API MPMS 3.4:1995 (R2016)

This standard provides guidance on the selection, installation, calibration, and verification of automatic tank gauges (ATGs) for measuring the level of liquid hydrocarbons having a Reid vapor pressure less than 15 pounds per square inch absolute (103 kPa), transported aboard marine vessels (tankers and barges). Marine ATGs are not normally used in custody transfers because of the limitations described in Appendix A. However, level measurement by marine ATGs may be used in custody transfer when no other alternative measurement is available. The use of marine vessel-based ATGs for custody transfer normally requires mutual contractual agreement between the buyer and the seller and may be subject to government regulations. This standard also provides guidance on the requirements for data collection, transmission, and receiving. The Appendix B briefly describes the operation of the most commonly used marine ATG equipment. This standard is not applicable to the following subjects: a. Conversion of tank level to liquid volume. b. Measurement of free water or sediment lying under the liquid hydrocarbon. c. Measurement of temperature, density, or sediment and water (S&W). These measurements are discussed in Chapters 7, 9, and 10 of the API Manual of Petroleum Measurement Standards (MPMS). d. Sampling for determination of the properties of the liquid hydrocarbon. This is discussed in API Chapter 8. e. Detection of tank leaks. Safety and material compatibility precautions shall be taken when using marine ATG equipment. The manufacturer's recommendations on the use and installation of the ATG equipment should be followed. Users shall comply with all applicable national and international codes and regulations.