Work Item
ASTM WK91255
Revision of E659-15(2023) Standard Test Method for Autoignition Temperature of Chemicals
Rationale
Background During the 1980s the ASTM E27 committee, on the urging of my predecessor Ian Swift and in view of the published study by Union Carbide's Carlos Hilado, changed the existing standard 200 ml test flask to a 500 ml flask which lowered many of the AIT numbers although not all of them. Most AIT data currently published in the US were obtained using the 200 ml flask and the rest of the world carried on using the 200 ml flask along with their own Standard test methods. The AIT database comprises mostly 200 ml data but also contains some 500 ml data based on the revised ASTM Standard plus most likely some older data obtained using various non-standard equipment and test methods. Published AIT compilations such as NFPA 497M fail to reference the test method used to determine each datum so all the results are jumbled together.
When applying AIT data to comply with important Codes and Standards the user can usually save money by using published data (which are mostly 200 ml values). The alternatives are redetermine the AIT using the current ASTM E659 Standard test method, or be conservative by using the smaller of the two values. This can be done by applying both the current ASTM Standard and the current European test method for the 200 ml flask. Users do not understand that AIT values are inconsistent and depend on the flask volume and shape plus the precise test method used so I doubt many will pay for a new ASTM test once an AIT value has been found in some published compilation or SDS!
The risk is gas/vapor autoignition on equipment that may include large and very expensive motors, compressors and the like, which in the US are governed by T-codes and whose cost increases substantially as their maximum surface temperatures are decreased to meet code requirements. Hence the need to add a caveat. What I wrote is partly based on unpublished AIT test work and is not well known even among committee members.
Work Item Status
Date Initiated: 06-18-2024
Technical Contact: Laurence Britton
Item: 000
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