ASTM D7621-16(2021)

5.1Excessive levels of hydrogen sulfide in the vapor phase above residual fuel oils in storage tanks can result in health hazards, violation of local occupational health and safety regulations, and public complaint. An additional concern is corrosion that can be caused by the presence of H₂S during refining or other activities. Control measures to maintain safe levels of H_{5.2This test method was developed so refiners, fuel terminal operators, and independent testing laboratory personnel can rapidly and precisely measure the amount of H2S in residual fuel oils and distillate blend stocks, with a minimum of training, in a wide range of locations.}

5.3Test Method D5705 provides a simple and consistent field test method for the rapid determination of H_{5.4Test Method D6021 does measure the H5.5H2S concentrations in the liquid and vapor phase attempt to reach equilibrium in a static system. However, this equilibrium and the related liquid and vapor concentrations can vary greatly depending on temperature and the chemical composition of the liquid phase. The equilibrium of the vapor phase is disrupted the moment a vent or access point is opened to collect a sample.}

1.1This test method covers procedures (A and B) for the determination of the hydrogen sulfide (H₂S) content of fuel oils such as marine residual fuels and blend stocks, with viscosity up to 3000mm²s^-1 at 50C, and marine distillate fuels, as measured in the liquid phase.

1.2Procedure A has been shown to eliminate interferences such as thiols (mercaptans) and alkyl sulfides. Procedure B can give elevated results if such interferences are present (see Annex A2).

1.3Valid ranges for the precision are given in Table2 and Table3. Measurements can be made outside these ranges however precision has not been determined.

1.4Samples containing FAME do not affect the measurement of hydrogen sulfide by this test method.

1.5The values stated in SI units are to be regarded as standard. Non-SI units given in parentheses are for information only.

1.6This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.7This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.