DIFF Subgroup
E21B 21/12 using drilling pipes with plural fluid passages, e.g. closed circulation systems
Introduced: January 1980
Full Title
Full titles differ between systems:
IPC:
Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor > using drilling pipes with plural fluid passages, e.g. closed circulation systems
CPC:
Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor (freeing objects stuck in boreholes by flushing E21B31/03) > using drilling pipes with plural fluid passages, e.g. closed circulation systems
No child classifications to compare. This is a leaf node in both IPC and CPC.