using drilling pipes with plural fluid passages, e.g. closed circulation systems

Full Title

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

Classification Context

Section:

FIXED CONSTRUCTIONS

Class:

EARTH OR ROCK DRILLING; MINING

Subclass:

EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS