Page 9 - Air and Gas Drilling Manual

x List of Symbols
d b
= inside diameter of the blooey line, ft
D b
= drill bit single orifice diameter, ft
D bi = inside diameter of blooey line, in
D c = approximate diameter of the rock cutting particle, ft (m)
d c = inside diameter of the casing at the tope of the well, in
D cl = diameter to the centerline of the nozzles, ft
d cl = diameter to the centerline of the nozzles, in
D e = equivalent single orifice inside diameter, ft
d h = drill bit diameter, in
D h = inside diameter of the borehole, ft
D hy = hydraulic diameter for annular cross-section, ft
D io = inside diameter of the outer tube of the dual wall pipe, ft
D n = inside diameter of each nozzle, ft
d n = inside diameter of each nozzle, in
D o = inside diameter of open orifices, ft
d o = inside diameter of open orifices, in
D oi = outside diameter of the innertube of the dual wall pipe, ft
D op = diameter of open orifice, ft
d op = diameter of open orifice, in
D p = outside diameter of the drill pipe, ft
d p = outside diameter of the drill pipe, in
D pp = inside diameter of air hammer bit passage, ft
d pp = inside diameter of air hammer bit passage, in
D sp = inside diameter of shank passage, ft
d sp = inside diameter of shank passage, in
D sp = inside diameter of the drive shaft passage, ft
d sp = inside diameter of the drive shaft passage, in
D sr = inside diameter of the surface return flow line, ft
e av = average absolute surface roughness, ft