Page 581 - Air and Gas Drilling Manual

2 635
.
V
(.
0 0430)
0 976) (.
.
V dci 62 6 ft/sec Chapter 11: Specialized Drilling Equipment 11-19
dci
For drilling at 10,000 ft, the estimated number of piston cycles is
N p 216 strikes/minute
The period of a single cycle of the piston is
60
p
216
0 278 sec
.
p
The flow to the air hammer is stopped for approximately one half of the cycle
period. Thus, distance the air flow is compressed inside the drill collars above the
hammer is approximately
0 278
.
.
L c ( 62 6)
2
L c 870 ft
.
The length of a cubic foot of the compressed air in the drill collars prior to the stop
is
1
L
.
0 0430
L 23 18 ft
.
The length of a cubic foot of the compressed air in the drill collars after the stop is
L c 23 18 8 70
.
.
.
L c 14 49 ft
The new compressed volume of the compressed air in the drill collars after the stop
is

Vol c (.49 ) ( .0430 )
14
0