API MPMS 3.1B:2021 covers the 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 verifcation 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 15 pounds per square inch (in.) absolute (100 kPa);
b) measurement of weight or mass with ATG equipment (this is covered in API MPMS Chapter 3.6 and Chapter 16.2);
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 API MPMS Chapter 12.1);
e) measurement of temperature, sampling, density, and sediment and water (S and W), which are discussed in API MPMS Chapters 7–10.
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 the NFPA National Electrical Code.
