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What is the difference between ASTM D92 or ASTM D93?

ASTM D92 and ASTM D93 are both test methods developed by ASTM International to determine the flash point of petroleum products. Here's a comparison of the two methods:

ASTM D92 (Standard Test Method for Flash and Fire Points by Cleveland Open Cup Tester):

ASTM D92 is a test method that determines the flash point and fire point of petroleum products using the Cleveland Open Cup (COC) apparatus. The COC tester is an open cup apparatus where a sample is heated, and a small flame is passed over the surface of the liquid at regular intervals. The flash point is the temperature at which the vapor above the sample momentarily ignites, while the fire point is the temperature at which sustained combustion occurs for at least 5 seconds.

ASTM D93 (Standard Test Methods for Flash Point by Pensky-Martens Closed Cup Tester):

ASTM D93 is a test method used to measure the flash point of petroleum products using the Pensky-Martens closed cup (PMCC) apparatus. In this method, a sample is placed in a closed cup with a small opening, and the cup is gradually heated. A flame is periodically passed over the cup's opening, and the flash point is determined by the temperature at which the vapor inside the closed cup ignites momentarily.

Differences:
Test Apparatus: The key difference between ASTM D92 and ASTM D93 lies in the apparatus used. D92 employs the open cup Cleveland apparatus, while D93 uses the closed cup Pensky-Martens apparatus.
Test Procedure: In ASTM D92, the sample is exposed to an open flame in an open cup, while in ASTM D93, the sample is heated in a closed cup with a small opening.
Precision and Accuracy: Both methods have been extensively used and standardized, and they provide reliable flash point measurements. However, the closed cup Pensky-Martens apparatus used in ASTM D93 is generally considered to provide more precise and reproducible results compared to the open cup Cleveland apparatus used in ASTM D92.
The choice between ASTM D92 and ASTM D93 depends on factors such as regulatory requirements, industry standard,and the specific characteristics of the petroleum product being tested.