This is a thermal cracking process. Like catalytic cracking, it breaks up large molecules into smaller ones. It is applied to the residue of vacuum distillation as part of the overall conversion process
EESiFlo North America, Terminology and Glossary: Oil & Gas Terms, Pennsylvania, USA 2002. flowmeterdirectory.com/flowmeter_terminology, (Mrtm/ Oil and Gas - Amer) {566}