COMPRESSED
AIR REQUIREMENTS
In general bailing velocities of 5000 ft/
min for soft materials like overburden and soft coal and 7000ft/min
for heavier materials like iron ore ,etc are considered optimum
for lifting off the bottom. It is better to have bailing velocity
upto 8000 ft/min for drilling materials that are wet as well
as heavy.
For Calculating bailing velocity, the following
simple formula can be used:
|
|
Annular
Velocity in FPM (feet per minute) |
| BIT DIAMETER |
DRILL PIPE DIA. |
3,500cfm |
4,000cfm |
5,000cfm |
6,000cfm |
7,000cfm |
| 4-3/4" |
2-7/8' |
273 |
312 |
390 |
468 |
546 |
| |
3-1/2" |
197 |
225 |
281 |
337 |
394 |
| |
4" |
125 |
143 |
178 |
214 |
250 |
| 5-1/8" |
2-7/8" |
344 |
393 |
491 |
589 |
687 |
| |
3-1/2" |
268 |
306 |
382 |
459 |
535 |
| |
4" |
196 |
224 |
280 |
336 |
392 |
| 5-7/8" |
2-7/8" |
501 |
573 |
716 |
859 |
1002 |
| |
3-1/2" |
425 |
486 |
607 |
729 |
850 |
| |
4" |
354 |
404 |
505 |
606 |
707 |
| 6-1/4" |
4-1/2" |
359 |
411 |
513 |
616 |
718 |
| |
5" |
269 |
307 |
384 |
460 |
537 |
| 6-3/4" |
4" |
564 |
645 |
806 |
968 |
1129 |
| |
4-1/2" |
483 |
552 |
960 |
829 |
967 |
| |
5" |
393 |
449 |
561 |
673 |
758 |
| 7-7/8" |
4-1/2" |
797 |
911 |
1139 |
1367 |
1595 |
| |
5-1/2" |
607 |
693 |
866 |
1040 |
1213 |
| |
6-1/4" |
438 |
501 |
626 |
751 |
877 |
| |
6-1/2" |
377 |
431 |
539 |
645 |
755 |
| 9" |
6-1/2" |
740 |
846 |
1057 |
1268 |
1480 |
| |
7" |
611 |
968 |
873 |
1047 |
1222 |
| |
7-5/8" |
436 |
499 |
624 |
748 |
873 |
| |
7-3/4" |
400 |
457 |
571 |
685 |
800 |
| 9-7/8" |
7" |
926 |
1059 |
1233 |
1588 |
1853 |
| |
7-3/4" |
715 |
817 |
1022 |
1226 |
1430 |
| |
8-5/8" |
442 |
504 |
631 |
757 |
883 |
| |
9-1/4" |
228 |
261 |
326 |
391 |
456 |
| 10-5/8' |
7-3/4" |
1009 |
1153 |
1441 |
1729 |
2017 |
| |
8-5/8" |
735 |
840 |
1050 |
1260 |
1470 |
| |
9" |
609 |
696 |
870 |
1044 |
1218 |
| |
9-1/4" |
521 |
596 |
754 |
895 |
1024 |
| 12-1/4" |
8-5/8" |
1445 |
1651 |
2064 |
2477 |
2890 |
| |
9" |
1390 |
1507 |
1844 |
2261 |
2637 |
| |
9-1/4" |
1232 |
1408 |
1759 |
2111 |
2463 |
| |
10-3/4" |
659 |
753 |
941 |
1129 |
1318 |
|
