Standard Test Method for Hardgrove Grindability Index (HGI
the hardgrove grindability index (HGI) of petroleum coke. Use of this test method or Test Method D 409 produces the same value for the sample of petroleum coke being analyzed. 1. Scope* 1.1 This test method covers the determination of the hard-grove grindability index (HGI) of those petroleum cokes that contain no dedusting additive.