard discusses automatic tank gauging in general, accuracy, installation, commissioning, calibration, and verification of ATGs that measure either innage or ullage. It covers both intrusive and non-intrusive ATGs used for either custody transfer or inventory control. The standard also covers the requirements for data collection, transmission, and receiving. This standard does not cover the following: a) Hydrocarbons having a Reid vapor pressure above 1 5 pounds per square inch (in.) absolute (1 00 kPa).
b) Measurement of weight or mass with ATG equipment. This is covered in Chapter 3.6 and Chapter 1 6.2 of the Manual of Petroleum Measurement Standards.
c) Measurement of the level in underground tanks or in pressurized tanks storing liquid hydrocarbons.
d) Conversion of the tank level to liquid volume. This is covered in Chapter 1 2.1 of the Manual of Petroleum Measurement Standards.
e) Measurement of temperature, sampling, density, and sediment and water (S & W), which are discussed in Chapters 7–1 0 of the Manual of Petroleum Measurement Standards.
Safety and material compatibility precautions should be taken when using ATG equipment. Manufacturers’ recommendations on the use and installation of the equipment should be followed. Users should comply with all applicable codes and regulations, API Standards, and NFPA 70 National Electric Code.
