ASTM G 74 : 2013

1.1This test method describes a method to determine the relative sensitivity of nonmetallic materials (including plastics, elastomers, coatings, etc.) and components (including valves, regulators flexible hoses, etc.) to dynamic pressure impacts by gases such as oxygen, air, or blends of gases containing oxygen.

1.2This test method describes the test apparatus and test procedures employed in the evaluation of materials and components for use in gases under dynamic pressure operating conditions up to gauge pressures of 69 MPa and at elevated temperatures.

1.3This test method is primarily a test method for ranking of materials and qualifying components for use in gaseous oxygen. The material test method is not necessarily valid for determination of the sensitivity of the materials in an “as-used” configuration since the material sensitivity can be altered because of changes in material configuration, usage, and service conditions/interactions. However, the component testing method outlined herein can be valid for determination of the sensitivity of components under service conditions. The current provisions of this method were based on the testing of components having an inlet diameter (ID bore) less than or equal to 14 mm (see Note 1).

1.4A 5 mm Gaseous Fluid Impact Sensitivity (GFIS) test system and a 14 mm GFIS test system are described in this standard. The 5 mm GFIS system is utilized for materials and components that are directly attached to a high-pressure source and have minimal volume between the material/component and the pressure source. The 14 mm GFIS system is utilized for materials and components that are attached to a high pressure source through a manifold or other higher volume or larger sized connection. Other sizes than these may be utilized but no attempt has been made to characterize the thermal profiles of other volumes and geometries (see Note 1).

1.5This test method can be utilized to provide batch-to-batch comparison screening of materials when the data is analyzed according to the methods described herein. Acceptability of any material by this test method may be based on its 50 % reaction pressure or its probability of ignition based on a logistic regression analysis of the data (described herein).

1.6Many ASTM, CGA, and ISO test standards require ignition testing of materials and components by gaseous fluid impact, also referred to as adiabatic compression testing. This test method provides the test system requirements consistent with the requirements of these other various standards. The pass/fail acceptance criteria may be provided within other standards and users should refer to those standards. Pass/fail guidance is provided in this standard such as that noted in section 4.6. This test method is designed to ensure that consistent gaseous fluid impact tests are conducted in different laboratories.

1.7The criteria used for the acceptance, retest, and rejection, or any combination thereof of materials and components for any given application shall be determined by the user and are not fixed by this method. However, it is recommended that at a minimum the 95 % confidence interval be established for all test results since ignition by this method is inherently probabilistic and should be treated by appropriate statistical methods.

1.8The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.9This 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 and health practices and determine the applicability of regulatory limitations prior to use. For specific precautions see Section 7.